| The occupational exposure to styrene is a common problem in the manufacture of reinforced plastic products. Two methods have been developed and validated for environmental control of the occupational exposure to styrene, and another two methods for its biological control. Environmental control methods are based on the use of passive devices, one for solvent desorption, and the other for thermal desorption. Biological control procedures are based on the determination of styrene in exhaled breath and urine. In both biological methods, styrene is collected in tubes filled with Tenax TA for thermal desorption. Analyses were performed using chromatographic techniques. The performance of environmental control methods were verified in field studies. There is no significant differences between the results obtained using passive methods and the obtained using an active method, based on activated charcoal tubes.;The main part of this work consisted of the toxicological evaluation of an occupational population exposed to styrene, using the developed methods. Environmental samples were taken in the breathing zone of the workers during the exposure time, while exhaled breath and urine samples were obtained from each worker at the end of their exposure. Environmental concentration of styrene, styrene metabolites-mandelic and phenylglioxilic acids in urine-, styrene in urine and styrene in end-exhaled breath were determined. 31% of the evaluated population was exposed to environmental concentrations above the threshold limit value established for a daily exposure of 8 hours (TLV-TWA). Linear regression analysis between the external dose received (obtained from the environmental concentration) and the internal dose (biological determinants concentrations) were performed, obtaining significant correlations. The best results of correlation were achieved for unmetabolized styrene. It was found that styrene concentration in end-exhaled breath depends on the exposure pattern, being lower when exposure was fluctuating than when environmental concentrations were more stable. Considering the external dose corresponding to the TLV-TWA, new biological exposure indices (BEI's) for styrene have been suggested. Finally, it is proposed that for exposure periods lower than 8 hours biological sampling must be performed at the end of these periods, in order not to underestimate the internal dose received, no matter whether that moment agrees or not with the end of the working day. |
