Low-Level Fiber-induced Radiographic Changes Caused by Libby Vermiculite

Abstract

This study indicates that exposure within an industrial process to Libby vermiculite ore is associated with pleural thickening at low lifetime CFE levels. The propensity of the Libby amphibole fibers to dramatically increase the prevalence of pleural changes 25 years after cessation of exposure at low CFE levels is a concern in view of the wide national distribution of this ore for commercial and residential use.

Localized pleural thickening: Smoking and exposure to Libby vermiculite

“…However, results for LPT specifically, or for the effect of smoking controlling for LAA exposure, were not reported. The follow-up study by Rohs et al 13 did not find a difference in smoking prevalence among those with and without any radiographic changes, but also did not report results for LPT specifically, or controlling for LAA exposure.…”

“…12 A follow-up study was conducted in 2002--2005, and included 298 (of the original 512) workers, of which 280 completed the study interview and chest X-ray. 13 As in the original study, workers were interviewed to obtain work and health history, and spirometry, pulmonary examination and chest X-rays were performed. Smoking was self-reported at in-person interview (2004--2005) and classified as any smoking history or no smoking history.…”

“…Smoking was self-reported at in-person interview (2004--2005) and classified as any smoking history or no smoking history. 13 Three boardcertified radiologists, blinded to any identifying information, independently classified the radiographs using the ILO classification system. 4 The exposure reconstruction in Rohs et al 13 was updated in this study for all workers in the Marysville, OH, USA, cohort.…”

“…13 Three boardcertified radiologists, blinded to any identifying information, independently classified the radiographs using the ILO classification system. 4 The exposure reconstruction in Rohs et al 13 was updated in this study for all workers in the Marysville, OH, USA, cohort. 13,31,32 The update took into account additional industrial hygiene data that were not available for the studies by Rohs et al 13 or Lockey et al 12 Exposure estimates up through the year 2000 were developed on the basis of fiber measurements from the plant when available, and estimated fiber concentrations (based on employee interview and later fiber measurements) for the period before industrial hygiene measurements were taken.…”

“…7,8 Libby amphibole asbestos (LAA) is a mixture of amphibole fibers identified in the Rainy Creek complex and present in ore from the vermiculite mine near Libby, MT, USA. 9 Epidemiological studies of worker cohorts in Libby, MT, USA, 10,11 and Marysville, OH, USA, 12,13 exposed to LAA fibers indicate increased risk of radiographic abnormalities, and that the latency period for development of radiographic abnormalities may be relatively short (median latency of 8.6 years for pleural plaques in retrospective investigation of serial radiographs). 14 Each of these cohort studies considered smoking in their analytic approach.…”