Quality assurance in biological monitoring of environmental exposure to pollutants: from reference materials to external quality assessment schemes

The presence of chemicals in the environment is a matter of concern in that it poses potential health risks. At present, exposure to toxic chemicals a nd their biological and biochemical effects can be better estimated by biol ogical monitoring, through the systematic collection of specimens from pote ntially exposed humans. Biological monitoring of human exposure to environm ental pollutants is hampered by the difficulty to assess data reliability. As a consequence, the validity of biological monitoring should depend on th e strict implementation of a quality assurance (QA) program, which includes a series of procedures aiming to ensure that laboratory results meet defin ed standards of quality and are reliable. For the validation and monitoring of methods' performance, to ensure the trueness of measurements and to war rant the traceability to international standards, reference materials (RMs) and certified reference materials should be used. Internal quality control and external quality assessment (EQA) are part of overall QA and are carri ed out to verify that analytical errors are compatible with the specific re quirements or needs of the user. In particular EQA schemes (EQAS) allow to test independently the analytical performance of participating laboratories . In the last decades, increasing concern has been raised by urban air poll ution; lead and benzene, two gasoline components released by motor vehicle exhausts, are known to be toxic to humans. For biological monitoring of lea d exposure of the general population, screening campaigns, utilizing lead i n blood as a biomarker, have been carried out since the 1970s. Strict strat egies were adopted to ensure data comparability, including the preparation of RMs, the organization of EQAS and the cross-exchange and analysis of blo od samples between laboratories. Biological monitoring of benzene exposure could be carried out by means of various biomarkers such as benzene in bloo d and benzene, trans,trans-muconic acid (t,t-MA) and S-phenylmercapturic ac id (S-PMA) in urine. At present, few RMs and EQAS are available for these b iomarkers. A pilot EQAS for t,t-MA in urine, adopted to assess the reliabil ity of data regarding benzene exposure, has been organized and carried out between 1996 and 1997 in Italy. From the accrued experience, it clearly eme rges the importance of strategies designed to guarantee the quality of biol ogical monitoring data. The use of RMs and the participation in EQAS are hi ghly recommended in order to improve the global performance of methods and laboratories involved in biological monitoring. (C) 2000 Elsevier Science B .V. All rights reserved.