Urinary alkyl phosphate metabolites

The detection of pesticide metabolites in the urine of workers indicates prior exposure. However, it is difficult to relate this level of urinary metabolite to the actual worker exposure, and it is equally difficult to Interpret the toxicological significance of the level. A preliminary study conducted in rats exposed dermally to 100, 200 and 400 ug of azinphos-methyl showed a significant linear correlation between the dermal dosage and the urinary alkyl phosphate metabolite levels (19). Further studies are being conducted in other species to determine whether a similar type of relationship occurs and to develop a standard curve in which urinary metabolite levels could be utilized to estimate the amount of dermal exposure. 

In addition to the above-described alkyl phosphates, a few less common metabolites can be mentioned, e.g. 3,5,6-trichloro-2-pyridinol (TCP). TCP is a major product of esterase cleavage of the OPi chlorpyrifos and chlopyrifos-methyl." ° Urinary TCP, like other... 

Stone). In the last-named situation, where there will be likely exposure to a mixture of OPs, there is a serious problem in that the biological significance of the findings will be unclear. Furthermore, alkyl phosphates may be present in the environment (presumably from biotic or abiotic degradation of OPs) so it cannot be assumed that all alkyl phosphate seen in human urine is derived from metabolism of OPs in humans. Substance-specific urinary metabolites can be measured as an alternative to, or in addition to alkyl phosphates,and one such is discussed above in relationship to propetamphos. Unlike the metabolite of propetamphos, which is an unusual alkyl phosphate, these are generally metabolites of the leaving group and include 2-isopropyl-6-methyl-pyrimidin-4-ol, a metabolite of diazinon, and 3,5,6-trichloro-2-pyridinol, a metabolite of chlorpyrifos. For a list of substance-specific urinary analytes available for seleeted OPs, see Jain. ... 

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