Occupational and Environmental Medicine

Martin, A M

doi: 10.1136/oem.36.1.1pmid: 444436

The relationship between incident sound level and acoustic attenuation for four types of earplug and four types of earmuff have been investigated using freshly prepared and instrumented cadaver ears. Pure tones and 1/3-octave bands of random noise in the frequency range 125-8000 Hz were employed as steady-state stimuli with sound pressure levels between 75 and 125 dB. Impulses with peak sound levels in the range 135-175 dB(P) were also presented. For the steady-state signals employed, the eight hearing protectors have been shown to have constant attenuation characteristics over the range of incident sound levels investigated. This was also the case for the six conventional protectors (with intentionally linear characteristics) for the impulse stimuli. The two intentionally amplitude-sensitive protectors provided attenuation which increased with incident sound level for impulse noises. Comparison of the protector attenuation-frequency characteristics determined for steady-state sounds shows good agreement with those obtained from subjective (threshold shift) national standard measurement procedures. It may be concluded, therefore, that the six conventional hearing protectors studied here have attenuation characteristics that are equal for incident sound levels at about 40 and 75 dB, and that they are constant for levels between 75 and 175 dB. Consequently, the results of national standard threshold-shift procedures, although measured at low sound levels, may be applied with confidence to occupations where hazardous high-level noises are present.

Cochrane, A L; Haley, T J; Moore, F; Hole, D

doi: 10.1136/oem.36.1.15pmid: 444437

A more detailed analysis of material from the 20-year follow-up of men in the Rhondda Fach confirms the similarity between the Standardised Mortality Ratios (SMRs) of miners and exminers with radiological categories 0, 1, 2, 3 and A (120.3, 116.5, 119.0, 115.7, and 120.1 respectively) as well as the difference between these SMRs and that of the non-moners (98.7). The specific death rates show a raised SMR for bronchitis and other respiratory diseases excluding pneumoconiosis for all categories including category 0, but little difference between those for category 0 and those for simple pneumoconiosis. The SMRs for ischaemic heart disease and other circulatory diseases for categories A, B and C combined are lower than those for simple pneumoconiosis and category 0 (84.2 and 85.0, compared with 109.8 and 121.8 for simple pneumoconiosis, and 117.5 and 114.6 for category 0). Fortunately the SMR for leukaemia is low. A comparison between the survival rates of men aged 55-64 in Leigh, Lancashire and those in the Rhondda Fach suggests that nonminers in the two areas have similar survival rates while the survival rates for category 0 and simple pneumoconiosis are lower in the Rhondda Fach.

Becklake, M. R.; Liddell, F. D. K.; Manfreda, J.; McDonald, J. C.

doi: 10.1136/oem.36.1.23pmid: 444438

ABSTRACT A group of 135 ex-employees of the Quebec chrysotile production industry comprising men who were born between 1901 and 1920, who had left the industry between 1950 and 1961, and had been radiographed before leaving, attended in 1972 for a medical examination and further chest radiograph. This report concerns 86 men whose withdrawal film was within 12 months of leaving and who had not been exposed subsequently to asbestos or other fibrogenic dust. Seven separate assessments were made of the paired radiographs, side by side in known temporal order. The assessments were classified as showing 'increse' or 'no change'. In 66 film-pairs from men with two years' employment or longer, at least four assessments were of parenchymal increase in six, of pleural increase in 13, and of both parenchymal and pleural increase in two, total 21 (or 31%). There was similar agreement of no change in 24 pairs (36%), and evidence was equivocal in the remaining 21 pairs. Parenchymal increase was not agreed in any of the 20 film-pairs from men with shorter employment, but pleural increase was seen in four of these men, a proportion similar to that in those exposed longer. We conclude that the parenchymal changes observed after leaving the industry, most of which were 'attacks' rather than 'progression', were attributable to the earlier occupational exposure to chrysotile; there were no important differences in age or smoking habit between those with and without parenchymal change.

Musk, A W; Smith, T J; Peters, J M; McLaughlin, E

doi: 10.1136/oem.36.1.29pmid: 444439

A group of 39 firefighters was examined during routine firefighing duty. Following smoke exposure the average decrease in one-second forced expiratory volume (FEV1.0) was 0.05 litre (137 observations). This decline in FEV1.0 was related to the severity of smoke exposure as estimated by the firefighter and to the measured particulate concentration of the smoke to which he was exposed. Decreases in FEV1.0 in excess of 0.10 litre were recorded in 30% of observations. Changes in FEV1.0 resulting from a second exposure to smoke on the same tour of duty were greater when smoke exposure at the previous fire was heavy. The repeated episodes of irritation of the bronchial tree that have been documented in this investigation may explain the origin of the previously observed chronic effect of firefighting on respiratory symptoms and pulmonary function.

Ainsworth, S K; Neuman, R E; Harley, R A

doi: 10.1136/oem.36.1.35pmid: 87216

Previous reports suggest that byssinosis, an asthma-like condition among textile workers, may be mediated in part by histamine liberated following inhalation of dust. A simple, sensitive, and reliable procedure using pig platelets which contain the unusually high concentration of 0.8-1.6 microgram histamine/10(9) cells has been devised for the assay of histamine-releasing factors in cotton mill dust and related materials, and has yielded results generally in accordance with earlier assays using chopped lung tissue. As little as 50--100 microgram of total extractable substances from cotton mill dust can be measured. The activity of the extract is associated with the non-dialysable high molecular weight portion. However, conditions of acid hydrolysis do not destroy the activity. Extracts of leaves from different varieties of plant are highly potent, which suggests that the factors responsible for byssinosis are widely distributed plant components, present in textile fibre plants and converted to a respirable form by handling processes. Ellagic acid and sodium metasilicate release histamine from pig platelets, and represent new classes of compounds with possible roles in the aetiology of byssinosis.

Whitaker, C. J.; Lee, W. R.; Downes, J. E.

doi: 10.1136/oem.36.1.43pmid: 444440

ABSTRACT During the three years 1967-69, 781 cases of squamous cell carcinoma of the skin were reported to the Manchester Regional Cancer Registry. The proportions of males to females were significantly different (p <0·001) among the skin cancer sites. The age-specific incidence rates were significantly different (p <0·001) between the sexes for the five-year age groups of 55 years and above. Full occupational histories were obtained on 598 (77%) patients; a further 148 (19%) patients gave one main occupation only, while the remaining 35 (4%) patients were untraced. The numbers of patients observed in broad occupational groups (occupational orders) were compared with the numbers expected using the 1931 and 1951 censuses. For all skin cancer sites combined the occupations of farming and textiles were found to have highly significant excesses of 150% and 135% respectively for males. The corresponding excesses for females were 30% for textile workers and varied from 1140% to 590% for farmers, but only for the farmers were the excesses highly significant. For males the occupation of metal worker also showed excesses of 38% and 23% which were of borderline significance. The association between occupation and individual skin cancer sites was then considered. For males there were excesses in the arm for the occupational orders of chemical workers, paper/printing workers and fishermen, and in the ears for builders, but these excesses were of borderline significance. There was a significant difference (p <0·05) in the proportion of male patients with atopic skin conditions in each cancer site. However, this was not found for the female patients. For both male and female patients no significant associations were found between the skin site and either eye colour, residence in the tropics or smoking habit.

Grandjean, P

doi: 10.1136/oem.36.1.52pmid: 444441

The zinc protoporphyrin/haemoglobin (ZPP/Hb) ratio was measured in the field with a haematofluorometer. A significant increase in ZPP/Hb ratio with advancing age was found in 1295 men who denied any excess exposure to lead. Ninety-seven per cent of the results were below 110 mumol ZPP/mol Hb(Fe) (4.4 microgram ZPP/g Hb). The ZPP/Hb ratio was determined in a lead-exposed population of 2275 men, and in 305 a blood lead analysis was also performed. A blood lead limit of 2.9 mumol/l (60 microgram/100 ml) corresponds to about 500 mumol ZPP/mol Hb(Fe) (20 microgram/g). This limit was exceeded in workers engaged in secondary lead smelting, storage battery manufacture, car radiator repair, crystal glass manufacture, storage battery repair, ship breaking, metal foundries, the ceramic industry, scrap metal handling, and PVC plastic manufacture. Other occupations caused lower lead exposures with ZPP/Hb ratios between 110 and 500 mumol ZPP/mol Hb(Fe): such ratios were found in men from shooting ranges, in leaded pane manufacturers, gunsmiths, car paint sprayers, type setters, steel rolling mill workers, shipbuilders and welders, car mechanics, lead pigment handlers, and solderers. Increased ZPP/Hb ratios and blood lead levels in 210 workers were associated with a decrease in haemoglobin concentration in the blood. Thus, the haematofluorometer has proved to be very useful for screening purposes. A blood lead determination should be performed if the ZPP/Hb ratio exceeds 300 microgram ZPP/mol Hb(Fe) (12 microgram/g).

Verberk, M M; Rooyakkers-Beemster, T; de Vlieger, M; van Vliet, A G

doi: 10.1136/oem.36.1.59pmid: 444442

In 33 methyl bromide users, slight electroencephalographic changes (in 10 subjects) and a small increase in serum transaminases were found which could be related to bromine concentration in blood. No relationship was found with subjective symptoms, general neurological examination or the results of serum protein electrophoresis.

Lyle, W H; Spence, T W; McKinneley, W M; Duckers, K

doi: 10.1136/oem.36.1.63pmid: 444443

Facial flushing and other symptoms were reported by 19 of a group of 102 men who worked with dimethylformamide (DMF). Twenty-six of the 34 episodes occurred after the workers had consumed alcoholic drinks. The metabolite N-methylformamide (MF) was detected in the urine on 45 occasions, the highest recorded concentration being 77 microliter/litre. The highest recorded concentration of DMF in air was 200 ppm. The DMF-ethanol reaction is possibly attributable to the inhibition of acetaldehyde metabolism, probably by MF.

Miller, D. M.

doi: 10.1136/oem.36.1.67-apmid: N/A