PLATELET MONOAMINE-OXIDASE-B ACTIVITY IN WORKERS EXPOSED TO STYRENE

A cross-sectional study was conducted to evaluate monoamine oxidase ty pe B (MAO-B) activity in platelets as a biomarker of effect of styrene and perchloroethylene exposures. MAO-B is an enzyme system involved i n dopamine catabolism, the impairment of which has been postulated as a mechanism of styrene-induced neurotoxicity. We previously observed a n inverse association between blood styrene and MAO-B among reinforced plastics manufacturing workers. The present study included 59 male bo at plant workers exposed to styrene (exposure range <1-144 ppm, 8-h TW A). Two comparison groups comprised six male dry cleaning workers expo sed to perchloroethylene (PCE; exposure range <2-37 ppm) and 14 male l aundry workers not exposed to either agent. Respiratory protection was not used by any of the styrene- or PCE-exposed workers; thus, air con centrations were regarded as valid exposure indicators. MAO-B activity (pmol/10(8) cells/h) was measured in peripheral blood platelets, usin g phenylethylamine as substrate. Only small overall mean differences i n MAO-B were observed among the three groups; mean Values were 4.21, 4 .51, and 4.12 for the styrene-exposed, PCE-exposed, and laundry worker s, respectively. Despite the absence of gross differences among the gr oups, styrene exposure was inversely related to MAO-B. Mean values for four increasing exposure group quartiles were: 5.60, 4.13, 3.69, and 3.44. The Spearman rank correlation coefficient for styrene with MAO-B was -0.41. Adjustment for age, medication use, smoking, and alcohol c onsumption had only a minimal effect on this trend. Duration of exposu re to styrene bore a weak positive relation to MAO-B (Spearman r = + 0 .29), which was nearly entirely explained by collinearity with age. Th e results from this study are in close quantitative agreement with pre vious findings of an inverse association between styrene exposure and MAO-B. More agents need to be evaluated to establish specificity, and longitudinal analyses of styrene-exposed workers will be required befo re confident conclusions can be reached about the predictive value of MAO-B as a biomarker of styrene-related neurotoxicity.