An updated evaluation of reported no-observed adverse effect levels for chrysotile asbestos for lung cancer and mesothelioma.

Although consumption of chrysotile asbestos has decreased since the 1970s, the latency period of asbestos-related cancers is thought to be at least 20-30 years, and therefore the potential health risks associated with historical exposures is still actively researched. This analysis represents an update to a previous paper in which we evaluated the exposure-response relationships for lung cancer and mesothelioma in chrysotile-exposed cohorts. Here, we review several recently published studies as well as updated information from previous studies. For each of the 14 studies considered, we identified the "no-observed adverse effect level" (NOAEL) for lung cancer and/or mesothelioma. NOAEL values for lung cancer ranged from 1.1 to <20 f/cc-years to 1600-3200 f/cc-years, and for mesothelioma ranged from 100-400 f/cc-years to 800-1599 f/cc-years. The range of "best estimate" NOAELs was estimated to be 89-168 f/cc-years for lung cancer and 208-415 f/cc-years for mesothelioma. None of the six cohorts of cement or friction product manufacturing workers exhibited an increased lung cancer risk at any exposure level, while all of the five studies of textile workers reported an increased risk at one or more exposure levels. This is likely because friction and cement workers were exposed to much shorter chrysotile fibers. Of the seven cases of peritoneal mesothelioma reported in the included studies, none were observed in the analyses of cement or friction product manufacturing workers in the absence of crocidolite exposure. These findings will help characterize potential worker and consumer health risks associated with historical and current chrysotile exposures.

The quality of fiber counts using improved slides with relocatable fields.

A parameter based on discrepancies between reported fibers and verified fibers of relocatable slides is shown to be effective in monitoring the quality of airborne fiber counts. Analysts report only the fibers in each field examined. The verified fibers were determined by two experienced analysts, and are here considered as a "true" value. Most of the verified fibers were confirmed by the reported fibers, and the disputed fibers or fiber counting errors were all located and accounted for. In this study, reference (REF) slides were manufactured from proficiency analytical test (PAT) filter samples from the American Industrial Hygiene Association containing chrysotile or amosite. The slides were made using coverglasses bearing a grid pattern to allow accurate re-examinations. These coverglasses are an improved version of those used in previous studies. Seventy-four out of 85 amosite results and 51 out of 60 chrysotile results of REF slides were within their PAT proficiency ranges. When all reported fibers were normalized against their respective verified fibers, the average fiber count was over-estimated for amosite by 38.3% and under-estimated for chrysotile by 30.4%. The error from counting short fibers (sizing-extra) was 82.6% of the extra fibers and accounted for the 38% over-estimation of amosite fibers. For chrysotile fibers, sizing-extra errors were 74.0% of the extra fibers, but by far the larger errors were oversight-missing errors, which were 96.7% of the missing fibers and accounted for the 30% under-estimation of the chrysotile fibers. The discrepancies were found to be linearly related to counting errors as had been noted in a previous study, giving further weight to a proposed score, calculated from the discrepancy parameter (SigmaD(+) + |SigmaD(-)|)/VF(total), for evaluating the proficiencies of analysts. If a proficiency score =60 is selected, 48 out of 85 amosite results and 17 out of 60 chrysotile results satisfied this criterion in this study. The number of fiber counting errors in this study was larger than could be expected by PAT proficiency criteria. It may be useful to complement existing proficiency test programs with these REF slides. At the end of each proficiency testing round, detailed reports of discrepancies can be provided to participants so that they can improve on their skills in searching and sizing fibers and minimize their counting errors. In addition, the internal quality control program of each laboratory could include counting REF slides regularly by all analysts with control charts of (SigmaD(+)/VF(total)), (SigmaD(-)/VF(total)), (SigmaD(+) + |SigmaD(-)|)/VF(total) and RF(total)/VF(total) maintained to monitor errors, proficiencies and intercounter variations. Ten percent of relocatable slides of routine samples could also be recounted to monitor intracounter variation.

Revising the British Occupational Hygiene Society asbestos standard: 1968-1982.

BACKGROUND: In 1968 the British Occupational Hygiene Society (BOHS) published a chrysotile asbestos hygiene standard. As a consequence of acknowledged inadequacies of the data, it underestimated the risks of exposure, but its influence was international and operated for longer than it merited. Five years later, BOHS reported the standard not to be in need of amending, despite its own doubts and no cognizance having been taken of the cancer hazard. Within months, stung by criticism from Dr. Irving J. Selikoff, industry required it to review the standard, which BOHS continued to do for a number of years before giving up. METHODS: Material obtained for the American Courts by means of legal discovery from an asbestos company's archive, provided information on the membership of the new BOHS committees, and on its operation. RESULTS: Alterations in the composition of the new committees included importantly the introduction of certain independent scientists, whose rigor militated against the ready production of a new hygiene standard acceptable to industry. CONCLUSIONS: There was a time in Britain when a learned society might with impunity omit to consult the views of workers or their representatives when making value judgments about their health and safety, but consider it proper to accede to industry's decision as to what hygiene standard it would accept. Health and Safety at Work legislation in 1974, established an organization on which industry and labor were represented, with the onus for recommending hygiene standards. For several years the BOHS Asbestos Sub-Committee continued attempting to reconcile the interests of industry, until finally abandoning hygiene standard setting as its mission.

[Content of asbestos fibers in water sources of the Bazhenovo deposit]. / Soderzhanie volokon asbesta v vodoistochnikakh Bazhenovskogo mestorozhdeniia.

The paper provides preliminary measurements of asbestos levels in water sources from an area of the Bazhenovo chrysotile-asbestos deposit. All study water samples have been found to contain chrysotile-asbestos fibers at concentrations one-three orders less that the values standardized in the USA (7 x 10(6) vol/l). The authors consider it advisable to continue studies to measure asbestos levels in the water sources in the areas in vicinity of other Russian deposits.