Summary of the 6th SETAC Europe Special Science Symposium: Environmental Endocrine Disrupter Testing and Evaluation
Christoph Schäfers, Fraunhofer Institute Molecular Biology and Applied Ecology
The issue of detection and regulation of environmental endocrine disrupters (ED) has developed during the last two decades. Thanks to scientific efforts to identify sexual (mostly estrogenic) EDs in vertebrates, it became obvious that some industrial chemicals (e.g. alkylphenols, phthalates, bisphenol A), but even more importantly contraceptive pharmaceuticals constituted the highest risk. In the following years, the ED issue was extended to additional mechanisms and to invertebrates. At the same time, national and international efforts developed and validated guidelines, testing and assessment schemes. In different areas of substance regulation in different parts of the world, different schemes evolved, partly referencing each other and partly neglecting each other. The attribution of ED with specific concerns (low dose effects, non-monotonic dose-response relationships) resulted in the European Union (EU) decision to regulate ED based on hazard properties. The EU is working at a final definition of ED for the European Community Regulation on chemicals and their safe use (REACH) (EC 1907/2006), biocide regulation and plant protection. Thus, time was ripe for the SETAC Europe Special Science Symposium on Environmental Endocrine Disrupter Testing and Evaluation.
The symposium provided a sound overview of the state of the art in ED regulation with all its unsolved issues and shortcomings as well as its achievements to date. It included 18 oral presentations and 19 posters. There were 127 attendees from 20 countries representing business (>50%), government (30%) and academia (13%) with a clear majority of stakeholders directly involved in ED regulation. Eastern and southern European countries were represented. The Organisation for Economic Co-operation and Development (OECD) perspective was obvious by the attendence of speakers and participants from Japan, the United States of America (US), Canada and Australia. The chairs, Annegaaike Leopold and Peter Matthiessen, were assisted by a steering committee of Will Davies, Tom Hutchinson, Laurent Lagadic, Tinka Murk, Veronique Poulsen, Henrik Tyle and James Wheeler.
A summary of the key issues covered by the speakers and during the panel discussions is presented below and was prepared by the co-chair Peter Matthiessen and slightly modified by the author.
EDs are a real-world concern
- Good evidence exists of serious physiological impacts in birds, fish and molluscs.
- Examples of evidence for population effects are limited.
- Both older and more modern chemicals have been associated with ED effects.
- Some natural substances (release by agricultural activities) also cause ED effects.
- There are several examples of EDs that evaded traditional chemical assessments. Sound regulation of EDs using new hazard evaluation tools is therefore required, but,
- There is still much uncertainty about the overall significance of EDs for humans and wildlife, so more monitoring and prospective epidemiology are also required.
Current regulatory requirements for EDs
- New regulations emphasize that EDs have special properties distinct from other chemicals,
- The US Environmental Protection Agency (USEPA) Endocrine Disruptor Screening Program (EDSP) is up and running at Tier 1 ($860K per chemical).
- The only selection criterion for chemicals is environmental exposure (no suspicion of endocrine disruption).
- EDSP Tier 1 screens are a mixture of in vitro and in vivo assays sensitive to estrogen/androgen/thyroid/steroidogenesis (EATS).
- Tier 1 data for 67 List 1 chemicals are due in 2013
- Tier 2 in vivo data will then be used for risk assessment of chemicals screening positive (no agreement yet on how to do risk assessment with EDs).
- Next,134 USEPA List 2 chemicals to be screened.
- In the EU, EDs are explicitly mentioned as a special group in the European directive on plant protection products, in the biocides directive and in REACH.
- Testing for ED properties in the EU awaits agreement on how to define EDs in regulatory terms (end 2013)
- The plant protection products regulation will regulate EDs on their endocrine hazard alone, i.e., no risk assessment.
- Essentially, regulation by hazard is also in REACH but with a socio-economic opt out and some consideration of tonnage.
- ED biocides may be approved if no unacceptable effects can be demonstrated in the field or by socio-economic opt out.
- No EU regulations on EDs exist at present for cosmetics and pharmaceuticals despite major impacts from synthetic estrogens.
- Other jurisdictions (e.g., Japan) have not yet enacted specific legislation but are conducting research and watching developments in the US and EU. Japan plans to use risk assessment.
Standardised tests for EDs
- Some in vitro and in vivo assays with specific sensitivity to EDs have now been standardised by OECD.
- These are focusing on EATS modalities.
- Standardised assays are mainly at Levels 2-4 of the OECD conceptual framework; in vivo assays include fish, amphibians and mammals.
- The existing testing suite is therefore mainly suitable for screening rather than full evaluation of adverse apical effects—apical endpoints are empirically verifiable outcomes of exposure such as developmental anomalies, breeding behaviors, impaired reproduction, physical changes and alterations in the size and histopathology of organs and mortality—www.niehs.nih.gov/news/newsletter/2007/september/toxicitytesting.cfm.
- Limited experience to date with OECD screening assays suggests that most do the job intended for them and can give valuable alerts to the possibility of adverse apical effects.
- Many assays require in-house revalidation when staff change and some have too many acceptance criteria.
- Some operational problems are at least partly attributable to inexperience in testing labs; staff training and advance planning are essential.
- Limited evaluations are yet to be done by regulators—guidance is needed on testing strategies and weight-of-evidence assessment.
EU regulatory criteria for EDs
- Fairly general approval exists for the World Health Organisation‘s scientific definition of EDs.
- There is still major controversy over regulatory criteria for EDs to be used in the EU.
- Some believe that any adverse in vivo effect caused by an endocrine mechanism should be sufficient to label a substance as an ED.
- Others feel that ED endpoints are irrelevant if they are of low potency and/or if non-endocrine adverse effects occur at much lower concentrations.
- Fundamental disagreement exists about ED risk assessment, analogous with disagreements about carcinogen and mutagen risk assessment.
- The aim is for the same criteria to apply to all EU legislation, but this may still lead to some conflicting outcomes, which is undesirable.
- There is no consensus on use of potency for defining ED categories or on the evidence needed to show causality.
- There is need to define what is meant by "negligible" exposure in the environment.
- Hopefully it will prove possible to differentiate between the ‘bad guys’ and those of less concern in relation to their benefit, or we may lose some important chemicals.
- Two EU working groups are now wrestling with these issues, which must be resolved in 2013.
Application of ED tests in assessment schemes
- OECD Guidance Document Number 150 provides detailed advice on how to assess assay outputs and draw conclusions about further testing.
- Some assays can give equivocal results that require expert judgement for their assessment in the light of other data.
- Weight-of-evidence assessment is crucial in all evaluations to make a reliable link between an endocrine mechanism and an adverse apical effect. No single assay does it all.
- Weight-of-evidence assessments can be done in many ways (e.g., hypothesis-driven scoring and weighting schemes such as that proposed by Borgert et al. (2011).
- ED tests also need to be fully integrated into overall chemical assessment schemes such as the proposed testing strategy in the OECD Fish Toxicity Testing Framework (OECD Series on Testing and Assessment Number 171).
- Low-dose and non-monotonic effects of EDs probably occur in some cases (although this remains controversial). However, these types of response may not preclude reliable risk assessment.
New and alternative tests
- We need more in vitro screens, especially with metabolic competence. Present risk of false negatives in vitro.
- Many in vivo ecotoxicity tests at OECD Levels 4 and 5 of the CF are now in validation.
- A reasonably complete screening and testing suite for evaluating EATS effects in vertebrates will be available within 3 years.
- Many other potential types of vertebrate EDs (e.g. corticosteroid effects) are still being investigated for which screening assays are not yet developed and/or validated—we will also need genomics, binding assays and a big focus on invertebrate ED mechanistic assays.
Intelligent testing strategies
- There is a desire to develop testing strategies that minimise the use of animal testing and maximise the speed/efficiency with which large numbers of chemicals can be evaluated.
- The development of adverse outcome pathways and computational biology (including bioinformatics) will assist in this.
- Efficiency/speed will also improve through the development of quicker in vitro testing (e.g., high throughput screens).
- Such mechanistic methods will not replace in vivo testing for many years (if ever), but they will at least be essential for prioritisation and screening.
- Finally, a more comprehensive strategy is required covering the whole animal kingdom (especially invertebrates) and relatively unexplored ‘beyond EATS’ modes of action, but this requires deeper endocrinological understanding.
During the symposium, discussions arose on the pros and cons of hazard versus risk assessment. Regulatory data generation is driven by regulatory requirements and supported by the possibility of industry to replace (over-)protective lower tier data/default values by data demonstrating environmental safety under realistic conditions. By focussing regulation only on hazard assessment, scientific efforts to identify thresholds for population-relevant adverse effects and/or to link exposure and effects by including spatial and temporal variability of exposure and organism dispersal, as identified as crucial scientific questions for other contaminants, are ignored. Instead, scientific efforts focus on understanding interactions with endocrine pathways. This was regarded a step forward for ED-specific academic research. However, as there is no way to demonstrate negligibility of findings by linking them to realistic exposure; the only way is to demonstrate population-irrelevance of the obeserved effect, which is hardly possible. This might disincentivize industry-sponsored data generation, which can be regarded as a step back for ED regulation.
In conclusion, the symposium was interesting and encouraged scientific dispute in an open and well-meaning atmosphere, more inspiring than frustrating. It underlined the importance of SETAC, with its tripartite structure, as a venue for exchanging information and opinions across the reulatory, business and academic sectors. This summary should end with Matthiessen’s last bullet point:
- The story of Endocrine Disrupter regulation is only just beginning!
Author’s contact information: email@example.com
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