Biomarkers of Exposure
Biomarkers of exposure are chemicals found in the body providing evidence of environmental exposure to that chemical or to a precursor chemical. Biomarkers have been utilized in occupational studies for more than a century, and in environmental studies more recently. Sometimes a biomarker is the most telling evidence of the effectiveness of an environmental regulation or societal behavioral change, as was shown by the decline of lead in blood following its removal from gasoline and the decline of cotinine (a tobacco derivative) in blood of children coinciding with the decline of cigarette smoking in this country. Some principles governing the use of biomarkers are described —they must be specific to the chemical of interest, quantitatively related to its level in the environmental medium, and be amenable to precise analytical measurements. Other factors affecting selection of biomarkers include the willingness of persons to provide exhaled breath, blood, urine, bone, fat, saliva, or other samples typically employed for biomarker identification. In some cases, biomarkers have provided important information that was not available by normal methods of measurement, as in the discovery that mainstream smoke (the smoke inhaled by the smoker, which is not measurable by air quality monitors) provides the dominant source of benzene and other aromatic compounds for active smokers. Biomarkers for three major pollutant groups are discussed.