Biological monitoring of standardized exposure to ethylbenzene: evaluationof a biological tolerance (BAT) value

The results of standardized 8 h lasting exposures of n = 18 volunteers to e thylbenzene (EthBz) at levels of 25 and 100% of the maximum allowable conce ntrations at the workplace (MAK) value of 100 ppm as well as the results of field studies are considered to evaluate a biological tolerance (BAT) valu e for EthBz. On the basis of the relationship between the external and inte rnal exposure a BAT value of 1.5 mg/l has been set for the EthBz concentrat ion in blood as the most sensitive and specific parameter of exposure to th is aromatic hydrocarbon. The interpretation of EthBz blood values has to ta ke into account the short half-life of t(1/2) = 0.5 +/- 0.08 h in the first hour after the end of exposure in which this aromatic hydrocarbon is elimi nated from the blood. The additional determination of the EthBz metabolites mandelic acid (MA) and phenylglyoxylic acid (PGA), respectively, excreted in post shift urine as well as in urine samples at the beginning of the nex t shift shows good correlations with the external exposure. The biological half-life of MA was calculated to t(1/2) = 5.3 +/- 1.1 h, Because the time of sampling can vary the relationship between the levels of MA to PGA the t otal concentration of the excreted metabolites depends less on this influen ce and is therefore better suited for monitoring exposed persons. On the ba sis of the standardized experiments a BAT value has been proposed of 2 g MA plus PCA corrected per gram creatinine. Both BAT values are adjusted to da ta which result from earlier standardized exposures during 30 min to EthBz under physical activity of 50 watt on a bicycle ergometer.