OBJECTIVETo establish the threshold of toxicological concern(TTC) approach and to apply it in the risk assessment of metabolites, degradation and reaction products of pirimicarb.

METHODSTTC decision tree approach based on Cramer classification was established and Lazar software was used to predict the genotoxicity of the seven transformation products of pirimicarb, namely, R34836, R34885, R35140, R31805, R34865, R16210 and R16192. Dietary exposure in general population as well as in six age population groups was estimated by using data from the Chinese National Nutrition and Health Survey and pirimicarb residue data from national chemical surveillance data in 2011. TTC decision tree approach was used for risk assessment and the exposure was compared with the corresponding TTC values.

RESULTSOf the seven transformations of pirimicarb active substance, namely, R34836, R34885, R35140, R31805, R34865, R16210 and R16192, the maximum dietary exposure of mean and large portion(P 97.5) were all belong to 2-6 age group. The mean exposures of the seven transformation products for 2-6 age group,were 0.0290, 0.0207, 0.0015, 0.0320, 0.0005, 0.6918 and 0.1274 µg/kg,respectively, and the corresponding P 97.5 exposures were 0.0817,0.0581,0.0042,0.0900,0.0014, 1.9459 and 0.3585 µg/kg. Besides, the mean and P 97.5 exposure of R16210 for 2-6 age group was the largest,which were 0.6918 and 1.9459 µg/kg, accounting for 46.12% and 129.73% of the TTC threshold,respectively.

CONCLUSIONTTC decision tree approach is a useful tool for prior screening and primary risk assessment of the transformation products of pesticide active substance.