We appreciate Price’s interest in our article (Peipins et al. 2003). We stated clearly that being a former W.R. Grace (WRG) worker was a significant risk factor for both pleura] and interstitial abnormalities. We also noted that only age was more strongly associated with these outcomes in multivariate analyses and that these results were not unexpected.

However, we disagree with Price’s statement that the obvious conclusion of our analysis is that risk associated with low-level environmental exposure is negligible. Such a conclusion ignores key results. For example, we found that playing in the vermiculite piles and longer duration of residence in Libby, Montana, were associated with pleural abnormalities, even after controlling for occupational and domestic exposures (Peipins et al. 2003). We also found that the prevalence of pleural abnormalities increased with increasing number of exposure pathways, even after we removed WRG workers from the analysis. This suggests a cumulative effect from multiple exposures that exclude working in the mine.

Price incorrectly labels our “no-apparent exposure” group as an “internal “control group.” We did not have an internal noexposure group (Peipins et al. 2003). Our no-apparent-exposure group consisted of participants who responded “no” to the exposure pathways listed in the questionnaire and who were likely exposed via ambient air and other pathways not assessed by our screening questionnaire. The rate of 6.7% for the no-apparent-exposure group in our analysis and the rate of 9.1% given by Price in his letter are considerably higher than the prevalence rates of pleural abnormalities found in published studies of other nonoccuparionally exposed populations in the United States, which range from 0.2% among blue-collar workers in North Carolina (Castellan et al. 1985) to 2.3% among patients at Veterans Affairs hospitals in New Jersey (Miller and Zurlo 1996). Of note, these studies did not exclude family contacts of workers or domestic exposures (Castellan et al. 1985; Anderson et al. 1979).

When assessing subpleural fat as a confounding factor, we found former WRG workers to have higher body mass indexes (BMIs) than those who were nor former WRG workers. We controlled for subpleural fat by including BMI in both our multivariate analyses and our pathways analyses. Therefore, the associations between environmental exposures, as well as occupational and domestic exposure, and pleural abnormalities remained when controlled for BMI.

In regard to Price’s comments on past exposures in Libby, sampling performed by WRG in 1975 showed markedly elevated ambient air asbestos concentrations in downtown Libby [U.S. Environmental Protection Agency (EPA 2002)]. These findings are consistent with the limited ambient air samples collected by the U.S. EPA (Dixon et al. 1985; Atkinson et al. 1982). Although Price points out that the variation in detectable laboratory results ranged from 0.02 to 0.5 fiber/[cm.sup.3], depending on the laboratory, it is clear that the ambient air concentrations in Libby easily approached, if not exceeded, occupational 8-hr limits. In a cross-sectional study of workers at an Ohio fertilizer plant that processed vermiculite from Libby, Montana, Lockey et al. (1984) found that workers with daily time-weighted-average exposures of 0.031-0.415 fiber/[cm.sup.3], similar to the ambient air concentrations reported in Libby, had significantly elevated radiographic pleural changes and pleuritic chest pain.

Price asserts that Agency for Toxic Substances and Disease Registry (ATSDR) mortality studies conducted for the Libby area have created a false perception of the community’s asbestos-related mortality experience. Results from ATSDR’s mortality study (ATSDR 2002) revealed significantly elevated rates of mesothelioma, asbestosis, and lung cancer when compared with the Montana and U.S. populations. Workers were included in the determination of asbestos-related mortality in Libby, as is done as a matter of practice throughout the nation to determine comparative standardized mortality rates. Nevertheless, there were several deaths found that did not appear to be occupationally related. Notably, one of the three mesothelioma cases identified for inclusion in our study (Peipins et al. 2003) did not occur among former mine workers (ATSDR 2002). Additionally, Lincoln County, Montana, had the highest age-adjusted asbestosis mortality rate in the United States for 1988-1997, even when compared to other counties that contain large asbestos exposed workforces (Castellan R. Unpublished data).

On the basis of our results, we conclude that both occupational and environmental risk factors are important predictors of asbestos-related radiographic abnormalities in this community. We thank Price for his comments and hope that this letter provides additional insights to these issues.