Document ZnBjymj3N4py5vnOYM7B3LBk8

A. Roach : half-life ere slow, .iagnosed ry many a the use ilid. It is ncer and after the mation a former ;ls might ocedures 73, then ributable n to true leer was on, lung :he same rount of on of the , if there airborne sw of the hange in lg; how- vorbidity 1 in two studied changes, :y sympsxposure bic foot at there gnificant mpcf-yr. :omplete es. Weill irements iographs relation>f simulid fibre se with ased on ixposure pointing lite contandard. se given y, 1968; evalence >bserved ibt that A sbestosis: a study of dose-response relationships in an asbestos textile factory 109 cumulative dose is an adequate measure of exposure, the prevalence of crepitations which would occur in those employed for a lifetime under the present standard can be predicted only within wide limits. Crepitations are not specific to asbestos exposure nor would their presence be considered as significant disease, defined as disability or shortening of life, possible asbestosis is a better indicator but may not be cither specific or. significant disease; however it correlates well with certification (Figure 2). In the group first employed after 1950 the average cumulat ive exposure was 84 f-yr/cm3, the average follow-up. since first exposure was 16 years, and the prevalence of possible asbestosis was 6-6 %. In view of these findings there is no room for complacency about the 2f/cm3 standard and efforts should be continued to reduce asbestos dust to as low a level as possible. At this stage it is impossible to.state definitely that the standard is inadequate, because its introduction is so recent, and it is essential to follow up groups exposed to low levels in order to improve the data necessary for the formulation of better standards. We are grateful to Drs P. G. Harries and V. H. Springett who read the chest radiographs (the other two readers were JCG and HCL); to Dr A. N. Dempsey of the Manchester Pneumoconiosis Medical Panel for allowing us access to data; to Dr P. C. Elmes who suggested making allowance for exponential elimination of dust from the lungs; to Dr J. C. Morris who provided extra information; to Mr J. Peto who suggested the alternative doseresponse model; to Dr J. C. Wagner who examined post-mortem material, and to all those who helped and encouraged us to carry out the study. dustry. Public Health Bulletin (Washington), No. 241. US Government Printing Office: Washington. Holmes, S. (1973). Environmental data in industry. In Biological Effects of Asbestos, pp. 135-137. Edited by P. Bogovski, J. C. Gilson, V. Timbrell, and J. C. Wagner. International Agency for Research on Cancer, Scientific Publication No, 8. IARC: Lyon. International Labour Office (1972). ILO UjC International Classification of Radiographs of the Pneumoconioses, 1971. Occupational Safety and Health Series No. 22 (revised). ILO: Geneva. Jahr, J. (1974). Dose-response basis for setting a quartz threshold limit value. A new simple formula for calculating the `lifetime dose' of quartz. Archives of Environmental Health, 29, 338-340. McDonald, J. C., Becklake, M. R., Gibbs, G. W., McDonald, A. D., and Rossiter, C. E. (1974). The health of chrysotile asbestos mine and mill workers in Quebec. Archives of Environmental Health, 28, 61-68. McVittie, J. C. (1965). Asbestosis in Great Britain. Annals of the New York Academy of Sciences, 132, 128-138. Morgan, A., Holmes, A., and Gold, C. (1971). Studies of the solubility of constituents of chrysotile asbestos In vivo using' radioactive tracer techniques. Environmental . Research, 4, 558-570. Morgan, A., Lally, A. E., and Holmes, A. (1973). Some observations on the distribution of trace metals in chrysotile asbestos. Annals ofOccupational Hygiene, 16, 231-240. Newhouse, M. L. (1973). Asbestos in the work place and the community. Annals of Occupational Hygiene, 16, 97-107. Weill, H., Ziskind, M. M., Waggenspack, C., and Rossiter, C. E. (1975). Lung function consequences of dust exposure in asbestos cement manufacturing plants. Archives of Environmental Health, 30, 88-97. Weiss, W. (1969). Cigarette smoking and diffuse pulmonary fibrosis. American Review of Respiratory Diseases, 99, 67-72. Weiss, W. (1971). Cigarette smoking, asbestos and pulmonary fibrosis. American Review of Respiratory Diseases, 104, 223-227. References Beattie, J., and Knox, J. (1961). Studies of mineral content and particle size distribution in the lungs of asbestos textile workers. In Inhaled Particles and Vapours, pp. 419-433. Edited by C. N. Davies. Pergamon Press: Oxford. Berry, G. (1973). Hygiene standards--theory and application. In Biological Effects of Asbestos, pp. 145-149. Edited by P. Bogovski, J. C. Gilson, V. Timbrell, and J. C. Wagner. International Agency for Research on Cancer, Scientific Publication No. 8. IARC: Lyon. British Occupational Hygiene Society (1968). Hygiene standards for chrysotile asbestos dust. Annals of Occupa tional Hygiene, 11, 47-69. British Occupational Hygiene Society (1973). Review of the hygiene standard for chrysotile asbestos dust. Annals of Occupational Hygiene, 16, 7. British Thoracic and Tuberculosis Association (1975). Opportunist mycobacterial pulmonary infection and occupational dust exposure: an investigation in England and Wales. Tubercle, 56, 295-310. Dreessen, W. C., Dallavalle, J. M., Edwards, T. I., Miller, J- W., Sayers, R. R., Easom, H. F., and Trice, M. F. (1938). A study of asbestosis in the asbestos textile in Appendix MEASURES OF EXPOSURE In this appendix, certain forms of dose-response relationships are discussed. First, it is necessary to define the dose, that is, to derive a measure of exposure in the situation in which exposure takes place over a period of years with different concentra tions. The simplest and most commonly used measute of exposure is the cumulative dose, which gives equal weight to the concentrations of airborne dust experienced in each year of exposure. Thus, for example, suppose a man started work ih the factory at time zero and was exposed to a concentration of ci up to time tv, this was followed by concentiation ca from time ti to /a; ca from fa to ta; and finally d up to time ti, the time the exposure is to be