Sabine Duquesne & Oliver Weisner on holistic, systems-based approach to pesticide risk assessment
Sabine Duquesne (UBA)
“There should be a reality check of the predictive risk assessment to better ensure environmental protection, i.e. a feedback loop between field observations and predictions with possibilities to adjust them.”
Could you please describe your roles and specific tasks within the project?
Oliver: As risk assessors, our role is to bring in our experience from assessing the environmental impact of chemicals and our knowledge on the limitations of the current assessment scheme to protect biodiversity. By doing so, we aim to assist in shaping the case studies to provide data that can deliver applicable information for environmental risk assessment. In the end, we will work with the whole consortium to translate the case studies’ findings and modelling results into steps to take for better, systems-based environmental risk assessment.
Sabine: In addition to these scientific tasks, we are also contributing to engaging stakeholders beyond the SYBERAC consortium by organising surveys or workshops with other project partners, and bridging project aims, approaches and results between SYBERAC and the related EU project PARC (Partnership for the Assessment of Risks from Chemicals).
How do you envision the project’s outcomes influencing your field of work or research area?
Sabine: The outcomes of SYBERAC should both highlight gaps in the environmental risk assessment and provide concepts for closing these to enable a better protection of the environment and biodiversity. Using the results from case studies and modelling, we will hopefully be able to better calibrate the risk assessment towards the reality in the field. The ultimate goal is to reframe the environmental risk assessment more deeply by having a more holistic, systems-based approach.
Oliver: As an example, we hope to find out more about how spray series of pesticides affect non-target organisms. For now, we mostly only assess the effects associated with the use of single pesticides. But in some SYBERAC case studies, the ecological effects of actual spray series commonly featuring the use of several pesticides throughout a growing season will be investigated.
What initially drew you to the field of pesticide risk assessment, and how has your approach evolved over your career?
Sabine: In my academic career, I was interested in the mechanisms and processes involved when chemicals affect aquatic life and on the propagation of effects from anthropogenic stress from lower to higher levels of organisation (suborganismal to individuals to populations); thus, I was also involved in monitoring and sampling of various ecosystems.
As a risk assessor, there are some similar aspects since the propagation and extrapolation of effects, mostly from individuals tested in laboratory (we consider e.g. time to reproduction or survival) to populations and communities living in the field and exposed to a multitude of stress is also a central part of the work; it can be summarised as defining if a pesticide applied in the field under certain conditions of use is likely to have acceptable or unacceptable effects, i.e. should it be authorised or not. The response should not be binary but the issue of margins of safety should be also considered, since the field situations are complex and some scenarios may be more vulnerable than others. That is why having a good calibration of the predictions to what is actually occurring under field situations is of utmost importance for improving the environmental risk assessment of pesticides.
In your view, what are the most pressing gaps in our understanding of the ecological impacts of pesticides, particularly in terms of long-term ecosystem health?
Oliver: It is the lack of knowledge and concepts to transfer our observations from simple and short-term standardized laboratory tests to the field. In other words: We just don’t know how to zoom out in time and space to protect biodiversity in the long run.
We do know that sublethal effects can propagate to the ecosystem level, we do know that environmental factors like temperature or food scarcity increase the sensitivity towards pollutants, we do know that organisms are repeatedly exposed to a multitude of chemicals throughout their life, etc. We just don’t know how to adequately consider all these factors in the environmental risk assessment without being overly protective.”
Oliver Weisner (UBA)
“The next big challenge is to have an environmental risk assessment that does not consider only one pesticide at a time, but a more integrative and holistic approach that allows for a more ecologically relevant characterisation of the risk. ”
How exactly can insights from pesticide risk assessment inform the development of safer, more eco-friendly biochemical products and processes?
Sabine: Pesticide risk assessment can provide information on risk profiles based on substance properties and the many data available. On this basis, pesticide products could be compared to each other and ranked according to their environmental risk which is related to their ecotoxicological characteristics and intended uses. This allows for selecting the least problematic specifically acting pesticide products, i.e. those with the best risk profile.
Oliver: Such analyses could also then be pursued further, outside the strict risk assessment process, by considering also aspects related to e.g. landscape characteristics or agronomy, especially integrated pest management.
Could you share an example of how exposure assessments have been used to drive meaningful changes in policy or practice?
Sabine: Measured concentrations of pesticides in the field should not be above specific limits or thresholds; these are concentrations that are defined as acceptable because they are expected not to exert unacceptable effects on the communities in the field. If these limits are exceeded, it should ideally lead to a reevaluation of the predictions for those pesticide products used under specific conditions and or a revision (or adaptation) of the risk mitigation measures. This means there should be a feedback loop between observations and adjustment of predictions. There are some steps in this direction in some member states, such as Switzerland and the Netherlands.
Can you walk us through the process of assessing ecological risks associated with pesticide mixtures?
Oliver: There are two major cases when assessing the ecological risks associated with pesticide mixtures we need to distinguish. In the first and more simple one, we know the pesticides that contribute to the mixture risk. This is the case when we have comprehensive monitoring data from pesticide concentrations in water or soil samples, for example. Fortunately, the effects from pesticides mostly tend to add up when occurring as a mixture. Hence, the ecological risk from the mixture can be estimated by simply adding up the individual risks of the mixture components. However, we need to bear in mind that there are mixtures, where this does not hold and the mixture risk exceeds what we would expect from the single components’ risk. For those mixtures, estimating the risk from the individual effects is not really possible and we would need to perform toxicity tests with the mixture.
The second major case deals with the consideration of pesticide mixtures within the risk assessment. While we know that various pesticides co-occur in water, soil or air, in the risk assessment it is assumed that the pesticide under assessment is released into a completely uncontaminated environment. The aim should be to account for those variable mixtures already present in the environment without knowing their exact composition. To do so, we need to estimate the ecological risks associated with those mixtures and derive assumptions for the risk assessment for representative scenarios.
Finally, when talking about mixtures over time, hence the ecological risk associated with repeated exposure to chemicals, we have a very limited understanding and even less of a concept on how to assess it so far.
What do you believe are the next big challenges in pesticide risk assessment?
Oliver: The next big challenge is to have an environmental risk assessment that does not consider only one pesticide at a time but a more integrative and holistic approach that allows for a more ecologically relevant characterisation of the risk. This means, for example, considering the aspects of mixture and multiple stressors as well as background contamination (baseline) appropriately.
Sabine: Another issue is that various components of the environmental risk assessment are still disconnected but should be regarded in a more holistic way. Also the evaluation methods should be simpler to enable faster assessments without endless - and often very detailed - refinements. Last but not least, the real situation in the field should be better understood and better coupled through comprehensive monitoring.
