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In a lindane (gamma-hexachlorocyclohexane = gamma-benzenehexachloride)-producing factor 57 workers were studied with regard to their blood levels of the three hexachlorocyclohexane isomers: alpha-, beta-, and gamma-HCH. The TLV-TWA (MAK value 1979) for gamma-HCH of 0.5 mg/m3 was not exceeded at any of the workplaces where HCH is synthesized and purified to lindane. Additionally, in some of the workers samples of s.c. adipose tissue were taken for determination of HCH-isomer content. An external group of 20 clerks was examined in the same way for control purposes. In contrast to the control persons, none of whom had HCH-concentrations in serum above the respective detection limits, the values determined in serum of the exposed workers were in the following ranges: alpha-HCH: 10-273 microgram/1, beta-HCH: 17-760 microgram/l, and gamma-HCH: 5-188 microgram/1. Of special interest is the observation of a significant increase of beta-HCH-concentration in serum with the time of employment in lindane production, indicating a pronounced accumulation of this substance in the human organism. Concentrations of this isomer in s.c. adipose tissues were about 300-fold higher than in serum. A significant correlation between both parameters could be established. The results of this study show that adherence to the TLV-TWA of gamma-HCH is not sufficient for control of HCH-exposure. Furthermore, biological monitoring of exposed workers is necessary taking into account the three more important isomers alpha-, beta-, and gamma-HCH.

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Biological monitoring of chemical exposure in the workplace and in the environment has become increasingly important in assessing health risk. The analysis must be carried out under a quality assurance scheme to guarantee that the results obtained in biological monitoring are comparable with the threshold limit values and results from other laboratories. Since 1982, the German Society for Occupational and Environmental Medicine has offered 28 intercomparison programs. These programs cover 96 analytes in urine, blood, and plasma for 47 substances and cover most parameters that are relevant in occupational and environmental medicine. The data obtained in these programs provide a good overview of the current quality of the determination of analytes that are assessed in occupational and environmental toxicological laboratories. For the analyses of inorganic substances in blood and urine, the tolerable variation ranges from 7.5% to 43.5%. For organic substances in urine, the tolerable variation ranges from 12% to 48%. For organic substances in urine, the tolerable variation ranges from 12% to 48%. The highest variations (36% to 60%) were found for the analysis of organochlorine compounds in plasma.The tolerable variations for determining solvents in blood by head space gas chromatography range from 26% to 57%. The overall average success rates for the participants of the external quality programs range from 65% to 75%.