Current Man-Made Mineral Fibers (MMMF) Exposures Among Ontario Construction Workers

Current occupational exposures to man-made mineral fibers (MMMF), including refractory ceramic fibers (RCF), were measured as part of an exposure assessment program for an epidemiological study pertaining to cancer and mortality patterns of Ontario construction workers. The assessments were carried out at commercial and residential sites. A total of 130 MMMF samples (104 personal and 26 area) was collected and included 21 RCF (16 personal and 5 area). The samples were analyzed by the World Health Organization method in which both respirable and nonrespirable airborne fibers are counted. The results show that Ontario construction workers' full-shift exposure to MMMF (excluding RCF) is generally lower than the American Conference of Governmental Industrial Hygienists' (ACGIH) recommended threshold limit value-time-weighted average (TLV-TWA) of 1 fibers/cc and thus should not present any significant hazard. However, approximately 40% of the occupational exposures to RCF are higher than ACGIH's TLV-TWA of 0.2 fibers/cc and present a significant potential hazard. Workers generally wore adequate approved respiratory protection, especially while performing particularly dusty tasks such as blowing, spraying, and cutting, so the actual exposure received by workers was lower than the reported values. Adequate control measures such as ventilation and respiratory protection should always be used when work involves RCF.