Workshop Report 28

Group 3B

group 3b

Whilst the original questions developed before the workshop were addressed in the other syndicates, group 3B choose to address another set of questions which were proposed by the workshop organisers immediately prior to this syndicate session. The new questions were:

  1. What can we do to improve regulatory use of species sensitivity distribution methods?
  2. How can we achieve this?

Syndicate session report

The 3 recommendations that arose from the syndicates discussions were to:

  1. develop a compendium of SSD best practice;
  2. use uncertainty to steer future research;
  3. improve communication.

1. A compendium of SSD best practices

It was agreed, that the SSD methodology is a valuable regulatory and management tool since it can give more insight into the potential ecological effects than the assessment factor method (enabling better problem definitions) and it yields more generalisable results than a mesocosm-based methodology.

It was felt that a compendium of current best practices, the state of the science and answers to frequently asked questions would facilitate acceptance of SSDs by regulators and risk managers and their implementation in regulation and management. The compendium should be a technical document aimed at users with knowledge of SSDs and ecosystems. However, this would limit the usefulness of the compendium and therefore another document suitable for a general audience is also necessary.

During the workshop it was shown that SSDs are being derived differently by different jurisdictions, e.g. they have different minimal data requirements to sufficiently represent ecosystems of concern. Despite this, analyses of HC5 values (the SSD output used for standards or thresholds setting), showed that SSDs give robust results based on a relatively low number of input data, if the data are distributed uni-modally and the most sensitive taxonomic groups are included. Less robust HC5 values have to be expected, if a very sensitive taxonomic group is overlooked or if the data are patchy and seem to have multiple-modes. This variability supports the idea of deriving a compendium that will highlight to the risk assessor and regulator when such considerations are important. Within such a compendium, decision trees to guide professional judgement were seen as a good way to avoid overly strict use of data requirements and derivation methods while ensuring clear identification of situations where the application of strict requirements are necessary, e.g. as laid down in the REACH Technical Guidance Document (ECHA, 2011). For example, while for some herbicides missing insect data might not have a severe impact on the accuracy of the SSD, the example of the chronic SSDs for triclosan shown by Anne Gosselin (section 3.18) underlines the general usefulness of falling back on a broader set of data requirements. Although the REACH criteria were pretty much fulfilled in the case of triclosan, the identification of the most relevant data was difficult, resulting in HC5 values, derived by considering different groups, ranging over 1 order of magnitude. In any case, the compendium should be flexible enough to allow the risk assessor to tailor the use of SSDs to the actual ecological question being considered.

To make the best use of the already existing SSD guidelines and methods, it was also proposed to promote databases to increase the availability of toxicity data and to reduce duplication of effort. Together with more research on the question of how in vitro and in silico approaches can be used within a compendium of best practices for use of SSDs in risk assessment, greater availability of such databases may boost the use of SSDs as a versatile, lower-tier approach within current environmental risk assessment schemes.

When using SSDs for predicting effects in the field, knowledge of effects of non-chemical stressors should be incorporated where available, to promote a multi-stress ecotoxicology/ecology analysis. This is very important to ensure risk managers or regulators do not ‘jump to the wrong conclusion’ and take action to fix a less important pressure, or fail to fix a problem that really does need attention. This multi-stress analysis may be based on existing ecological knowledge on optimal population growth conditions, as well as existing knowledge on ecosystem modelling. Improved liaising to ecology is indeed possible within SSD-derivation and interpretation, as shown in various presentations.

The compendium should also answer ‘frequently asked questions’ such as whether the use of an SSD partially or totally based on species from regionally or climatically different ecosystems would be scientifically sound, and if not – which options are suggested.

Finally the compendium would be an important document that will facilitate international harmonisation of the use of SSDs. It will not be possible to have a single internationally agreed method for deriving water quality guidelines/limits/standards. However, by presenting the state of the science it should be possible to harmonise individual components of the overall methodology. For example, agreement could be reached on the types of toxicity data (measures and endpoints) that can be used, or methods for assessing the quality of toxicity data. By providing a common platform the compendium could be used to establish international peer groups that could provide guidance on the appropriateness of decisions based on professional (expert) judgement. Such peer review conducted during the derivation of Environmental Quality Standards (EQSs) for specific pollutants under the EU Water Framework Directive has proven valuable and could help promote consistency when standards for the same substance are derived by different authorities. A compendium could also facilitate the implementation of SSDs in newly established environmental risk assessment schemes in other countries, both for deriving criteria and for evaluation of risk management scenarios for contaminated ecosystems.

2. Uncertainty driven research

Throughout the workshop and in all 3 sessions from syndicate B, uncertainty was identified as an important and recurring issue. Studies should be conducted to identify the magnitude of the uncertainty of various components of the SSD methodology. Uncertainty may be related to lack of data, (non)representativity of data, mode of action considerations, and many other aspects of real exposure situations. An understanding of the mathematical magnitude of uncertainty alone may not be enough as it is possible that large sources of error may have little ecological importance, and vice-versa. Research should then be focussed on reducing the uncertainty of the most important sources uncertainty in the SSD methodology. The group felt that uncertainty-driven research would be an important means to improve SSDs and maximise their usefulness in a cost-efficient manner. An uncertainty driven research agenda is also likely to increase uptake of the other methods that can be used in combination with SSDs e.g. QSARs, Web-ICE.

A simple example of uncertainty-driven research would be the selection of chemicals (or species) to be used in ecotoxicity tests. If the toxicity of a chemical to a large number of species belonging to different taxonomic groups has been determined then the need for further research for that chemical may be low compared to a chemical that has been the subject of no or minimal toxicity testing. Another example is that very few SSDs have been conducted for non-chemical stressors (e.g. temperature, salinity) or the combined action of chemical and non-chemical stressors. Conducting such research could dramatically reduce uncertainty in the ecological relevance of single chemical SSDs, and place the risks posed by chemicals into a more meaningful context that addresses all possible pressures.

  1. Communication

Communicating the success and limitations of the SSD methodology was felt to be essential. 2 targets of communication were identified: (1) regulators and stakeholders and (2) users and potential users, representing passive (results) and active (analysers) users, respectively. For the first group some basic communication gaps need to be bridged such as how the SSD method works, its underlying assumptions as well as the magnitude of the uncertainties of SSD-based risk assessments. It was also felt important to explain the implications of the fact that regulatory decisions are often based on single numerical values, which ignores the underlying uncertainties in the estimate and model assumptions. The compendium (the first of our proposals) would certainly help address some of these issues, but is likely to be quite technical and not appropriate for all users and potential SSD- result users. Hence, a way must be found to also simply communicate the boundaries of certainty around the predicted HC estimate. A clear and easy to understand communication strategy is needed including ‘success stories’ of the SSD method. Such communication should assist stakeholder acceptance of risk management measures and hence be an important step in improving environmental quality by regulatory means. Proposals for communication with the second group (active users) focussed mainly around the establishment of communities of practice – whereby users were constantly informing and educating colleagues of the latest developments and the state of the science. This could also be of great benefit to scientists and regulators in developing countries who are just beginning the task of environmental regulation and management of chemicals.