TY - JOUR
AU1 - Zhao,, Guanlan
AU2 - Erazo,, Boris
AU3 - Ronda,, Elena
AU4 - Brocal,, Francisco
AU5 - Regidor,, Enrique
AB - Abstract Objectives The objective of this study was to compare mortality rates for the main causes of death and the most frequent sites of cancer in firefighters and all other occupations. Methods Mortality was calculated from a longitudinal study conducted between 2001 and 2011 following a total of 9.5 million men aged 20–64 years old who were in employment in 2001. The age-standardized mortality rate for firefighters was calculated for cancer and other causes of death and compared with that for all other occupations using the mortality rate ratio (MRR). Results No differences were observed between firefighters and all other occupations for overall mortality [MRR = 0.99, 95% confidence interval (CI): 0.91–1.07] or for mortality from cancer in general (MRR = 1.00, 95% CI: 0.89–1.12). No significant differences were observed in mortality by site of cancer, except for mortality from cancer of larynx (MRR = 1.77, 95% CI: 1.01–3.09) and hypopharynx (MRR = 2.96, 95% CI: 1.31–6.69), which presented a higher magnitude in firefighters. Neither was any significant differences observed between the two groups in mortality due to cardiovascular, respiratory, or digestive diseases or in mortality due to external causes. Conclusions Exposure to carcinogens combined with a possible failure to use respiratory protection when fighting fires may be responsible for excess mortality from laryngeal and hypopharyngeal cancer in firefighters. In the future, more research is needed on the health of firefighters and strengthening preventive policies for these workers. cancer, firefighters, mortality, Spain Introduction In the performance of their occupational functions, firefighters engage in a wide range of activities that expose them to multiple risks with potentially harmful health effects. When fighting fires, they are exposed to intense physical effort, heat stress, emotional trauma, and the smoke generated by the fire, which contains particulate matter and a complex mixture of toxic chemical agents (Lubin et al., 2000; Glass et al., 2016). Also firefighters’ personal protective equipment and other work equipment can be a source of occupational hazardous substances exposures (Jalilian et al., 2019), like accumulation of plasticizers absorbed by the personal protective clothing during the exposure (Alexander and Baxter, 2014; Alexander and Baxter, 2016), metals (Easter et al., 2016), and polycyclic aromatic hydrocarbons (Fabian et al., 2014). In addition, firefighters may experience alterations in circadian rhythm due to shift work (Ahn and Jeong, 2015). Nevertheless, several studies have shown a lower risk of overall mortality in this group (Ahn and Jeong, 2015; Amadeo et al., 2015; Glass et al., 2016) and lower mortality for non-malignant cardiovascular (Ahn and Jeong, 2015; Amadeo et al., 2015; Glass et al., 2016) and respiratory diseases (Daniels et al., 2014) compared with the general population, a difference that has been attributed to the selection bias known as the healthy worker effect. Firefighters exhibit this phenomenon on recruitment, because candidates who present or are predisposed to pathology are not recruited, and throughout their working lives because they undertake rigorous physical training programmes and are subject to regular medical check-ups. In an effort to ensure and improve the health and wellness of firefighters, two major fire service organizations, the International Association of Fire Fighters and the International Association of Fire Chiefs, worked jointly to develop a comprehensive wellness-fitness program designed specifically to address the hazards faced by firefighters (Winter et al., 2010). One Swedish study has reported by the risk of this profession and it is currently mandatory that firefighters attend regular medical checks to assess their eligibility (Bigert et al., 2020). In Indiana of USA (Muegge et al., 2018), the largest fire department in the state has implemented an occupational health program a few years ago that Firefighter have been required to pass a pre-employment physical agility test for the past 15 years, a mandatory physical fitness test annually for approximately 20 years in this department. A number of cohort studies were conducted among firefighters in USA (Baris et al., 2001; Ma et al., 2005; Daniels et al., 2014; Tsai et al., 2015; Muegge et al., 2018), Canada (Aronson et al., 1994), Australia (Glass et al., 2016), and Korea (Ahn and Jeong, 2015). In Europe, the overall and cancer mortality have been studied in French (Amadeo et al., 2015) and the cancer incidence has been studied in a large cohort (16 422 firefighters) from five Nordic countries (Pukkala et al., 2014). The mixed study of cancer incidence and mortality has been analysed in Scotland (Ide, 2014). LeMasters’ research showed the excess mortality in some cancer sites, such as multiple myeloma, non-Hodgkin lymphoma, prostate, and testicle among firefighters (LeMasters et al., 2006). Recently, another meta-analysis (Jalilian et al., 2019) reported an increased risk for death from rectal cancer as well as non-Hodgkin lymphoma. There is evidence suggesting firefighters may be at elevated risk of cancer of kidney (Daniels et al., 2014; Ide, 2014; Tsai et al., 2015; Glass et al., 2016; Muegge et al., 2018), brain (Haas et al., 2003; LeMasters et al., 2006; Daniels et al., 2014; Tsai et al., 2015; Muegge et al., 2018), and leukaemia (Baris et al., 2001; LeMasters et al., 2006; Tsai et al., 2015; Muegge et al., 2018). In Spain, the pattern of mortality in firefighters is unknown. The objectives of the present study were to examine the main causes of mortality in firefighters between 1 November 2001 and 31 December 2011. Methods Study design and population The data source for the mortality study was the national follow-up study of the Spanish population in the 2001 census. All persons residing in Spain on 1 November 2001 were included in the study. The follow-up was conducted by the Spanish National Statistics Institute by linking the information contained in the census for each subject with the information from the population registry and the mortality registry. Each person was followed for up for 10 years and 2 months to determine if the person had died or not. The deceased were censored on the date of death and the people who emigrated were censored on the date of emigration. 1% of census participants were censored because they had moved out of Spain. The National Statistics Institute provided the investigators the final data file after eliminating personal identifying information to maintain confidentiality. The final cohort is composed of 40 148 305 individuals, after excluding the 1.7% of those who could not be found in the population registry or mortality registry. The present study includes 9 579 759 men who, on the date the census was carried out, were employed on the census date and were between 20 and 64 years of age. The number of firefighters in this study was 27 365. Study variables A person was considered to be employed if he had been working in the week before the census date. Employed subjects were asked what their occupation was. Occupations were coded according to the 1994 Spanish Classification of Occupations (CNO-94). For the present study, we grouped occupations into two categories: firefighters, corresponding to the code CNO-5230, and non-firefighters (all other occupations). The underlying cause of death was coded in accordance with the International Classification of Diseases and Causes of Death, 10th revision. We analysed the total deaths and the deaths from cancer sites and from all other causes. Statistical analysis For total deaths and each cause of death, we calculated the age-standardized mortality rate (aSMR) per 100 000 person-years of follow-up in firefighter and all other occupations. The European standard population was used for standardization. Subsequently, we calculated the mortality rate ratio (MRR) for the firefighter with respect to all other occupations. The confidence intervals (CIs) of the MRR were calculated using the variance estimated by the Mantel–Haenszel method for person-time data. The study database did not include individual identifiers, so approval by the Ethics Committee was not required. Results During the follow-up, a total of 266 562 person-years were analysed in the population studied. Table 1 shows the distribution of deaths from all causes, age groups and person-years of follow-up for the firefighter cohort. Age groups above 50 years old accounted for more than half of total deaths observed in the population studied. Table 1. Distribution of deaths by age group and person-years of follow-up for the firefighter cohort and all other occupations in Spain between 2001 and 2011. Age group . Firefighters . All other occupations . . Number of death . Person-years . Number of death . Person-years . 20–24 3 8087.50 5146 871 081.50 25–29 21 27 995.42 8352 13 521 156.33 30–34 34 45 197.58 12 552 14 224 313.83 35–39 61 53 972.08 19 966 13 941 896.75 40–44 61 49 029.42 30 309 12 760 777.67 45–49 98 31 859.50 41 066 10 751 751.75 50–54 147 21 973.00 53 331 9 367 251.75 55–59 138 18 024.75 56 803 7 008 605.42 60–64 146 10 422.92 41 523 3 466 362.42 Total 709 266 562.17 269 048 93 752 897.42 Age group . Firefighters . All other occupations . . Number of death . Person-years . Number of death . Person-years . 20–24 3 8087.50 5146 871 081.50 25–29 21 27 995.42 8352 13 521 156.33 30–34 34 45 197.58 12 552 14 224 313.83 35–39 61 53 972.08 19 966 13 941 896.75 40–44 61 49 029.42 30 309 12 760 777.67 45–49 98 31 859.50 41 066 10 751 751.75 50–54 147 21 973.00 53 331 9 367 251.75 55–59 138 18 024.75 56 803 7 008 605.42 60–64 146 10 422.92 41 523 3 466 362.42 Total 709 266 562.17 269 048 93 752 897.42 Open in new tab Table 1. Distribution of deaths by age group and person-years of follow-up for the firefighter cohort and all other occupations in Spain between 2001 and 2011. Age group . Firefighters . All other occupations . . Number of death . Person-years . Number of death . Person-years . 20–24 3 8087.50 5146 871 081.50 25–29 21 27 995.42 8352 13 521 156.33 30–34 34 45 197.58 12 552 14 224 313.83 35–39 61 53 972.08 19 966 13 941 896.75 40–44 61 49 029.42 30 309 12 760 777.67 45–49 98 31 859.50 41 066 10 751 751.75 50–54 147 21 973.00 53 331 9 367 251.75 55–59 138 18 024.75 56 803 7 008 605.42 60–64 146 10 422.92 41 523 3 466 362.42 Total 709 266 562.17 269 048 93 752 897.42 Age group . Firefighters . All other occupations . . Number of death . Person-years . Number of death . Person-years . 20–24 3 8087.50 5146 871 081.50 25–29 21 27 995.42 8352 13 521 156.33 30–34 34 45 197.58 12 552 14 224 313.83 35–39 61 53 972.08 19 966 13 941 896.75 40–44 61 49 029.42 30 309 12 760 777.67 45–49 98 31 859.50 41 066 10 751 751.75 50–54 147 21 973.00 53 331 9 367 251.75 55–59 138 18 024.75 56 803 7 008 605.42 60–64 146 10 422.92 41 523 3 466 362.42 Total 709 266 562.17 269 048 93 752 897.42 Open in new tab The firefighter cohort presented a total of 709 deaths. The aSMR for overall mortality among firefighters was 356.8/100 000 person-years, and was similar to that for all other occupations (360.7/100 000), with an MRR of 0.99 (95% CI: 0.91–1.07). Cancer accounted for approximately half of the causes of death, with an aSMR of 117.4/100 000 person-years in firefighters, although the risk of mortality from cancer was similar to that of all other occupations, with an MRR of 1.00 (95% CI: 0.89–1.12) (Table 2). In the rest of the main causes of death, the differences in mortality in firefighters with respect to the rest of the workers were not significant either. Table 2. aSMR per 100 000 person-years and MRR for the main causes of deaths in the firefighter cohort and all other occupations in Spain between 2001 and 2011. Causes of death . (ICD-10) . Firefighters . All other occupations . MRR . . . Obs. . aSMR . Obs. . aSMR . MRR . 95% CI . All causes (A00–Y98) 709 356.78 269 048 360.67 0.99 0.91–1.07 Infectious diseases (A00–A99) 3 1.70 1951 2.61 0.65 0.20–2.13 All cancers (C00–C97) 335 177.37 126 445 177.32 1.00 0.89–1.12 Endocrine diseases (E00–E90) 13 8.08 3933 5.62 1.44 0.81–2.54 Diseases of the nervous system (G00–G99) 10 5.94 4145 5.80 1.02 0.54–1.96 Cardiovascular diseases (I00–I99) 127 65.07 53 566 74.08 0.88 0.73–1.06 Diseases of the respiratory system (J00–J99) 31 19.11 10 586 15.33 1.25 0.86–1.81 Diseases of the digestive system (K00–K99) 38 19.25 15 814 20.18 0.95 0.68–1.34 Urogenital diseases (N00–N99) 1 0.55 1404 2.12 0.27 0.01–1.86 External causes (V00–Y99) 101 38.15 33 637 36.72 1.04 0.83–1.29 Causes of death . (ICD-10) . Firefighters . All other occupations . MRR . . . Obs. . aSMR . Obs. . aSMR . MRR . 95% CI . All causes (A00–Y98) 709 356.78 269 048 360.67 0.99 0.91–1.07 Infectious diseases (A00–A99) 3 1.70 1951 2.61 0.65 0.20–2.13 All cancers (C00–C97) 335 177.37 126 445 177.32 1.00 0.89–1.12 Endocrine diseases (E00–E90) 13 8.08 3933 5.62 1.44 0.81–2.54 Diseases of the nervous system (G00–G99) 10 5.94 4145 5.80 1.02 0.54–1.96 Cardiovascular diseases (I00–I99) 127 65.07 53 566 74.08 0.88 0.73–1.06 Diseases of the respiratory system (J00–J99) 31 19.11 10 586 15.33 1.25 0.86–1.81 Diseases of the digestive system (K00–K99) 38 19.25 15 814 20.18 0.95 0.68–1.34 Urogenital diseases (N00–N99) 1 0.55 1404 2.12 0.27 0.01–1.86 External causes (V00–Y99) 101 38.15 33 637 36.72 1.04 0.83–1.29 ICD-10, International Classification of Diseases, 10th revision; Obs., observed. MRR: calculated from aSMR firefighters/aSMR all other occupations. Open in new tab Table 2. aSMR per 100 000 person-years and MRR for the main causes of deaths in the firefighter cohort and all other occupations in Spain between 2001 and 2011. Causes of death . (ICD-10) . Firefighters . All other occupations . MRR . . . Obs. . aSMR . Obs. . aSMR . MRR . 95% CI . All causes (A00–Y98) 709 356.78 269 048 360.67 0.99 0.91–1.07 Infectious diseases (A00–A99) 3 1.70 1951 2.61 0.65 0.20–2.13 All cancers (C00–C97) 335 177.37 126 445 177.32 1.00 0.89–1.12 Endocrine diseases (E00–E90) 13 8.08 3933 5.62 1.44 0.81–2.54 Diseases of the nervous system (G00–G99) 10 5.94 4145 5.80 1.02 0.54–1.96 Cardiovascular diseases (I00–I99) 127 65.07 53 566 74.08 0.88 0.73–1.06 Diseases of the respiratory system (J00–J99) 31 19.11 10 586 15.33 1.25 0.86–1.81 Diseases of the digestive system (K00–K99) 38 19.25 15 814 20.18 0.95 0.68–1.34 Urogenital diseases (N00–N99) 1 0.55 1404 2.12 0.27 0.01–1.86 External causes (V00–Y99) 101 38.15 33 637 36.72 1.04 0.83–1.29 Causes of death . (ICD-10) . Firefighters . All other occupations . MRR . . . Obs. . aSMR . Obs. . aSMR . MRR . 95% CI . All causes (A00–Y98) 709 356.78 269 048 360.67 0.99 0.91–1.07 Infectious diseases (A00–A99) 3 1.70 1951 2.61 0.65 0.20–2.13 All cancers (C00–C97) 335 177.37 126 445 177.32 1.00 0.89–1.12 Endocrine diseases (E00–E90) 13 8.08 3933 5.62 1.44 0.81–2.54 Diseases of the nervous system (G00–G99) 10 5.94 4145 5.80 1.02 0.54–1.96 Cardiovascular diseases (I00–I99) 127 65.07 53 566 74.08 0.88 0.73–1.06 Diseases of the respiratory system (J00–J99) 31 19.11 10 586 15.33 1.25 0.86–1.81 Diseases of the digestive system (K00–K99) 38 19.25 15 814 20.18 0.95 0.68–1.34 Urogenital diseases (N00–N99) 1 0.55 1404 2.12 0.27 0.01–1.86 External causes (V00–Y99) 101 38.15 33 637 36.72 1.04 0.83–1.29 ICD-10, International Classification of Diseases, 10th revision; Obs., observed. MRR: calculated from aSMR firefighters/aSMR all other occupations. Open in new tab Table 3 shows the number of deaths by site of cancer in the two follow-up cohorts, and the aSMR and MRR by site of cancer in the firefighter cohort compared with all other occupations. The mortality rate for cancer of hypopharynx presented an aSMR of 2.9/100 000 person-years and a higher risk of mortality, with an MRR of 2.96 (95% CI: 1.31–6.69). A similar result was observed for laryngeal cancer, with an aSMR of 7.9/100 000 person-years and an MRR of 1.77 (95% CI: 1.01–3.09) in the firefighter cohort compared with all other occupations (Table 3). For the remaining sites of cancer, no statistically significant differences were detected between firefighters and all other occupations. Nevertheless, the highest aSMR for site of cancer was for lung cancer, at 55.3/100 000 person-years in the firefighter cohort. Table 3. aSMR per 100 000 person-years and MRR for sites of cancer in the firefighter cohort and all other occupations in Spain between 2001 and 2011. Main sites of cancer . (ICD-10) . Firefighters . All other occupations . MRR . . . Obs. . aSMR . Obs. . aSMR . MRR . 95% CI . All cancers (C00–C97) 335 177.37 126 445 177.32 1.00 0.89–1.12 Mouth and pharynx (C00–C14) 18 8.58 5015 6.40 1.34 0.81–2.21 Hypopharynx (C12 + C13) 6 2.9 774 1.0 2.96 1.31–6.69 Oesophagus (C15) 13 6.57 4427 5.94 1.11 0.64–1.92 Stomach (C16) 26 13.73 7443 10.40 1.32 0.88–1.98 Colon (C18) 17 8.78 9778 14.25 0.62 0.37–1.02 Rectum (C19–C20) 10 5.65 3648 5.25 1.08 0.57–2.04 Liver (C22) 14 8.44 5937 8.34 1.01 0.59–1.74 Pancreas (C25) 8 4.29 7101 10.00 0.43 0.21–0.88 Larynx (C32) 14 7.88 3291 4.45 1.77 1.01–3.09 Lung (C33–C34) 104 55.33 42 056 59.09 0.94 0.77–1.15 Bone (C40–C41) 1 0.53 396 0.48 1.11 0.16–7.92 Melanoma (C43) 3 1.16 1456 1.83 0.63 0.19–2.10 Mesothelioma (C45) 1 0.55 635 0.89 0.62 0.09–4.42 Breast (C50) 1 0.55 128 0.18 3.04 0.42–21.78 Prostate (C61) 10 7.26 3408 5.78 1.26 0.67–2.36 Kidney (C64) 8 4.33 2710 3.68 1.18 0.57–2.44 Renal pelvis (C65) 1 0.55 51 0.07 7.42 1.02–53.82 Bladder (C67) 10 4.52 4800 7.33 0.62 0.32–1.17 CNS (C70–C72) 17 7.10 5138 6.63 1.07 0.63–1.81 Thyroid (C73) 2 0.81 253 0.35 2.34 0.53–10.29 Lymphomas (C81–C83) 11 5.51 3246 4.26 1.29 0.69–2.34 Hodgkin (C81) 2 0.60 365 0.43 1.41 0.34–5.85 Leukaemia (C91–C95) 7 3.69 2935 4.10 0.90 0.40–2.01 All other cancers (Rest of C00–C97) 31 16.96 11 454 16.42 1.02 0.72–1.53 Main sites of cancer . (ICD-10) . Firefighters . All other occupations . MRR . . . Obs. . aSMR . Obs. . aSMR . MRR . 95% CI . All cancers (C00–C97) 335 177.37 126 445 177.32 1.00 0.89–1.12 Mouth and pharynx (C00–C14) 18 8.58 5015 6.40 1.34 0.81–2.21 Hypopharynx (C12 + C13) 6 2.9 774 1.0 2.96 1.31–6.69 Oesophagus (C15) 13 6.57 4427 5.94 1.11 0.64–1.92 Stomach (C16) 26 13.73 7443 10.40 1.32 0.88–1.98 Colon (C18) 17 8.78 9778 14.25 0.62 0.37–1.02 Rectum (C19–C20) 10 5.65 3648 5.25 1.08 0.57–2.04 Liver (C22) 14 8.44 5937 8.34 1.01 0.59–1.74 Pancreas (C25) 8 4.29 7101 10.00 0.43 0.21–0.88 Larynx (C32) 14 7.88 3291 4.45 1.77 1.01–3.09 Lung (C33–C34) 104 55.33 42 056 59.09 0.94 0.77–1.15 Bone (C40–C41) 1 0.53 396 0.48 1.11 0.16–7.92 Melanoma (C43) 3 1.16 1456 1.83 0.63 0.19–2.10 Mesothelioma (C45) 1 0.55 635 0.89 0.62 0.09–4.42 Breast (C50) 1 0.55 128 0.18 3.04 0.42–21.78 Prostate (C61) 10 7.26 3408 5.78 1.26 0.67–2.36 Kidney (C64) 8 4.33 2710 3.68 1.18 0.57–2.44 Renal pelvis (C65) 1 0.55 51 0.07 7.42 1.02–53.82 Bladder (C67) 10 4.52 4800 7.33 0.62 0.32–1.17 CNS (C70–C72) 17 7.10 5138 6.63 1.07 0.63–1.81 Thyroid (C73) 2 0.81 253 0.35 2.34 0.53–10.29 Lymphomas (C81–C83) 11 5.51 3246 4.26 1.29 0.69–2.34 Hodgkin (C81) 2 0.60 365 0.43 1.41 0.34–5.85 Leukaemia (C91–C95) 7 3.69 2935 4.10 0.90 0.40–2.01 All other cancers (Rest of C00–C97) 31 16.96 11 454 16.42 1.02 0.72–1.53 ICD-10, International Classification of Diseases, 10th revision; Obs., observed; CNS, central nervous system. MRR: calculated from aSMR firefighters/aSMR all other occupations. Open in new tab Table 3. aSMR per 100 000 person-years and MRR for sites of cancer in the firefighter cohort and all other occupations in Spain between 2001 and 2011. Main sites of cancer . (ICD-10) . Firefighters . All other occupations . MRR . . . Obs. . aSMR . Obs. . aSMR . MRR . 95% CI . All cancers (C00–C97) 335 177.37 126 445 177.32 1.00 0.89–1.12 Mouth and pharynx (C00–C14) 18 8.58 5015 6.40 1.34 0.81–2.21 Hypopharynx (C12 + C13) 6 2.9 774 1.0 2.96 1.31–6.69 Oesophagus (C15) 13 6.57 4427 5.94 1.11 0.64–1.92 Stomach (C16) 26 13.73 7443 10.40 1.32 0.88–1.98 Colon (C18) 17 8.78 9778 14.25 0.62 0.37–1.02 Rectum (C19–C20) 10 5.65 3648 5.25 1.08 0.57–2.04 Liver (C22) 14 8.44 5937 8.34 1.01 0.59–1.74 Pancreas (C25) 8 4.29 7101 10.00 0.43 0.21–0.88 Larynx (C32) 14 7.88 3291 4.45 1.77 1.01–3.09 Lung (C33–C34) 104 55.33 42 056 59.09 0.94 0.77–1.15 Bone (C40–C41) 1 0.53 396 0.48 1.11 0.16–7.92 Melanoma (C43) 3 1.16 1456 1.83 0.63 0.19–2.10 Mesothelioma (C45) 1 0.55 635 0.89 0.62 0.09–4.42 Breast (C50) 1 0.55 128 0.18 3.04 0.42–21.78 Prostate (C61) 10 7.26 3408 5.78 1.26 0.67–2.36 Kidney (C64) 8 4.33 2710 3.68 1.18 0.57–2.44 Renal pelvis (C65) 1 0.55 51 0.07 7.42 1.02–53.82 Bladder (C67) 10 4.52 4800 7.33 0.62 0.32–1.17 CNS (C70–C72) 17 7.10 5138 6.63 1.07 0.63–1.81 Thyroid (C73) 2 0.81 253 0.35 2.34 0.53–10.29 Lymphomas (C81–C83) 11 5.51 3246 4.26 1.29 0.69–2.34 Hodgkin (C81) 2 0.60 365 0.43 1.41 0.34–5.85 Leukaemia (C91–C95) 7 3.69 2935 4.10 0.90 0.40–2.01 All other cancers (Rest of C00–C97) 31 16.96 11 454 16.42 1.02 0.72–1.53 Main sites of cancer . (ICD-10) . Firefighters . All other occupations . MRR . . . Obs. . aSMR . Obs. . aSMR . MRR . 95% CI . All cancers (C00–C97) 335 177.37 126 445 177.32 1.00 0.89–1.12 Mouth and pharynx (C00–C14) 18 8.58 5015 6.40 1.34 0.81–2.21 Hypopharynx (C12 + C13) 6 2.9 774 1.0 2.96 1.31–6.69 Oesophagus (C15) 13 6.57 4427 5.94 1.11 0.64–1.92 Stomach (C16) 26 13.73 7443 10.40 1.32 0.88–1.98 Colon (C18) 17 8.78 9778 14.25 0.62 0.37–1.02 Rectum (C19–C20) 10 5.65 3648 5.25 1.08 0.57–2.04 Liver (C22) 14 8.44 5937 8.34 1.01 0.59–1.74 Pancreas (C25) 8 4.29 7101 10.00 0.43 0.21–0.88 Larynx (C32) 14 7.88 3291 4.45 1.77 1.01–3.09 Lung (C33–C34) 104 55.33 42 056 59.09 0.94 0.77–1.15 Bone (C40–C41) 1 0.53 396 0.48 1.11 0.16–7.92 Melanoma (C43) 3 1.16 1456 1.83 0.63 0.19–2.10 Mesothelioma (C45) 1 0.55 635 0.89 0.62 0.09–4.42 Breast (C50) 1 0.55 128 0.18 3.04 0.42–21.78 Prostate (C61) 10 7.26 3408 5.78 1.26 0.67–2.36 Kidney (C64) 8 4.33 2710 3.68 1.18 0.57–2.44 Renal pelvis (C65) 1 0.55 51 0.07 7.42 1.02–53.82 Bladder (C67) 10 4.52 4800 7.33 0.62 0.32–1.17 CNS (C70–C72) 17 7.10 5138 6.63 1.07 0.63–1.81 Thyroid (C73) 2 0.81 253 0.35 2.34 0.53–10.29 Lymphomas (C81–C83) 11 5.51 3246 4.26 1.29 0.69–2.34 Hodgkin (C81) 2 0.60 365 0.43 1.41 0.34–5.85 Leukaemia (C91–C95) 7 3.69 2935 4.10 0.90 0.40–2.01 All other cancers (Rest of C00–C97) 31 16.96 11 454 16.42 1.02 0.72–1.53 ICD-10, International Classification of Diseases, 10th revision; Obs., observed; CNS, central nervous system. MRR: calculated from aSMR firefighters/aSMR all other occupations. Open in new tab Discussion In our study, we did not observe any differences in mortality due to all causes or due to specific causes between firefighters employed in Spain and workers in all other occupations. However, we did detect an excess risk of mortality from laryngeal and hypopharyngeal cancer in firefighters. The population selected in our study to compare the risk of mortality was workers in all other occupations, and we found no significant differences in risk of overall mortality, in agreement with other studies that have also reported a lower or equal risk of mortality in this group (Haas et al., 2003; Ma et al., 2005; LeMasters et al., 2006; Daniels et al., 2014; Ahn and Jeong, 2015; Amadeo et al., 2015; Glass et al., 2016). Of all causes of death, cancer presented the highest standardized mortality rate in the firefighter cohort; however, this rate did not present a difference with that for all other occupations, consistent with studies by Baris et al. (2001) and Glass et al. (2016). The excess risk of mortality from laryngeal and hypopharyngeal cancer was notable. No studies have reported a risk of mortality from cancer located in the larynx, and much less in the hypopharynx, in this group. However, other studies examining cancers located in the mouth and pharynx in general in firefighters (Baris et al., 2001; Daniels et al., 2014) have reported an increased risk of mortality from this cause, which includes hypopharyngeal and laryngeal cancer. All fires generate a large quantity of toxic products as a result of combustion, including substances identified by the International Agency for Research on Cancer (IARC) as known or potential carcinogens, such as formaldehyde, polycyclic aromatic hydrocarbons, and asbestos. There is some evidence to suggest that exposure to these agents could be associated with an increased risk of developing hypopharyngeal cancer (Berrino et al., 2003; Puñal-Riobóo et al., 2010; Langevin et al., 2013; Wagner et al., 2015). Among the potential carcinogens present in fires, peak exposure to benzene, 1.3-butadiene, and formaldehyde can be extremely high compared with other carcinogens. Of these three pollutants, formaldehyde is the only one associated with pharyngeal cancer. The risk of exposure to formaldehyde in the combustion processes typical of urban fires may be considered in general and qualitative terms as high risk, expressed as a combination of likelihood and consequences. IARC identifies three main sources of exposure above background—during production of formaldehyde solutions, during the manufacture and use of products containing formaldehyde (particularly formaldehyde-containing resins), and through the burning of products containing formaldehyde (IARC Working Group on the Evaluation of Carcinogenic Risks to Humans, 2006). Formaldehyde can be released into the environment through incomplete combustion of various organic materials as well as some inorganic materials such as plastics and polymers. It is used in many raw material manufacturing processes and is a frequent component in building materials such as adhesives, sealants, coating products, fillers, putties, and plasters. Airborne formaldehyde concentrations measured while extinguishing fires range between 0.01 and 15 ppm. These data indicate that urban fires generate a much wider range of formaldehyde concentrations than wildfires, probably as a result of the combustion process and the widespread uses of formaldehyde described above. The values in this range are especially alarming when compared with short-term and ceiling exposure limits for formaldehyde. Also, this study has showed a higher risk of laryngeal cancer in firefighters. Several studies have suggested an association between laryngeal cancer and occupational exposure to agents such as diesel/gasoline fumes (Ahrens et al., 1991) and formaldehyde (Berrino et al., 2003). Respiratory protection using positive pressure self-contained breathing apparatus has been developed to protect firefighters from airborne toxic chemicals and carcinogens released during fires, and have been found suitable for the level of contaminants detected. However, there are occasions when firefighters might not use respiratory protection at all or only during some of the stages of extinguishing a fire (Austin et al., 2001; Grant, 2010) because it is not possible to visually assess levels of contamination in the smoke generated (Grant, 2010). A recent Danish studies show that firefighters did not use the effective respiratory devices regularly during all phases of firefighting (Pedersen et al., 2019) and one Australia study (Driscoll et al., 2016) also shows about 40% of firefighters reported always or usually using Respiratory Personal Equipment (RPE) where appropriate while working, that means more than half were commonly not protected for their RPE. This implies that a very short period of time without respiratory protection could pose a high risk of exposure to carcinogens such as formaldehyde, due to the high likelihood of exceeding the ceiling limit or the Short-Term Exposure Limit (STEL) exposure limit. For example, assuming a mean airborne concentration of formaldehyde in a fire of 10 ppm, the failure to use respiratory protection for 55 s or more would lead to exposure in excess of the Spanish STEL exposure limit of 0.6 ppm (Limón et al., 2013). It has also been demonstrated that the personal protective equipment worn by firefighters becomes impregnated with the volatile organic compounds generated during fires. These subsequently vaporize from protective clothing and may be inhaled via the respiratory tract or ingested (Alexander and Baxter, 2016; Fent et al., 2017). This can increase the risk of exposure to carcinogens such as formaldehyde, due not only to its low ceiling limit associated with the respiratory tract, but also to its toxicity when absorbed through the skin or ingested. For example it has been reported that exposure to high concentrations of insoluble chemical contaminants in solid state, such as silica in the metal, glass, ceramics, and stone industries, is associated with an increased incidence of stomach cancer, even though they have been inhaled via the respiratory tract. This finding might be related to particles swallowed after clearance from the airways (Moshammer and Neuberger, 2004). Alcohol and tobacco consumption are also associated with an increased risk of laryngeal and hypopharyngeal cancer (Jayalekshmi et al., 2013). However, tobacco consumption among firefighters is lower than among the general population (Haddock et al., 2011). Nonetheless, we found no significant differences between firefighters and all other occupations in the incidence of respiratory diseases that could be related to tobacco consumption. As regards alcohol consumption, some studies have reported that firefighters may present a higher consumption of alcohol (Haddock et al., 2012; Haddock et al., 2015); however, the prevalence in Spain is lower in firefighters than in the general population and we found no differences between the two cohorts for cancer of the oesophagus, stomach, or liver, all associated with this risk factor. A number of limitations should be taken into account when interpreting these results. First, this study is that the subjects were classified according to occupancy at the baseline stage. A firefighter has been able to leave that occupation throughout the follow-up period because he was too ill to work in a heavy work, and this can contribute to a reverse causality bias. On the other hand, the number of deaths in firefighters during the follow-up was small; we could not differentiate the analyses in two periods in order to assess the extent to which such reverse causality bias has influenced our findings. A greater number of years of follow-up would have increased the power of the study. Consistent with previous firefighters’ mortality research (Amadeo et al., 2015; Tsai et al., 2015; Muegge et al., 2018), another major limitation of this study was lack of lifestyle information like smoking, alcohol abuse, obesity, length of employment, actual job duties, and occupational exposures of workplace. One study (Haddock et al., 2011) suggested that firefighters working in the central region of the USA were less likely to smoke compared with the general population, but have high rates of excessive consumption of alcohol on their off-duty days (Haddock et al., 2012). Murphy and Volinn also concluded that in work condition of firefighting (e.g. time pressure, accurate decision-making, potential injury, or death) was significantly associated with negative health outcomes including alcohol abuse (Murphy and Volinn, 1999). In addition to the possible contact of occupational exposure like formaldehyde, cancer of hypopharyngeal and laryngeal are also commonly associated with an excessive tobacco use or alcohol abuse. To our knowledge, no data are available on the diet, use of tobacco and consumption of alcohol of firefighters in Spain, and it is not possible to examine whether their risk behaviours could be in favour of a potential excess risk of cancer. Other limitation was that no specific data were available on the tasks performed by firefighters in their institutions, such as the number, type, or duration of incidents attended, and thus it was not possible to link mortality to specific activities or exposure levels. Studies suggested that training fires may constitute a major firefighter’s occupational exposures to smoke (Fent et al., 2019). Another limitation of the present study was that we only analysed mortality and not incidence. This can be important in the case of cancers with early diagnosis and a high survival rate, such as prostate, testicular, and even colorectal cancer, with survival rates of 76, 95, and 50%, respectively (Chirlaque et al., 2010). Consequently, we may have lost cancers associated with occupation or economic activity because they are controlled, cured, or under-reported. Finally, to eliminate the health worker effect in occupational studies, the best way is to avoid using general population as a reference group (Li and Sung, 1999). The healthy worker effect has two components: healthy hire effect (those who have better health, meaning that the healthiest workers are the most likely to enter the workforce) (Pearce et al., 2007; Johnson et al., 2019) and healthy worker survivor effect (those who don’t have great motivation to work and change jobs frequently or retire early due to different reasons including health problems) (Li and Sung, 1999; Buckley et al., 2015). Both of these effects will be strong on employees in certain professions, such as firefighters, because firefighters are highly selected and firefighting is physically demanding job. It is possible that the healthy worker effect has not been completely eliminated in our study and firefighters should be compared with an equally selected comparison group. Further research should compare to other formaldehyde-exposed workers (including woodworkers, labtechs, funeral home/undertakers/morgue employees, dentists, hairdressers, etc.) to take into account this exposure. Conclusion We found no differences in the risk of overall mortality, main causes of death or cancer, despite selecting a population other than the general population, namely workers in all other occupations. However, we did observe an increased risk of mortality from laryngeal and hypopharyngeal cancer in firefighters, which could be due to exposure to carcinogens combined with a possible failure to use respiratory protection when fighting fires or to the lack of effective maintenance and cleaning protocols after attending a fire. More research is required to further elucidate these risk factors and also to consider the characteristics of Spanish buildings (structure and content) and their differences with respect to other countries as regards the presence of carcinogens during the combustion processes, such as formaldehyde. Funding None declared. Authors’ Contributions Elena Ronda and Enrique Regidor originated and designed the study and coordinated the writing of the article. Enrique Regidor contributed to obtaining the data. Guanlan Zhao and Boris Erazo contributed to the analysis of the data and to the drafting of the paper. Elena Ronda and Guanlan Zhao contributed to the interpretation of the results and to the drafting of the paper. Francisco Brocal contributed to the design of the study and to the drafting of the paper. All authors contributed to the final version of the article. Conflicts of Interest The authors declare that there are no conflicts of interest. References Ahn YS , Jeong KS. 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TI - Mortality Among Firefighters in Spain: 10 Years of Follow-up
JF - Annals of Work Exposures and Health (formerly Annals Of Occupational Hygiene)
DO - 10.1093/annweh/wxaa036
DA - 2020-07-01
UR - https://www.deepdyve.com/lp/oxford-university-press/mortality-among-firefighters-in-spain-10-years-of-follow-up-s6J0fQh4zz
SP - 614
EP - 621
VL - 64
IS - 6
DP - DeepDyve
ER -