Effects of Personal Protective Equipment Use and Good Workplace Hygiene on Symptoms of Neurotoxicity in Solvent-Exposed Vehicle Spray Painters

Effects of Personal Protective Equipment Use and Good Workplace Hygiene on Symptoms of... Abstract Objectives To assess the association between the use of personal protective equipment (PPE) and good workplace hygiene and symptoms of neurotoxicity in solvent-exposed vehicle spray painters. Methods Exposure control measures including PPE-use and workplace hygiene practices and symptoms of neurotoxicity were assessed in 267 vehicle repair spray painters. Symptoms were assessed using an adapted version of the EUROQUEST Questionnaire. Results Frequent respirator and glove use was inversely and significantly associated with symptoms of neurotoxicity in a dose-dependent manner (P < 0.05 for trend) with the strongest protective effect found for consistent glove use (odds ratios [OR] 0.1–0.2, P < 0.01, for reporting ≥10 and ≥5 symptoms). A clear dose–response trend was also observed when combining frequency of respirator and glove use (P < 0.05 for reporting ≥5 and ≥10 symptoms), with an overall reduction in risk of 90% (OR, 0.1, P < 0.01) for those who consistently used both types of PPE. Protective effects were most pronounced for the symptom domains of psychosomatic (P < 0.05 for trend, for combined PPE use), mood (P < 0.05), and memory and concentration symptoms combined (P < 0.05), with reductions in risk of >80%. Poor hygiene workplace practices, such as solvent exposure to multiple body parts (OR 3.4, P = 0.11 for reporting ≥10 symptoms), were associated with an increased risk of symptoms. When using a general workplace hygiene score derived from a combination of PPE-use and (good) workplace practice factors an inverse and significant dose–response trend was observed for reporting ≥5 (P < 0.01) and ≥10 symptoms (P < 0.01). Conclusions This study has shown that PPE-use and good workplace hygiene are associated with a strongly reduced risk of symptoms of neurotoxicity in solvent-exposed vehicle spray painters. behavioural, dermal exposure, EUROQUEST, intervention, neurotoxic, personal protective equipment, solvents, symptoms of neurotoxicity, workplace hygiene Introduction Solvent exposure in the vehicle collision repair industry has long been associated with symptoms of neurotoxicity (Hänninen et al. 1976; Husman 1980; Elofsson et al. 1980; Hänninen et al. 1991; Daniell et al. 1993; Keer et al. 2016) and deficits in cognitive performance (Maizlish et al. 1985; Daniell et al. 1993; Böckelmann et al. 2002). Although considerable changes in health and safety practices have occurred in this industry with an associated decline in solvent exposures internationally over the past 20 years (Kauppinen et al. 2013), an increased risk of symptoms of neurotoxicity continues to be reported. In particular, we have recently shown that spray painters and panel beaters (or auto-body repair workers) in New Zealand report more symptoms of neurotoxicity than non-exposed reference workers, with the strongest associations observed for neurological, psychosomatic, mood, memory, and concentration symptoms (Keer et al. 2016). These effects were shown at ‘airborne’ solvent levels well below current exposure standards suggesting that ‘dermal’ exposures may be important. Previous studies have shown that personal protective equipment (PPE) and good workplace hygiene reduce both airborne and dermal exposure to solvents and subsequent total body burden in spray painters (Jang et al. 1999; Chang et al. 2007) and other solvent-exposed workers (Löf et al. 1993; Nakayama et al. 2004; Wang et al. 2006; Triebig et al. 2009). In particular, quasi-experimental studies involving PPE-use enforced by researchers showed that the total body burden was reduced by between 26% and 99% compared to no or minimal use of PPE (Löf et al. 1993; Chang et al. 2007; Triebig et al. 2009). The efficacy was dependent upon the type, quality, and maintenance level of PPE, which along with consistency of use is known to vary greatly between workplaces and workers (Fidler et al. 1987; Winder and Turner 1992; Oestenstad and Perkins 1992; Jang et al. 1999; Liu et al. 2006). Low airborne and dermal exposures and a reduced body burden of solvents have been associated with reduced risks of self-reported symptoms of neurotoxicity and abnormal neuropsychological performance (Dick et al. 1984; Jang et al. 1999), but few studies have directly assessed the impact of PPE use on symptoms, and none have assessed the effects of workplace hygiene. In the current study, using a cross-sectional study design, we assessed the effect of PPE-use and workplace hygiene practices on symptoms of neurotoxicity in 267 vehicle collision repair spray painters. Methods Study population Participants comprised 267 spray painters from our previous questionnaire survey in 370 collision repair workers (267 spray painters and 103 panel beaters or auto-body repair workers, including office staff who were ex-tradesmen), recruited from workshops throughout the north island of New Zealand. Office staff (n = 46) were all ex-tradesmen and were recoded according to their previous job title (31 as spray painters), as this more accurately reflected their working life exposures. They generally also performed at least some repair work and were therefore still at risk of exposure. All spray painters conducted the same core tasks including mixing paint, spray painting, and degreasing/cleaning before and after spray painting, with variations in the time spent on each task. Exclusion criteria for the previous study were no history of work involving solvent exposure or any history of major head injury or neurological/neurodegenerative disease, including meningitis, major depression, or epilepsy. All data on PPE-use and/or workplace hygiene practices was missing for three spray painters, leaving 264 for inclusion in the final analyses. No data on PPE-use and workplace hygiene practices was available for panel beaters. Questionnaire Information on demographics, symptoms of neurotoxicity, work characteristics, use of solvents and solvent-based products, use of PPE and potential confounders was obtained by a face-to-face interview (Keer et al. 2016). Questions on PPE focused on respirator and glove use during key spray painting-related tasks including mixing paint, spray painting, and cleaning equipment or bodywork. Current (i.e. in the past 3 months) symptoms were assessed using an adapted version of the EUROQUEST questionnaire (Carter et al. 2002; Keer et al. 2016), which included 59 core items covering the following domains: neurological (e.g. numbness and tingling in extremities, balance problems), psychosomatic (e.g. headaches, nausea, tinnitus), mood, memory, concentration, fatigue, and sleep quality. Symptom frequency was reported on a 4-point scale, “seldom or never”, “sometimes”, “often”, or “very often”. The EUROQUEST also assessed anxiety (6 items, e.g., “Are you generally a nervous person?”, “Do you worry a lot about trivial things”), rated on a different 4-point scale of “strongly disagree”, “disagree”, “agree”, or “strongly agree”, and perceived general health (4 items, e.g., “how good is your health?”, “How do you feel about your life in general?”), where participants were asked to rate different aspects of their general health and wellness as “very good” “good”, “poor”, or “very poor”. For PPE use, participants were asked to indicate how often they wear a respirator or gloves during each task on a 5 point scale: “Seldom/never”, “Sometimes”, “Often”, “very often”, or “Always”. They were also asked what types of respirator they used i.e. a positive pressure “Air-fed” unit, or one fitted with disposable absorbent cartridges, or both. Questions on the types of glove used (i.e. material) were not included, but field observations showed that nitrile gloves were used by the vast majority of workers for tasks with a high risk of solvent exposure (mixing paint, spray painting, degreasing/cleaning). Additional questions on workplace behaviours and characteristics included: number of body parts exposed during spray painting, with a possible score of 0 to 3 (hands and wrists, upper arms and forearms, and/or head, face and neck); whether workers washed their hands in solvents and how often (“seldom”, “sometimes”, “often”, or “very often”); and the frequency with which the absorbent cartridges were changed in the worker’s respirator (“as and when required”, “less than once a month”, “1–2 times a month”, or “weekly”). Questions also included the type of spray equipment washer used and whether local exhaust ventilation was present i.e. “un-enclosed and un-extracted”, “enclosed and un-extracted”, “un-enclosed and extracted”, or “enclosed and extracted”. We also asked for the type of paint used i.e. “mostly water based”, “mostly solvent based”, and “both solvent and water based”, and how many hours (on a continuous scale) over ‘a typical working day’ workers spent spray painting, mixing paint, and degreasing (panels or parts). As the vast majority of spray painting was conducted in spray booths (with down-draft or cross-draft exhaust ventilation), we were unable to assess the effect of spraying outside the booth. Almost all booths (>90%) were commercially produced, single vehicle capacity units with down-draft extraction systems (ceiling to floor air flow), built to similar specifications and compliant with New Zealand health and safety and emission control standards (confirmed through testing by regulatory authorities). The remainder were cross-draft booths (which were also compliant with New Zealand health and safety and emission control standards), a small number of which were owner-built. For the purpose of subsequent analyses, we dichotomized the EUROQUEST symptoms, with “seldom or never” or “sometimes”, “strongly disagree” or “disagree”, and “very good” or “good” constituting a negative response and “often” or “very often”, “agree” or “strongly agree”, and “poor” or “very poor” constituting a positive response (Kaukiainen et al. 2009; Keer et al. 2016). Anxiety and perceived general health were included to control the analyses for individual personality traits which have been found to lead to under or over reporting of symptoms (Kaukiainen et al. 2009). Responses to these questions were aggregated to produce a total score for each domain as described previously (Keer et al. 2016). Responses to the PPE and workplace practice questions were also dichotomized, with “seldom/never” or “sometimes” and “as and when required” or “less than once a month”, constituting a negative (i.e. infrequent) response and ‘often’, ‘very often’ or ‘always’, and “1–2 times a month” or “weekly” constituting a positive (i.e. frequent) response. For the sum of skin exposures, those with an overall ‘score’ of 0 (n = 21) or 1 (92) were combined for all future analyses due to small numbers in the “0” category. Also, only a small number of workers reported using ‘mostly water-based’ paint (n = 13), so they were combined with those who reported using “both water and solvent based” paints (n = 60). Statistical analyses All analyses were conducted using Stata version 13.1 (StataCorp LP, Texas, USA). Associations between PPE-use and workplace practices and symptoms were assessed using logistic regression with results expressed as prevalence odds ratios (OR). EUROQUEST symptoms were grouped according to the total number of positive responses, i.e. ≥5 or ≥10 (Keer et al. 2016). For symptoms clustered by specific domains, we used a cut-point of ≥3 positive responses, an approach previously shown to be sensitive and specific in the classification of patients diagnosed with chronic solvent neurotoxicity (Kaukiainen et al. 2009). Memory and concentration symptoms were included as a combined domain with a cut-point of ≥3 positive responses to reduce under-detection of potential cases (Kaukiainen et al. 2009). Concentration symptoms were not analysed as a standalone domain due to low numbers in many strata. Initially analyses were conducted for each measure of PPE use and workplace practice separately, adjusted for age, ethnicity, smoking status, alcohol consumption, education level, and general health and personality traits. Other potential confounders including sleep quality, chronic diseases (e.g., diabetes), minor head injuries, concussion, chronic fatigue, prescription drug use, and pre-existing health issues were also tested, but these did not appreciably affect the observed associations (data not shown) and were therefore not used in subsequent analyses. Non-convergence did occur occasionally for some potential confounders in the regression models; however, additional restricted analyses including or excluding these variables had little effect on the relevant outcomes (data not shown). In addition to analysing frequency of respirator or glove use by each work task (mixing paint, spraying, or degreasing/cleaning), we created a combined metric for each type of PPE by summing their frequency of use (0 or 1) across tasks. This gave a possible ‘score’ of 0–3, with 0 representing infrequent PPE use for all tasks. We also created an ‘overall’ measure of PPE-use by combining glove and respirator use, giving a possible score of 0–6; those who scored 0 (n = 4) or 1 (n = 32) were combined due to low numbers. Finally, as a measure of overall workplace hygiene we created a ‘hygiene’ metric by dichotomising each of the respirator and glove use metrics (score of 0 or 1 = 0, score of 2 or 3 = 1) and combining them with outcomes related to the use of an air-fed respirator (0 = no use; 1 = any use), frequency that respirator cartridges were changed (0 = infrequently 1 = frequently) and frequency that hands are washed in solvents (0 = frequently; 1 = infrequently), giving a possible score of 0–5 (0 representing generally ‘poor’ hygiene). For subsequent analyses, those who scored 0 (n = 20) or 1 (n = 42) were combined into single categories due to low numbers; we also combined scores of 4 (n = 60) and 5 (n = 16) for the same reason. For the analyses of PPE use by individual work tasks (e.g. respirator use during paint mixing) and workplace practices, a number of workers were excluded due to missing data. Workers were also excluded from the respirator use metric (n = 19), glove use metric (n = 10), combined PPE use metric (n = 21), and hygiene metric (n = 30) if data were missing for one or more of the variables used to construct the metric. After analysing each PPE use measure and workplace practice separately, we repeated the analyses mutually adjusting for all PPE use measures and workplace practices. Although this showed similar ORs and trends (data not shown), there was significant colinearity and non-convergence (Greenland et al. 2016). To address this, we applied a more restricted model including only variables showing significant associations when analysed separately. Due to further colinearity we were not able to include respirator use and glove use separately, so included only the combined PPE use metric. For the same reason only one of the two variables on hand washing with solvents was included i.e. frequency that hands were washed (rather than never or ever washed hands) which is more likely to be representative of exposure intensity. Sum of skin exposure was correlated with the combined PPE metric, so this was also analysed separately. The ‘hygiene’ metric (described above) was analysed separately as it was derived from variables already included in the mutually adjusted model. Neurological symptoms were not analysed as a standalone domain for the mutually adjusted analyses due to low numbers in many strata. Results The demographic characteristics of study participants are shown in Table 1. Over three quarters of spray painters reported infrequent respirator use when mixing paint, and over half when cleaning or degreasing equipment/parts (Table 2). Approximately 20% used respirators consistently across multiple tasks and 45% consistently used gloves. Twenty-seven percent of workers frequently washed their hands (by immersion and direct application) in solvent mixtures used for degreasing, cleaning spray equipment or thinning paint (comprised of varying proportions of naphtha, toluene, acetone, methyl ethyl ketone, and methanol), primarily to remove paint overspray deposited on the hands and/or forearms as a result of not wearing gloves or other protective clothing. Eight percent of workers reported exposure to hands, forearms, and head (top of face and/or neck) when spray painting, while ~70% reported exposure to one or two skin areas when painting. The majority of painters reported the use of primarily solvent-based paints, with only 5% using ‘mostly water-based paints’. Painters spent on average two-and-a-half hours spray painting [ranging from 0 to 8.5 h/day, with those spray painting 0 h/day being ex-tradesmen now in management (n = 9) who occasionally perform some spray painting work during busy periods (Keer et al. 2016)], 1 hour mixing paint, and 1 hour degreasing parts and cleaning spray equipment. Table 1. Demographic characteristics of workers.   Spray painters (n = 267)  n  %  Ethnicity   Maori  37  13.9   Pacific  17  6.4   Other (incl. NZ European)  213  80.8  Smoking status   Non-smoker  112  42.0   Ex-smoker  76  28.5   Current smoker  79  29.6  Education level   Primary  5  1.9   Secondary  194  72.7   Trade cert.  58  21.7   Tertiary  10  3.7    Mean  Range  Age  36.0  17–64  Alcohol (mean drinks per week)  13.4  0–140  Duration of employment (years)  16.6  0.3 - 50    Spray painters (n = 267)  n  %  Ethnicity   Maori  37  13.9   Pacific  17  6.4   Other (incl. NZ European)  213  80.8  Smoking status   Non-smoker  112  42.0   Ex-smoker  76  28.5   Current smoker  79  29.6  Education level   Primary  5  1.9   Secondary  194  72.7   Trade cert.  58  21.7   Tertiary  10  3.7    Mean  Range  Age  36.0  17–64  Alcohol (mean drinks per week)  13.4  0–140  Duration of employment (years)  16.6  0.3 - 50  View Large Table 2. Prevalence of PPE use and particular workplace practices.   Frequency/n (%)  PPE use   Respirator use  Infrequently  Frequently    Mixing paint  192 (77.1%)  57 (22.9%)    Spray painting  8 (3.1%)  249 (96.9%)    Cleaning equipment/etc.  151 (60.9%)  97 (39.1%)   Sum of respirator use  N (%)    0 (respirator not worn for all 3 tasks)  7 (2.9%)    1  137 (55.9%)    2  52 (21.2%)    3 (respirator worn for all 3 tasks)  49 (20.0%)   Glove use  Infrequently  Frequently    Mixing paint  130 (50.6%)  127 (49.4%)    Spray painting  80 (31.2%)  176 (68.8%)    Cleaning equipment/etc.  65 (25.3%)  192 (74.7%)   Sum of glove use  N (%)    0 (gloves not worn for all 3 tasks)  41 (16.1%)    1  53 (20.9%)    2  45 (17.7%)    3 (Gloves worn for all 3 tasks)  115 (45.3%)    Infrequently  Frequently   Combined PPE metric  N (%)    0 (No gloves or respirator worn for all 3 tasks)  4 (1.7%)    1  32 (13.2%)    2  37 (15.2%)    3  42 (17.3%)    4  56 (23.1%)    5  32 (13.2%)    6 (Both gloves and respirator worn for all 3 tasks)  40 (16.5%)    No  Yes   Ever use air-fed mask  123 (46.6%)  141 (53.4%)    Infrequently  Frequently   Frequency respirator cartridges changed  169 (67.4%)  82 (32.7%)  Workplace practices    No  Yes   Wash hands in solventsa  87 (33.0%)  177 (67.1%)    Infrequently  Frequently   Frequency wash hands in solventsa  193 (73.1%)  71 (26.9%)   Skin exposure (body parts exposed)  N (%)    0  61 (23.1%)    1  90 (34.1%)    2  92 (34.9%)    3  21 (8.0%)   Gun cleaning method      Unenclosed + un-extracted  55 (21.6%)    Enclosed + un-extracted  50 (19.6%)    Unenclosed + extracted  57 (22.4%)    Enclosed + extracted  93 (36.5%)   Paint type      Mostly water based  13 (5.0%)    Mostly solvent based  185 (71.7%)    Both water and solvent based  60 (23.3%)   Hours on a typical day  Mean (range)    Mixing paint  0.9 (0.0–5.0)    Spray painting  2.6 (0.0–8.5)    Degreasing/cleaning  0.9 (0.0–7.5)  Combined measures of workplace hygiene     ‘Hygiene’ metric  N (%)    0 (poor hygiene)  18 (7.7%)    1  38 (16.2%)    2  46 (19.7%)    3  60 (25.6%)    4  56 (23.9%)    5 (good hygiene)  16 (6.8%)    Frequency/n (%)  PPE use   Respirator use  Infrequently  Frequently    Mixing paint  192 (77.1%)  57 (22.9%)    Spray painting  8 (3.1%)  249 (96.9%)    Cleaning equipment/etc.  151 (60.9%)  97 (39.1%)   Sum of respirator use  N (%)    0 (respirator not worn for all 3 tasks)  7 (2.9%)    1  137 (55.9%)    2  52 (21.2%)    3 (respirator worn for all 3 tasks)  49 (20.0%)   Glove use  Infrequently  Frequently    Mixing paint  130 (50.6%)  127 (49.4%)    Spray painting  80 (31.2%)  176 (68.8%)    Cleaning equipment/etc.  65 (25.3%)  192 (74.7%)   Sum of glove use  N (%)    0 (gloves not worn for all 3 tasks)  41 (16.1%)    1  53 (20.9%)    2  45 (17.7%)    3 (Gloves worn for all 3 tasks)  115 (45.3%)    Infrequently  Frequently   Combined PPE metric  N (%)    0 (No gloves or respirator worn for all 3 tasks)  4 (1.7%)    1  32 (13.2%)    2  37 (15.2%)    3  42 (17.3%)    4  56 (23.1%)    5  32 (13.2%)    6 (Both gloves and respirator worn for all 3 tasks)  40 (16.5%)    No  Yes   Ever use air-fed mask  123 (46.6%)  141 (53.4%)    Infrequently  Frequently   Frequency respirator cartridges changed  169 (67.4%)  82 (32.7%)  Workplace practices    No  Yes   Wash hands in solventsa  87 (33.0%)  177 (67.1%)    Infrequently  Frequently   Frequency wash hands in solventsa  193 (73.1%)  71 (26.9%)   Skin exposure (body parts exposed)  N (%)    0  61 (23.1%)    1  90 (34.1%)    2  92 (34.9%)    3  21 (8.0%)   Gun cleaning method      Unenclosed + un-extracted  55 (21.6%)    Enclosed + un-extracted  50 (19.6%)    Unenclosed + extracted  57 (22.4%)    Enclosed + extracted  93 (36.5%)   Paint type      Mostly water based  13 (5.0%)    Mostly solvent based  185 (71.7%)    Both water and solvent based  60 (23.3%)   Hours on a typical day  Mean (range)    Mixing paint  0.9 (0.0–5.0)    Spray painting  2.6 (0.0–8.5)    Degreasing/cleaning  0.9 (0.0–7.5)  Combined measures of workplace hygiene     ‘Hygiene’ metric  N (%)    0 (poor hygiene)  18 (7.7%)    1  38 (16.2%)    2  46 (19.7%)    3  60 (25.6%)    4  56 (23.9%)    5 (good hygiene)  16 (6.8%)  a’Frequently’ or ‘Yes’ represents poorer hygiene. View Large Analyses of the effects of PPE-use showed that frequent use of a respirator when mixing paint or cleaning equipment was associated with fewer total symptoms (significant only for the cut-point of ≥5 symptoms) with overall significant (P < 0.05) and borderline significant (P < 0.1) dose–response trends for ≥5 and ≥10 symptoms, respectively (Table 3). Table 3. Prevalence odds ratios for symptoms of neurotoxicity and PPE use/workplace practices.     ≥5 Symptomsan (%)    ≥10 Symptomsan (%)    ≥15 Symptomsan (%)    ≥3 Neurologicaln (%)    ≥3 Psychosomaticn (%)    ≥3 Moodn (%)    ≥3 Memoryn (%)    ≥3 Fatiguen (%)    ≥3 Sleep disturbancen (%)    ≥3 Memory and concentrationn (%)    99 (37.5)    35 (13.3)    17 (6.4)    11 (4.2)    17 (6.4)    31 (11.7)    21 (8.0)    35 (13.3)    26 (9.9)    34 (12.9)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)  PPE use   Respirator use    Mixing paint    0.4 (0.2–0.8)*    0.4 (0.1–1.4)    0.5 (0.1–4.8)    -    0.5 (0.1–3.4)    0.6 (0.2–2.0)    0.7 (0.2–3.1)    0.5 (0.2–1.7)    0.1 (0.0–1.0)^    0.4 (0.1–1.4)    Spray painting    0.7 (0.2–3.3)    0.3 (0.0–2.0)    -    0.1 (0.0–1.7)    -    -    -    1.2 (0.1–11.7)    0.6 (0.1–4.0)    0.5 (0.0–4.9)    Cleaning equipment/degreasing    0.4 (0.2–0.8)**    0.5 (0.2–1.3)    0.4 (0.1–2.3)    -    0.8 (0.2–3.8)    0.7 (0.2–2.8)    0.5 (0.2–1.2)    0.6 (0.2–1.5)    0.1 (0.0–0.7)*    0.5 (0.2–1.3)   Sum of respirator use    0/1 (REF)                                            2    0.5 (0.3–1.1)    0.9 (0.3–2.6)    1.5 (0.3–7.7)    -    1.1 (0.3–4.7)    0.7 (0.2–2.1)    0.8 (0.2–3.1)    1.2 (0.5–3.2)    0.3 (0.1–1.3)    0.8 (0.3–2.1)    3    0.3 (0.1–0.7)**    0.1 (0.0–1.1)^    0.4 (0.0–5.2)    -    0.4 (0.0–3.8)    0.3 (0.1–1.6)    0.5 (0.1–2.9)    0.3 (0.1–1.4)    -    0.3 (0.1–1.3)    P value for trend    0.00    0.08    0.63    -    0.50    0.14    0.46    0.23    0.01    0.10   Glove use    Mixing paint    0.4 (0.2–0.8)**    0.3 (0.1–0.7)**    0.6 (0.1–2.7)    -    0.2 (0.0–1.0)*    0.5 (0.2–1.2)    0.3 (0.1–1.1)^    0.6 (0.2–1.3)    0.4 (0.1–1.1)^    0.2 (0.1–0.6)**    Spray painting    0.5 (0.3–0.9)*    0.4 (0.2–0.9)*    0.4 (0.1–1.8)    -    0.3 (0.1–1.2)^    0.4 (0.2–1.1)^    1.3 (0.4–4.2)    0.4 (0.2–1.0)*    0.9 (0.3–2.5)    0.7 (0.3–1.5)    Cleaning    0.5 (0.2–0.9)*    0.4 (0.2–1.0)*    0.3 (0.1–1.4)    -    0.3 (0.1–0.9)*    0.4 (0.2–1.1)^    0.5 (0.2–1.5)    0.5 (0.2–1.1)^    0.4 (0.2–1.1)^    0.4 (0.1–0.9)*   Sum of glove use    0 (REF)                                            1    0.4 (0.2–1.0)^    0.3 (0.1–1.2)^    0.2 (0.0–1.6)    -    0.2 (0.0–1.2)^    0.7 (0.2–2.4)    0.3 (0.0–1.7)    0.3 (0.1–1.2)^    1.1 (0.3–4.3)    0.6 (0.2–1.9)    2    0.7 (0.2–1.7)    0.7 (0.2–2.3)    0.2 (0.0–1.7)    -    0.3 (0.1–1.8)    0.4 (0.1–1.7)    1.2 (0.3–5.1)    0.6 (0.2–2.1)    1.1 (0.3–4.5)    1.1 (0.4–3.6)    3    0.2 (0.1–0.6)**    0.1 (0.0–0.5)**    0.2 (0.0–1.4)    -    0.1 (0.0–0.6)**    0.3 (0.1–1.0)^    0.3 (0.1–1.3)^    0.3 (0.1–0.8)*    0.4 (0.1–1.5)    0.2 (0.0–0.6)**    P value for trend    0.00    0.00    0.18    -    0.02    0.04    0.26    0.04    0.12    0.01   Combined PPE metric    0/1 (REF)                                            2    0.6 (0.2–1.6)    0.7 (0.2–2.7)    0.2 (0.0–2.4)    -    0.2 (0.0–1.6)    0.8 (0.2–3.3)    0.5 (0.1–3.0)    0.7 (0.2–2.6)    1.1 (0.3–4.6)    0.7 (0.2–2.7)    3    0.7 (0.2–1.8)    0.8 (0.2–2.9)    0.1 (0.0–1.4)*    -    0.1 (0.0–0.9)*    0.9 (0.2–3.6)    0.5 (0.1–3.1)    0.5 (0.1–2.0)    0.5 (0.1–2.6)    1.1 (0.3–3.9)    4    0.7 (0.3–1.8)    0.3 (0.1–1.2)^    0.3 (0.0–2.4)    -    0.2 (0.0–1.1)^    0.5 (0.1–2.0)    0.8 (0.2–3.8)    0.8 (0.3–2.7)    0.7 (0.2–2.9)    0.5 (0.1–1.7)    5    0.4 (0.1–1.2)^    0.2 (0.0–1.4)    0.3 (0.0–3.8)    -    0.3 (0.0–2.3)    0.3 (0.1–2.0)    0.2 (0.0–2.7)    0.4 (0.1–2.1)    0.2 (0.0–2.0)    0.1 (0.0–1.2)^    6    0.1 (0.0–0.3)**    0.1 (0.0–0.9)*    0.1 (0.0–2.6)    -    -    0.1 (0.0–1.3)^    0.2 (0.0–2.2)    0.1 (0.0–1.0)*    -    0.1 (0.0–1.0)^    P value for trend    0.00    0.01    0.23    -    0.04    0.04    0.24    0.08    0.03    0.01   Ever use air-fed mask    0.8 (0.4–1.3)    0.3 (0.1–0.7)**    0.3 (0.1–1.6)    -    0.8 (0.2–2.5)    0.3 (0.1–0.8)*    0.5 (0.2–1.5)    0.6 (0.3–1.5)    1.4 (0.6–3.6)    0.8 (0.3–1.8)   Frequency respirator cartridges changed    0.5 (0.3–1.0)^    0.3 (0.1–0.9)*    0.8 (0.2–3.7)    0.3 (0.1–2.2)    1.4 (0.4–5.1)    0.3 (0.1–1.0)^    0.9 (0.3–3.0)    0.5 (0.2–1.4)    0.7 (0.2–2.0)    0.7 (0.3–1.9)  Workplace practices   Wash hands in solvents (yes/no)    1.7 (0.9–3.1)^    3.2 (1.1–9.3)*    1.4 (0.3–6.9)    -    1.6 (0.4–6.3)    1.9 (0.7–4.9)    4.6 (1.0–20.1)*    2.7 (1.0–7.5)^    1.5 (0.5–4.0)    3.1 (1.1–8.5)*   Frequently wash hands in solvents    2.0 (1.1–3.7)*    3.1 (1.3–7.4)*    2.7 (0.7–10.8)    -    2.2 (0.6–7.5)    2.0 (0.8–4.9)    1.9 (0.6–5.8)    1.9 (0.8–4.4)    3.0 (1.2–7.6)*    1.8 (0.7–4.2)   Skin exposure (body parts exposed)    0/1 (REF)                                            2    1.5 (0.8–2.7)    1.4 (0.6–3.7)    1.4 (0.3–7.3)    -    0.5 (0.1–2.9)    1.5 (0.6–3.7)    1.8 (0.6–5.6)    1.6 (0.7–3.8)    1.4 (0.5–3.8)    2.0 (0.8–5.0)    3    3.5 (1.2–9.9)*    5.7 (1.6–20.2)**    7.8 (1.1–57.3)*    -    19.3 (3.4–108.5)**    2.4 (0.6–9.0)    0.6 (0.1–7.4)    3.5 (1.0–12.9)^    2.2 (0.5–10.0)    3.9 (1.1–14.1)*    P value for trend    0.02    0.02    0.08    -    0.01    0.17    0.71    0.06    0.26    0.02   Gun cleaning method    Unenclosed + un-extracted (REF)                                            Enclosed + un-extracted    0.9 (0.4–2.2)    0.8 (0.2–3.0)    5.2 (0.4–65.8)    1.5 (0.2–10.4)    3.7 (0.5–29.3)    1.5 (0.4–5.8)    3.3 (0.4–23.5)    1.1 (0.3–3.9)    2.7 (0.6–12.2)    2.8 (0.7–11.5)    Unenclosed + extracted    0.7 (0.3–1.6)    1.6 (0.5–5.1)    11.0 (0.9–135.0)^    -    6.0 (0.8–45.3)^    2.0 (0.6–7.1)    5.3 (0.8–37.3)^    0.9 (0.2–3.0)    3.0 (0.7–12.8)    2.7 (0.7–10.7)    Enclosed + extracted    0.9 (0.4–2.0)    0.7 (0.2–2.3)    4.2 (0.4–45.3)    0.9 (0.1–6.3)    1.3 (0.2–9.9)    1.0 (0.3–3.5)    3.7 (0.6–22.6)    1.1 (0.4–3.3)    1.7 (0.4–6.8)    1.8 (0.5–6.6)   Paint type    Both water and solvent based (REF)                                            Mostly solvent based    0.5 (0.3–1.1)^    0.4 (0.1–1.4)    1.0 (0.2–5.0)    -    0.5 (0.1–2.7)    0.6 (0.2–2.0)    1.1 (0.3–3.8)    0.5 (0.2–1.6)    0.7 (0.2–2.5)    0.9 (0.3–2.3)   Hours on a typical dayb                                            Mixing paint    1.1 (0.8–1.5)    0.8 (0.5–1.5)    0.6 (0.2–1.6)    -    0.6 (0.3–1.4)    1.1 (0.7–1.8)    0.7 (0.4–1.5)    1.1 (0.7–1.8)    1.7 (1.2–2.6)**    0.8 (0.4–1.4)    Spray painting    1.0(0.8–1.1)    1.3 (1.0–1.7)*    1.2 (0.8–1.8)    -    1.2 (0.8–1.7)    1.3 (1.0–1.6)*    0.9 (0.6–1.2)    1.3 (1.0–1.6)*    1.1 (0.8–1.4)    0.8 (0.6–1.1)    Degreasing/cleaning    1.1 (0.8–1.4)    1.1 (0.7–1.6)    1.3 (0.7–2.3)    -    0.9 (0.5–1.7)    1.2 (0.8–1.7)    1.4 (0.9–2.1)    1.4 (1.0–1.9)^    1.6 (1.1–2.3)**    1.2 (0.8–1.7)  Combined measures of workplace hygiene   ‘Hygiene’ metric    0/1 (poor hygiene)                                            2    0.7 (0.3–1.8)    0.5 (0.2–1.6)    0.9 (0.1–5.9)    -    0.8 (0.2–4.3)    1.0 (0.3–3.2)    0.7 (0.2–3.3)    0.9 (0.3–2.7)    1.0 (0.3–3.5)    1.0 (0.3–3.2)    3    0.5 (0.2–1.2)    0.3 (0.1–1.0)*    0.2 (0.0–1.7)    -    0.2 (0.0–1.8)    0.3 (0.1–1.2)    0.7 (0.2–2.9)    0.5 (0.2–1.7)    0.5 (0.1–2.2)    0.7 (0.2–2.1)    4/5 (good hygiene)    0.3 (0.1–0.7)**    0.1 (0.0–0.6)**    0.5 (0.1–3.3)    -    0.7 (0.2–3.4)    0.3 (0.1–1.0)*    0.4 (0.1–1.7)    0.3 (0.1–1.1)^    0.1 (0.0–0.8)*    0.4 (0.1–1.3)    P value for trend    0.00    0.00    0.25    -    0.48    0.02    0.22    0.06    0.02    0.10      ≥5 Symptomsan (%)    ≥10 Symptomsan (%)    ≥15 Symptomsan (%)    ≥3 Neurologicaln (%)    ≥3 Psychosomaticn (%)    ≥3 Moodn (%)    ≥3 Memoryn (%)    ≥3 Fatiguen (%)    ≥3 Sleep disturbancen (%)    ≥3 Memory and concentrationn (%)    99 (37.5)    35 (13.3)    17 (6.4)    11 (4.2)    17 (6.4)    31 (11.7)    21 (8.0)    35 (13.3)    26 (9.9)    34 (12.9)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)  PPE use   Respirator use    Mixing paint    0.4 (0.2–0.8)*    0.4 (0.1–1.4)    0.5 (0.1–4.8)    -    0.5 (0.1–3.4)    0.6 (0.2–2.0)    0.7 (0.2–3.1)    0.5 (0.2–1.7)    0.1 (0.0–1.0)^    0.4 (0.1–1.4)    Spray painting    0.7 (0.2–3.3)    0.3 (0.0–2.0)    -    0.1 (0.0–1.7)    -    -    -    1.2 (0.1–11.7)    0.6 (0.1–4.0)    0.5 (0.0–4.9)    Cleaning equipment/degreasing    0.4 (0.2–0.8)**    0.5 (0.2–1.3)    0.4 (0.1–2.3)    -    0.8 (0.2–3.8)    0.7 (0.2–2.8)    0.5 (0.2–1.2)    0.6 (0.2–1.5)    0.1 (0.0–0.7)*    0.5 (0.2–1.3)   Sum of respirator use    0/1 (REF)                                            2    0.5 (0.3–1.1)    0.9 (0.3–2.6)    1.5 (0.3–7.7)    -    1.1 (0.3–4.7)    0.7 (0.2–2.1)    0.8 (0.2–3.1)    1.2 (0.5–3.2)    0.3 (0.1–1.3)    0.8 (0.3–2.1)    3    0.3 (0.1–0.7)**    0.1 (0.0–1.1)^    0.4 (0.0–5.2)    -    0.4 (0.0–3.8)    0.3 (0.1–1.6)    0.5 (0.1–2.9)    0.3 (0.1–1.4)    -    0.3 (0.1–1.3)    P value for trend    0.00    0.08    0.63    -    0.50    0.14    0.46    0.23    0.01    0.10   Glove use    Mixing paint    0.4 (0.2–0.8)**    0.3 (0.1–0.7)**    0.6 (0.1–2.7)    -    0.2 (0.0–1.0)*    0.5 (0.2–1.2)    0.3 (0.1–1.1)^    0.6 (0.2–1.3)    0.4 (0.1–1.1)^    0.2 (0.1–0.6)**    Spray painting    0.5 (0.3–0.9)*    0.4 (0.2–0.9)*    0.4 (0.1–1.8)    -    0.3 (0.1–1.2)^    0.4 (0.2–1.1)^    1.3 (0.4–4.2)    0.4 (0.2–1.0)*    0.9 (0.3–2.5)    0.7 (0.3–1.5)    Cleaning    0.5 (0.2–0.9)*    0.4 (0.2–1.0)*    0.3 (0.1–1.4)    -    0.3 (0.1–0.9)*    0.4 (0.2–1.1)^    0.5 (0.2–1.5)    0.5 (0.2–1.1)^    0.4 (0.2–1.1)^    0.4 (0.1–0.9)*   Sum of glove use    0 (REF)                                            1    0.4 (0.2–1.0)^    0.3 (0.1–1.2)^    0.2 (0.0–1.6)    -    0.2 (0.0–1.2)^    0.7 (0.2–2.4)    0.3 (0.0–1.7)    0.3 (0.1–1.2)^    1.1 (0.3–4.3)    0.6 (0.2–1.9)    2    0.7 (0.2–1.7)    0.7 (0.2–2.3)    0.2 (0.0–1.7)    -    0.3 (0.1–1.8)    0.4 (0.1–1.7)    1.2 (0.3–5.1)    0.6 (0.2–2.1)    1.1 (0.3–4.5)    1.1 (0.4–3.6)    3    0.2 (0.1–0.6)**    0.1 (0.0–0.5)**    0.2 (0.0–1.4)    -    0.1 (0.0–0.6)**    0.3 (0.1–1.0)^    0.3 (0.1–1.3)^    0.3 (0.1–0.8)*    0.4 (0.1–1.5)    0.2 (0.0–0.6)**    P value for trend    0.00    0.00    0.18    -    0.02    0.04    0.26    0.04    0.12    0.01   Combined PPE metric    0/1 (REF)                                            2    0.6 (0.2–1.6)    0.7 (0.2–2.7)    0.2 (0.0–2.4)    -    0.2 (0.0–1.6)    0.8 (0.2–3.3)    0.5 (0.1–3.0)    0.7 (0.2–2.6)    1.1 (0.3–4.6)    0.7 (0.2–2.7)    3    0.7 (0.2–1.8)    0.8 (0.2–2.9)    0.1 (0.0–1.4)*    -    0.1 (0.0–0.9)*    0.9 (0.2–3.6)    0.5 (0.1–3.1)    0.5 (0.1–2.0)    0.5 (0.1–2.6)    1.1 (0.3–3.9)    4    0.7 (0.3–1.8)    0.3 (0.1–1.2)^    0.3 (0.0–2.4)    -    0.2 (0.0–1.1)^    0.5 (0.1–2.0)    0.8 (0.2–3.8)    0.8 (0.3–2.7)    0.7 (0.2–2.9)    0.5 (0.1–1.7)    5    0.4 (0.1–1.2)^    0.2 (0.0–1.4)    0.3 (0.0–3.8)    -    0.3 (0.0–2.3)    0.3 (0.1–2.0)    0.2 (0.0–2.7)    0.4 (0.1–2.1)    0.2 (0.0–2.0)    0.1 (0.0–1.2)^    6    0.1 (0.0–0.3)**    0.1 (0.0–0.9)*    0.1 (0.0–2.6)    -    -    0.1 (0.0–1.3)^    0.2 (0.0–2.2)    0.1 (0.0–1.0)*    -    0.1 (0.0–1.0)^    P value for trend    0.00    0.01    0.23    -    0.04    0.04    0.24    0.08    0.03    0.01   Ever use air-fed mask    0.8 (0.4–1.3)    0.3 (0.1–0.7)**    0.3 (0.1–1.6)    -    0.8 (0.2–2.5)    0.3 (0.1–0.8)*    0.5 (0.2–1.5)    0.6 (0.3–1.5)    1.4 (0.6–3.6)    0.8 (0.3–1.8)   Frequency respirator cartridges changed    0.5 (0.3–1.0)^    0.3 (0.1–0.9)*    0.8 (0.2–3.7)    0.3 (0.1–2.2)    1.4 (0.4–5.1)    0.3 (0.1–1.0)^    0.9 (0.3–3.0)    0.5 (0.2–1.4)    0.7 (0.2–2.0)    0.7 (0.3–1.9)  Workplace practices   Wash hands in solvents (yes/no)    1.7 (0.9–3.1)^    3.2 (1.1–9.3)*    1.4 (0.3–6.9)    -    1.6 (0.4–6.3)    1.9 (0.7–4.9)    4.6 (1.0–20.1)*    2.7 (1.0–7.5)^    1.5 (0.5–4.0)    3.1 (1.1–8.5)*   Frequently wash hands in solvents    2.0 (1.1–3.7)*    3.1 (1.3–7.4)*    2.7 (0.7–10.8)    -    2.2 (0.6–7.5)    2.0 (0.8–4.9)    1.9 (0.6–5.8)    1.9 (0.8–4.4)    3.0 (1.2–7.6)*    1.8 (0.7–4.2)   Skin exposure (body parts exposed)    0/1 (REF)                                            2    1.5 (0.8–2.7)    1.4 (0.6–3.7)    1.4 (0.3–7.3)    -    0.5 (0.1–2.9)    1.5 (0.6–3.7)    1.8 (0.6–5.6)    1.6 (0.7–3.8)    1.4 (0.5–3.8)    2.0 (0.8–5.0)    3    3.5 (1.2–9.9)*    5.7 (1.6–20.2)**    7.8 (1.1–57.3)*    -    19.3 (3.4–108.5)**    2.4 (0.6–9.0)    0.6 (0.1–7.4)    3.5 (1.0–12.9)^    2.2 (0.5–10.0)    3.9 (1.1–14.1)*    P value for trend    0.02    0.02    0.08    -    0.01    0.17    0.71    0.06    0.26    0.02   Gun cleaning method    Unenclosed + un-extracted (REF)                                            Enclosed + un-extracted    0.9 (0.4–2.2)    0.8 (0.2–3.0)    5.2 (0.4–65.8)    1.5 (0.2–10.4)    3.7 (0.5–29.3)    1.5 (0.4–5.8)    3.3 (0.4–23.5)    1.1 (0.3–3.9)    2.7 (0.6–12.2)    2.8 (0.7–11.5)    Unenclosed + extracted    0.7 (0.3–1.6)    1.6 (0.5–5.1)    11.0 (0.9–135.0)^    -    6.0 (0.8–45.3)^    2.0 (0.6–7.1)    5.3 (0.8–37.3)^    0.9 (0.2–3.0)    3.0 (0.7–12.8)    2.7 (0.7–10.7)    Enclosed + extracted    0.9 (0.4–2.0)    0.7 (0.2–2.3)    4.2 (0.4–45.3)    0.9 (0.1–6.3)    1.3 (0.2–9.9)    1.0 (0.3–3.5)    3.7 (0.6–22.6)    1.1 (0.4–3.3)    1.7 (0.4–6.8)    1.8 (0.5–6.6)   Paint type    Both water and solvent based (REF)                                            Mostly solvent based    0.5 (0.3–1.1)^    0.4 (0.1–1.4)    1.0 (0.2–5.0)    -    0.5 (0.1–2.7)    0.6 (0.2–2.0)    1.1 (0.3–3.8)    0.5 (0.2–1.6)    0.7 (0.2–2.5)    0.9 (0.3–2.3)   Hours on a typical dayb                                            Mixing paint    1.1 (0.8–1.5)    0.8 (0.5–1.5)    0.6 (0.2–1.6)    -    0.6 (0.3–1.4)    1.1 (0.7–1.8)    0.7 (0.4–1.5)    1.1 (0.7–1.8)    1.7 (1.2–2.6)**    0.8 (0.4–1.4)    Spray painting    1.0(0.8–1.1)    1.3 (1.0–1.7)*    1.2 (0.8–1.8)    -    1.2 (0.8–1.7)    1.3 (1.0–1.6)*    0.9 (0.6–1.2)    1.3 (1.0–1.6)*    1.1 (0.8–1.4)    0.8 (0.6–1.1)    Degreasing/cleaning    1.1 (0.8–1.4)    1.1 (0.7–1.6)    1.3 (0.7–2.3)    -    0.9 (0.5–1.7)    1.2 (0.8–1.7)    1.4 (0.9–2.1)    1.4 (1.0–1.9)^    1.6 (1.1–2.3)**    1.2 (0.8–1.7)  Combined measures of workplace hygiene   ‘Hygiene’ metric    0/1 (poor hygiene)                                            2    0.7 (0.3–1.8)    0.5 (0.2–1.6)    0.9 (0.1–5.9)    -    0.8 (0.2–4.3)    1.0 (0.3–3.2)    0.7 (0.2–3.3)    0.9 (0.3–2.7)    1.0 (0.3–3.5)    1.0 (0.3–3.2)    3    0.5 (0.2–1.2)    0.3 (0.1–1.0)*    0.2 (0.0–1.7)    -    0.2 (0.0–1.8)    0.3 (0.1–1.2)    0.7 (0.2–2.9)    0.5 (0.2–1.7)    0.5 (0.1–2.2)    0.7 (0.2–2.1)    4/5 (good hygiene)    0.3 (0.1–0.7)**    0.1 (0.0–0.6)**    0.5 (0.1–3.3)    -    0.7 (0.2–3.4)    0.3 (0.1–1.0)*    0.4 (0.1–1.7)    0.3 (0.1–1.1)^    0.1 (0.0–0.8)*    0.4 (0.1–1.3)    P value for trend    0.00    0.00    0.25    -    0.48    0.02    0.22    0.06    0.02    0.10  Adjusted for age, ethnicity, smoking status, alcohol consumption, education status, general health, and personality traits. “-” No ORs available due to non-convergence in model. CI = confidence interval. ^P < 0.1; *P < 0.05; **P < 0.01. aAll EUROQUEST symptoms (all domains combined). bOR for every unit increase (1 hour) in time spent on task. View Large Frequent glove use was also associated with a strongly reduced risk of symptoms (significant for the cut-points of ≥5 and ≥10 symptoms) following a clear and statistically significant dose–response trend (Table 3). In addition, combined respirator and glove use was inversely and significantly associated with total symptoms with an observed 90% reduction of risk for those with the most consistent use of both types of PPE, and a significant dose–response trend was also observed. Associations with specific symptom domains showed reduced risks for all domains, particularly for psychosomatic, mood, sleep disturbance, and memory and concentration symptoms combined, with the strongest and most significant effects observed for frequent and consistent glove use and combined glove and respirator use (Table 3). Use of an air-fed respirator (ever) was associated with a reduction in risk for reporting both ≥10 and ≥15 symptoms; a similar effect was seen for ≥5 and ≥10 symptoms with frequent changing of absorbent respirator cartridges, washing of hands and infrequent versus frequent washing of hands in solvents. Surprisingly, those using mostly solvent-based paints reported fewer symptoms than those using both water-based and solvent-based paints. A trend of increasing number of symptoms with more body parts exposed during spray painting was also observed (Table 3). An inverse and significant dose–response trend was observed for hygiene scores with a 70–90% reduction in risk of reporting ≥5 and ≥10 symptoms for those workers with the best hygiene score (score of 4/5). No clear associations with symptoms were found for type of gun cleaning method. Results for the combined PPE metric mutually adjusting for other workplace practices showed similar trends, but confidence intervals were generally wider and fewer individual results reached statistical significance (Table 4). Nonetheless, an inverse dose–response trend remained (P for trend of 0.02 and 0.06 for reporting ≥5 and ≥10 symptoms, respectively), including for the domains of psychosomatic (P for trend = 0.02) and memory and concentration symptoms combined (P for trend = 0.05). The strength of the associations seen for use of an air-fed respirator, frequency of mask cartridge changes, frequency of hand washing in solvents, and time spent on work tasks were generally weaker compared to when analysed separately. Table 4. Prevalence odds ratios for symptoms of neurotoxicity and combined PPE-use mutually adjusted for other variables in the table.     ≥5 Symptoms†    ≥10 Symptoms†    ≥15 Symptoms†    ≥3 Psychosomatic    ≥3 Mood    ≥3 Memory    ≥3 Fatigue    ≥3 Sleep disturbance    ≥3 Memory and concentration    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)  PPE use   Combined PPE metric    0/1 (REF)                                        2    0.6 (0.2–1.8)    0.9 (0.2–3.9)    0.2 (0.0–3.3)    0.3 (0.0–2.2)    0.8 (0.2–3.5)    0.4 (0.1–3.2)    1.2 (0.3–5.3)    1.0 (0.2–5.3)    1.0 (0.2–4.4)    3    0.9 (0.3–2.8)    1.3 (0.3–5.3)    0.1 (0.0–2.0)    0.1 (0.0–0.8)*    1.3 (0.3–5.6)    0.8 (0.1–5.3)    0.8 (0.2–3.7)    0.6 (0.1–3.8)    2.0 (0.5–7.9)    4    0.9 (0.3–2.5)    0.3 (0.1–1.5)    0.3 (0.0–2.8)    0.2 (0.0–1.1)^    0.5 (0.1–2.2)    1.1 (0.2–6.2)    1.2 (0.3–4.5)    0.5 (0.1–3.0)    0.8 (0.2–3.4)    5    0.6 (0.2–1.9)    0.5 (0.1–3.2)    0.4 (0.0–6.2)    0.2 (0.0–1.9)    0.5 (0.1–3.2)    0.3 (0.0–3.8)    0.9 (0.2–4.9)    0.2 (0.0–3.5)    0.2 (0.0–2.1)    6    0.1 (0.0–0.5)**    0.1 (0.0–1.7)    0.1 (0.0–3.1)    -    0.2 (0.0–1.7)    0.2 (0.0–2.7)    0.1 (0.0–1.7)    -    0.2 (0.0–1.8)    P value for trend    0.02    0.06    0.21    0.02    0.10    0.37    0.26    0.06    0.05  Workplace practices   Ever use air-fed mask    0.8 (0.4–1.7)    0.3 (0.1–0.9)*    0.4 (0.1–2.6)    1.2 (0.3–5.7)    0.3 (0.1–0.9)*    0.7 (0.2–2.5)    0.5 (0.2–1.3)    2.3 (0.6–8.8)    0.9 (0.3–2.3)   Frequency respirator cartridges changed    0.8 (0.4–1.7)    0.5 (0.1–1.7)    2.3 (0.3–15.4)    3.6 (0.7–17.6)    0.6 (0.2–2.0)    1.5 (0.4–5.9)    0.7 (0.2–2.0)    0.4 (0.1–2.2)    1.2 (0.4–3.6)   Frequency wash hands in solvents    1.8 (0.8–3.7)    1.3 (0.5–3.8)    1.3 (0.2–7.3)    1.6 (0.4–7.4)    0.7 (0.2–2.0)    1.9 (0.5–7.7)    1.2 (0.5–3.2)    2.8 (0.7–10.4)    1.8 (0.6–5.1)   Hours on a typical dayb    Mixing paint    1.2 (0.7–1.8)    0.6 (0.3–1.5)    0.2 (0.0–1.1)^    0.2 (0.1–1.0)^    0.9 (0.5–1.9)    0.4 (0.1–1.3)    0.8 (0.4–1.5)    1.2 (0.6–2.4)    0.7 (0.3–1.4)    Spray painting    0.9 (0.7–1.1)    1.4 (1.0–1.8)*    1.3 (0.7–2.3)    1.3 (0.8–2.0)    1.3 (0.9–1.7)    0.7 (0.5–1.2)    1.5 (1.1–1.9)**    0.9 (0.6–1.3)    0.8 (0.6–1.1)    Degreasing/cleaning    1.2 (0.8–1.7)    1.5 (0.8–2.7)    2.0 (0.8–4.8)    1.5 (0.7–3.3)    1.4 (0.8–2.4)    2.1 (1.1–4.0)*    1.6 (1.0–2.7)*    2.2 (1.2–4.1)*    1.6 (0.9–2.7)      ≥5 Symptoms†    ≥10 Symptoms†    ≥15 Symptoms†    ≥3 Psychosomatic    ≥3 Mood    ≥3 Memory    ≥3 Fatigue    ≥3 Sleep disturbance    ≥3 Memory and concentration    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)  PPE use   Combined PPE metric    0/1 (REF)                                        2    0.6 (0.2–1.8)    0.9 (0.2–3.9)    0.2 (0.0–3.3)    0.3 (0.0–2.2)    0.8 (0.2–3.5)    0.4 (0.1–3.2)    1.2 (0.3–5.3)    1.0 (0.2–5.3)    1.0 (0.2–4.4)    3    0.9 (0.3–2.8)    1.3 (0.3–5.3)    0.1 (0.0–2.0)    0.1 (0.0–0.8)*    1.3 (0.3–5.6)    0.8 (0.1–5.3)    0.8 (0.2–3.7)    0.6 (0.1–3.8)    2.0 (0.5–7.9)    4    0.9 (0.3–2.5)    0.3 (0.1–1.5)    0.3 (0.0–2.8)    0.2 (0.0–1.1)^    0.5 (0.1–2.2)    1.1 (0.2–6.2)    1.2 (0.3–4.5)    0.5 (0.1–3.0)    0.8 (0.2–3.4)    5    0.6 (0.2–1.9)    0.5 (0.1–3.2)    0.4 (0.0–6.2)    0.2 (0.0–1.9)    0.5 (0.1–3.2)    0.3 (0.0–3.8)    0.9 (0.2–4.9)    0.2 (0.0–3.5)    0.2 (0.0–2.1)    6    0.1 (0.0–0.5)**    0.1 (0.0–1.7)    0.1 (0.0–3.1)    -    0.2 (0.0–1.7)    0.2 (0.0–2.7)    0.1 (0.0–1.7)    -    0.2 (0.0–1.8)    P value for trend    0.02    0.06    0.21    0.02    0.10    0.37    0.26    0.06    0.05  Workplace practices   Ever use air-fed mask    0.8 (0.4–1.7)    0.3 (0.1–0.9)*    0.4 (0.1–2.6)    1.2 (0.3–5.7)    0.3 (0.1–0.9)*    0.7 (0.2–2.5)    0.5 (0.2–1.3)    2.3 (0.6–8.8)    0.9 (0.3–2.3)   Frequency respirator cartridges changed    0.8 (0.4–1.7)    0.5 (0.1–1.7)    2.3 (0.3–15.4)    3.6 (0.7–17.6)    0.6 (0.2–2.0)    1.5 (0.4–5.9)    0.7 (0.2–2.0)    0.4 (0.1–2.2)    1.2 (0.4–3.6)   Frequency wash hands in solvents    1.8 (0.8–3.7)    1.3 (0.5–3.8)    1.3 (0.2–7.3)    1.6 (0.4–7.4)    0.7 (0.2–2.0)    1.9 (0.5–7.7)    1.2 (0.5–3.2)    2.8 (0.7–10.4)    1.8 (0.6–5.1)   Hours on a typical dayb    Mixing paint    1.2 (0.7–1.8)    0.6 (0.3–1.5)    0.2 (0.0–1.1)^    0.2 (0.1–1.0)^    0.9 (0.5–1.9)    0.4 (0.1–1.3)    0.8 (0.4–1.5)    1.2 (0.6–2.4)    0.7 (0.3–1.4)    Spray painting    0.9 (0.7–1.1)    1.4 (1.0–1.8)*    1.3 (0.7–2.3)    1.3 (0.8–2.0)    1.3 (0.9–1.7)    0.7 (0.5–1.2)    1.5 (1.1–1.9)**    0.9 (0.6–1.3)    0.8 (0.6–1.1)    Degreasing/cleaning    1.2 (0.8–1.7)    1.5 (0.8–2.7)    2.0 (0.8–4.8)    1.5 (0.7–3.3)    1.4 (0.8–2.4)    2.1 (1.1–4.0)*    1.6 (1.0–2.7)*    2.2 (1.2–4.1)*    1.6 (0.9–2.7)  Adjusted for age, ethnicity, smoking status, alcohol consumption, education status, general health, and personality traits, as well as all other variables listed in table. “-” No ORs available due to non-convergence in model. CI = confidence interval. ^P < 0.1; *P < 0.05; **P < 0.01. aAll EUROQUEST symptoms (all domains combined). bOR for every unit increase (1 hour) in time spent on task. View Large Analyses for skin exposure similarly adjusted also showed fewer statistically significant results, but again a dose–response trend remained (P for trend of 0.05 and 0.06 for ≥5 and ≥15 symptoms, respectively; see Table S3 in the online supplementary material, available at Annals of Work Exposures and Health online) with the strongest associations observed in the symptom domains of psychosomatic, fatigue, and memory and concentration symptoms combined. Finally, in the mutually adjusted analyses, we found a significant inverse dose–response trend with increased hygiene scores and total symptoms (P for trend of 0.005 and 0.003 for reporting ≥5 and ≥10 symptoms), and symptoms in the domains of mood (P = 0.02), sleep disturbance (P = 0.02), fatigue, and memory and concentration symptoms combined, although the last two did not reach statistical significance (P = 0.05 and 0.12, respectively, see Table S4 in the online supplementary material, available at Annals of Work Exposures and Health online). Discussion This study showed that reported frequent PPE use and good workplace hygiene practices were associated with a reduced risk of total symptoms of neurotoxicity, and symptoms in the psychosomatic, mood, and memory and concentration domains. In general, the strongest effects were seen for glove use but dose–response trends were also observed with other PPE-use and hygiene practices. Previous studies in spray painters (Chang et al. 2007) and other solvent-exposed workers (Nakayama et al. 2004; Wang et al. 2006; Triebig et al. 2009) have shown that the use of respirators, gloves, and/or chemical protective suits is effective in reducing total body burden of solvents. Also, one study in solvent-exposed gun factory workers found that self-reported glove use was associated with some measures of cognitive performance, but not self-reported symptoms (Jang et al. 1999). To our knowledge, our study is therefore one of the first to show a direct protective effect of consistent PPE-use on symptoms of neurotoxicity in solvent-exposed workers. Similar protective effects of PPE on neuropsychological performance have been reported for other occupational settings/exposures such as farm workers exposed to organophosphate pesticides (Cataño et al. 2008). PPE-use has also previously been associated with reduced incidence and prevalence of occupational asthma in workers exposed to toluene diisocyanate, including spray painters (Cullen et al. 1996; Petsonk et al. 2000). As expected, in our study, PPE-use was protective for symptom domains (psychosomatic, mood, and memory and concentration combined) previously identified to be associated with solvent exposure in spray painters (Meyer-Baron et al. 2008), including in our previous study in which the current study was nested (Keer et al. 2016). Taken together, this strongly suggests that PPE-use and good workplace hygiene practices and behaviours are important determinants of exposure (and related health risks) in these workers. Due to some correlation between the use of several types of PPE, workplace hygiene measures, and risk behaviours, it was difficult to assess the relative contribution of each measure individually. Nonetheless, multivariate analyses including combined individual measures and mutually adjusting for workplace hygiene practices and risk behaviours showed similar trends to analyses for each of these individual variables separately, suggesting results are valid. Also, additional analyses including only those workers who wore one type of PPE [respirator only when spray painting (N = 76), gloves only when mixing paint (N = 79), and gloves only when degreasing/cleaning (N = 102)] showed highly comparable results, although the models were less stable due to smaller numbers (data not shown). Overall, we found that consistent glove use was most protective (Table 2), which is consistent with evidence from other studies suggesting that dermal exposures may contribute >50% of the total body burden of solvents, particularly when airborne exposures are well controlled (Brooke et al. 1998; Semple et al. 2001; Semple 2004; Chang et al. 2007). Although there was some variation in the type of gloves used (predominantly nitrile and latex), nitrile gloves were used by the vast majority of workers for tasks with a high risk of solvent exposure (mixing paint, spray painting, degreasing/cleaning). Latex gloves were used, but mostly for low exposure-risk tasks (e.g. sanding, final polishing). As a result, differences in the protection provided by different glove materials (i.e. permeability, breakthrough times, etc.; Tran et al. 2012) are unlikely to have had an impact on the associations observed. A strong positive dose–response trend was also observed with increased skin exposure (Table 4) further highlighting the critical role that dermal exposure may play in developing symptoms of neurotoxicity. Frequent respirator use was also associated with fewer symptoms (Table 2), which is unlikely to be entirely explained by correlation with glove use. In particular, when we combined glove and respirator use (Table 3), we found a stronger protective effect than with glove use alone, thus showing, as previously suggested by others (Jang et al. 1999), that respirators provide additional protection, even when airborne exposures were low (Keer et al. 2016). Of the two respirator types used, air-fed respirators showed the greatest reduction in risk (Table 4), which is consistent with previous studies (Triebig et al. 2009). Frequent changing of absorbent respirator cartridges was associated with a reduction in risk of 50–70%, which is consistent with previous research showing that poorly maintained PPE is associated with increased exposure (Nakayama et al. 2004). Nearly 70% of workers had no defined cartridge replacement schedule or changed them ‘less than once a month’ (Table 2), which given the association with symptoms of neurotoxicity observed in our study is of concern. In particular, as cartridge masks were worn by all spray painters for at least some tasks, this may provide a false sense of protection for painters and shop owners. We found that frequent washing of hands in solvents was associated with an increased risk of symptoms. With almost 70% of workers reporting hand washing in solvents, and 27% reporting they did this frequently (Table 2), this is also of considerable concern. Inconsistent glove use was, as expected, moderately correlated with washing of hands in solvents (r = 0.32), but also with respirator-use (r = 0.41); in turn, respirator-use was moderately correlated with the frequency that respirator cartridges were changed (r = 0.27). This suggests that poor workplace hygiene practices are likely to cluster together within workers and/or workplaces and contribute to an increased risk of neurotoxic effects, as demonstrated by the significant inverse dose–response trend between hygiene score and symptoms of neurotoxicity (see Table S4 in the online supplementary material, available at Annals of Work Exposures and Health online). Interestingly, the use of water-based paints (which in New Zealand at the time of the study were only available for coloured paints and not for primer and top-coat paints) was associated with a greater risk of symptoms, although this failed to reach statistical significance. The reason for this is unclear, although the fact that both primer and top-coat paints and many preparatory products were still solvent-based suggests those who use water-based paints are still at risk of regular solvent exposure. There were several limitations to this study. Neurotoxicity was assessed using self-reported symptoms, which were not confirmed by a clinical assessment, and therefore some misclassification may have occurred. However, EUROQUEST was specifically designed to assess symptoms associated with occupational exposure to neurotoxic agents (Karlson et al. 2000) and is widely used and well validated against clinical criteria (Carter et al. 2002; Rouch et al. 2003; Williamson 2007; Kaukiainen et al. 2009). PPE-use and workplace behaviours were also self-reported, which may result in bias, e.g. from over-reporting of PPE-use through fear of admitting non-compliance. However, any bias, if present, would most likely lead to an underestimation of the true effect. A further limitation is that the effects observed may be attributable to historical exposures, PPE-use, and workplace practices (Dick 2006). However, including duration of employment in multivariate regression models (as a proxy for potential years of exposure) had little effect on the effect measures (see Table S1 in the online supplementary material, available at Annals of Work Exposures and Health online), and in any case, exposure misclassification would likely lead to an underestimation of the true effect. Also, we included 31 office workers (reclassified as spray painters, see above) who may not have been comparable to the other participants in terms of work performed, use of PPE, and workplace practices. However, at the time of the study, 22 reported performing repair work on the shop floor and were therefore at risk of being exposed. From our observations and discussions with workers, it was clear the remaining nine also performed some repair work, especially during busy periods, so were at least occasionally at risk of exposure. Furthermore, almost all (n = 28) provided responses to at least some the questions on PPE use when mixing paint, spray painting, or degreasing/cleaning, indicating they performed these tasks, even if irregularly. Analyses excluding the nine workers who reported not performing work on the shop floor had no effect (see Table S2 in the online supplementary material, available at Annals of Work Exposures and Health online), suggesting results are robust. The ‘hygiene’ metric was constructed and analysed in a way that assumed every unit increase represented an equal increase in exposure, despite being derived from a combination of different PPE-use and workplace practice factors. Nonetheless, highly comparable trends were observed when the metric was constructed using different combinations of these variables and different response weightings within variables (data not shown), suggesting the use of this metric was valid. As discussed by the authors of the EUROQUEST and others, symptoms may be at least partially reversible upon removal from exposure (Dick 2006; Kaukiainen et al. 2009) but memory and concentration symptoms and those associated with mood liability (i.e. those symptoms inversely associated with PPE use and good workplace hygiene in our study) have also been shown to persist after exposure cessation in more severely affected individuals (Kaukiainen et al. 2009). Due to the cross-sectional design, we were unable to assess whether symptoms were reversible in this study. It is feasible that workers who have developed symptoms as a result of higher historical exposures are more likely to avoid current exposures by using PPE more frequently and applying better workplace hygiene, but this would again likely lead to an underestimation of the true effect. Also, it may be that in workshops where PPE is used more consistently and good hygiene practices are promoted, exposure controls are more likely to be in place and efficacious (e.g. newer, higher quality engineering controls which are more regularly maintained) and therefore contribute to at least part of the associations observed. We have extensively assessed a large number of exposure controls, hygiene measures, and risk behaviours and therefore consider this unlikely, but we were unable to collect data on all potential exposure determinants, so it cannot be excluded. For example, variations in the design, quality, and maintenance of spray booths between workshops may have affected exposure levels (and risk of symptoms). However, ‘spot’ measurements in booths across a range of the workshops showed consistently low solvent levels in the breathing zone of workers whilst spray painting (data not shown), suggesting that spray booths used in New Zealand are generally highly effective in controlling airborne exposures. Our findings have considerable relevance for the development of improved intervention strategies in the collision repair industry involving increased use of PPE and promoting good workplace hygiene, at least until higher level controls to minimize/eliminate exposure are developed and more widely implemented. Improvements in spray booth technology and local exhaust ventilation have already resulted in significantly reduced emissions and most likely explain the low airborne exposures observed in our study (reported in Keer et al. 2016). However, the results of the current study indicate that more action may be required particularly focused on reducing dermal exposure. Although the focus of this study has been on neurotoxicity, a reduction in both dermal and airborne solvent exposures will also likely reduce the risk of solvent-related cancer and diisocyanate-induced asthma (Séguin et al. 1987; De Roos and Bhatti 2014; Stocks et al. 2015; Hadkhale et al. 2016). In conclusion, this study has shown that application of relatively basic exposure control measures such as PPE-use and good workplace hygiene is associated with a strongly reduced risk of symptoms of neurotoxicity in the collision repair industry. Programmes to encourage and support the use of these controls in this industry are feasible and would likely result in significantly reduced ill-health. Supplementary Data Supplementary data are available at Annals of Work Exposures and Health online. Acknowledgements We thank the study participants and their employers and the New Zealand Collision Repair Association (CRA) for their participation in this study, and Elizabeth Harding, Leigh Emmerton, Angela Thurston, Tracey Whaanga, Hannah Buchanan, and Phoebe Taptiklis for their help with conducting interviews and exposure measurements. The study was funded by a grant from the Health Research Council (HRC) of New Zealand. The authors declare no conflict of interest relating to the material presented in this Article. Its contents, including any opinions and/or conclusions expressed, are solely those of the authors. References Böckelmann I, Darius S, McGauran Net al.  ( 2002) The psychological effects of exposure to mixed organic solvents on car painters. Disabil Rehabil ; 24: 455– 61. Google Scholar CrossRef Search ADS PubMed  Brooke I, Cocker J, Delic JIet al.  ( 1998) Dermal uptake of solvents from the vapour phase: an experimental study in humans. Ann Occup Hyg ; 42: 531– 40. 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Effects of Personal Protective Equipment Use and Good Workplace Hygiene on Symptoms of Neurotoxicity in Solvent-Exposed Vehicle Spray Painters

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Oxford University Press
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© The Author(s) 2018. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
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2398-7308
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2398-7316
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10.1093/annweh/wxx100
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Abstract

Abstract Objectives To assess the association between the use of personal protective equipment (PPE) and good workplace hygiene and symptoms of neurotoxicity in solvent-exposed vehicle spray painters. Methods Exposure control measures including PPE-use and workplace hygiene practices and symptoms of neurotoxicity were assessed in 267 vehicle repair spray painters. Symptoms were assessed using an adapted version of the EUROQUEST Questionnaire. Results Frequent respirator and glove use was inversely and significantly associated with symptoms of neurotoxicity in a dose-dependent manner (P < 0.05 for trend) with the strongest protective effect found for consistent glove use (odds ratios [OR] 0.1–0.2, P < 0.01, for reporting ≥10 and ≥5 symptoms). A clear dose–response trend was also observed when combining frequency of respirator and glove use (P < 0.05 for reporting ≥5 and ≥10 symptoms), with an overall reduction in risk of 90% (OR, 0.1, P < 0.01) for those who consistently used both types of PPE. Protective effects were most pronounced for the symptom domains of psychosomatic (P < 0.05 for trend, for combined PPE use), mood (P < 0.05), and memory and concentration symptoms combined (P < 0.05), with reductions in risk of >80%. Poor hygiene workplace practices, such as solvent exposure to multiple body parts (OR 3.4, P = 0.11 for reporting ≥10 symptoms), were associated with an increased risk of symptoms. When using a general workplace hygiene score derived from a combination of PPE-use and (good) workplace practice factors an inverse and significant dose–response trend was observed for reporting ≥5 (P < 0.01) and ≥10 symptoms (P < 0.01). Conclusions This study has shown that PPE-use and good workplace hygiene are associated with a strongly reduced risk of symptoms of neurotoxicity in solvent-exposed vehicle spray painters. behavioural, dermal exposure, EUROQUEST, intervention, neurotoxic, personal protective equipment, solvents, symptoms of neurotoxicity, workplace hygiene Introduction Solvent exposure in the vehicle collision repair industry has long been associated with symptoms of neurotoxicity (Hänninen et al. 1976; Husman 1980; Elofsson et al. 1980; Hänninen et al. 1991; Daniell et al. 1993; Keer et al. 2016) and deficits in cognitive performance (Maizlish et al. 1985; Daniell et al. 1993; Böckelmann et al. 2002). Although considerable changes in health and safety practices have occurred in this industry with an associated decline in solvent exposures internationally over the past 20 years (Kauppinen et al. 2013), an increased risk of symptoms of neurotoxicity continues to be reported. In particular, we have recently shown that spray painters and panel beaters (or auto-body repair workers) in New Zealand report more symptoms of neurotoxicity than non-exposed reference workers, with the strongest associations observed for neurological, psychosomatic, mood, memory, and concentration symptoms (Keer et al. 2016). These effects were shown at ‘airborne’ solvent levels well below current exposure standards suggesting that ‘dermal’ exposures may be important. Previous studies have shown that personal protective equipment (PPE) and good workplace hygiene reduce both airborne and dermal exposure to solvents and subsequent total body burden in spray painters (Jang et al. 1999; Chang et al. 2007) and other solvent-exposed workers (Löf et al. 1993; Nakayama et al. 2004; Wang et al. 2006; Triebig et al. 2009). In particular, quasi-experimental studies involving PPE-use enforced by researchers showed that the total body burden was reduced by between 26% and 99% compared to no or minimal use of PPE (Löf et al. 1993; Chang et al. 2007; Triebig et al. 2009). The efficacy was dependent upon the type, quality, and maintenance level of PPE, which along with consistency of use is known to vary greatly between workplaces and workers (Fidler et al. 1987; Winder and Turner 1992; Oestenstad and Perkins 1992; Jang et al. 1999; Liu et al. 2006). Low airborne and dermal exposures and a reduced body burden of solvents have been associated with reduced risks of self-reported symptoms of neurotoxicity and abnormal neuropsychological performance (Dick et al. 1984; Jang et al. 1999), but few studies have directly assessed the impact of PPE use on symptoms, and none have assessed the effects of workplace hygiene. In the current study, using a cross-sectional study design, we assessed the effect of PPE-use and workplace hygiene practices on symptoms of neurotoxicity in 267 vehicle collision repair spray painters. Methods Study population Participants comprised 267 spray painters from our previous questionnaire survey in 370 collision repair workers (267 spray painters and 103 panel beaters or auto-body repair workers, including office staff who were ex-tradesmen), recruited from workshops throughout the north island of New Zealand. Office staff (n = 46) were all ex-tradesmen and were recoded according to their previous job title (31 as spray painters), as this more accurately reflected their working life exposures. They generally also performed at least some repair work and were therefore still at risk of exposure. All spray painters conducted the same core tasks including mixing paint, spray painting, and degreasing/cleaning before and after spray painting, with variations in the time spent on each task. Exclusion criteria for the previous study were no history of work involving solvent exposure or any history of major head injury or neurological/neurodegenerative disease, including meningitis, major depression, or epilepsy. All data on PPE-use and/or workplace hygiene practices was missing for three spray painters, leaving 264 for inclusion in the final analyses. No data on PPE-use and workplace hygiene practices was available for panel beaters. Questionnaire Information on demographics, symptoms of neurotoxicity, work characteristics, use of solvents and solvent-based products, use of PPE and potential confounders was obtained by a face-to-face interview (Keer et al. 2016). Questions on PPE focused on respirator and glove use during key spray painting-related tasks including mixing paint, spray painting, and cleaning equipment or bodywork. Current (i.e. in the past 3 months) symptoms were assessed using an adapted version of the EUROQUEST questionnaire (Carter et al. 2002; Keer et al. 2016), which included 59 core items covering the following domains: neurological (e.g. numbness and tingling in extremities, balance problems), psychosomatic (e.g. headaches, nausea, tinnitus), mood, memory, concentration, fatigue, and sleep quality. Symptom frequency was reported on a 4-point scale, “seldom or never”, “sometimes”, “often”, or “very often”. The EUROQUEST also assessed anxiety (6 items, e.g., “Are you generally a nervous person?”, “Do you worry a lot about trivial things”), rated on a different 4-point scale of “strongly disagree”, “disagree”, “agree”, or “strongly agree”, and perceived general health (4 items, e.g., “how good is your health?”, “How do you feel about your life in general?”), where participants were asked to rate different aspects of their general health and wellness as “very good” “good”, “poor”, or “very poor”. For PPE use, participants were asked to indicate how often they wear a respirator or gloves during each task on a 5 point scale: “Seldom/never”, “Sometimes”, “Often”, “very often”, or “Always”. They were also asked what types of respirator they used i.e. a positive pressure “Air-fed” unit, or one fitted with disposable absorbent cartridges, or both. Questions on the types of glove used (i.e. material) were not included, but field observations showed that nitrile gloves were used by the vast majority of workers for tasks with a high risk of solvent exposure (mixing paint, spray painting, degreasing/cleaning). Additional questions on workplace behaviours and characteristics included: number of body parts exposed during spray painting, with a possible score of 0 to 3 (hands and wrists, upper arms and forearms, and/or head, face and neck); whether workers washed their hands in solvents and how often (“seldom”, “sometimes”, “often”, or “very often”); and the frequency with which the absorbent cartridges were changed in the worker’s respirator (“as and when required”, “less than once a month”, “1–2 times a month”, or “weekly”). Questions also included the type of spray equipment washer used and whether local exhaust ventilation was present i.e. “un-enclosed and un-extracted”, “enclosed and un-extracted”, “un-enclosed and extracted”, or “enclosed and extracted”. We also asked for the type of paint used i.e. “mostly water based”, “mostly solvent based”, and “both solvent and water based”, and how many hours (on a continuous scale) over ‘a typical working day’ workers spent spray painting, mixing paint, and degreasing (panels or parts). As the vast majority of spray painting was conducted in spray booths (with down-draft or cross-draft exhaust ventilation), we were unable to assess the effect of spraying outside the booth. Almost all booths (>90%) were commercially produced, single vehicle capacity units with down-draft extraction systems (ceiling to floor air flow), built to similar specifications and compliant with New Zealand health and safety and emission control standards (confirmed through testing by regulatory authorities). The remainder were cross-draft booths (which were also compliant with New Zealand health and safety and emission control standards), a small number of which were owner-built. For the purpose of subsequent analyses, we dichotomized the EUROQUEST symptoms, with “seldom or never” or “sometimes”, “strongly disagree” or “disagree”, and “very good” or “good” constituting a negative response and “often” or “very often”, “agree” or “strongly agree”, and “poor” or “very poor” constituting a positive response (Kaukiainen et al. 2009; Keer et al. 2016). Anxiety and perceived general health were included to control the analyses for individual personality traits which have been found to lead to under or over reporting of symptoms (Kaukiainen et al. 2009). Responses to these questions were aggregated to produce a total score for each domain as described previously (Keer et al. 2016). Responses to the PPE and workplace practice questions were also dichotomized, with “seldom/never” or “sometimes” and “as and when required” or “less than once a month”, constituting a negative (i.e. infrequent) response and ‘often’, ‘very often’ or ‘always’, and “1–2 times a month” or “weekly” constituting a positive (i.e. frequent) response. For the sum of skin exposures, those with an overall ‘score’ of 0 (n = 21) or 1 (92) were combined for all future analyses due to small numbers in the “0” category. Also, only a small number of workers reported using ‘mostly water-based’ paint (n = 13), so they were combined with those who reported using “both water and solvent based” paints (n = 60). Statistical analyses All analyses were conducted using Stata version 13.1 (StataCorp LP, Texas, USA). Associations between PPE-use and workplace practices and symptoms were assessed using logistic regression with results expressed as prevalence odds ratios (OR). EUROQUEST symptoms were grouped according to the total number of positive responses, i.e. ≥5 or ≥10 (Keer et al. 2016). For symptoms clustered by specific domains, we used a cut-point of ≥3 positive responses, an approach previously shown to be sensitive and specific in the classification of patients diagnosed with chronic solvent neurotoxicity (Kaukiainen et al. 2009). Memory and concentration symptoms were included as a combined domain with a cut-point of ≥3 positive responses to reduce under-detection of potential cases (Kaukiainen et al. 2009). Concentration symptoms were not analysed as a standalone domain due to low numbers in many strata. Initially analyses were conducted for each measure of PPE use and workplace practice separately, adjusted for age, ethnicity, smoking status, alcohol consumption, education level, and general health and personality traits. Other potential confounders including sleep quality, chronic diseases (e.g., diabetes), minor head injuries, concussion, chronic fatigue, prescription drug use, and pre-existing health issues were also tested, but these did not appreciably affect the observed associations (data not shown) and were therefore not used in subsequent analyses. Non-convergence did occur occasionally for some potential confounders in the regression models; however, additional restricted analyses including or excluding these variables had little effect on the relevant outcomes (data not shown). In addition to analysing frequency of respirator or glove use by each work task (mixing paint, spraying, or degreasing/cleaning), we created a combined metric for each type of PPE by summing their frequency of use (0 or 1) across tasks. This gave a possible ‘score’ of 0–3, with 0 representing infrequent PPE use for all tasks. We also created an ‘overall’ measure of PPE-use by combining glove and respirator use, giving a possible score of 0–6; those who scored 0 (n = 4) or 1 (n = 32) were combined due to low numbers. Finally, as a measure of overall workplace hygiene we created a ‘hygiene’ metric by dichotomising each of the respirator and glove use metrics (score of 0 or 1 = 0, score of 2 or 3 = 1) and combining them with outcomes related to the use of an air-fed respirator (0 = no use; 1 = any use), frequency that respirator cartridges were changed (0 = infrequently 1 = frequently) and frequency that hands are washed in solvents (0 = frequently; 1 = infrequently), giving a possible score of 0–5 (0 representing generally ‘poor’ hygiene). For subsequent analyses, those who scored 0 (n = 20) or 1 (n = 42) were combined into single categories due to low numbers; we also combined scores of 4 (n = 60) and 5 (n = 16) for the same reason. For the analyses of PPE use by individual work tasks (e.g. respirator use during paint mixing) and workplace practices, a number of workers were excluded due to missing data. Workers were also excluded from the respirator use metric (n = 19), glove use metric (n = 10), combined PPE use metric (n = 21), and hygiene metric (n = 30) if data were missing for one or more of the variables used to construct the metric. After analysing each PPE use measure and workplace practice separately, we repeated the analyses mutually adjusting for all PPE use measures and workplace practices. Although this showed similar ORs and trends (data not shown), there was significant colinearity and non-convergence (Greenland et al. 2016). To address this, we applied a more restricted model including only variables showing significant associations when analysed separately. Due to further colinearity we were not able to include respirator use and glove use separately, so included only the combined PPE use metric. For the same reason only one of the two variables on hand washing with solvents was included i.e. frequency that hands were washed (rather than never or ever washed hands) which is more likely to be representative of exposure intensity. Sum of skin exposure was correlated with the combined PPE metric, so this was also analysed separately. The ‘hygiene’ metric (described above) was analysed separately as it was derived from variables already included in the mutually adjusted model. Neurological symptoms were not analysed as a standalone domain for the mutually adjusted analyses due to low numbers in many strata. Results The demographic characteristics of study participants are shown in Table 1. Over three quarters of spray painters reported infrequent respirator use when mixing paint, and over half when cleaning or degreasing equipment/parts (Table 2). Approximately 20% used respirators consistently across multiple tasks and 45% consistently used gloves. Twenty-seven percent of workers frequently washed their hands (by immersion and direct application) in solvent mixtures used for degreasing, cleaning spray equipment or thinning paint (comprised of varying proportions of naphtha, toluene, acetone, methyl ethyl ketone, and methanol), primarily to remove paint overspray deposited on the hands and/or forearms as a result of not wearing gloves or other protective clothing. Eight percent of workers reported exposure to hands, forearms, and head (top of face and/or neck) when spray painting, while ~70% reported exposure to one or two skin areas when painting. The majority of painters reported the use of primarily solvent-based paints, with only 5% using ‘mostly water-based paints’. Painters spent on average two-and-a-half hours spray painting [ranging from 0 to 8.5 h/day, with those spray painting 0 h/day being ex-tradesmen now in management (n = 9) who occasionally perform some spray painting work during busy periods (Keer et al. 2016)], 1 hour mixing paint, and 1 hour degreasing parts and cleaning spray equipment. Table 1. Demographic characteristics of workers.   Spray painters (n = 267)  n  %  Ethnicity   Maori  37  13.9   Pacific  17  6.4   Other (incl. NZ European)  213  80.8  Smoking status   Non-smoker  112  42.0   Ex-smoker  76  28.5   Current smoker  79  29.6  Education level   Primary  5  1.9   Secondary  194  72.7   Trade cert.  58  21.7   Tertiary  10  3.7    Mean  Range  Age  36.0  17–64  Alcohol (mean drinks per week)  13.4  0–140  Duration of employment (years)  16.6  0.3 - 50    Spray painters (n = 267)  n  %  Ethnicity   Maori  37  13.9   Pacific  17  6.4   Other (incl. NZ European)  213  80.8  Smoking status   Non-smoker  112  42.0   Ex-smoker  76  28.5   Current smoker  79  29.6  Education level   Primary  5  1.9   Secondary  194  72.7   Trade cert.  58  21.7   Tertiary  10  3.7    Mean  Range  Age  36.0  17–64  Alcohol (mean drinks per week)  13.4  0–140  Duration of employment (years)  16.6  0.3 - 50  View Large Table 2. Prevalence of PPE use and particular workplace practices.   Frequency/n (%)  PPE use   Respirator use  Infrequently  Frequently    Mixing paint  192 (77.1%)  57 (22.9%)    Spray painting  8 (3.1%)  249 (96.9%)    Cleaning equipment/etc.  151 (60.9%)  97 (39.1%)   Sum of respirator use  N (%)    0 (respirator not worn for all 3 tasks)  7 (2.9%)    1  137 (55.9%)    2  52 (21.2%)    3 (respirator worn for all 3 tasks)  49 (20.0%)   Glove use  Infrequently  Frequently    Mixing paint  130 (50.6%)  127 (49.4%)    Spray painting  80 (31.2%)  176 (68.8%)    Cleaning equipment/etc.  65 (25.3%)  192 (74.7%)   Sum of glove use  N (%)    0 (gloves not worn for all 3 tasks)  41 (16.1%)    1  53 (20.9%)    2  45 (17.7%)    3 (Gloves worn for all 3 tasks)  115 (45.3%)    Infrequently  Frequently   Combined PPE metric  N (%)    0 (No gloves or respirator worn for all 3 tasks)  4 (1.7%)    1  32 (13.2%)    2  37 (15.2%)    3  42 (17.3%)    4  56 (23.1%)    5  32 (13.2%)    6 (Both gloves and respirator worn for all 3 tasks)  40 (16.5%)    No  Yes   Ever use air-fed mask  123 (46.6%)  141 (53.4%)    Infrequently  Frequently   Frequency respirator cartridges changed  169 (67.4%)  82 (32.7%)  Workplace practices    No  Yes   Wash hands in solventsa  87 (33.0%)  177 (67.1%)    Infrequently  Frequently   Frequency wash hands in solventsa  193 (73.1%)  71 (26.9%)   Skin exposure (body parts exposed)  N (%)    0  61 (23.1%)    1  90 (34.1%)    2  92 (34.9%)    3  21 (8.0%)   Gun cleaning method      Unenclosed + un-extracted  55 (21.6%)    Enclosed + un-extracted  50 (19.6%)    Unenclosed + extracted  57 (22.4%)    Enclosed + extracted  93 (36.5%)   Paint type      Mostly water based  13 (5.0%)    Mostly solvent based  185 (71.7%)    Both water and solvent based  60 (23.3%)   Hours on a typical day  Mean (range)    Mixing paint  0.9 (0.0–5.0)    Spray painting  2.6 (0.0–8.5)    Degreasing/cleaning  0.9 (0.0–7.5)  Combined measures of workplace hygiene     ‘Hygiene’ metric  N (%)    0 (poor hygiene)  18 (7.7%)    1  38 (16.2%)    2  46 (19.7%)    3  60 (25.6%)    4  56 (23.9%)    5 (good hygiene)  16 (6.8%)    Frequency/n (%)  PPE use   Respirator use  Infrequently  Frequently    Mixing paint  192 (77.1%)  57 (22.9%)    Spray painting  8 (3.1%)  249 (96.9%)    Cleaning equipment/etc.  151 (60.9%)  97 (39.1%)   Sum of respirator use  N (%)    0 (respirator not worn for all 3 tasks)  7 (2.9%)    1  137 (55.9%)    2  52 (21.2%)    3 (respirator worn for all 3 tasks)  49 (20.0%)   Glove use  Infrequently  Frequently    Mixing paint  130 (50.6%)  127 (49.4%)    Spray painting  80 (31.2%)  176 (68.8%)    Cleaning equipment/etc.  65 (25.3%)  192 (74.7%)   Sum of glove use  N (%)    0 (gloves not worn for all 3 tasks)  41 (16.1%)    1  53 (20.9%)    2  45 (17.7%)    3 (Gloves worn for all 3 tasks)  115 (45.3%)    Infrequently  Frequently   Combined PPE metric  N (%)    0 (No gloves or respirator worn for all 3 tasks)  4 (1.7%)    1  32 (13.2%)    2  37 (15.2%)    3  42 (17.3%)    4  56 (23.1%)    5  32 (13.2%)    6 (Both gloves and respirator worn for all 3 tasks)  40 (16.5%)    No  Yes   Ever use air-fed mask  123 (46.6%)  141 (53.4%)    Infrequently  Frequently   Frequency respirator cartridges changed  169 (67.4%)  82 (32.7%)  Workplace practices    No  Yes   Wash hands in solventsa  87 (33.0%)  177 (67.1%)    Infrequently  Frequently   Frequency wash hands in solventsa  193 (73.1%)  71 (26.9%)   Skin exposure (body parts exposed)  N (%)    0  61 (23.1%)    1  90 (34.1%)    2  92 (34.9%)    3  21 (8.0%)   Gun cleaning method      Unenclosed + un-extracted  55 (21.6%)    Enclosed + un-extracted  50 (19.6%)    Unenclosed + extracted  57 (22.4%)    Enclosed + extracted  93 (36.5%)   Paint type      Mostly water based  13 (5.0%)    Mostly solvent based  185 (71.7%)    Both water and solvent based  60 (23.3%)   Hours on a typical day  Mean (range)    Mixing paint  0.9 (0.0–5.0)    Spray painting  2.6 (0.0–8.5)    Degreasing/cleaning  0.9 (0.0–7.5)  Combined measures of workplace hygiene     ‘Hygiene’ metric  N (%)    0 (poor hygiene)  18 (7.7%)    1  38 (16.2%)    2  46 (19.7%)    3  60 (25.6%)    4  56 (23.9%)    5 (good hygiene)  16 (6.8%)  a’Frequently’ or ‘Yes’ represents poorer hygiene. View Large Analyses of the effects of PPE-use showed that frequent use of a respirator when mixing paint or cleaning equipment was associated with fewer total symptoms (significant only for the cut-point of ≥5 symptoms) with overall significant (P < 0.05) and borderline significant (P < 0.1) dose–response trends for ≥5 and ≥10 symptoms, respectively (Table 3). Table 3. Prevalence odds ratios for symptoms of neurotoxicity and PPE use/workplace practices.     ≥5 Symptomsan (%)    ≥10 Symptomsan (%)    ≥15 Symptomsan (%)    ≥3 Neurologicaln (%)    ≥3 Psychosomaticn (%)    ≥3 Moodn (%)    ≥3 Memoryn (%)    ≥3 Fatiguen (%)    ≥3 Sleep disturbancen (%)    ≥3 Memory and concentrationn (%)    99 (37.5)    35 (13.3)    17 (6.4)    11 (4.2)    17 (6.4)    31 (11.7)    21 (8.0)    35 (13.3)    26 (9.9)    34 (12.9)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)  PPE use   Respirator use    Mixing paint    0.4 (0.2–0.8)*    0.4 (0.1–1.4)    0.5 (0.1–4.8)    -    0.5 (0.1–3.4)    0.6 (0.2–2.0)    0.7 (0.2–3.1)    0.5 (0.2–1.7)    0.1 (0.0–1.0)^    0.4 (0.1–1.4)    Spray painting    0.7 (0.2–3.3)    0.3 (0.0–2.0)    -    0.1 (0.0–1.7)    -    -    -    1.2 (0.1–11.7)    0.6 (0.1–4.0)    0.5 (0.0–4.9)    Cleaning equipment/degreasing    0.4 (0.2–0.8)**    0.5 (0.2–1.3)    0.4 (0.1–2.3)    -    0.8 (0.2–3.8)    0.7 (0.2–2.8)    0.5 (0.2–1.2)    0.6 (0.2–1.5)    0.1 (0.0–0.7)*    0.5 (0.2–1.3)   Sum of respirator use    0/1 (REF)                                            2    0.5 (0.3–1.1)    0.9 (0.3–2.6)    1.5 (0.3–7.7)    -    1.1 (0.3–4.7)    0.7 (0.2–2.1)    0.8 (0.2–3.1)    1.2 (0.5–3.2)    0.3 (0.1–1.3)    0.8 (0.3–2.1)    3    0.3 (0.1–0.7)**    0.1 (0.0–1.1)^    0.4 (0.0–5.2)    -    0.4 (0.0–3.8)    0.3 (0.1–1.6)    0.5 (0.1–2.9)    0.3 (0.1–1.4)    -    0.3 (0.1–1.3)    P value for trend    0.00    0.08    0.63    -    0.50    0.14    0.46    0.23    0.01    0.10   Glove use    Mixing paint    0.4 (0.2–0.8)**    0.3 (0.1–0.7)**    0.6 (0.1–2.7)    -    0.2 (0.0–1.0)*    0.5 (0.2–1.2)    0.3 (0.1–1.1)^    0.6 (0.2–1.3)    0.4 (0.1–1.1)^    0.2 (0.1–0.6)**    Spray painting    0.5 (0.3–0.9)*    0.4 (0.2–0.9)*    0.4 (0.1–1.8)    -    0.3 (0.1–1.2)^    0.4 (0.2–1.1)^    1.3 (0.4–4.2)    0.4 (0.2–1.0)*    0.9 (0.3–2.5)    0.7 (0.3–1.5)    Cleaning    0.5 (0.2–0.9)*    0.4 (0.2–1.0)*    0.3 (0.1–1.4)    -    0.3 (0.1–0.9)*    0.4 (0.2–1.1)^    0.5 (0.2–1.5)    0.5 (0.2–1.1)^    0.4 (0.2–1.1)^    0.4 (0.1–0.9)*   Sum of glove use    0 (REF)                                            1    0.4 (0.2–1.0)^    0.3 (0.1–1.2)^    0.2 (0.0–1.6)    -    0.2 (0.0–1.2)^    0.7 (0.2–2.4)    0.3 (0.0–1.7)    0.3 (0.1–1.2)^    1.1 (0.3–4.3)    0.6 (0.2–1.9)    2    0.7 (0.2–1.7)    0.7 (0.2–2.3)    0.2 (0.0–1.7)    -    0.3 (0.1–1.8)    0.4 (0.1–1.7)    1.2 (0.3–5.1)    0.6 (0.2–2.1)    1.1 (0.3–4.5)    1.1 (0.4–3.6)    3    0.2 (0.1–0.6)**    0.1 (0.0–0.5)**    0.2 (0.0–1.4)    -    0.1 (0.0–0.6)**    0.3 (0.1–1.0)^    0.3 (0.1–1.3)^    0.3 (0.1–0.8)*    0.4 (0.1–1.5)    0.2 (0.0–0.6)**    P value for trend    0.00    0.00    0.18    -    0.02    0.04    0.26    0.04    0.12    0.01   Combined PPE metric    0/1 (REF)                                            2    0.6 (0.2–1.6)    0.7 (0.2–2.7)    0.2 (0.0–2.4)    -    0.2 (0.0–1.6)    0.8 (0.2–3.3)    0.5 (0.1–3.0)    0.7 (0.2–2.6)    1.1 (0.3–4.6)    0.7 (0.2–2.7)    3    0.7 (0.2–1.8)    0.8 (0.2–2.9)    0.1 (0.0–1.4)*    -    0.1 (0.0–0.9)*    0.9 (0.2–3.6)    0.5 (0.1–3.1)    0.5 (0.1–2.0)    0.5 (0.1–2.6)    1.1 (0.3–3.9)    4    0.7 (0.3–1.8)    0.3 (0.1–1.2)^    0.3 (0.0–2.4)    -    0.2 (0.0–1.1)^    0.5 (0.1–2.0)    0.8 (0.2–3.8)    0.8 (0.3–2.7)    0.7 (0.2–2.9)    0.5 (0.1–1.7)    5    0.4 (0.1–1.2)^    0.2 (0.0–1.4)    0.3 (0.0–3.8)    -    0.3 (0.0–2.3)    0.3 (0.1–2.0)    0.2 (0.0–2.7)    0.4 (0.1–2.1)    0.2 (0.0–2.0)    0.1 (0.0–1.2)^    6    0.1 (0.0–0.3)**    0.1 (0.0–0.9)*    0.1 (0.0–2.6)    -    -    0.1 (0.0–1.3)^    0.2 (0.0–2.2)    0.1 (0.0–1.0)*    -    0.1 (0.0–1.0)^    P value for trend    0.00    0.01    0.23    -    0.04    0.04    0.24    0.08    0.03    0.01   Ever use air-fed mask    0.8 (0.4–1.3)    0.3 (0.1–0.7)**    0.3 (0.1–1.6)    -    0.8 (0.2–2.5)    0.3 (0.1–0.8)*    0.5 (0.2–1.5)    0.6 (0.3–1.5)    1.4 (0.6–3.6)    0.8 (0.3–1.8)   Frequency respirator cartridges changed    0.5 (0.3–1.0)^    0.3 (0.1–0.9)*    0.8 (0.2–3.7)    0.3 (0.1–2.2)    1.4 (0.4–5.1)    0.3 (0.1–1.0)^    0.9 (0.3–3.0)    0.5 (0.2–1.4)    0.7 (0.2–2.0)    0.7 (0.3–1.9)  Workplace practices   Wash hands in solvents (yes/no)    1.7 (0.9–3.1)^    3.2 (1.1–9.3)*    1.4 (0.3–6.9)    -    1.6 (0.4–6.3)    1.9 (0.7–4.9)    4.6 (1.0–20.1)*    2.7 (1.0–7.5)^    1.5 (0.5–4.0)    3.1 (1.1–8.5)*   Frequently wash hands in solvents    2.0 (1.1–3.7)*    3.1 (1.3–7.4)*    2.7 (0.7–10.8)    -    2.2 (0.6–7.5)    2.0 (0.8–4.9)    1.9 (0.6–5.8)    1.9 (0.8–4.4)    3.0 (1.2–7.6)*    1.8 (0.7–4.2)   Skin exposure (body parts exposed)    0/1 (REF)                                            2    1.5 (0.8–2.7)    1.4 (0.6–3.7)    1.4 (0.3–7.3)    -    0.5 (0.1–2.9)    1.5 (0.6–3.7)    1.8 (0.6–5.6)    1.6 (0.7–3.8)    1.4 (0.5–3.8)    2.0 (0.8–5.0)    3    3.5 (1.2–9.9)*    5.7 (1.6–20.2)**    7.8 (1.1–57.3)*    -    19.3 (3.4–108.5)**    2.4 (0.6–9.0)    0.6 (0.1–7.4)    3.5 (1.0–12.9)^    2.2 (0.5–10.0)    3.9 (1.1–14.1)*    P value for trend    0.02    0.02    0.08    -    0.01    0.17    0.71    0.06    0.26    0.02   Gun cleaning method    Unenclosed + un-extracted (REF)                                            Enclosed + un-extracted    0.9 (0.4–2.2)    0.8 (0.2–3.0)    5.2 (0.4–65.8)    1.5 (0.2–10.4)    3.7 (0.5–29.3)    1.5 (0.4–5.8)    3.3 (0.4–23.5)    1.1 (0.3–3.9)    2.7 (0.6–12.2)    2.8 (0.7–11.5)    Unenclosed + extracted    0.7 (0.3–1.6)    1.6 (0.5–5.1)    11.0 (0.9–135.0)^    -    6.0 (0.8–45.3)^    2.0 (0.6–7.1)    5.3 (0.8–37.3)^    0.9 (0.2–3.0)    3.0 (0.7–12.8)    2.7 (0.7–10.7)    Enclosed + extracted    0.9 (0.4–2.0)    0.7 (0.2–2.3)    4.2 (0.4–45.3)    0.9 (0.1–6.3)    1.3 (0.2–9.9)    1.0 (0.3–3.5)    3.7 (0.6–22.6)    1.1 (0.4–3.3)    1.7 (0.4–6.8)    1.8 (0.5–6.6)   Paint type    Both water and solvent based (REF)                                            Mostly solvent based    0.5 (0.3–1.1)^    0.4 (0.1–1.4)    1.0 (0.2–5.0)    -    0.5 (0.1–2.7)    0.6 (0.2–2.0)    1.1 (0.3–3.8)    0.5 (0.2–1.6)    0.7 (0.2–2.5)    0.9 (0.3–2.3)   Hours on a typical dayb                                            Mixing paint    1.1 (0.8–1.5)    0.8 (0.5–1.5)    0.6 (0.2–1.6)    -    0.6 (0.3–1.4)    1.1 (0.7–1.8)    0.7 (0.4–1.5)    1.1 (0.7–1.8)    1.7 (1.2–2.6)**    0.8 (0.4–1.4)    Spray painting    1.0(0.8–1.1)    1.3 (1.0–1.7)*    1.2 (0.8–1.8)    -    1.2 (0.8–1.7)    1.3 (1.0–1.6)*    0.9 (0.6–1.2)    1.3 (1.0–1.6)*    1.1 (0.8–1.4)    0.8 (0.6–1.1)    Degreasing/cleaning    1.1 (0.8–1.4)    1.1 (0.7–1.6)    1.3 (0.7–2.3)    -    0.9 (0.5–1.7)    1.2 (0.8–1.7)    1.4 (0.9–2.1)    1.4 (1.0–1.9)^    1.6 (1.1–2.3)**    1.2 (0.8–1.7)  Combined measures of workplace hygiene   ‘Hygiene’ metric    0/1 (poor hygiene)                                            2    0.7 (0.3–1.8)    0.5 (0.2–1.6)    0.9 (0.1–5.9)    -    0.8 (0.2–4.3)    1.0 (0.3–3.2)    0.7 (0.2–3.3)    0.9 (0.3–2.7)    1.0 (0.3–3.5)    1.0 (0.3–3.2)    3    0.5 (0.2–1.2)    0.3 (0.1–1.0)*    0.2 (0.0–1.7)    -    0.2 (0.0–1.8)    0.3 (0.1–1.2)    0.7 (0.2–2.9)    0.5 (0.2–1.7)    0.5 (0.1–2.2)    0.7 (0.2–2.1)    4/5 (good hygiene)    0.3 (0.1–0.7)**    0.1 (0.0–0.6)**    0.5 (0.1–3.3)    -    0.7 (0.2–3.4)    0.3 (0.1–1.0)*    0.4 (0.1–1.7)    0.3 (0.1–1.1)^    0.1 (0.0–0.8)*    0.4 (0.1–1.3)    P value for trend    0.00    0.00    0.25    -    0.48    0.02    0.22    0.06    0.02    0.10      ≥5 Symptomsan (%)    ≥10 Symptomsan (%)    ≥15 Symptomsan (%)    ≥3 Neurologicaln (%)    ≥3 Psychosomaticn (%)    ≥3 Moodn (%)    ≥3 Memoryn (%)    ≥3 Fatiguen (%)    ≥3 Sleep disturbancen (%)    ≥3 Memory and concentrationn (%)    99 (37.5)    35 (13.3)    17 (6.4)    11 (4.2)    17 (6.4)    31 (11.7)    21 (8.0)    35 (13.3)    26 (9.9)    34 (12.9)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)  PPE use   Respirator use    Mixing paint    0.4 (0.2–0.8)*    0.4 (0.1–1.4)    0.5 (0.1–4.8)    -    0.5 (0.1–3.4)    0.6 (0.2–2.0)    0.7 (0.2–3.1)    0.5 (0.2–1.7)    0.1 (0.0–1.0)^    0.4 (0.1–1.4)    Spray painting    0.7 (0.2–3.3)    0.3 (0.0–2.0)    -    0.1 (0.0–1.7)    -    -    -    1.2 (0.1–11.7)    0.6 (0.1–4.0)    0.5 (0.0–4.9)    Cleaning equipment/degreasing    0.4 (0.2–0.8)**    0.5 (0.2–1.3)    0.4 (0.1–2.3)    -    0.8 (0.2–3.8)    0.7 (0.2–2.8)    0.5 (0.2–1.2)    0.6 (0.2–1.5)    0.1 (0.0–0.7)*    0.5 (0.2–1.3)   Sum of respirator use    0/1 (REF)                                            2    0.5 (0.3–1.1)    0.9 (0.3–2.6)    1.5 (0.3–7.7)    -    1.1 (0.3–4.7)    0.7 (0.2–2.1)    0.8 (0.2–3.1)    1.2 (0.5–3.2)    0.3 (0.1–1.3)    0.8 (0.3–2.1)    3    0.3 (0.1–0.7)**    0.1 (0.0–1.1)^    0.4 (0.0–5.2)    -    0.4 (0.0–3.8)    0.3 (0.1–1.6)    0.5 (0.1–2.9)    0.3 (0.1–1.4)    -    0.3 (0.1–1.3)    P value for trend    0.00    0.08    0.63    -    0.50    0.14    0.46    0.23    0.01    0.10   Glove use    Mixing paint    0.4 (0.2–0.8)**    0.3 (0.1–0.7)**    0.6 (0.1–2.7)    -    0.2 (0.0–1.0)*    0.5 (0.2–1.2)    0.3 (0.1–1.1)^    0.6 (0.2–1.3)    0.4 (0.1–1.1)^    0.2 (0.1–0.6)**    Spray painting    0.5 (0.3–0.9)*    0.4 (0.2–0.9)*    0.4 (0.1–1.8)    -    0.3 (0.1–1.2)^    0.4 (0.2–1.1)^    1.3 (0.4–4.2)    0.4 (0.2–1.0)*    0.9 (0.3–2.5)    0.7 (0.3–1.5)    Cleaning    0.5 (0.2–0.9)*    0.4 (0.2–1.0)*    0.3 (0.1–1.4)    -    0.3 (0.1–0.9)*    0.4 (0.2–1.1)^    0.5 (0.2–1.5)    0.5 (0.2–1.1)^    0.4 (0.2–1.1)^    0.4 (0.1–0.9)*   Sum of glove use    0 (REF)                                            1    0.4 (0.2–1.0)^    0.3 (0.1–1.2)^    0.2 (0.0–1.6)    -    0.2 (0.0–1.2)^    0.7 (0.2–2.4)    0.3 (0.0–1.7)    0.3 (0.1–1.2)^    1.1 (0.3–4.3)    0.6 (0.2–1.9)    2    0.7 (0.2–1.7)    0.7 (0.2–2.3)    0.2 (0.0–1.7)    -    0.3 (0.1–1.8)    0.4 (0.1–1.7)    1.2 (0.3–5.1)    0.6 (0.2–2.1)    1.1 (0.3–4.5)    1.1 (0.4–3.6)    3    0.2 (0.1–0.6)**    0.1 (0.0–0.5)**    0.2 (0.0–1.4)    -    0.1 (0.0–0.6)**    0.3 (0.1–1.0)^    0.3 (0.1–1.3)^    0.3 (0.1–0.8)*    0.4 (0.1–1.5)    0.2 (0.0–0.6)**    P value for trend    0.00    0.00    0.18    -    0.02    0.04    0.26    0.04    0.12    0.01   Combined PPE metric    0/1 (REF)                                            2    0.6 (0.2–1.6)    0.7 (0.2–2.7)    0.2 (0.0–2.4)    -    0.2 (0.0–1.6)    0.8 (0.2–3.3)    0.5 (0.1–3.0)    0.7 (0.2–2.6)    1.1 (0.3–4.6)    0.7 (0.2–2.7)    3    0.7 (0.2–1.8)    0.8 (0.2–2.9)    0.1 (0.0–1.4)*    -    0.1 (0.0–0.9)*    0.9 (0.2–3.6)    0.5 (0.1–3.1)    0.5 (0.1–2.0)    0.5 (0.1–2.6)    1.1 (0.3–3.9)    4    0.7 (0.3–1.8)    0.3 (0.1–1.2)^    0.3 (0.0–2.4)    -    0.2 (0.0–1.1)^    0.5 (0.1–2.0)    0.8 (0.2–3.8)    0.8 (0.3–2.7)    0.7 (0.2–2.9)    0.5 (0.1–1.7)    5    0.4 (0.1–1.2)^    0.2 (0.0–1.4)    0.3 (0.0–3.8)    -    0.3 (0.0–2.3)    0.3 (0.1–2.0)    0.2 (0.0–2.7)    0.4 (0.1–2.1)    0.2 (0.0–2.0)    0.1 (0.0–1.2)^    6    0.1 (0.0–0.3)**    0.1 (0.0–0.9)*    0.1 (0.0–2.6)    -    -    0.1 (0.0–1.3)^    0.2 (0.0–2.2)    0.1 (0.0–1.0)*    -    0.1 (0.0–1.0)^    P value for trend    0.00    0.01    0.23    -    0.04    0.04    0.24    0.08    0.03    0.01   Ever use air-fed mask    0.8 (0.4–1.3)    0.3 (0.1–0.7)**    0.3 (0.1–1.6)    -    0.8 (0.2–2.5)    0.3 (0.1–0.8)*    0.5 (0.2–1.5)    0.6 (0.3–1.5)    1.4 (0.6–3.6)    0.8 (0.3–1.8)   Frequency respirator cartridges changed    0.5 (0.3–1.0)^    0.3 (0.1–0.9)*    0.8 (0.2–3.7)    0.3 (0.1–2.2)    1.4 (0.4–5.1)    0.3 (0.1–1.0)^    0.9 (0.3–3.0)    0.5 (0.2–1.4)    0.7 (0.2–2.0)    0.7 (0.3–1.9)  Workplace practices   Wash hands in solvents (yes/no)    1.7 (0.9–3.1)^    3.2 (1.1–9.3)*    1.4 (0.3–6.9)    -    1.6 (0.4–6.3)    1.9 (0.7–4.9)    4.6 (1.0–20.1)*    2.7 (1.0–7.5)^    1.5 (0.5–4.0)    3.1 (1.1–8.5)*   Frequently wash hands in solvents    2.0 (1.1–3.7)*    3.1 (1.3–7.4)*    2.7 (0.7–10.8)    -    2.2 (0.6–7.5)    2.0 (0.8–4.9)    1.9 (0.6–5.8)    1.9 (0.8–4.4)    3.0 (1.2–7.6)*    1.8 (0.7–4.2)   Skin exposure (body parts exposed)    0/1 (REF)                                            2    1.5 (0.8–2.7)    1.4 (0.6–3.7)    1.4 (0.3–7.3)    -    0.5 (0.1–2.9)    1.5 (0.6–3.7)    1.8 (0.6–5.6)    1.6 (0.7–3.8)    1.4 (0.5–3.8)    2.0 (0.8–5.0)    3    3.5 (1.2–9.9)*    5.7 (1.6–20.2)**    7.8 (1.1–57.3)*    -    19.3 (3.4–108.5)**    2.4 (0.6–9.0)    0.6 (0.1–7.4)    3.5 (1.0–12.9)^    2.2 (0.5–10.0)    3.9 (1.1–14.1)*    P value for trend    0.02    0.02    0.08    -    0.01    0.17    0.71    0.06    0.26    0.02   Gun cleaning method    Unenclosed + un-extracted (REF)                                            Enclosed + un-extracted    0.9 (0.4–2.2)    0.8 (0.2–3.0)    5.2 (0.4–65.8)    1.5 (0.2–10.4)    3.7 (0.5–29.3)    1.5 (0.4–5.8)    3.3 (0.4–23.5)    1.1 (0.3–3.9)    2.7 (0.6–12.2)    2.8 (0.7–11.5)    Unenclosed + extracted    0.7 (0.3–1.6)    1.6 (0.5–5.1)    11.0 (0.9–135.0)^    -    6.0 (0.8–45.3)^    2.0 (0.6–7.1)    5.3 (0.8–37.3)^    0.9 (0.2–3.0)    3.0 (0.7–12.8)    2.7 (0.7–10.7)    Enclosed + extracted    0.9 (0.4–2.0)    0.7 (0.2–2.3)    4.2 (0.4–45.3)    0.9 (0.1–6.3)    1.3 (0.2–9.9)    1.0 (0.3–3.5)    3.7 (0.6–22.6)    1.1 (0.4–3.3)    1.7 (0.4–6.8)    1.8 (0.5–6.6)   Paint type    Both water and solvent based (REF)                                            Mostly solvent based    0.5 (0.3–1.1)^    0.4 (0.1–1.4)    1.0 (0.2–5.0)    -    0.5 (0.1–2.7)    0.6 (0.2–2.0)    1.1 (0.3–3.8)    0.5 (0.2–1.6)    0.7 (0.2–2.5)    0.9 (0.3–2.3)   Hours on a typical dayb                                            Mixing paint    1.1 (0.8–1.5)    0.8 (0.5–1.5)    0.6 (0.2–1.6)    -    0.6 (0.3–1.4)    1.1 (0.7–1.8)    0.7 (0.4–1.5)    1.1 (0.7–1.8)    1.7 (1.2–2.6)**    0.8 (0.4–1.4)    Spray painting    1.0(0.8–1.1)    1.3 (1.0–1.7)*    1.2 (0.8–1.8)    -    1.2 (0.8–1.7)    1.3 (1.0–1.6)*    0.9 (0.6–1.2)    1.3 (1.0–1.6)*    1.1 (0.8–1.4)    0.8 (0.6–1.1)    Degreasing/cleaning    1.1 (0.8–1.4)    1.1 (0.7–1.6)    1.3 (0.7–2.3)    -    0.9 (0.5–1.7)    1.2 (0.8–1.7)    1.4 (0.9–2.1)    1.4 (1.0–1.9)^    1.6 (1.1–2.3)**    1.2 (0.8–1.7)  Combined measures of workplace hygiene   ‘Hygiene’ metric    0/1 (poor hygiene)                                            2    0.7 (0.3–1.8)    0.5 (0.2–1.6)    0.9 (0.1–5.9)    -    0.8 (0.2–4.3)    1.0 (0.3–3.2)    0.7 (0.2–3.3)    0.9 (0.3–2.7)    1.0 (0.3–3.5)    1.0 (0.3–3.2)    3    0.5 (0.2–1.2)    0.3 (0.1–1.0)*    0.2 (0.0–1.7)    -    0.2 (0.0–1.8)    0.3 (0.1–1.2)    0.7 (0.2–2.9)    0.5 (0.2–1.7)    0.5 (0.1–2.2)    0.7 (0.2–2.1)    4/5 (good hygiene)    0.3 (0.1–0.7)**    0.1 (0.0–0.6)**    0.5 (0.1–3.3)    -    0.7 (0.2–3.4)    0.3 (0.1–1.0)*    0.4 (0.1–1.7)    0.3 (0.1–1.1)^    0.1 (0.0–0.8)*    0.4 (0.1–1.3)    P value for trend    0.00    0.00    0.25    -    0.48    0.02    0.22    0.06    0.02    0.10  Adjusted for age, ethnicity, smoking status, alcohol consumption, education status, general health, and personality traits. “-” No ORs available due to non-convergence in model. CI = confidence interval. ^P < 0.1; *P < 0.05; **P < 0.01. aAll EUROQUEST symptoms (all domains combined). bOR for every unit increase (1 hour) in time spent on task. View Large Frequent glove use was also associated with a strongly reduced risk of symptoms (significant for the cut-points of ≥5 and ≥10 symptoms) following a clear and statistically significant dose–response trend (Table 3). In addition, combined respirator and glove use was inversely and significantly associated with total symptoms with an observed 90% reduction of risk for those with the most consistent use of both types of PPE, and a significant dose–response trend was also observed. Associations with specific symptom domains showed reduced risks for all domains, particularly for psychosomatic, mood, sleep disturbance, and memory and concentration symptoms combined, with the strongest and most significant effects observed for frequent and consistent glove use and combined glove and respirator use (Table 3). Use of an air-fed respirator (ever) was associated with a reduction in risk for reporting both ≥10 and ≥15 symptoms; a similar effect was seen for ≥5 and ≥10 symptoms with frequent changing of absorbent respirator cartridges, washing of hands and infrequent versus frequent washing of hands in solvents. Surprisingly, those using mostly solvent-based paints reported fewer symptoms than those using both water-based and solvent-based paints. A trend of increasing number of symptoms with more body parts exposed during spray painting was also observed (Table 3). An inverse and significant dose–response trend was observed for hygiene scores with a 70–90% reduction in risk of reporting ≥5 and ≥10 symptoms for those workers with the best hygiene score (score of 4/5). No clear associations with symptoms were found for type of gun cleaning method. Results for the combined PPE metric mutually adjusting for other workplace practices showed similar trends, but confidence intervals were generally wider and fewer individual results reached statistical significance (Table 4). Nonetheless, an inverse dose–response trend remained (P for trend of 0.02 and 0.06 for reporting ≥5 and ≥10 symptoms, respectively), including for the domains of psychosomatic (P for trend = 0.02) and memory and concentration symptoms combined (P for trend = 0.05). The strength of the associations seen for use of an air-fed respirator, frequency of mask cartridge changes, frequency of hand washing in solvents, and time spent on work tasks were generally weaker compared to when analysed separately. Table 4. Prevalence odds ratios for symptoms of neurotoxicity and combined PPE-use mutually adjusted for other variables in the table.     ≥5 Symptoms†    ≥10 Symptoms†    ≥15 Symptoms†    ≥3 Psychosomatic    ≥3 Mood    ≥3 Memory    ≥3 Fatigue    ≥3 Sleep disturbance    ≥3 Memory and concentration    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)  PPE use   Combined PPE metric    0/1 (REF)                                        2    0.6 (0.2–1.8)    0.9 (0.2–3.9)    0.2 (0.0–3.3)    0.3 (0.0–2.2)    0.8 (0.2–3.5)    0.4 (0.1–3.2)    1.2 (0.3–5.3)    1.0 (0.2–5.3)    1.0 (0.2–4.4)    3    0.9 (0.3–2.8)    1.3 (0.3–5.3)    0.1 (0.0–2.0)    0.1 (0.0–0.8)*    1.3 (0.3–5.6)    0.8 (0.1–5.3)    0.8 (0.2–3.7)    0.6 (0.1–3.8)    2.0 (0.5–7.9)    4    0.9 (0.3–2.5)    0.3 (0.1–1.5)    0.3 (0.0–2.8)    0.2 (0.0–1.1)^    0.5 (0.1–2.2)    1.1 (0.2–6.2)    1.2 (0.3–4.5)    0.5 (0.1–3.0)    0.8 (0.2–3.4)    5    0.6 (0.2–1.9)    0.5 (0.1–3.2)    0.4 (0.0–6.2)    0.2 (0.0–1.9)    0.5 (0.1–3.2)    0.3 (0.0–3.8)    0.9 (0.2–4.9)    0.2 (0.0–3.5)    0.2 (0.0–2.1)    6    0.1 (0.0–0.5)**    0.1 (0.0–1.7)    0.1 (0.0–3.1)    -    0.2 (0.0–1.7)    0.2 (0.0–2.7)    0.1 (0.0–1.7)    -    0.2 (0.0–1.8)    P value for trend    0.02    0.06    0.21    0.02    0.10    0.37    0.26    0.06    0.05  Workplace practices   Ever use air-fed mask    0.8 (0.4–1.7)    0.3 (0.1–0.9)*    0.4 (0.1–2.6)    1.2 (0.3–5.7)    0.3 (0.1–0.9)*    0.7 (0.2–2.5)    0.5 (0.2–1.3)    2.3 (0.6–8.8)    0.9 (0.3–2.3)   Frequency respirator cartridges changed    0.8 (0.4–1.7)    0.5 (0.1–1.7)    2.3 (0.3–15.4)    3.6 (0.7–17.6)    0.6 (0.2–2.0)    1.5 (0.4–5.9)    0.7 (0.2–2.0)    0.4 (0.1–2.2)    1.2 (0.4–3.6)   Frequency wash hands in solvents    1.8 (0.8–3.7)    1.3 (0.5–3.8)    1.3 (0.2–7.3)    1.6 (0.4–7.4)    0.7 (0.2–2.0)    1.9 (0.5–7.7)    1.2 (0.5–3.2)    2.8 (0.7–10.4)    1.8 (0.6–5.1)   Hours on a typical dayb    Mixing paint    1.2 (0.7–1.8)    0.6 (0.3–1.5)    0.2 (0.0–1.1)^    0.2 (0.1–1.0)^    0.9 (0.5–1.9)    0.4 (0.1–1.3)    0.8 (0.4–1.5)    1.2 (0.6–2.4)    0.7 (0.3–1.4)    Spray painting    0.9 (0.7–1.1)    1.4 (1.0–1.8)*    1.3 (0.7–2.3)    1.3 (0.8–2.0)    1.3 (0.9–1.7)    0.7 (0.5–1.2)    1.5 (1.1–1.9)**    0.9 (0.6–1.3)    0.8 (0.6–1.1)    Degreasing/cleaning    1.2 (0.8–1.7)    1.5 (0.8–2.7)    2.0 (0.8–4.8)    1.5 (0.7–3.3)    1.4 (0.8–2.4)    2.1 (1.1–4.0)*    1.6 (1.0–2.7)*    2.2 (1.2–4.1)*    1.6 (0.9–2.7)      ≥5 Symptoms†    ≥10 Symptoms†    ≥15 Symptoms†    ≥3 Psychosomatic    ≥3 Mood    ≥3 Memory    ≥3 Fatigue    ≥3 Sleep disturbance    ≥3 Memory and concentration    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)    OR (95% CI)  PPE use   Combined PPE metric    0/1 (REF)                                        2    0.6 (0.2–1.8)    0.9 (0.2–3.9)    0.2 (0.0–3.3)    0.3 (0.0–2.2)    0.8 (0.2–3.5)    0.4 (0.1–3.2)    1.2 (0.3–5.3)    1.0 (0.2–5.3)    1.0 (0.2–4.4)    3    0.9 (0.3–2.8)    1.3 (0.3–5.3)    0.1 (0.0–2.0)    0.1 (0.0–0.8)*    1.3 (0.3–5.6)    0.8 (0.1–5.3)    0.8 (0.2–3.7)    0.6 (0.1–3.8)    2.0 (0.5–7.9)    4    0.9 (0.3–2.5)    0.3 (0.1–1.5)    0.3 (0.0–2.8)    0.2 (0.0–1.1)^    0.5 (0.1–2.2)    1.1 (0.2–6.2)    1.2 (0.3–4.5)    0.5 (0.1–3.0)    0.8 (0.2–3.4)    5    0.6 (0.2–1.9)    0.5 (0.1–3.2)    0.4 (0.0–6.2)    0.2 (0.0–1.9)    0.5 (0.1–3.2)    0.3 (0.0–3.8)    0.9 (0.2–4.9)    0.2 (0.0–3.5)    0.2 (0.0–2.1)    6    0.1 (0.0–0.5)**    0.1 (0.0–1.7)    0.1 (0.0–3.1)    -    0.2 (0.0–1.7)    0.2 (0.0–2.7)    0.1 (0.0–1.7)    -    0.2 (0.0–1.8)    P value for trend    0.02    0.06    0.21    0.02    0.10    0.37    0.26    0.06    0.05  Workplace practices   Ever use air-fed mask    0.8 (0.4–1.7)    0.3 (0.1–0.9)*    0.4 (0.1–2.6)    1.2 (0.3–5.7)    0.3 (0.1–0.9)*    0.7 (0.2–2.5)    0.5 (0.2–1.3)    2.3 (0.6–8.8)    0.9 (0.3–2.3)   Frequency respirator cartridges changed    0.8 (0.4–1.7)    0.5 (0.1–1.7)    2.3 (0.3–15.4)    3.6 (0.7–17.6)    0.6 (0.2–2.0)    1.5 (0.4–5.9)    0.7 (0.2–2.0)    0.4 (0.1–2.2)    1.2 (0.4–3.6)   Frequency wash hands in solvents    1.8 (0.8–3.7)    1.3 (0.5–3.8)    1.3 (0.2–7.3)    1.6 (0.4–7.4)    0.7 (0.2–2.0)    1.9 (0.5–7.7)    1.2 (0.5–3.2)    2.8 (0.7–10.4)    1.8 (0.6–5.1)   Hours on a typical dayb    Mixing paint    1.2 (0.7–1.8)    0.6 (0.3–1.5)    0.2 (0.0–1.1)^    0.2 (0.1–1.0)^    0.9 (0.5–1.9)    0.4 (0.1–1.3)    0.8 (0.4–1.5)    1.2 (0.6–2.4)    0.7 (0.3–1.4)    Spray painting    0.9 (0.7–1.1)    1.4 (1.0–1.8)*    1.3 (0.7–2.3)    1.3 (0.8–2.0)    1.3 (0.9–1.7)    0.7 (0.5–1.2)    1.5 (1.1–1.9)**    0.9 (0.6–1.3)    0.8 (0.6–1.1)    Degreasing/cleaning    1.2 (0.8–1.7)    1.5 (0.8–2.7)    2.0 (0.8–4.8)    1.5 (0.7–3.3)    1.4 (0.8–2.4)    2.1 (1.1–4.0)*    1.6 (1.0–2.7)*    2.2 (1.2–4.1)*    1.6 (0.9–2.7)  Adjusted for age, ethnicity, smoking status, alcohol consumption, education status, general health, and personality traits, as well as all other variables listed in table. “-” No ORs available due to non-convergence in model. CI = confidence interval. ^P < 0.1; *P < 0.05; **P < 0.01. aAll EUROQUEST symptoms (all domains combined). bOR for every unit increase (1 hour) in time spent on task. View Large Analyses for skin exposure similarly adjusted also showed fewer statistically significant results, but again a dose–response trend remained (P for trend of 0.05 and 0.06 for ≥5 and ≥15 symptoms, respectively; see Table S3 in the online supplementary material, available at Annals of Work Exposures and Health online) with the strongest associations observed in the symptom domains of psychosomatic, fatigue, and memory and concentration symptoms combined. Finally, in the mutually adjusted analyses, we found a significant inverse dose–response trend with increased hygiene scores and total symptoms (P for trend of 0.005 and 0.003 for reporting ≥5 and ≥10 symptoms), and symptoms in the domains of mood (P = 0.02), sleep disturbance (P = 0.02), fatigue, and memory and concentration symptoms combined, although the last two did not reach statistical significance (P = 0.05 and 0.12, respectively, see Table S4 in the online supplementary material, available at Annals of Work Exposures and Health online). Discussion This study showed that reported frequent PPE use and good workplace hygiene practices were associated with a reduced risk of total symptoms of neurotoxicity, and symptoms in the psychosomatic, mood, and memory and concentration domains. In general, the strongest effects were seen for glove use but dose–response trends were also observed with other PPE-use and hygiene practices. Previous studies in spray painters (Chang et al. 2007) and other solvent-exposed workers (Nakayama et al. 2004; Wang et al. 2006; Triebig et al. 2009) have shown that the use of respirators, gloves, and/or chemical protective suits is effective in reducing total body burden of solvents. Also, one study in solvent-exposed gun factory workers found that self-reported glove use was associated with some measures of cognitive performance, but not self-reported symptoms (Jang et al. 1999). To our knowledge, our study is therefore one of the first to show a direct protective effect of consistent PPE-use on symptoms of neurotoxicity in solvent-exposed workers. Similar protective effects of PPE on neuropsychological performance have been reported for other occupational settings/exposures such as farm workers exposed to organophosphate pesticides (Cataño et al. 2008). PPE-use has also previously been associated with reduced incidence and prevalence of occupational asthma in workers exposed to toluene diisocyanate, including spray painters (Cullen et al. 1996; Petsonk et al. 2000). As expected, in our study, PPE-use was protective for symptom domains (psychosomatic, mood, and memory and concentration combined) previously identified to be associated with solvent exposure in spray painters (Meyer-Baron et al. 2008), including in our previous study in which the current study was nested (Keer et al. 2016). Taken together, this strongly suggests that PPE-use and good workplace hygiene practices and behaviours are important determinants of exposure (and related health risks) in these workers. Due to some correlation between the use of several types of PPE, workplace hygiene measures, and risk behaviours, it was difficult to assess the relative contribution of each measure individually. Nonetheless, multivariate analyses including combined individual measures and mutually adjusting for workplace hygiene practices and risk behaviours showed similar trends to analyses for each of these individual variables separately, suggesting results are valid. Also, additional analyses including only those workers who wore one type of PPE [respirator only when spray painting (N = 76), gloves only when mixing paint (N = 79), and gloves only when degreasing/cleaning (N = 102)] showed highly comparable results, although the models were less stable due to smaller numbers (data not shown). Overall, we found that consistent glove use was most protective (Table 2), which is consistent with evidence from other studies suggesting that dermal exposures may contribute >50% of the total body burden of solvents, particularly when airborne exposures are well controlled (Brooke et al. 1998; Semple et al. 2001; Semple 2004; Chang et al. 2007). Although there was some variation in the type of gloves used (predominantly nitrile and latex), nitrile gloves were used by the vast majority of workers for tasks with a high risk of solvent exposure (mixing paint, spray painting, degreasing/cleaning). Latex gloves were used, but mostly for low exposure-risk tasks (e.g. sanding, final polishing). As a result, differences in the protection provided by different glove materials (i.e. permeability, breakthrough times, etc.; Tran et al. 2012) are unlikely to have had an impact on the associations observed. A strong positive dose–response trend was also observed with increased skin exposure (Table 4) further highlighting the critical role that dermal exposure may play in developing symptoms of neurotoxicity. Frequent respirator use was also associated with fewer symptoms (Table 2), which is unlikely to be entirely explained by correlation with glove use. In particular, when we combined glove and respirator use (Table 3), we found a stronger protective effect than with glove use alone, thus showing, as previously suggested by others (Jang et al. 1999), that respirators provide additional protection, even when airborne exposures were low (Keer et al. 2016). Of the two respirator types used, air-fed respirators showed the greatest reduction in risk (Table 4), which is consistent with previous studies (Triebig et al. 2009). Frequent changing of absorbent respirator cartridges was associated with a reduction in risk of 50–70%, which is consistent with previous research showing that poorly maintained PPE is associated with increased exposure (Nakayama et al. 2004). Nearly 70% of workers had no defined cartridge replacement schedule or changed them ‘less than once a month’ (Table 2), which given the association with symptoms of neurotoxicity observed in our study is of concern. In particular, as cartridge masks were worn by all spray painters for at least some tasks, this may provide a false sense of protection for painters and shop owners. We found that frequent washing of hands in solvents was associated with an increased risk of symptoms. With almost 70% of workers reporting hand washing in solvents, and 27% reporting they did this frequently (Table 2), this is also of considerable concern. Inconsistent glove use was, as expected, moderately correlated with washing of hands in solvents (r = 0.32), but also with respirator-use (r = 0.41); in turn, respirator-use was moderately correlated with the frequency that respirator cartridges were changed (r = 0.27). This suggests that poor workplace hygiene practices are likely to cluster together within workers and/or workplaces and contribute to an increased risk of neurotoxic effects, as demonstrated by the significant inverse dose–response trend between hygiene score and symptoms of neurotoxicity (see Table S4 in the online supplementary material, available at Annals of Work Exposures and Health online). Interestingly, the use of water-based paints (which in New Zealand at the time of the study were only available for coloured paints and not for primer and top-coat paints) was associated with a greater risk of symptoms, although this failed to reach statistical significance. The reason for this is unclear, although the fact that both primer and top-coat paints and many preparatory products were still solvent-based suggests those who use water-based paints are still at risk of regular solvent exposure. There were several limitations to this study. Neurotoxicity was assessed using self-reported symptoms, which were not confirmed by a clinical assessment, and therefore some misclassification may have occurred. However, EUROQUEST was specifically designed to assess symptoms associated with occupational exposure to neurotoxic agents (Karlson et al. 2000) and is widely used and well validated against clinical criteria (Carter et al. 2002; Rouch et al. 2003; Williamson 2007; Kaukiainen et al. 2009). PPE-use and workplace behaviours were also self-reported, which may result in bias, e.g. from over-reporting of PPE-use through fear of admitting non-compliance. However, any bias, if present, would most likely lead to an underestimation of the true effect. A further limitation is that the effects observed may be attributable to historical exposures, PPE-use, and workplace practices (Dick 2006). However, including duration of employment in multivariate regression models (as a proxy for potential years of exposure) had little effect on the effect measures (see Table S1 in the online supplementary material, available at Annals of Work Exposures and Health online), and in any case, exposure misclassification would likely lead to an underestimation of the true effect. Also, we included 31 office workers (reclassified as spray painters, see above) who may not have been comparable to the other participants in terms of work performed, use of PPE, and workplace practices. However, at the time of the study, 22 reported performing repair work on the shop floor and were therefore at risk of being exposed. From our observations and discussions with workers, it was clear the remaining nine also performed some repair work, especially during busy periods, so were at least occasionally at risk of exposure. Furthermore, almost all (n = 28) provided responses to at least some the questions on PPE use when mixing paint, spray painting, or degreasing/cleaning, indicating they performed these tasks, even if irregularly. Analyses excluding the nine workers who reported not performing work on the shop floor had no effect (see Table S2 in the online supplementary material, available at Annals of Work Exposures and Health online), suggesting results are robust. The ‘hygiene’ metric was constructed and analysed in a way that assumed every unit increase represented an equal increase in exposure, despite being derived from a combination of different PPE-use and workplace practice factors. Nonetheless, highly comparable trends were observed when the metric was constructed using different combinations of these variables and different response weightings within variables (data not shown), suggesting the use of this metric was valid. As discussed by the authors of the EUROQUEST and others, symptoms may be at least partially reversible upon removal from exposure (Dick 2006; Kaukiainen et al. 2009) but memory and concentration symptoms and those associated with mood liability (i.e. those symptoms inversely associated with PPE use and good workplace hygiene in our study) have also been shown to persist after exposure cessation in more severely affected individuals (Kaukiainen et al. 2009). Due to the cross-sectional design, we were unable to assess whether symptoms were reversible in this study. It is feasible that workers who have developed symptoms as a result of higher historical exposures are more likely to avoid current exposures by using PPE more frequently and applying better workplace hygiene, but this would again likely lead to an underestimation of the true effect. Also, it may be that in workshops where PPE is used more consistently and good hygiene practices are promoted, exposure controls are more likely to be in place and efficacious (e.g. newer, higher quality engineering controls which are more regularly maintained) and therefore contribute to at least part of the associations observed. We have extensively assessed a large number of exposure controls, hygiene measures, and risk behaviours and therefore consider this unlikely, but we were unable to collect data on all potential exposure determinants, so it cannot be excluded. For example, variations in the design, quality, and maintenance of spray booths between workshops may have affected exposure levels (and risk of symptoms). However, ‘spot’ measurements in booths across a range of the workshops showed consistently low solvent levels in the breathing zone of workers whilst spray painting (data not shown), suggesting that spray booths used in New Zealand are generally highly effective in controlling airborne exposures. Our findings have considerable relevance for the development of improved intervention strategies in the collision repair industry involving increased use of PPE and promoting good workplace hygiene, at least until higher level controls to minimize/eliminate exposure are developed and more widely implemented. Improvements in spray booth technology and local exhaust ventilation have already resulted in significantly reduced emissions and most likely explain the low airborne exposures observed in our study (reported in Keer et al. 2016). However, the results of the current study indicate that more action may be required particularly focused on reducing dermal exposure. Although the focus of this study has been on neurotoxicity, a reduction in both dermal and airborne solvent exposures will also likely reduce the risk of solvent-related cancer and diisocyanate-induced asthma (Séguin et al. 1987; De Roos and Bhatti 2014; Stocks et al. 2015; Hadkhale et al. 2016). In conclusion, this study has shown that application of relatively basic exposure control measures such as PPE-use and good workplace hygiene is associated with a strongly reduced risk of symptoms of neurotoxicity in the collision repair industry. Programmes to encourage and support the use of these controls in this industry are feasible and would likely result in significantly reduced ill-health. Supplementary Data Supplementary data are available at Annals of Work Exposures and Health online. 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Journal

Annals of Work Exposures and Health (formerly Annals Of Occupational Hygiene)Oxford University Press

Published: Apr 1, 2018

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