The German external quality assessment scheme in occupational and environmental medicine.

According to a technical guideline for dangerous substances (TRGS 410) issued in 1979 by the Ministry of Labour of the Federal Republic of Germany, toxicological analyses in biological materials must be performed under conditions of "statistical quality control". The German Society for Occupational and Environmental Medicine is entrusted with the organization of the German external quality assessment scheme (EQAS). Since 1982 about 100 laboratories regularly take part in each run. Blood and urine samples spiked with two different concentrations (A, B) are distributed to the laboratories. Since 1991 additional samples with environmental exposure levels are also included in the EQAS. A laboratory is certified as successful if both its results (A, B) fall within the tolerance range given by the reference laboratories. The thirteenth (1994) external quality assessment exercise included blood and urine samples containing 21 inorganic and 29 organic substances, besides 8 inorganic and 14 organic analytes within the environmental concentration range.