Workshop Report 28

Workshop aims and objectives

Workshop aims

The workshop reviewed current thinking on when and how species sensitivity distributions (SSDs), should be used and discussed how the methodology might be further developed. The workshop considered 3 key aspects:

1) What is the ecological relevance of an SSD?

  • Are ecologically relevant assessments being made? Are regulatory protection goals explicit and clear? Are they set in relation to environmental quality? How do prospective and retrospective approaches differ?
  • Are all species of equal importance, or are there keystone species that are more important than others? If so, how might these be accounted for?
  • Is a generic PNEC derived from an SSD overly simplistic in terms of ecological representativeness? Should representative assemblages/communities (archetypes) to represent different typologies be developed? Should protection goals account for local community composition?
  • How does aquatic community sensitivity vary with species composition? (summary of and developments since Pellston Classic workshop 2001- Ecological Variability: Separating Natural from Anthropogenic Causes of Ecosystem impairment)
  • How can knowledge of chemical mode of action (MoA) help construct SSDs for HC5 estimation?

2) What SSD statistical models are available for deriving toxic thresholds (HC5/PNEC) for aquatic communities?

  • Review current tools and key (statistical) methodology, including assumptions about distributions of sensitivity, use of hierarchical models, interspecies correlations. Identify where there are important differences and what the implications of these could be.
  • As sensitivity to chemical stress seems to be related to taxonomic closeness, how could this be used in the construction and interpretation of SSDs?
  • Do models that utilise prior knowledge, e.g. aquatic toxicity data sets on many species, provide advantages over other methods?
  • Are current modelling success criteria, such as those identified in the REACH Technical Guidance Document (TGD) (ECHA, 2011), sufficient, overly prescriptive or insufficient?

3) Regulatory application

  • Would the methods reviewed in this workshop be accepted for use in regulatory assessments under current guidance? If not, what steps would be needed to facilitate their acceptance in the future?
  • Should current guidance on the use of SSDs be revised in the light of the issues and approaches discussed in this workshop?
  • What implications are there for the interpretation of SSDs and HC5s in risk assessment and risk management?