Home Current Issue Previous Issues Published Ahead-of-Print Collections CME For Authors Journal Info
Skip Navigation LinksHome > November 2012 - Volume 54 - Issue 11 > Exposure Estimates for Workers in a Facility Expanding Libby...
Journal of Occupational & Environmental Medicine:
doi: 10.1097/JOM.0b013e31824fe174
Original Articles

Exposure Estimates for Workers in a Facility Expanding Libby Vermiculite: Updated Values and Comparison With Original 1980 Values

Borton, Eric K. MS; LeMasters, Grace K. PhD; Hilbert, Timothy J. MS; Lockey, James E. MD, MS; Dunning, Kari K. PhD; Rice, Carol H. PhD



There was an error in the methods section of this article. In the Plant Description section, the fourth sentence states, “The expanded material was mixed with additives to treat lawns to improve turf or bagged for use as a soil additive.” The sentence should read, “The expanded material was mixed with additives to treat lawns to improve turf.”

Journal of Occupational and Environmental Medicine. 55(1):110, January 2013.

Collapse Box


Objective: Low cumulative fiber exposure (CFE) has been associated with health effects in a cohort exposed to Libby vermiculite. This study refines the original 1980 exposure estimates and compares the CFE results.

Methods: Cumulative fiber exposure estimates were developed using three times more industrial hygiene measurements and long-term workers' input. New adjustments included vermiculite ore source, seasonal overtime hours, time spent in various tasks, and recollection of historical dustiness.

Results: The overall mean (95% confidence interval) CFE (n = 513) in 1980 (0.80 [0.69 to 0.93]) was statistically similar to the overall mean (95% confidence interval) CFE in 2010 (0.74 [0.61 to 0.90]). The mean CFE in the lowest exposure category (<2 fiber-years/cm3) decreased from 0.36 to 0.22 fiber-years/cm3 (P < 0.05). The 2010 CFE estimate extended the upper bound of the range of previous estimates from 28.10 to 106.31 fiber-years/cm3.

Conclusions: The range of CFE values was expanded. These estimates may impact the understanding of Libby vermiculite health outcomes.

©2012The American College of Occupational and Environmental Medicine


Article Tools