Waters, W. E., Cochrane, A. L., and Moore, F. (1974).British Journal of Industrial Medicine,31, 196-200. Mortality in punctiform type of coalworkers' pneumoconiosis. Recent studies conducted on miners at necropsy and on those attending a pneumoconiosis medical panel have suggested that the punctiform type of opacities are associated with a significant gas transfer defect and with emphysema. However, a 10-year follow-up of a random sample of miners and ex-miners in the Rhondda Fach found that the mortality experience of those with the punctiform type was, if anything, more favourable than that for other types of pneumoconiosis. This may be related to radiographic technique, but there may also be physiological reasons. There was no evidence that those with the punctiform type had different smoking habits from those with other types of pneumoconiosis.

Wallace, J., Sweetnam, P. M., Warner, C. G., Graham, P. A., and Cochrane, A. L. (1971).Brit. J. industr. Med.,28, 265-271. An epidemiological study of lens opacities among steel workers. To investigate the relationship between the prevalence of cataract and heat exposure, two groups of steel workers, differing widely in their heat exposure, were examined. Estimates of heat exposure were based on detailed industrial histories and (a) subjective estimates of heat exposure associated with various occupations and (b) actual measurements. Only two cases of cataract were found that would be generally accepted as `occupational' in origin, but a higher prevalence of the common form of cataract was found in the heat-exposed group than in the non-exposed group.

The changes in the prevalence of pneumoconiosis among miners and ex-miners in the Rhondda Fach in three age groups at three different times (1951, 1953, and 1961) have been investigated. The radiographs were re-read with the dates concealed, in a randomized order, by one observer. Later a stratified sample was classified for technique. The results of the randomized readings, standardized for technique, suggest an increase in prevalence in the older age groups and a slight decrease in the youngest.

Further analysis suggests that the changes are not due to differential migration and mortality, and it is concluded that they are probably due to the progression of simple pneumoconiosis. This is thought to be mainly due to dust exposure, but the possibility of progression occurring in the absence of dust exposure is not excluded.

Associations between exposure to asbestos and carcinoma of the lung, diffuse mesothelioma of the pleura, and diffuse abdominal tumours have been demonstrated. Only by an epidemiological approach can the total risks of exposure to asbestos be estimated, and such a study is reported here. This suggests that white asbestos (chrysotile) may not be a serious hazard as far as mesothelioma or abdominal tumours are concerned, though there is some evidence of an excess in the number of deaths from carcinoma of the lung and bronchus.

A six-year follow-up of 6,474 miners and ex-miners, originally radiographed in 1950-51, has been completed. They represent 97% of all those who were then resident in the Rhondda Fach. In addition, 2,750 non-miners living in the same area were also studied. Death certificates were obtained for all those who had died, including those who had left the area. Standardized mortality ratios (S.M.R.s) have been calculated for the various age and ϰ-ray category groups.

The results suggest that (1) progressive massive fibrosis (P.M.F.) is a more serious disease than a previous study suggested; (2) the S.M.R. of miners and ex-miners without P.M.F. is also significantly raised; (3) there is no sign of any relation between the ϰ-ray category of simple pneumoconiosis and the S.M.R.; and (4) the S.M.R. of ex-miners is significantly higher than that of miners.

A radiological follow-up of the miners and ex-miners in two Welsh mining valleys whose chest radiographs showed simple pneumoconiosis in 1950/51 has been carried out to study the factors associated with the attack rate of progressive massive fibrosis. The radiographs were read in pairs, and also with the pairs separated, the radiographs being randomized and identifying features concealed. The relative value of these two types of reading is discussed.

An attempt to investigate the importance of exogenous tuberculous infection by comparing the attack rate in the two mining valleys, in one of which great efforts had been made to eradicate tuberculosis, failed. The reasons for the failure are discussed.

No evidence was found of any association between the attack rate of progressive massive fibrosis and age, energy expenditure at work, smoking habits, body type, exogenous tuberculous infection, or endogenous infection as measured by the presence of primary complexes in the first radiographs. The only factor related to the attack rate was the average category of simple pneumoconiosis. The attack rate is zero at category ½ and rises to 30 or more per 100 in eight years for category 3. It is argued from this that the logical way to control the appearance of progressive massive fibrosis is to concentrate on preventing miners reaching category 2 of simple pneumoconiosis. Evidence is also presented that considerable progression of simple pneumoconiosis has been occurring during the past eight years amongst coal-face workers at the collieries in this area.

To investigate the high death rates for bronchitis in South Wales miners a survey of respiratory symptoms and ventilatory capacity in 90% of a random sample of 600 men between the ages of 35 and 64 and 200 women between 55 and 64 living in the Rhondda Fach was carried out. The sample of men was stratified by age and occupation, 100 miners and ex-miners, and 100 non-miners being studied in each decade.

The higher prevalence of symptoms and lower mean indirect maximum breathing capacity (I.M.B.C.) of the miners and ex-miners, observed previously, was confirmed and within the mining group there was little relation of symptoms to radiological category of pneumoconiosis. Miners and ex-miners with progressive massive fibrosis had a lower mean I.M.B.C. than the rest at all ages.

Analysis of symptoms and I.M.B.C. by length of time spent working on the coal-getting shift in both miners and ex-miners did not suggest that the total dust dosage to which a man had been exposed during his working life was closely related to chronic respiratory disease. A lower prevalence of symptoms and a higher mean indirect M.B.C. was found in those who had worked for under one year on the coal-getting shift. Above one year no clear pattern of symptom prevalence was discerned although there was a slight downward trend in the mean indirect M.B.C. with increased time spent working on the coal-getting shift. When working miners alone were considered the reduction in ventilatory function with increasing duration of work was slightly greater.

Dust exposure alone seemed unlikely to account for all the excess respiratory disease in miners compared with the rest of the community and other possible explanations are discussed.

The women recorded a lower prevalence of symptoms than the men who had never worked in mining. This prevalence was, however, higher than that previously found in rural areas in Wales and Scotland. The mean indirect M.B.C. recorded for the women in this survey was also lower than that observed in Scots women.

Analysis of the findings in the women according to the occupation of their husbands showed that miners' wives recorded a higher prevalence of symptoms and lower mean indirect M.B.C. than non-miners' wives, suggesting the importance of social rather than occupational factors in miners.

Smoking was associated with an increased prevalence of symptoms and lower indirect M.B.C. in the men but not in the women. Differnces in smoking habits could not, however, account for the differences between miners and non-miners, as these remained after standardization for smoking.

Mortality and morbidity statistics suggest that miners and foundryworkers are more prone to bronchitis than other industrial workers but it is not yet certain that this excess is due to occupational factors. The present investigation was designed to compare the prevalence of bronchitis and respiratory disability in a representative sample of miners, foundryworkers, and other industrial groups living in Staveley, Derbyshire, a town of some 18,000 inhabitants, and to study some of the possible aetiological factors. A random sample of 776 men, stratified by age into two groups, 25 to 34 and 55 to 64 years, and by occupation into four groups, non-dusty, miners and ex-miners, foundry and ex-foundryworkers, and other dusty jobs, was used. Respiratory symptoms were recorded on a standardized questionnaire and the ventilatory capacity was assessed by means of the forced expiratory volume (F.E.V.0·75) and recorded as the indirect maximum breathing capacity (M.B.C.).

Miners and ex-miners recorded a higher prevalence of respiratory symptoms and a lower mean M.B.C. than men who had worked only in dust-free occupations. In the older age group the differences were not large and were not statistically significant but in the younger men the difference in the mean M.B.C. was significant. Foundry and ex-foundryworkers with a pure industrial history recorded a similar prevalence of symptoms to the men who had never worked in dusty occupations and their mean M.B.C. was only slightly and insignificantly lower. A higher prevalence of symptoms and a lower mean M.B.C. was, however, recorded by the foundrymen who had also been exposed to other dusts or fumes and the occupational histories suggested that such exposure was more likely than foundry work to account for the findings.

The number of years spent on the coal-getting shift was used to assess the importance of exposure to coal dust. In the elderly miners without pneumoconiosis there was a significant increase in the prevalence of breathlessness, accompanied by a reciprocal fall in the mean M.B.C. with increasing years spent on the coal-getting shift; but in no other group was a consistent trend found.

In both age groups the prevalence of respiratory symptoms was lower and the mean M.B.C. higher in non-smokers than in smokers and ex-smokers. Heavy smokers (those smoking 15g. and over/day) recorded a higher prevalence of symptoms and a lower mean M.B.C. than light smokers, and the values for ex-smokers approximated to those of the non-smokers.

The wives of the elderly men in the sample were studied to try to determine how far the apparently high rates of bronchitis shown by national mortality statistics are attributable to social factors. The findings suggested that the wives of the men who worked in dusty jobs had a somewhat higher prevalence of cough and/or sputum and of chest illness during the past three years than the wives of those who had worked only in dust-free occupations.

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