Current pesticide dietary risk assessment in light of comparable animal study NOAELs after chronic and short-termed exposure durations

Dietary risk assessment (DRA) of pesticides includes the estimation of chronic and acute exposures from crop residues, but assesses acute exposures only for pesticides with an acute reference dose (ARfD). Acute estimation uses high percentiles of food consumption surveys which are considerably higher than per capita lifetime averaged food consumption values which are used for chronic estimations. Assessing acute risks only for pesticides with an ARfD tacitly assumes that chronic risk assessment covers also intermittent occurring exposures which could significantly exceed chronic estimates. The present investigation conducted on 2200 rat studies from 436 pesticides provides evidence demonstrating that pesticides with and without ARfD have no-observed-adverse-effect levels (NOAELs) which remain statistically unchanged in developmental, subacute, subchronic, reproductive and chronic toxicity studies covering exposure durations between 2 and 104 weeks. DRA of pesticides without ARfD needs reconsideration in light of equally high toxic dose levels after short- and long-term exposures, suggesting that intermittent exposures could be toxic, if they repeatedly exceed the acceptable chronic daily intake (ADI; conceptually the human counterpart of chronic animal NOAEL). As such risks are currently not assessed for pesticides without ARfD, the current DRA concept, which automatically presumes the use of low chronic exposure estimates entirely covers the risks of not acutely toxic pesticides, needs reconsideration. Furthermore, risks to intermittent occurring high exposures are probably also insufficiently assessed for pesticides where the ARfD is significantly higher than the ADI. As an example, the maximum residue limit for bifenazate in peaches is discussed.