Vermiculite ore bodies in the Rainy Creek Mining District of Lincoln County, Montana are associated with amphibole asbestos concentrations ranging to nearly 100% in selected areas. During the 1980s NIOSH researchers found that vermiculite mine and processing workers had significantly increased occurrence of asbestosis, lung cancer, mesothelioma, and asbestos-related pleural disease associated with exposure. Since the cessation of vermiculite mining and processing operations in 1990 area physicians have continued to identify individuals suffering from asbestos-related disease. Investigations by NIOSH and ATSDR indicate mortality rates for asbestosis 40 to 60 times the national rate. Preliminary analysis of medical screening of 6200 area residents conducted by ATSDR, EPA, and the USPHS from July to November 2000 indicated that overall about 20% had chest x-ray abnormalities (identified by at least 2 of 3 B-readers) consistent with asbestos exposure (ATSDR, 2001). Almost 40% of those identified with chest x-ray abnormalities had no occupationally-related vermiculite exposures.
We have conducted task-based monitoring to quantify possible ongoing fiber exposures and risks to the residential population and remodeling workers. Airborne fiber concentrations were evaluated during normal household and common remodeling activities. Simulated household tasks were monitored using Hazdust real-time particulate monitors operated concurrently with particulate collection on 0.8 um filter cartridges. Airborne fiber was collected in the personal breathing zone of simulation workers and enumerated by phase contrast (PCM) and transmission electron microscopy (TEM) to estimate activity-specific fiber exposure. The results indicate that both fiber source concentrations and activity patterns influence exposure.
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Presenting author's disclosure statement:
Organization/institution whose products or services will be discussed: None
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.