Radiographic evidence of nonoccupational asbestos exposure from processing Libby vermiculite in Minneapolis, Minnesota

Environmental asbestos exposure from nephrite jade mining and lung cancer

BACKGROUND

Nephrite is an asbestos mineral composed of tremolite and actinolite. Fengtian is a community where nephrite was mined between 1970 and 1980 and asbestos was mined between 1960 and 1985. The lung cancer risk to the surrounding community is unknown.

AIMS

To analyse the trend of lung cancer caused by environmental contamination from nephrite mining.

METHODS

We conducted a field survey of nephrite mines and tracked new cases of lung cancer from 1980 to 2019. We calculated the age-standardized incidence rates (ASIRs) and applied join-point regression to examine the lung cancer trend. We assessed the age effect, period effect, and birth cohort effect on lung cancer risk.

RESULTS

The nephrite mines were contaminated with chrysotile and tremolite/actinolite asbestos. A total of 278 new cases of lung cancer were reported during the study period. There was an apparent age effect and a slight period effect for lung cancer. After adjustment for the age and period effects, the birth cohort born between 1970 and 1980 during the period of nephrite mass production had the highest relative risk compared with other birth cohorts. The ASIR of lung cancer increased significantly from 1980 to 2010 (the annual percentage change = 6.8 %, 95 % CI: 4.0-9.7 %, P < 0.01) and then decreased 30 years after the cessation of nephrite jade mining.

CONCLUSION

Nephrite mining increases the risk of lung cancer in nearby communities.

Mineralogical investigation of asbestos contamination of soil near old vermiculite processing plant in Honolulu, Hawai'i

From 1954 to 1983, a vermiculite processing facility operated near the Honolulu airport and processed raw material from the Libby, Montana mine, which is now well known for the high asbestos content of its clay deposits. The factory was closed in 1983 due to health hazard concerns, and remediation was performed in 2001 as part of the Libby mine superfund project. However, because of close proximity of the closed-down facility to residential areas of metropolitan Honolulu, some concerns remain regarding the possible environmental persistence of the harmful contaminant. To assess the dispersion of asbestos-contaminated vermiculite and explore the impact of trade winds on its distribution, air samples, and soil samples were collected from multiple locations near the former vermiculite plant. Polarized light microscopy was employed to identify elongated minerals, including potential asbestos. Quantitative mineralogical analysis utilizing X-ray powder diffraction and Rietveld refinement revealed an average content of approximately 7% vermiculite and 4% tremolite at the site. The asbestiform nature of tremolite was confirmed through X-ray micro-diffraction. Detailed analysis of airborne samples using transmission electron microscopy revealed no detectable levels of asbestos fibers in the vicinity of the former processing facilities, but the possibility of asbestos fibers becoming airborne due to mechanical disturbance during dry weather cannot be ruled out.

Measurement of asbestos emissions associated with demolition of abandoned residential dwellings

Many cities are revitalizing their urban cores through the demolition of abandoned residential dwellings (ARDs). However, data regarding the emissions of asbestos during such an operation are sparse. We measured airborne asbestos emissions from emergency demolitions (demolitions on structures deemed too dangerous to enter and remove asbestos) of ARDs in Detroit. High-flow air sampling was conducted during ARD demolitions. Air samples were analyzed using Phased Contrast Microscopy (PCM), and a subset using Transmission Electron Microscopy (TEM). One hundred and one air samples were collected on 25 emergency demolitions. Fifty-four of the 101 PCM samples (53%) exceeded the limit of detection (LOD). However, only 2 of 46 TEM samples (4%) exceeded the LOD for asbestos; these latter samples were from two different demolitions and each contained a single chrysotile asbestos fiber. Using conservative exposure assumptions and commonly-accepted risk estimation formulae, we estimated the lifetime risk of mesothelioma and lung cancer combined to be less than one case per one million people. Emissions of airborne asbestos during emergency (unabated) ARD demolition operations appear to be negligible. As a result, the associated health risk for asbestos-related disease is also negligible. Reconsideration of current regulatory mandates for asbestos abatement in ARDs may be warranted.

Follow-Up of the Libby, Montana Screening Cohort: A 17-Year Mortality Study

OBJECTIVE

To evaluate mortality patterns among participants in a community-based screening program for asbestos-related disease.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Lung cancer screening in patients with Libby amphibole disease: High yield despite predominantly environmental and household exposure

Background

Lung cancer screening with low‐dose computed tomography (CT) scanning (LDCT) is accepted as a screening tool, but its application to populations exposed to recognized occupational or environmental carcinogens is limited. We apply LDCT to a population with a predominantly nonoccupational exposure to a recognized human lung carcinogen, Libby amphibole asbestos (LA).

Methods

Patients in an asbestos disease clinic in Libby, Montana who were aged 50 to 84 years, greater than or equal to 20 pack‐year history of tobacco use (irrespective of quit date), and asbestos‐related pleuropulmonary disease on high‐resolution CT scan were offered free annual lung cancer screening over a 39‐month period.

Results

Of 2897 clinic patients, 1149 (39.7%) met eligibility criteria, and 567 (49%) were screened with 1014 low‐dose CT scans. Most screened patients had principally environmental (333 or 59%) or household exposure (145 or 25%) to LA. Seventeen primary lung cancers were identified, mostly in early stages: 10 at stage 1, two at stage 2, three at stages 3 to 4, and two at limited small‐cell cancers. The screening yield was 1.9 at baseline scan and 1.5% on the first annual scan.

Conclusions

Consistent with the guidelines of the National Comprehensive Cancer Network and American Association of Thoracic Surgery, LDCT for early lung cancer detection should be offered to people with significant exposure to occupational or environmental human lung carcinogens.

Libby Amphibole Disease: Pulmonary Function and CT Abnormalities in Vermiculite Miners

OBJECTIVE

This article describes radiologic and pulmonary function findings among miners exposed to Libby amphibole. Computed tomography (CT) permits the detection of the characteristic thin, lamellar pleural thickening (LPT).

METHODS

Individuals who worked at the mine for a minimum of 6 months had chest CT and pulmonary function tests.

RESULTS

Pleural thickening was noted in 223 (87%) of the 256 miners, parenchymal abnormalities in 49 (19%). LPT, found in 151 (68%), was associated with low values of forced vital capacity and diffusion capacity and significantly lower values in all pulmonary function tests when associated with parenchymal abnormalities.

CONCLUSION

Eighty-seven percent of miners exposed to Libby Amphibole had pleural abnormalities on CT. LPT alone, and more so with parenchymal abnormalities, resulted in decreased pulmonary function. The importance of this easily missed LPT is demonstrated by its high frequency and significant functional effects.

Cancer incidence and mortality associated with non-occupational and low dose exposure to Libby vermiculite in Minnesota

BACKGROUND

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.

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Pleural abnormalities and exposure to elongate mineral particles in Minnesota iron ore (taconite) workers

BACKGROUND

Iron ore (taconite) mining and processing are an important industry in northern Minnesota and western Michigan. Concerns around exposures have centered largely on exposure to non-asbestiform amphibole elongate mineral particles (EMPs) found in the eastern portion of the Minnesota iron range.

METHODS

A cross sectional survey was undertaken of current and former taconite workers and spouses along with a detailed exposure assessment. Participants provided an occupational history and had a chest radiograph performed.

RESULTS

A total of 1188 workers participated. Potential exposures to non-amphibole EMPs were evident across multiple jobs in all active mines. Pleural abnormalities were found in 16.8% of workers. There was an association of pleural abnormalities with cumulative EMP exposure that was not specific to the eastern portion of the range.

CONCLUSION

There was evidence of a mild to moderate increase in pleural abnormalities in this population of miners, associated with geographically non-specific cumulative EMP exposure.

Childhood exposure to Libby amphibole asbestos and respiratory health in young adults

OBJECTIVES

Vermiculite ore containing Libby amphibole asbestos (LAA) was mined in Libby, MT, from the 1920s-1990. Recreational and residential areas in Libby were contaminated with LAA. This objective of this study was to characterize childhood exposure to LAA and investigate its association with respiratory health during young adulthood.

METHODS

Young adults who resided in Libby prior to age 18 completed a health and activity questionnaire, pulmonary function testing, chest x-ray and HRCT scan. LAA exposure was estimated based on participant report of engaging in activities with potential LAA exposure. Quantitative LAA estimates for activities were derived from sampling data and literature reports.

RESULTS

A total of 312 participants (mean age 25.1 years) were enrolled and reported respiratory symptoms in the past 12 months including pleuritic chest pain (23%), regular cough (17%), shortness of breath (18%), and wheezing or whistling in the chest (18%). Cumulative LAA exposure was significantly associated with shortness of breath (aOR = 1.12, 95% CI 1.01-1.25 per doubling of exposure). Engaging in recreational activities near Rainy Creek Road (near the former mine site) and the number of instances heating vermiculite ore to make it expand or pop were also significantly associated with respiratory symptoms. LAA exposure was not associated with pulmonary function or pleural or interstitial changes on either chest x-ray or HRCT.

CONCLUSIONS

Pleural or interstitial changes on x-ray or HRCT were not observed among this cohort of young adults. However, childhood exposure to LAA was significantly associated with respiratory symptoms during young adulthood. Pleuritic chest pain, in particular, has been identified as an early symptom associated with LAA exposure and therefore warrants continued follow-up given findings of progressive disease in other LAA exposed populations.

Libby amphibole-induced mesothelial cell autoantibodies bind to surface plasminogen and alter collagen matrix remodeling

Lamellar pleural thickening (LPT) is a fibrotic disease induced by exposure to Libby amphibole (LA) asbestos that causes widespread scarring around the lung, resulting in deterioration of pulmonary function. Investigating the effects of autoantibodies to mesothelial cells (MCAA) present in the study populations has been a major part of the effort to understand the mechanism of pathogenesis. It has been shown in vitro that human mesothelial cells (Met5a) exposed to MCAA increase collagen deposition into the extracellular matrix (ECM). In this study, we sought to further elucidate how MCAA drive increased collagen deposition by identifying the protein targets bound by MCAA on the cellular surface using biotinylation to label and isolate surface proteins. Isolated surface protein fractions were identified as containing MCAA targets using ELISA. The fractions that demonstrated binding by MCAA were then analyzed by tandem mass spectrometry (MS/MS) and MASCOT analysis. The most promising result from the MASCOT analysis, plasminogen (PLG), was tested for MCAA binding using purified human PLG in an ELISA. We report that serum containing MCAA bound at an optical density (OD) 3 times greater than that of controls, and LA‐exposed subjects had a high frequency of positive tests for anti‐PLG autoantibodies. This work implicates the involvement of the plasminogen/plasmin system in the mechanism of excess collagen deposition in Met5a cells exposed to MCAA. Elucidating this mechanism could contribute to the understanding of LPT.

Mortality from asbestos-associated disease in Libby, Montana 1979-2011

Research on asbestos exposure in Libby, MT, has focused on occupational exposure in vermiculite mining and processing, but less attention has been paid to asbestos-related mortality among community members without vermiculite mining occupational history. Our study reports on asbestos-related mortality in Libby over 33 years (1979-2011) while controlling for occupational exposure. We calculated sex-specific 33-year standardized mortality ratios (SMRs) for Libby residents who died from 1979 to 2011 with an asbestos-related cause of death. Decedent address at time of death was geocoded to confirm inclusion in the Libby County Division. We controlled for past W.R. Grace employment by including and then removing them from the SMR analysis. Six hundred and ninety-four decedents were identified as having at least one asbestos-related cause of death and residing in our study area boundary. Statistically significant (P<0.05) 33-year SMRs, both before and after controlling for W.R. Grace employment, were found for: male and female non-malignant respiratory diseases, female COPD, and asbestosis for both sexes combined. Eighty-five men and two women were matched to employment records. We observed elevated asbestos-related mortality rates among males and females. SMR results for asbestosis were high for both sexes, even after controlling for past W.R. Grace employment. These results suggest that the general population may be experiencing asbestos-related effects, not just former vermiculite workers. Additional research is needed to determine whether SMRs remain elevated after controlling for secondary exposure, such as living with vermiculite workers.

Pulmonary abnormalities as a result of exposure to Libby amphibole during childhood and adolescence-The Pre-Adult Latency Study (PALS)

BACKGROUND

The purpose of Pre-Adult Latency Study was to evaluate lung findings among adults who had been environmentally exposed to Libby Amphibole only during childhood and adolescence.

METHODS

Recruitment was restricted to volunteers who attended primary and/or secondary school, lived in Libby, MT, prior to age 23 years for males and 21 years for females and subsequently left the area. Subjects completed exposure and respiratory questionnaires, underwent pulmonary function tests (PFTs), and chest CT scans. A Pleural Score was calculated for degree and extent of pleural thickening. Logistic regression and multivariate linear regression were used.

RESULTS

Of the 219 who met inclusion criteria, 198 participated. Pleural thickening was found in 96 (48%) of 198 participants. In almost half of these, it was of the lamellar type, not generally seen in exposure to other asbestos. Environmental Libby amphibole exposure was associated with pleural thickening, and the likelihood of pleural thickening increased with the number of years lived in the area. An inverse association between Pleural Score and PFT was found, which remained significant for FVC and DLco after additional sensitivity analyses.

CONCLUSIONS

Cumulative environmental exposure was associated with risk of pleural thickening. Among this cohort, quantitative measures of pleural thickening were associated with decreased PFT. Am. J. Ind. Med. 60:20-34, 2017. © 2016 Wiley Periodicals, Inc.

Toxicological and epidemiological studies on effects of airborne fibers: coherence and public [corrected] health implications

Airborne fibers, when sufficiently biopersistent, can cause chronic pleural diseases, as well as excess pulmonary fibrosis and lung cancers. Mesothelioma and pleural plaques are caused by biopersistent fibers thinner than ∼0.1 μm and longer than ∼5 μm. Excess lung cancer and pulmonary fibrosis are caused by biopersistent fibers that are longer than ∼20 μm. While biopersistence varies with fiber type, all amphibole and erionite fibers are sufficiently biopersistent to cause pathogenic effects, while the greater in vivo solubility of chrysotile fibers makes them somewhat less causal for the lung diseases, and much less causal for the pleural diseases. Most synthetic vitreous fibers are more soluble in vivo than chrysotile, and pose little, if any, health pulmonary or pleural health risk, but some specialty SVFs were sufficiently biopersistent to cause pathogenic effects in animal studies. My conclusions are based on the following: 1) epidemiologic studies that specified the origin of the fibers by type, and especially those that identified their fiber length and diameter distributions; 2) laboratory-based toxicologic studies involving fiber size characterization and/or dissolution rates and long-term observation of biological responses; and 3) the largely coherent findings of the epidemiology and the toxicology. The strong dependence of effects on fiber diameter, length, and biopersistence makes reliable routine quantitative exposure and risk assessment impractical in some cases, since it would require transmission electronic microscopic examination, of representative membrane filter samples, for determining statistically sufficient numbers of fibers longer than 5 and 20 μm, and those thinner than 0.1 μm, based on the fiber types.

Childhood exposure to Libby amphibole during outdoor activities

Residents of Libby, MT were exposed to amphibole asbestos through multiple environmental pathways. Previous exposure characterization has primarily relied on qualitative report of these exposure activities. The objectives of this study were to describe available data from the US EPA preremediation actions for Libby amphibole (LA) exposure in Libby, MT and develop an approach to characterize outdoor residential exposure to LA among children. Homes in Libby, MT included in the US EPA preremediation Contaminant Screening Survey (CSS) were categorized by the presence of interior and/or exterior visible vermiculite and concentrations of LA were measured in samples of dust and soil. Airborne exposure to LA while digging/gardening, raking, and mowing were estimated using US EPA activity-based sampling (ABS) results. Residential histories and frequency/duration of childhood activities were combined with ABS to demonstrate the approach for estimating potential exposure. A total of 3154 residential properties participated in the CSS and 44% of these had visible exterior vermiculite. Airborne concentrations of LA where there was visible vermiculite outdoors were 3-15 times higher during digging/gardening, raking, and mowing activities compared with homes without visible outdoor vermiculite. Digging and gardening activities represented the greatest contribution to estimated exposures and 73% of the participants reported this activity before the age of 6 years. This methodology demonstrated the use of historical preremediation data to estimate residential exposures of children for specific activities. Children younger than age 6 years may have been exposed to LA while digging/gardening, especially at homes where there is visible outdoor vermiculite. This approach may be extended to other activities and applied to the entire cohort to examine health outcomes.

Low levels of exposure to libby amphibole asbestos and localized pleural thickening

OBJECTIVE

To explore the relationship between low levels of exposure to Libby amphibole asbestos (LAA) and pleural abnormalities, specifically localized pleural thickening (LPT).

METHODS

Three studies presenting the risks associated with quantitative LAA exposure estimates were reviewed, paying particular attention to lower exposure ranges.

RESULTS

Studies reviewed were conducted among workers exposed to LAA at mining and milling operations in Libby, Montana, at a vermiculite processing facility in Marysville, Ohio, and community residents exposed to LAA from a vermiculite processing facility in Minneapolis, Minnesota. Pleural abnormalities were evaluated using radiographs. Despite differences in study populations and design, each study found that cumulative inhalation LAA exposure was associated with increased risk of LPT even at low levels of exposure.

CONCLUSIONS

Inhalation exposure to LAA is associated with increased risk of LPT even at the lowest levels of exposure in each study.

Compensation for environmental asbestos-related diseases in South Africa: a neglected issue

Background

Environmentally acquired asbestos-related diseases (ARDs) are of concern globally. In South Africa, there is widespread contamination of the environment due to historical asbestos mining operations that were poorly regulated. Although the law makes provision for the compensation of occupationally acquired ARDs, compensation for environmentally acquired ARDs is only available through the Asbestos Relief Trust (ART) and Kgalagadi Relief Trust, both of which are administered by the ART. This study assessed ARDs and compensation outcomes of environmental claims submitted to the Trusts.

Methods

The personal details, medical diagnoses, and exposure information of all environmental claims considered by the Trusts from their inception in 2003 to April 2010 were used to calculate the numbers and proportions of ARDs and compensation awards.

Results

There were 146 environmental claimants of whom 35 (23.9%) had fibrotic pleural disease, 1 (0.7%) had lung cancer, and 77 (52.7%) had malignant mesothelioma. 53 (36.3%) claimants were compensated: 20 with fibrotic pleural disease and 33 with mesothelioma. Of the 93 (63.7%) claimants who were not compensated, 33 had no ARDs, 18 had fibrotic pleural disease, 1 had lung cancer, and 44 had mesothelioma. In addition to having ARDs, those that were compensated had qualifying domestic (33; 62.2%) or neighbourhood (20; 37.8%) exposures to asbestos. Most of the claimants who were not compensated had ARDs but their exposures did not meet the Trusts’ exposure criteria.

Conclusions

This study demonstrates the environmental impact of asbestos mining on the burden of ARDs. Mesothelioma was the most common disease diagnosed, but most cases were not compensated. This highlights that there is little redress for individuals with environmentally acquired ARDs in South Africa. To stop this ARD epidemic, there is a need for the rehabilitation of abandoned asbestos mines and the environment. These issues may not be unique to South Africa as many countries continue to mine and use asbestos.

Descriptive analysis of the respiratory health status of persons exposed to Libby amphibole asbestos

OBJECTIVE

Describe respiratory health and quality of life in persons exposed to Libby amphibole asbestos (LAA) contaminated vermiculite.

DESIGN

Cross-sectional descriptive.

SETTING

Asbestos-related disease clinic in Libby, Montana USA.

PARTICIPANTS

329 individuals exposed to LAA; mostly men, married, between 50 and 69 years; two-thirds lived in the surrounding county; one-third lived elsewhere in the state and USA.

PRIMARY OUTCOME MEASURES

Chest radiograph (CXR), pulmonary function data and the St George Respiratory Questionnaire (SGRQ).

RESULTS

Exposure categories included vermiculite workers=7.6%; family/household contact of vermiculite worker=32%; and environmental exposure only=60%. Of the participants, 55% had only pleural abnormalities; 5.4% had only interstitial abnormalities; nearly 21% had both abnormalities and 18% had no lung abnormality on chest x-ray. Mean forced vital capacity (FVC) 95.3% (SD=18.7); forced expiratory volume (FEV(1)) mean 87% (SD=20.2); ratio of FEV1(1)/FVC 95.5% (SD=12.0); and diffusing capacity (DLCO) of 83% (SD=21.7) of the percent predicted. The mean total SGRQ (38.5; SD=22.1) indicated a lower quality of life than healthy persons and persons with other chronic conditions. SGRQ subscale means were Symptoms 52.1 (SD=24.9), activity 49.4 (SD=26.9) and impacts 27.5 (SD=21.9). Participants with normal CXR differed significantly from those with both interstitial and pleural abnormalities on total, activity and impacts scores. For activity alone, subjects with normal CXR differed significantly from those with pleural disease; no differences were found for those with interstitial disease. Significant findings were found for smoking history across all pulmonary measures, and for exposure status, radiographic findings, age and gender for select pulmonary parameters. Subjects with any smoking history had significantly worse average total and subscale scores on the SGRQ.

CONCLUSIONS

Of 329 persons exposed to LAA, the majority (182) had pleural abnormalities identified on CXR. SGRQ scores for persons with abnormalities (pleural, interstitial or both) (269) differed significantly from those with a normal CXR.