Exposure markers

Biomarkers are broadly defined as indicators signaling events in biologic systems or samples. They have been classified as markers of exposure, markers of effect, and markers of susceptibility (NAS/NRC 1989). 

Besides alkylphosphates, OP metabolism gives rise to the production of other metabolites that can be used as exposure markers (Table 4). Unchanged OP compounds in blood or urine can also be measured to confirm exposure (Table 4), but this method is of limited use for routine biological monitoring of occupational exposure, as OP compounds are rapidly excreted in urine. Moreover, most OP pesticides are unstable, and, with a few exceptions, they are not detectable in biological specimens after a few hours. So far, the measurement of unchanged compounds in biological fluids has been performed primarily for research purposes and has limited practical applicability. 

Graziano J. 1994. Validity of lead exposure markers in diagnosis and surveillance. Clin Chem 40 1387-1390. 

Vanden Heuvel, R. L., et. al., Immunologic biomarkers in relation to exposure markers of PCBs and dioxins in Flemish adolescents, Environ. Health Perspect., 110, 595, 2002. 

Interestingly, it was shown that 8-oxodGuo 46, an ubiquitous exposure marker of DNA exposed to most oxidizing agents , is a much better substrate than dGuo 36 to further oxidation by O2 and one-electron oxidants. 

Culver, B.D., P.T. Shen, T.H. Taylor, A. Lee-Eeldstein, H. Anton-Culver, and P.L. Strong. 1994. The relationship of blood- and urine-boron to boron exposure in borax-workers and the usefulness of urine-boron as an exposure marker. Environ. Health Perspec. 102(Suppl. 7) 133-137. 

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