Document zQ14y005NVbdmjOLgwrjM7Yx0

- OCTOBER 1992/JANUARY 1993 5 e n s i b ,1 e management of a n a t u r a ( r e s o u r .c e Important Study Finds That at Exposure Levels Below a Threshold of 50 f/cc, Chrysotile Asbestos Is Not Linked to Any Increased Incidence of Lung Cancer. Preliminary results from the largest cohort study of chrysotile workers ever undertaken were released this past. September at the 9th International Symposium on Epidemiology and Occupational health held in Cincinnati, Ohio. The study, conducted by Doctors F.D.K. Liddell, AID. McDonald and J.C. McDonald of McGill University evaluated more than 11,000 chrysotile miners in Qudbec born between 1891 and 1926. Initiated in 1966, the study was designed to define as accurately as possible the quantitative relationship between expo sures chrysotile asbestos and the inci dence of lung cancer. Cohort data has been collected five times since, the latest in May of 1992. Based on exposure data gathered by the mines, and comparisons of Standard, Mortality Ratios (SMR = observed mortal-, ity / expected mortality) the authors con cluded that any excess cancer mortality was found only among workers exposed to more than 50 f/cc for a period of 20 years or more. . (see No Excess Lung Cancer onpage 2) Inside Previous Data on Chrysotile Exposure Support New Findings A/C Pipe Makes a Resurgence in the TJ.S. EPA's Science Advisory Board Critical of Agency's Asbestos Program Overturning the Verdict on Carcinogens Code of Practice for Synthetic Mineral Fibres U.S. Study Links Fiberglass to Lung Disease Policy Considerations and Theory, Not Science Have Guided Asbestos For years the linear model of risk analysis has been applied to the regulation of chrysotile asbestos expo sure. Today scientists are questioning the validity of this approach. The linear model of risk analysis holds that a substance which is toxic at extremely high doses can have a health Impact at levels many orders of magni tude lower - even if there are no observ able effects at these levels. The linear model maintain that effects may exist, yet are not detectable with current tech niques. This model has traditionally served as a guideline for setting exposure limits and other regulatory action. In the face of mounting evidence that for many known carcinogens there appears to be a threshold level of exposure below (see Policy Considerations onpage 4) 1 HWBUI0012300 Does prolonged exposure to fiberglass adversely affect pulmonary functions or produce radiographic abnormalities in humans ? ' A recent study by researchers at the University of Southern California (USC) School of Medicine concluded that com mercial rotary spun fiberglass appears to produce human disease that is similar to asbestosis. The study, conducted by K. Kilburn, D, Powers and R.H. Warshaw was published in the October issue of The British Journal ofindustrial Medicine. It examined 284 workers at an appliance factory where refrigerator doors and cabi nets were insulated with fiberglass sheet ing and loose rotary spun fiberglass.Workers with exposures of twenty years or more were evaluated on a num ber of tests of respiratory functioning including lung volumes, chest x-rays and physical examination. . The researchers found that in addition to eye and throat irritation in about 20% of . the population studied, expiratory flows, which indicate pulmonary dysfunction, were significantly impaired. 43 workers also had evidence of pneumoconiosis on chest radiographs. The authors believe that 36 (13%) of these pulmonary opaci ties or plural abnormalities were due to fiberglass exposure. A postmortem analysis of one worker who died just prior to the study showed a sub stantial accumulation of glass fibres in. the lungs. A transmission electron microscopy examination showed that each lung contained approximately 178,000 fibres. Code of Practice Q for Synthetic Mineral Fibres Charles Rossiter, former professor at the London School of Hygiene and Tropical Medicine who currently acts as a consul tant to the insulation industry disputes die study's conclusions. He argues that the study does not adequately, recognize the compounding effects of smoking and that the control group was not represen tative. Me Rossiter does nonetheless urge the Man Made Mineral Fibre industry to; undertake further study into the health effects on users.' Jirn Merchant, a leading American authority and director of the Occupa tional and Environmental Health Department at the University of Iowa believes that this study is " in line with what we know about fiberglass". Mr. Merchant warns that "this may have a lot of implications for people who work in building and construction." Other major American and European cohort studies of the occupational: health risks for workers in the Man Made Mineral Fibre (MMMF) manufacturing sector have found lung, trachea and bronchus cancer rates in excess of those expected. Sources: Marsh, G.M., EnterUne, P., Stone, R. & Henderson, V.L., Mortality among a Cohort of USD Man-Made Mineral Fibre Workers 1985 FoUow-up. J. Occ. Med. 32, 594- 604, 1990. Simonato, L et al. The man-made mineral fibre European Historical Cohort study: Extension of the Follow-up. Scand. J. Work, Env. Hlth, 12, SuppI 1,34-47,1986 In response to recent human and ani mal data, representatives from the Quebec Federation of Labour (QFL) , ' with the support of the Canadian Labour Congress have written a draft Code of Practice for the use of Synthetic Mineral Fibres (SMF). The; code would include descriptions of SMF, summaries of their : health effects, as well as recommenda tions for proper monitoring, safe work practices and exposure limits) The code would detail work practices based on the different risk factors accorded to various fibres. . , A number of recent studies (see article. U.S. Study...) have found evidence that exposures to some types of SMFs; can have serious health effects, including eye and throat irritation, pulmonary dys function, non-malignant disease and cancer. Despite the growing concerns of scientists, regulators and the labour movement, some industry representatives such as Frank Cereghini, manager of Occupational Health and Safety at Owens-Corning/Fiberglass Canada maintain that insulation fibres are not carcinogenic. A new Code of Practice is intended to eliminate the inter-provincial inconsis tencies which exist in worker protection policies across Canada and provide guidelines for government policy and ; industry practices. * w 6 THE ASBESTOS 1002 Sherbrooke Street West Suite 1750, Montreal (Quebec) Telephone: (514) 844-3956 Telex: 055-60565 (INSTAM) INSTITUTE Canada H3A 3L6 Telecopier: (514) 844-1381 HWBUI0012301