Amphibole asbestos in tree bark--a review of findings for this inhalational exposure source in Libby, Montana

Case-fatality study of workers and residents with radiographic asbestos disease in Libby, Montana

Background

Vermiculite ore from Libby, Montana contains on average 24% of a mixture of toxic and carcinogenic amphibole asbestiform fibers. These comprise primarily winchite (84%), with smaller quantities of richterite (11%) and tremolite (6%), which are together referred to as Libby amphibole (LA).

Methods

 A total of 1883 individuals who were occupationally and/or environmentally exposed to LA and were diagnosed with asbestos‐related pleuropulmonary disease (ARPPD) following participation in communitywide screening programs supported by the Agency for Toxic Substances and Disease Registry (ATSDR) and followed up at the Center for Asbestos Related Disease (CARD) between 2000 and 2010. There were 203 deaths of patients with sufficient records and radiographs. Best clinical and radiologic evidence was used to determine the cause of death, which was compared with death certificates.

Results

Asbestos‐related mortality was 55% (n = 112) in this series of 203 patients. Of the 203 deaths, 34 (17%) were from asbestos‐related malignancy, 75 (37%) were from parenchymal asbestosis, often with pleural fibrosis, and 3 (1.5%) were from respiratory failure secondary to pleural thickening.

Conclusions

Asbestos is the leading cause of mortality following both occupational and nonoccupational exposure to LA in those with asbestos‐related disease.

Case series: rheumatological manifestations attributed to exposure to Libby Asbestiform Amphiboles

An increased risk for Systemic Autoimmune Diseases (SAID) has been reported in Libby, Montana, where extensive exposures to fibrous amphiboles occurred due to mining and use of asbestos-laden vermiculite. In addition, positive antinuclear autoantibody tests are associated with exposure to Libby Asbestiform Amphiboles (LAA) in both humans and mice. Among 6603 subjects who underwent health screening at the Center for Asbestos Related Diseases (CARD, Libby MT), 13.8% were diagnosed with an autoimmune disease, with prevalence values for the most common SAID being significantly higher than expected in the United States. Among the CARD screening population, serological and clinical profiles are diverse, representing symptoms and autoantibodies reflective of systemic lupus erythematosus (SLE), scleroderma, rheumatoid arthritis, and other rheumatic syndromes, including undifferentiated connective tissue disease (UCTD). Based upon screening of medical records by physicians with rheumatology expertise, the evolving nature of rheumatological disease in these patients is often atypical, with mixed diagnostic criteria and with a 1:1 male-to-female ratio. Through the Libby Epidemiology Research Program, cases were identified that illustrate clinical autoimmune outcomes with LAA exposure. Our goal was to better characterize SAID in Libby, MT in order to improve recognition of autoimmune outcomes associated with this exposure. In view of recent discoveries of widespread exposure to fibrous minerals in several areas of the U.S. and globally, it is critical to evaluate rheumatologic manifestations in other cohorts so that screening, surveillance, and diagnostic procedures are able to detect and recognize potential autoimmune outcomes of asbestos exposure.

ABBREVIATIONS

ANA, antinuclear autoantibody; ARD, Asbestos-Related Diseases; ATSDR, Agency for Toxic Substances & Disease Registry; CARD, Center for Asbestos Related Diseases; CCP, Cyclic citrullinated peptide antibody; CREST, limited cutaneous form of scleroderma; CT, computed tomography; DIP, Distal Interphalangeal Joint; DLCO, Diffusing Capacity of the Lung for CO₂; DMARD, Disease Modifying Anti-Rheumatic Drugs; ENA, Extractable Nuclear Antigen antibodies; FVC, Forced Vital Capacity; LAA, Libby Asbestiform Amphiboles; LERP, Libby Epidemiology Research Program; MCP, Metacarpal Phalangeal Joint; PIP, Proximal Interphalangeal Joint; PIP, rheumatoid arthritis; RV, Residual Volume; SAID, Systemic autoimmune diseases; SLE, systemic lupus erythematosus; SSc, Systemic Sclerosis; TLC, Total Lung Capacity.

Rapid progression of pleural disease due to exposure to Libby amphibole: "Not your grandfather's asbestos related disease"

BACKGROUND

Residents and mine employees from Libby, Montana, have been exposed to asbestiform amphiboles from the vermiculite mine that operated in this location from the mid-1920s until 1990. Clinical observations show a different form of asbestos-related toxicity than other forms of asbestos.

METHODS

Five illustrative cases from the Center for Asbestos-Related Diseases in Libby were selected. All had clear exposure histories, multiple follow-up visits, illustrative chest radiographic studies, serial pulmonary function tests, and sufficient length of follow-up to characterize disease progression.

RESULTS

These cases developed increasing symptoms of dyspnea and chest pain, progressive radiological changes that were predominantly pleural, and a restrictive pattern of impaired spirometry that rapidly progressed with significant loss of pulmonary function.

CONCLUSIONS

LA exposure can cause a non-malignant pleural disease that is more rapidly progressive and more severe than the usual asbestos-related disease.

Use of dust fall filters as passive samplers for metal concentrations in air for communities near contaminated mine tailings

Mine tailings are a source of metal exposures in many rural communities. Multiple air samples are necessary to assess the extent of exposures and factors contributing to these exposures. However, air sampling equipment is costly and requires trained personnel to obtain measurements, limiting the number of samples that can be collected. Simple, low-cost methods are needed to allow for increased sample collection. The objective of our study was to assess if dust fall filters can serve as passive air samplers and be used to characterize potential exposures in a community near contaminated mine tailings. We placed filters in cylinders, concurrently with active indoor air samplers, in 10 occupied homes. We calculated an estimated flow rate by dividing the mass on each dust fall filter by the bulk air concentration and the sampling duration. The mean estimated flow rate for dust fall filters was significantly different during sampling periods with precipitation. The estimated flow rate was used to estimate metal concentration in the air of these homes, as well as in 31 additional homes in another rural community impacted by contaminated mine tailings. The estimated air concentrations had a significant linear association with the measured air concentrations for beryllium, manganese and arsenic (p < 0.05), whose primary source in indoor air is resuspended soil from outdoors. In the second rural community, our estimated metal concentrations in air were comparable to active air sampling measurements taken previously. This passive air sampler is a simple low-cost method to assess potential exposures near contaminated mining sites.

The classic pneumoconioses: new epidemiological and laboratory observations

The purpose of this article is to provide an update on selected issues of current interest and recent developments related to 3 types of inorganic mineral dust exposures causing classic forms of pneumoconiosis: coal mine dust, crystalline silica, and asbestos. Common themes include new imaging modalities, emerging exposures, and evolving appreciation of additional adverse health effects associated with exposure to these inorganic mineral dusts.