The Composition and Morphology of Amphiboles from the Rainy Creek Complex, Near Libby, Montana

Meeker, Gregory P.; Bern, Amy M.; Brownfield, Isabelle K.; Lowers, Heather A.; Sutley, S.J.; Hoefen, Todd M.; Vance, J.S.

doi:10.2138/am-2003-11-1239

Cited by 198 publications

(147 citation statements)

References 18 publications

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Section: Background the Nature Of Asbestosmentioning

confidence: 99%

“…Five amphibole asbestos types make up the remaining set of minerals traditionally recognized as asbestos, including asbestiform reibeckite (crocidolite), asbestiform grunerite (amosite), anthophyllite asbestos, tremolite asbestos, and actinolite asbestos (IARC, 1977;Klein, 1993). Although other amphibole varieties were not included in the traditional definition of asbestos, the asbestiform habits of some of these amphiboles (such as winchite-richterite asbestos) occur as contaminants in deposits of a variety of other mined minerals, such as vermiculite from Libby, MT, and have raised health concerns (Meeker et al, 2003).While unique names have been assigned to the asbestiform habit of serpentine (chrysotile) and two commercially mined amphibole minerals (crocidolite and amosite) to distinguish them from their more common, massive forms, such nomenclature has not been developed for other mineral types of asbestos. Hence the term "asbestos" is added to these mineral names to denote the asbestiform habit.…”

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confidence: 99%

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Update of Potency Factors for Asbestos-Related Lung Cancer and Mesothelioma

Berman¹,

Crump

2008

Critical Reviews in Toxicology

153

125

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The most recent update of the U.S. Environmental Protection Agency (EPA) health assessment document for asbestos (Nicholson, 1986, referred to as "the EPA 1986 update") is now 20 years old. That document contains estimates of "potency factors" for asbestos in causing lung cancer (K L 's) and mesothelioma (K M 's) derived by fitting mathematical models to data from studies of occupational cohorts. The present paper provides a parallel analysis that incorporates data from studies published since the EPA 1986 update.The EPA lung cancer model assumes that the relative risk varies linearly with cumulative exposure lagged 10 years. This implies that the relative risk remains constant after 10 years from last exposure. The EPA mesothelioma model predicts that the mortality rate from mesothelioma increases linearly with the intensity of exposure and, for a given intensity, increases indefinitely after exposure ceases, approximately as the square of time since first exposure lagged 10 years. These assumptions were evaluated using raw data from cohorts where exposures were principally to chrysotile (South Carolina Although the linear EPA model generally provided a good description of exposure response for lung cancer, in some cases it did so only by estimating a large background risk relative to the comparison population. Some of these relative risks seem too large to be due to differences in smoking rates and are probably due at least in part to errors in exposure estimates. There was some equivocal evidence that the relative risk decreased with increasing time since last exposure in the Wittenoom cohort, but none either in the South Carolina cohort up to 50 years from last exposure or in the New Jersey cohort up to 35 years from last exposure.textileThe mesothelioma model provided good descriptions of the observed patterns of mortality after exposure ends, with no evidence that risk increases with long times since last exposure at rates that vary from that predicted by the model (i.e., with the square of time). In particular, the model adequately described the mortality rate in Quebec chrysotile miners and millers up through >50 years from last exposure. There was statistically significant evidence in both the Wittenoom and Quebec cohorts that the exposure intensity-response is supralinear 1 rather than linear. The best-fitting models predicted that the mortality rate varies as [intensity] 0.47 for Wittenoom and as [intensity] 0.19 for Quebec and, in both cases, the exponent was significantly less than 1 ( p < .0001).Using the EPA models, K L 's and K M 's were estimated from the three sets of raw data and also from published data covering a broader range of environments than those originally addressed in the EPA 1986 update. Uncertainty in these estimates was quantified using "uncertainty bounds" that reflect both statistical and nonstatistical uncertainties. Lung cancer potency factors (K L 's) were developed from 20 studies from 18 locations, compared to 13 locations covered in the EPA 1986 update. Mesothelioma p...

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Section: Background the Nature Of Asbestosmentioning

confidence: 99%

mentioning

confidence: 99%

Update of Potency Factors for Asbestos-Related Lung Cancer and Mesothelioma

Berman¹,

Crump

2008

Critical Reviews in Toxicology

153

125

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“…7,8 Libby amphibole asbestos (LAA) is a mixture of amphibole fibers identified in the Rainy Creek complex and present in ore from the vermiculite mine near Libby, MT, USA. 9 Epidemiological studies of worker cohorts in Libby, MT, USA, 10,11 and Marysville, OH, USA, 12,13 exposed to LAA fibers indicate increased risk of radiographic abnormalities, and that the latency period for development of radiographic abnormalities may be relatively short (median latency of 8.6 years for pleural plaques in retrospective investigation of serial radiographs). 14 Each of these cohort studies considered smoking in their analytic approach.…”

Section: Introductionmentioning

confidence: 99%

Localized pleural thickening: Smoking and exposure to Libby vermiculite

Christensen

Kopylev

2012

J Expo Sci Environ Epidemiol

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There is limited research on the combined effects of smoking and asbestos exposure on risk of localized pleural thickening (LPT). This analysis uses data from the Marysville cohort of workers occupationally exposed to Libby amphibole asbestos (LAA). Workers were interviewed to obtain work and health history, including ever/never smoking and chest X-rays. Cumulative exposure estimates were developed on the basis of fiber measurements from the plant and work history. Benchmark concentration (BMC) methodology was used to evaluate the exposure--response relationship for exposure to LAA and a 10% increased risk of LPT, considering potential confounders and statistical model forms. There were 12 LPT cases among 118 workers in the selected study population. The mean exposure was 0.42 (SD ¼ 0.77) fibers/cc-year, and the prevalence of smoking history was 75.0% among cases and 51.9% among non-cases. When controlling for LAA exposure, smoking history was of borderline statistical significance (P-value ¼ 0.099), and its inclusion improved model fit, as measured by Akaike's Information Criterion. A comparison of BMC estimates was made to gauge the potential effect of smoking status. The BMC was 0.36 fibers/ cc-year, overall. The BMC for non-smokers was approximately three times as high (1.02 fibers/cc-year) as that for the full cohort, whereas the BMC for smokers was about 1/2 that of the full cohort (0.17 fibers/cc-year).

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“…Meeker et al [3] conducted the first comprehensive study on Libby asbestos to determine the mineralogy and morphology of both fibrous and non-fibrous amphiboles, supporting the earlier results of Wylie and Verkouteren [41] and Gunter et al [42]. They described the Libby AA as winchite, richterite, tremolite, and magnesioriebeckite, with the majority of structures displaying a gradient of morphologies between prismatic crystals and asbestiform fibers.…”

Section: Discussionmentioning

confidence: 63%

“…The vermiculite ore mined from Zonolite Mountain seven miles northeast of Libby was contaminated with fibrous and asbestiform amphibole in veins throughout the deposit [2], containing a combination of winchite (84%), richterite (11%) and tremolite (6%) [3]. As a result of this contamination, occupational exposure to Libby amphibole asbestos (AA) has led to a significant increase of serious respiratory diseases such as lung cancer, pleural cancer and asbestosis among the former mine workers [4][5][6].…”

Section: Introductionmentioning

confidence: 99%