Document 1Rj98K9Qk1OQ0YJny58xYqNa

LETTERS grouped 4000 individuals whose "ex posure histories" were determined by Chrysotile Asbestos: Effects this method, and for whom mortality of Human Exposure data existed, on the basis of total ex posure (based on "MI'CE-years"), not In his letter of 23 September (p. 1232). by years from the onset of exposure. John T. Hack correctly indicates that the What this meant was that individuals environmental asbestos pollution in with 400 MPCF-years exposure could be Rockville. Maryland, is primarily from those exposed to 40 MPCF for It) years. chrysotile. since that type of asbestos is 80 MPCF for 5 years, or 10 MPCF for found in the Rockville quarry. How 40 years. Years from onset of exposure ever. Hack is incorrect in suggesting were not separately evaluated. Individ that studies U, 2) of the health and uals included in this study were those mortality rates of workers in the chryso- w'ith both short and long latency periods. tile-producing mines of Quebec. Canada, The authors of one of the Quebec studies exonerate the crushed rock from the state that ", . . the length of exposure Rockville quarry as a carcinogen and may be related to length of survival and that the general health of Quebec chryso thus might tend to obscure differences in tile miners and millers "is comparable mortality between exposure groups . . . . to that of Quebec Province as a whole." deaths accumulated over many years Many studies have been made of the were used in a single calculation of mor effects of human exposure to chrysotile tality" (/. p. 63). Even so, among those (.?. 4). These studies take into account considered to be most heavily exposed, a long period of clinical latency which individuals with 400 to 800 MPCF-years occurs between the onset of exposure to exposure have a 2.1 elevated risk of de mineral liber and the clinical appearance veloping respiratory cancer, and those ol malignant disease. Tor asbestos fiber, with greater than 800 MPCF-years expo the latent periods appear to extend from sure have a 3.6 times elevated risk (2, 20 to 4(1 years or more from the onset p. 525). These calculated risks should be ol exposure (4). Exposure intensity is considered conservative, as each data another factor in that it determines the group may include individuals who have competitive risk of contracting asbestosis not completed the long clinical latency or malignant disease and also influences period required for "elevated risk." the length of the latency period. The Beaudry Commission has report McDonald and Becklake state in their ed similar data in its study of the chryso 1976 study (2, p. 521), "In Canada, as tile miners in Thetford. Quebec (5). It elsewhere, diseases recognized to have found that the Quebec asbestos industry an association with asbestos exposure had failed to educate the workers to the include pulmonary fibrosis which may dangers associated with mining and mill alTcct the lungs (giving rise to asbestosis) ing of chrysotile; that outdated, dan and/or the pleura (giving rise to pleural gerous methods were being used in the thickening and calcification) and malig production of fiber; that the government nant tumors, which may be respiratory, inspectors had been negligent; that there mesothelial. or gastrointestinal in ori was a lack of medical surveillance and gin." The only variance with other stud protection for the workers; and that no ies is the calculated relative risk of each proper controls had been installed, even disease. This variance may be explained in new plants and mills. in purl by their study design. Chrysotile mining and milling has thus In the Quebec studies to which Hack been established as hazardous. Review refers (/, 2), the authors assessed the ing available data, an agency of the relationship between the intensity of World Health Organization recently con dust exposure and the resultant mortality cluded. "Uncontrolled exposure to rates, x-ray changes, pulmonary func chrysotile asbestos, as to other types of tion changes, respiratory symptoms, and asbestos, has the potential for serious ' other effects among workers in the Que human disease. Reassurance is unwar bec asbestos mining and milling indus ranted as experiences with asbestos can try. They estimated dust exposure on the cer in the United States, Canada. Great basis of the job type in the mine or mill Britain, the U.S.S.R. and other coun and the number of years a worker spent tries have shown. Unnecessary exposure at each job site. They calculated an ex should be avoided" (6). posure index for each worker based on Arthur N. Rohl, Arthur M. Lancer "million particles per cubic foot" J.Irving Selikoff (MECF) multiplied by the number of Environmental Sciences Laboratory, years exposed at that level, which yield Mount Sinai School of Medicine ofthe ed a hybrid dubbed "total MlKT-years" City University of New York, for each worker. More important, they New York 1002V 1202 Reference I. i. C. McDonald, M. R. BccUair o A. D. McDonald. C. Rosulcf, As 4 i ttrutih 2H, 61 (IV74I. J C. McDonald and M. R % fallheilkd. 126, 521 (1976). 1. R. Doll, Hr. J. htiiust. MrJ. D *' * Howard. L. J. Kinlcn, H. I ' keto. K. Doll, paper presented 1 national Conference on Occupy*.***1 Brighton. England, 1975; W M : H. Mann, J. 1.. Gro<h. Camet I* 1 I.1' Mancuso and E. J. t outtet. 4' * * Health 6. 210(1961); F M. Kojc*- * * nikova, M. K. (iulcvskava. Cat (1972); J. Wagoner. W. M John'*** * Confr. Hec. (14 March 1975), pp 4. I. J. Selikoff. J. Churg. t l H*:** J. Med. 272. 560 < l%<) J. Comite d'Etudesur laSalubnie d*** de J'Amiante. Rapport Fi/tahO&ttrm Quebec. Quebec, 1976). vol. I fi. l.\R( Mom>nr<iphs on the Fuji**-*-1* * otfenic Risk uf Chenticah to ^ htwios (International .A genev k* Cancer. I.yon. 1977). p. I9X Outer Continental Shelf Operating Regulations The Secretary of the Intel ' " posed controversial reM-nTo existing outer continental shelf '' and gas operating regulation' <-* f ing postlease sale actbmc' ' owners. Despite poteiitwlb and Far-reaching adverse etn; consequences that could rc>u.i visions are adopted, the Interne *' ment has decided not to prefer * ronmental impact statement such consequences. If there <' '' opposition from other Executo r ' ments or from Congress, the r may become law as earls - ` 197X. The stated intent of the reso^ provide states affected by DO gas activities with (i) timely formation regarding planned o, tion, development, and product-'-* ations and (ii) opportunity 10 if'** comment on federal decision* such operations. Although the o`i>r. may be worthy, the proposed fensmby w'hich they would he achief'C unnecessarily intricate, cue*'*1* and duplicative. The revisions require that 6* * any exploration activities, owner must prepare and suHw* * * of elaborately detailed plan* ***1 ronmental reports for revie* * ** ance by cognizant federal a affected states and subsequent? i second series of detailed pi** ** ports must be submitted ft* ctwtl** review and acceptance beta* opment and production **^ * stipulations would supple*** **** federal regulations requiringH1*** (Continued on pet* l,i SCIE.Vrt.