vermiculite and Lung-Neoplasms

U.S. Environmental Protection Agency (EPA) recently conducted a risk assessment for exposure to Libby amphibole asbestos that is precedent-setting for two reasons. First, the Agency has not previously conducted a risk assessment for a specific type of asbestos fiber. Second, the risk assessment includes not only an inhalation unit risk (IUR) for the cancer endpoints, but also a reference concentration (RfC) for nonmalignant disease. In this paper, we review the procedures used by the Agency for both cancer and nonmalignant disease and discuss the strengths and limitations of these procedures. The estimate of the RfC uses the benchmark dose method applied to pleural plaques in a small subcohort of vermiculite workers in Marysville, Ohio. We show that these data are too sparse to inform the exposure-response relationship in the low-exposure region critical for estimation of an RfC, and that different models with very different exposure-response shapes fit the data equally well. Furthermore, pleural plaques do not represent a disease condition and do not appear to meet the EPA's definition of an adverse condition. The estimation of the IUR for cancer is based on a subcohort of Libby miners, discarding the vast majority of lung cancers and mesotheliomas in the entire cohort and ignoring important time-related factors in exposure and risk, including effect modification by age. We propose that an IUR based on an endpoint that combines lung cancer, mesothelioma, and nonmalignant respiratory disease (NMRD) in this cohort would protect against both malignant and nonmalignant disease. However, the IUR should be based on the entire cohort of Libby miners, and the analysis should properly account for temporal factors. We illustrate our discussion with our own independent analyses of the data used by the Agency.

Topics: Aluminum Silicates; Asbestos, Amphibole; Endpoint Determination; Humans; Inhalation Exposure; Lung Neoplasms; Mesothelioma; Occupational Exposure; Ohio; Risk Assessment; Risk Factors; Smoking; United States; United States Environmental Protection Agency

The vermiculite ore formerly mined in Libby, Montana, contains asbestiform amphibole fibers of winchite, richterite, and tremolite asbestos. Because of the public health impact of widespread occupational and nonoccupational exposure to amphiboles in Libby vermiculite, numerous related studies have been published in recent years. Here we review current research related to this issue.. Excess morbidity and mortality classically associated with asbestos exposure have been well documented among persons exposed to Libby vermiculite. Excess morbidity and mortality have likewise been documented among persons with only nonoccupational exposure. A strong exposure-response relationship exists for many malignant and nonmalignant outcomes and the most common outcome, pleural plaques, may occur at low lifetime cumulative exposures.. The public health situation related to Libby, Montana, has led to huge investments in public health actions and research. The resulting studies have added much to the body of knowledge concerning health effects of exposures to Libby amphibole fibers specifically and asbestos exposure in general.

Topics: Aluminum Silicates; Asbestos, Amphibole; Asbestosis; Cohort Studies; Female; Humans; Lung Neoplasms; Male; Mining; Montana; Occupational Exposure; Pleural Neoplasms; Risk Factors

Tremolite is a noncommercial form of amphibole mineral that is present in some chrysotile, talc, and vermiculite deposits. Inhalation of asbestiform tremolite is suspected to have caused or contributed to an increased incidence of mesothelioma in certain mining settings; however, very little is known about the magnitude of tremolite exposure that occurred at these locations, and even less is known regarding tremolite exposures that might have occurred during consumer use of chrysotile, talc, and vermiculite containing products. The purpose of this analysis is to evaluate the exposure-response relationship for tremolite asbestos and mesothelioma in high exposure settings (mining) and to develop estimates of tremolite asbestos exposure for various product use scenarios. Our interpretation of the tremolite asbestos exposure metrics reported for the Thetford chrysotile mines and the Libby vermiculite deposits suggests a lowest-observed-adverse-effect level (LOAEL) for mesothelioma of 35-73 f/cc-year. Using measured and estimated airborne tremolite asbestos concentrations for simulated and actual product use, we conservatively estimated the following cumulative tremolite asbestos exposures: career auto mechanic: 0.028 f/cc-year; non-occupational use of joint compound: 0.0006 f/cc-year; non-occupational use of vermiculite-containing gardening products: 0.034 f/cc-year; home-owner removal of Zonolite insulation: 0.0002 f/cc-year. While the estimated consumer tremolite exposures are far below the tremolite LOAELs derived herein, this analysis examines only a few of the hundreds of chrysotile- and talc-containing products.

Topics: Aluminum Silicates; Animals; Asbestos, Amphibole; Asbestos, Serpentine; Humans; Incidence; Lung Neoplasms; Mesothelioma; Occupational Diseases; Occupational Exposure; Risk Assessment; Talc; Toxicity Tests

To evaluate mortality patterns among participants in a community-based screening program for asbestos-related disease.. We calculated standardized mortality ratios (SMRs) and stratified results by exposure group (three occupational exposure groups, household contacts and residents without occupational asbestos exposure) and by radiographic abnormality presence.. All-cause mortality (15.8%; 1,429/8,043) was statistically lower than expected. Asbestosis was statistically elevated in all exposure groups. Lung cancer was moderately associated with vermiculite miner/miller employment. Mesothelioma was elevated in that same exposure group and among residents. Systemic autoimmune disease mortality was also elevated. Radiographic parenchymal abnormalities were associated with lung cancer mortality.. In addition to asbestos-related mortality in occupational exposure groups, this initial follow-up of this cohort also shows elevated mortality for some asbestos-related causes in non-occupational exposure groups.

Topics: Adult; Aluminum Silicates; Asbestos; Asbestos, Amphibole; Asbestosis; Biometry; Cohort Studies; Environmental Exposure; Female; Follow-Up Studies; Humans; Lung; Lung Neoplasms; Male; Mesothelioma; Middle Aged; Montana; Occupational Exposure

Vermiculite mining operations near Libby, Montana were active from the 1920s to 1990. Rail facilities for shipment of the mined material as well as some vermiculite processing activities were ongoing within the community of Libby. A fibrous component within the mined material has been associated with asbestos-related diseases in vermiculite miners and in the local citizens of the community.. We present a clinical case history and tissue fiber burden analysis of an individual with a multifocal adenocarcinoma of the lung who was a lifelong resident of Libby and whose history of exposure was as a member of the general population there.. To our knowledge this is the first time tissue from a member of the general population of Libby, Montana has been evaluated and shown to contain an appreciable presence of "Libby amphibole" fibers.

Topics: Adenocarcinoma; Air Pollutants; Aluminum Silicates; Environmental Exposure; Female; Humans; Lung; Lung Neoplasms; Lymphoid Tissue; Middle Aged; Mining; Montana; Tumor Burden

A vermiculite processing plant in a Minneapolis, Minnesota neighborhood utilized asbestos-containing ore from Libby, Montana from the late 1930's until 1989. Multiple pathways of exposure to Libby asbestos were characterized in a cohort of over 6000 plant workers and residents living near the plant.. We conducted a cohort linkage study to assess the impact of cumulative low dose exposure and the role of occupational history on asbestos-related mortality and cancer morbidity among cohort members residing near a vermiculite plant.. Cohort members alive in 1988 (n = 5848) were linked to the Minnesota Cancer Surveillance System to identify incident cases of mesothelioma, lung cancer, and all-cancer diagnosed from 1988 to 2010. Proportional incidence ratios (PIRs) were calculated for mesothelioma and lung cancer. Vital status and cause of death were ascertained from Minnesota vital records and the National Death Index (1988-2011). Mortality rates of the cohort (2001-2011) for asbestos-related outcomes were compared to the Minnesota population to estimate standardized mortality ratios (SMRs) and stratified by gender, exposure, and occupational history categories.. We identified seven cases of mesothelioma, with elevated incidence only in females (PIR = 11.76, 95% CI: 3.17, 30.12). Lung cancer was elevated in both genders: PIR = 1.54 (95% CI: 1.19, 2.0) in males and 1.62 (95% CI: 1.21, 2.12) in females. We found elevated mortality from COPD, lung cancer, and mesothelioma among females (SMR for mesothelioma in females = 18.97, CI: 3.91, 55.45), among the 546 deaths identified. All four deaths from mesothelioma occurred in the >75th percentile of exposure (>0.0156 fiber/cc x months). The SMR for lung cancer and all respiratory cancer was elevated even after controlling for occupation.. Community exposure to Libby amphibole asbestos from a vermiculite processing plant is associated with increased risk of COPD, lung cancer and mesothelioma incidence and mortality, most notably among females, and is likely to remain a public health issue for years to come.

Topics: Aluminum Silicates; Asbestos; Asbestos, Amphibole; Female; Humans; Incidence; Lung Neoplasms; Male; Mesothelioma; Minnesota; Montana; Occupational Exposure

Occupational exposure to certain substances would cause cancer. Herein, we report on a case of a 58-year-old former orthoprostethist who died from a lung adenocarcinoma. He had a 3 pack-year history of smoking and a single exposure to asbestos during his professional career. Between 1979 and 2010, he used vermiculite plaques daily to build medical prostheses, using no personal protective equipment. Contamination of vermiculite with amphibole asbestos has been described in Libby, Montana. Expert opinion on this case has raised the hypothesis of the use of this kind of vermiculite during this period and the occupational etiology of this cancer. It seems important to point out the possibility of vermiculite-related lung cancers in unusual occupations in order to better document such cases in the future.

Topics: Aluminum Silicates; Humans; Lung Neoplasms; Male; Middle Aged; Occupational Exposure

The National Institute for Occupational Safety and Health (NIOSH) conducted an evaluation of exposures to asbestiform amphibole, known as Libby Amphibole (LA), to personnel from the US Department of Agriculture-Forest Service (USFS) working in the Kootenai National Forest near a former vermiculite mine close to Libby, Montana. LA is associated with vermiculite that was obtained from this mine; mining and processing over many years have resulted in the spread of LA into the surrounding Kootenai Forest where it has been found in tree bark, soil, and forest floor litter. As a result of this and other contamination, Libby and surrounding areas have been designated a "Superfund" site by the US Environmental Protection Agency (EPA). This article describes the application of EPA methods for assessing cancer risks to NIOSH sampling results. Phase-contrast microscopy for airborne asbestos fiber evaluation was found to be less useful than transmission electron microscopy in the presence of interfering organic (plant) fibers. NIOSH Method 7402 was extended by examination of larger areas of the filter, but fiber counts remained low. There are differences between counting rules in NIOSH 7402 and the ISO method used by EPA but these are minor in the context of the uncertainty in concentration estimates from the low counts. Estimates for cancer risk are generally compatible with those previously estimated by the EPA. However, there are limitations to extrapolating these findings of low risk throughout the entire area and to tasks that were not evaluated.

Topics: Aluminum Silicates; Asbestos, Amphibole; Environmental Monitoring; Forestry; Humans; Lung Neoplasms; Montana; National Institute for Occupational Safety and Health, U.S.; Occupational Exposure; Particulate Matter; Plant Bark; Risk Assessment; Trees; United States

To describe asbestos-related mortality among manufacturing workers who expanded and processed Libby vermiculite that contained amphibole fiber.. Standardized mortality ratio was calculated for 465 white male workers 31 years after last Libby vermiculite exposure.. Two workers died from mesothelioma, resulting in a significantly increased standardized mortality ratio of 10.5 (95% confidence interval, 1.3 to 38.0). These workers were in the upper 10th percentile of cumulative fiber exposure, that is, 43.80 and 47.23 fiber-years/cm, respectively. One additional worker with cumulative fiber exposure of 5.73 fiber-years/cm developed mesothelioma but is not deceased. There were no other significantly increased standardized mortality ratios.. Workers expanding and processing Libby vermiculite in a manufacturing setting demonstrated an increased risk for the development of mesothelioma following exposure to the amphibole fiber contained within this vermiculite ore source.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Aluminum Silicates; Cause of Death; Cohort Studies; Confidence Intervals; Extraction and Processing Industry; Female; Humans; Inhalation Exposure; Lung Neoplasms; Male; Mesothelioma; Middle Aged; Occupational Exposure; Respiratory Tract Diseases; Young Adult

We reanalyzed the Libby vermiculite miners' cohort assembled by Sullivan to estimate potency factors for lung cancer, mesothelioma, nonmalignant respiratory disease (NMRD), and all-cause mortality associated with exposure to Libby fibers. Our principal statistical tool for analyses of lung cancer, NMRD, and total mortality in the cohort was the time-dependent proportional hazards model. For mesothelioma, we used an extension of the Peto formula. For a cumulative exposure to Libby fiber of 100 f/mL-yr, our estimates of relative risk (RR) are as follows: lung cancer, RR = 1.12, 95% confidence interval (CI) =[1.06, 1.17]; NMRD, RR = 1.14, 95% CI =[1.09, 1.18]; total mortality, RR = 1.06, 95% CI =[1.04, 1.08]. These estimates were virtually identical when analyses were restricted to the subcohort of workers who were employed for at least one year. For mesothelioma, our estimate of potency is K(M) = 0.5 x 10(-8), 95% CI =[0.3 x 10(-8), 0.8 x 10(-8)]. Finally, we estimated the mortality ratios standardized against the U.S. population for lung cancer, NMRD, and total mortality and obtained estimates that were in good agreement with those reported by Sullivan. The estimated potency factors form the basis for a quantitative risk assessment at Libby.

Topics: Adult; Aged; Aluminum Silicates; Cohort Studies; Environmental Exposure; Humans; Lung Neoplasms; Male; Mesothelioma; Middle Aged; Mining; Montana; Occupational Diseases; Occupational Exposure; Proportional Hazards Models; Respiratory Tract Diseases; Risk Assessment

In the 1960s and 1970s, well designed case-referent studies put beyond doubt that exposure to airborne asbestos fibres was a cause of malignant mesothelioma. Some 35 cohort mortality studies in a large variety of industries during the 20-year period, 1974-1994, showed a wide range of outcomes, but in general that the risk was higher in exposures which included amphiboles rather than chrysotile alone. Real progress began, however, with discoveries along several lines: the link between pleural changes and mineralogy, the concept and importance of biopersistence, the developments in counting and typing mineral fibres in lung tissue, and data on amphibole mining in South Africa and Australia for comparison with that on chrysotile in Canada and Italy. This led to the recognition of the potential contamination in North America of chrysotile with tremolite. A survey in Canada in 1980-1988 and other surveys demonstrated that crocidolite, amosite, and tremolite could explain almost all cases of mesothelioma. Effective confirmation of this was finally achieved with data on vermiculite miners in Libby, Montana, in the years 1983-1999, where exposure was to tremolite-actinolite and/or other amphibole fibres alone.

Topics: Air Pollutants, Occupational; Aluminum Silicates; Asbestos; Asbestos, Amphibole; Canada; Carcinogens; Case-Control Studies; Cohort Studies; Humans; Italy; Lung Neoplasms; Mesothelioma; Mineral Fibers; Mining; North America; Occupational Diseases; Occupational Exposure; Risk Factors; South Africa; United Kingdom; United States

Vermiculite from the mine near Libby, Montana, is contaminated with tremolite asbestos and other amphibole fibers (winchite and richterite). Asbestos-contaminated Libby vermiculite was used in loose-fill attic insulation that remains in millions of homes in the United States, Canada, and other countries.. This report describes asbestos-related occupational respiratory disease mortality among workers who mined, milled, and processed the Libby vermiculite.. This historical cohort mortality study uses life table analysis methods to compare the age-adjusted mortality experience through 2001 of 1,672 Libby workers to that of white men in the U.S. population.. Libby workers were significantly more likely to die from asbestosis [standardized mortality ratio (SMR) = 165.8; 95% confidence interval (CI), 103.9-251.1], lung cancer (SMR = 1.7; 95% CI, 1.4-2.1), cancer of the pleura (SMR = 23.3; 95% CI, 6.3-59.5), and mesothelioma. Mortality from asbestosis and lung cancer increased with increasing duration and cumulative exposure to airborne tremolite asbestos and other amphibole fibers.. The observed dose-related increases in asbestosis and lung cancer mortality highlight the need for better understanding and control of exposures that may occur when homeowners or construction workers (including plumbers, cable installers, electricians, telephone repair personnel, and insulators) disturb loose-fill attic insulation made with asbestos-contaminated vermiculite from Libby, Montana.

Topics: Aged; Aluminum Silicates; Asbestos, Amphibole; Asbestosis; Cohort Studies; Humans; Lung Neoplasms; Male; Mesothelioma; Middle Aged; Mining; Montana; Occupational Exposure; Pleural Neoplasms; Retrospective Studies

Fibrous tremolite is a widespread amphibole asbestiform mineral, airborne fibres of which constitute an environmental hazard in Libby, Montana, northern California, and elsewhere.. To determine excess risk from lung cancer, mesothelioma, and all-cause mortality in a cohort of men exposed to tremolite, but no other form of asbestos.. Mortality by certified cause and various measures of exposure to tremolite and related amphibole fibres was assessed in a cohort of 406 vermiculite mineworkers in Libby, Montana, employed before 1963 and followed until 1999.. Total deaths were: lung cancer 44 (SMR 2.40), non-malignant respiratory disease (NMRD) 51 (SMR 3.09), all causes 285 (SMR 1.27); included among the total were 12 deaths ascribed to mesothelioma (4.21% of all deaths). Adjusted linear increments in relative risks (per 100 f/ml.y), estimated by Poisson regression, were: lung cancer (0.36, 95% CI 0.03 to 1.20), NMRD (0.38, 95% CI 0.12 to 0.96), and all deaths (0.14, 95% CI 0.05 to 0.26).. The all-cause linear model would imply a 14% increase in mortality for mine workers exposed occupationally to 100 f/ml.y or about 3.2% for a general population exposed for 50 years to an ambient concentration of 0.1 f/ml. Amphibole fibres, tremolite in particular, are likely to be disproportionately responsible for cancer mortality in persons exposed to commercial chrysotile, but to what extent cannot be readily assessed.

Topics: Aluminum Silicates; Asbestos, Amphibole; Cohort Studies; Humans; Lung Neoplasms; Male; Mesothelioma; Mining; Montana; Regression Analysis; Risk Factors

Estimation of exposure-response relations from epidemiological data is complicated by the fact that exposures usually vary in intensity over time. Cumulative exposure indices, which do not separate the effects of intensity and duration, are commonly used to circumvent this problem. In this paper the estimation of relative risk for specific ranges of exposure intensity from such data is considered using existing statistical methods for fitting multivariate relative risk models. This has the advantage that it does not assume that exposure intensity and duration have equivalent effects on risk. It also throws light on the possible existence of a threshold. The procedure was applied to data from a cohort of 406 vermiculite miners to examine the lung cancer risk associated with exposure to fibrous tremolite, which contaminated the vermiculite. The pattern of exposure-response differed substantially from that obtained using a cumulative exposure index to assess risk.

Topics: Aluminum Silicates; Asbestos, Amphibole; Case-Control Studies; Humans; Lung Neoplasms; Male; Mining; Occupational Diseases; Occupational Exposure; Regression Analysis; Risk Factors; Silicic Acid; Time Factors

A small cohort of 194 men with low exposure to fibrous tremolite (mean 0.75 f/ml y) in the mining and milling of vermiculite in South Carolina experienced 51 deaths 15 years or more from first employment. The SMR (all causes) was 1.17 reflecting excess deaths from circulatory disease. There were four deaths from lung cancer and 3.31 expected (SMR 1.21, 95% CI 0.33-3.09). Three of the four deaths were in the lowest exposure category (less than 1 f/ml y); no death was attributed to mesothelioma or pneumoconiosis. These findings contrast with those in Montana where the vermiculite ore was heavily contaminated with fibrous tremolite. A radiographic survey of 86 current and recent South Carolina employees found four with small parenchymal opacities (greater than or equal to 1/0) and seven with pleural thickening. These proportions were not higher than in a non-exposed group and much lower than had been observed in Montana. Examination of sputum from 76 current employees showed that only two specimens contained typical ferruginous bodies, confirming low cumulative fibre exposure. Any possible adverse effects of work with vermiculite, minimally contaminated with fibrous or non-fibrous tremolite, were thus beyond the limits of detection in this workforce.

Topics: Aluminum Silicates; Asbestos, Amphibole; Canada; Cohort Studies; Humans; Lung Neoplasms; Mesothelioma; Mining; Occupational Diseases; Pulmonary Fibrosis; Silicic Acid; Silicon Dioxide

The vermiculite ore and concentrate of a mine and mill located near Libby, Montana was found to be contaminated with a fiber of the tremolite/acetinolite series. A study was conducted to estimate the exposure-response relationship for mortality for 575 men who had been hired prior to 1970 and employed at least 1 year at the Montana site. Individual cumulative fiber exposure (fiber-years) was calculated. Results indicated that mortality from nonmalignant respiratory disease (NMRD) and lung cancer was significantly increased compared to the U.S. white male population. For those workers more than 20 years since hire, the standard mortality rate (SMR) for lung cancer (ICDA 162-163) was 84.7, 225.1, 109.3, and 671.3 for less than 50, 50-99, 100-399, and more than 399 fiber-years respectively. Corresponding results for NMRD (ICDA 460-519) were 327.8, 283.5, 0, and 278.4. Based on a linear model for greater than 20 years since hire, the estimated percentage increase in lung cancer mortality risk was 0.6% for each fiber-year of exposure. At 5 fiber-years, the estimated percentage was 2.9% from an unrestricted (nonthreshold) linear model and 0.6% from a survival model.

Topics: Aluminum Silicates; Asbestos, Amphibole; Humans; Lung Neoplasms; Male; Mesothelioma; Minerals; Mining; Montana; Occupational Diseases; Silicon Dioxide; Smoking; Time Factors