LONGITUDINAL ESTIMATES OF PULMONARY-FUNCTION IN REFRACTORY CERAMIC FIBER MANUFACTURING WORKERS

Refractory ceramic fibers (RCF) are man-made vitreous fibers (MMVF) us ed in high-temperature industrial applications. Between 1987 and 1994, a prospective study evaluated pulmonary function of 361 male workers currently employed in RCF manufacturing and related operations for pla usibility of a causal relationship between RCF exposure and pulmonary function changes. Workers included in the analysis provided at least f ive pulmonary function tests. The exposure-response relationship was m odeled with two exposure variables: years in a production job, and cum ulative fiber exposure (fiber-mo/cc). Comparison groups were nonproduc tion workers and workers with up to 15 fiber-mo/cc cumulative exposure . A statistically significant decrease in FVC was demonstrated among w orkers employed in production jobs more than 7 yr prior to initial tes t. A similar but nonstatistically significant result was demonstrated for FVC in workers with greater than 60 fiber-mo/cc cumulative exposur e prior to initial pulmonary function test. Similar but nonstatistical ly significant results were obtained for FEV1. These findings, which p rimarily reflect workers employed before 1980, did not persist with an alysis of follow-up production years and accumulated RCF exposure from initial pulmonary function test. Since longitudinal analyses are sens itive to influences that continue to affect annual decline during the study period, lower RCF exposure levels since the 1980s may be respons ible for eliminating any further effect on pulmonary function.