Risk assessment of 'endocrine substances': guidance on identifying endocrine disruptors.

The European regulation on plant protection products (1107/2009) and other related legislation only support the marketing and use of chemical products on the basis that they do not induce endocrine disruption in humans or wildlife species. This legislation would appear to make the assumption that endocrine active chemicals should be managed differently from other chemicals presumably due to an assumed lack of a threshold for adverse effects. In the absence of agreed scientific criteria and guidance on how to identify and evaluate endocrine activity and disruption within these pieces of legislation, a European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) task force was formed to provide scientific criteria that may be used within the context of these three legislative documents. The first ECETOC technical report and associated workshop, held in 2009, presented a science-based concept on how to identify endocrine activity and disrupting properties of chemicals for both human health and the environment. Specific scientific criteria for the determination of endocrine activity and disrupting properties that integrate information from both regulatory toxicity studies and mechanistic/screening studies were proposed. These criteria combined the nature of the adverse effects detected in studies which give concern for endocrine toxicity with an understanding of the mode of action of toxicity so that adverse effects can be explained scientifically. A key element in the data evaluation is the consideration of all available information in a weight-of-evidence approach. Both sets of data (evidence of the adverse effect in apical studies and conclusive mode of action knowledge) are essential in order to correctly identify endocrine disruption according to accepted definitions. As the legislation seeks to regulate chemicals on a mode of action rather than the more traditional approach of adverse endpoints, then conclusive evidence of the mode of action of concern should be presented. From a human safety perspective and in the absence of any compelling data that endocrine active chemicals exert their adverse effects through anything other than a threshold mechanism there is no scientific justification for not using a margin of exposure approach to risk assessment in order to best protect human health.

The mouse carcinogenicity study is no longer a scientifically justifiable core data requirement for the safety assessment of pesticides.

Regulatory tests investigating pesticide carcinogenicity potential routinely comprise a battery of in vitro and in vivo genotoxicity studies and two cancer bioassays, one in rats and one in mice. The genotoxicity testing strategy essentially ensures that genotoxic compounds are eliminated, and any carcinogens identified in subsequent lifetime studies are probably nongenotoxic in character. Assessment of 202 pesticide evaluations from the European Union review programme under Directive 91/414/EEC indicated that the mouse carcinogenicity study contributed little or nothing to either derivation of an acceptable daily intake (ADI) for assessment of chronic risk to humans, or hazard classification for labelling purposes. From a pesticide approval perspective, the mouse study did not influence a single outcome. From a risk assessment perspective, the ADI for just one pesticide was based on tumours in mice and this would have barely changed if the mouse data had not been available. In total, only 10 (5%) pesticide ADIs were based solely on the mouse carcinogenicity study and even in these few cases, a similar value would have been identified from other studies if the mouse study had not been available. For pesticides with treatment-related tumours only in mice, just three, or 1.5%, were classified as carcinogens and all were in the lowest category, Category 3 (R40). For pesticides with treatment-related tumours in mice and rats, the mouse data were probably the main, if not the only, cause for another three cases of R40 classification. Absence of the mouse studies would not have influenced assignment of the higher, Category 2 (R45), cancer classification for any substance with treatment-related tumours in both species as all decisions for these substances were limited to Category 3 or 'unclassified' outcomes. Over 100,000 mice were used to test these pesticides. This review shows that the mouse carcinogenicity studies did not provide significant information over and above that provided by the rat studies, and underpins the opportunity, from both a scientific and an animal welfare perspective, to remove the mouse carcinogenicity study from regulatory data requirements for the testing of pesticides.