An account is given of work in an asbestos textile factory and of the steps taken to reduce exposure to dust since the introduction of the Asbestos Industry Regulations in 1931.
Measurements of the amount of dust to which men were exposed in the scheduled areas have been made by various methods since 1951, but the data obtained by these methods are not directly comparable. Measurements made since 1960 show that the mean yearly dust level has been fairly constant from year to year and has varied from place to place between 1 and 8 particles (5 to 100 microns long and at least three times as long as they were wide) per c.c. of air.
Chrysotile was used predominantly in the factory, but small amounts of crocidolite were also processed at all relevant periods.
Death rates have been recorded for all the 256 men who were employed for at least 20 years in the scheduled areas since the first man completed 20 years' exposure in 1916, and for the 538 men and 220 women who were employed for at least 10 years in the scheduled areas but were never employed in these areas before 1933.
The results show a substantially increased mortality for men who were exposed for 10 or more years before 1933 (48 deaths from all causes against 17·1 expected).
The increased mortality among these men can be accounted for by an increased mortality from cancer of the lung (12 deaths against 1·2 expected) and from diseases of the respiratory and circulatory systems associated with asbestosis.
Men employed before 1933, but for less than 10 years, showed an increased mortality from lung cancer (5 deaths against 2·6 expected), but no significant increase from other causes. Men and women who were exposed only since January 1, 1933, have had a mortality experience close to the national average.
Analysis of the trends in mortality shows (1) a decrease in mortality from lung cancer and other deaths associated with asbestosis with reduction in length of employment before 1933, and (2) an increase in mortality from lung cancer and other deaths without asbestosis with age.
Twenty-three cases of lung cancer occurred in men who had been employed in the scheduled areas for at least 20 years. One was regarded as a pleural mesothelioma and the rest (approximately 18 in excess of expected) appear to have been ordinary bronchial carcinomas.
Four other mesotheliomas have been diagnosed since 1963, all in men and women with less than 10 years' exposure, one with only seven months' exposure, and one in a man who had been employed in the scheduled areas only since 1937.
The results provide grounds for believing that the occupational hazard of bronchial carcinoma has been largely eliminated, but the data are insufficient to estimate the extent of the risk which may remain.