Abstract
Objective: Studies were carried out in Kumamoto, Japan to examine 1) the winter-summer differences in the average individual exposure to styrene (8hr-TWA) and to end-shift-urinary mandelic acid (MA in g/g Cr), 2) the possible seasonal difference in their relationship, and 3) the protective effect of a disposable particulate respirator containing charcoal fiber (called a “charcoal mask”) and a charcoal granule cartridge-mask (called a “gas mask”) in the real working conditions. Methods: Approximately 100 male and female workers from about 10 small industries were subjected to the studies first in winter and second in summer. Individual exposure to styrene was monitored with a passive sampler during work time, and end-shift-urine was collected to determine urinary MA excretion. The content of their activities and the types of protective equipment were observed and recorded by the minute throughout the working day. Results: Neither individual exposure to styrene nor urinary MA excretion differed at the time of the study in both “no-mask” and “gas mask” groups. The urinary MA excretion was related to individual exposure to styrene in both seasons, with the highest correlation coefficient in the “no-mask” group. Since the regression slope for the “charcoal mask” group did not differ from that for “no-mask” group, the “charcoal mask” was judged to have little protective effect in practical working conditions. From the difference in urinary MA values at 50 ppm (previous TLV-TWA by ACGIH) of individual exposure to styrene in the two regressions for “no-mask” and “gas mask” groups, 49% of styrene was protected against by the “gas mask” in winter, and 45% in summer. Conclusions: Despite different physical environmental conditions, individual exposure to styrene and urinary MA excretion did not differ by season in FRP-making industries. A “gas mask” is more recommended than a “charcoal mask” when treating styrene, although their protective effects are decreased in practical working settings. It is basically necessary to give correct information on and free access to such protective equipment to styrene-treating workers.
