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

Jürg A Zarn,Caitlyn D O'Brien

doi:10.1007/s00204-017-2052-4

Jürg A Zarn, Caitlyn D O'Brien

Open Access

https://doi.org/10.1007/s00204-017-2052-4

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Abstract

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.

Highlights

Dietary risk assessment (DRA) is an integral part of the authorization process of plant protection products (PPP), within which exposure risks related to residues remaining in treated crops are assessed
acceptable daily intake (ADI) Acceptable daily intake acceptable operator exposure level (AOEL) Acceptable operator exposure level acute reference dose (ARfD) Acute reference dose bw Body weight complete data set (CS)/CS5/CS8 Complete data set of studies/subset of studies with dose spacing ≤5/subset of studies with dose spacing ≤8 DRA Dietary risk assessment EFSA European Food Safety Authority healthbased guidance values (HBGVs) Health-based guidance value international estimated daily intake (IEDI) International estimated daily intake international estimated short-term intake (IESTI) International estimated short-term intake JMPR Joint FAO/WHO Meeting on Pesticide Residues LOAEL Lowest-observed-adverse-effect level maximum residue limits (MRLs) Maximum residue level no-observed-adverse-effect levels (NOAELs) No-observed-adverse-effect level PPP Plant protection product US EPA United States Environmental Protection Agency
Toxicity data were managed by means of a Microsoft Office Access 2007 database (Zarn et al 2011, 2015) populated with publicly available PPP evaluations, which were retrieved from the European Food Safety Authority (EFSA 2014), the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) (WHO 2011) and the United States Environmental Protection Agency (USEPA 2011)

Summary

Introduction

Dietary risk assessment (DRA) is an integral part of the authorization process of plant protection products (PPP), within which exposure risks related to residues remaining in treated crops are assessed. DRA compares estimates of acute and chronic exposures of the compound to human healthbased guidance values (HBGVs). DRA is conducted for the purpose of defining legally binding safe maximum residue limits (MRLs) for each pesticide–crop pair. For this purpose, DRA needs to adequately integrate the toxic potency and the exposure for different exposure durations. HBGVs such as acute reference dose (ARfD), acceptable daily intake (ADI) and acceptable operator exposure level (AOEL) are derived from toxicological data and represent maximum acceptable exposure limits for humans at different exposure scenarios (FAO/WHO 2009). The AOEL corresponds to the short-term HBGV for operators and workers exposed only over a short time (EU 2006)

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