The biological exposure index: its use in assessing chemical exposures in the workplace.

Human exposure to chemicals in the workplace has traditionally been assessed by determining the concentration of an airborne chemical in the workroom air. More recently, biological monitoring has been used to assess worker uptake of chemicals by all routes of exposure. Both approaches for the assessment of exposure and uptake are complementary. This relationship is examined, along with the advantages and limitations of using biological monitoring. The concept of the biological exposure index (BEI), developed by the American Conference of Governmental Industrial Hygienists (ACGIH), and information on the intended use and interpretation of BEIs are described. Examples are presented on the use of biological monitoring in NIOSH Health Hazard Evaluations (e.g., carboxyhemoglobin in blood to assess exposure to carbon monoxide, urinary metabolites of trichloroethylene to assess exposure to trichloroethanol, and 2-ethoxyacetic acid in urine to assess exposure to 2-ethoxyethanol). The progress of current research studies on the biological monitoring of volunteers exposed to paint spray solvents is presented, along with speculation on the future directions of biological monitoring research.