6. Conclusions and future perspectives

We lack an overview of the status of pesticides in Europe’s waters. There are a number of reasons for this gap, with the omission nevertheless representing a significant cause for concern in our attempts to protect and improve water quality. Improving our understanding will take time, but by starting the process, the aim of this report is to set in train the developments necessary to achieve that overview.

Pesticide monitoring in surface waters and groundwater of the EU Member States and reporting to the EEA is nowadays oriented on the monitoring obligations under the WFD. Additionally, regional monitoring efforts are made to tackle regional problems. Such monitoring is often designed together between environmental, drinking water and agricultural administrations and stakeholders. These monitored pesticide concentrations together with information on agricultural activities (including pesticide usage) could be the basis for regional management of environmental contamination of pesticides.

This report has considered the data available for pesticides in waters at European level. There are relatively few datasets that are comparable across Europe, leading to the current work focusing on those data reported under WISE SoE water quality (WISE 4).

The pesticide concentration data found in the Waterbase - Water Quality database were investigated for pesticide groups (herbicides, insecticides and fungicides), pesticide substances (including metabolites), monitoring sites (including major and minor rivers and water bodies). Additionally, but seldom reported, the limits of quantification were of interest. Our statistical checks to unravel concentration values lower than the limits of quantification (LOQ) are an example of the need to improve harmonisation of the reporting. At present, with the assumption that remaining uncertainties within these checks could be solved, we consider that the existing data could be used to describe pesticide concentrations. Comparison with environmental quality standards (EQS) could allow these data to describe the pesticide risk.

The Waterbase – Water Quality database on pesticide concentrations in the different European countries differ widely in terms of numbers of substances reported but also monitored stations. Different LOQs also hint towards the use of different chemical analytical techniques. Hence, to improve comparability, harmonisation with regard to monitored substances, density of monitoring stations and methodology is warranted. More streamlining of approaches towards data collection and monitoring, (such as the application of common analytical quality rules, such as those under the WFD (EC, 2009) would improve comparability. Focusing effort at relevant times, e.g. monitoring only before, at and after the pesticide application season, rather than continuously, could facilitate effective use of scarce resources.

Enhanced monitoring and further harmonisation of data collection would be beneficial for more specific management to protect water quality. Together with agricultural area usage, one would be able to compare the relative contribution and thus toxic pressure of pesticide usage types (e.g. corn herbicides, wheat insecticides) for a specific region, as a basis for management. Additional analysis of spatial and temporal distribution would increase understanding of the risks and management options. Pesticide metabolites (transformation products) should be considered, as these substances not only hint to their ‘mother’ substance, but many of these still have toxic potential (assigned to an EQS) and therefore increase the overall toxicity to organisms.

Data availability from scientific projects seems to be very diverse and their quality may also differ. However, even though not using harmonised procedures, these projects may provide important input with regard to relevant substances and novel assessment techniques. Thus, the comparison of the Waterbase – Water Quality database deliveries to EEA and the data reported in scientific literature may be challenging.

The implementation of measures to reduce pesticide pollution is crucial for the sustainable management of surface waters and groundwater. Information on quantitative effects of reduction measures are also relevant to indicate the progress to reach environmental objectives, but available data on this are rare. Other data sources mainly focus on strategies (e.g. National Action Plans). The implementation of measures and monitoring is of particular importance when evaluating the success and the effectiveness of measures. It is also necessary to improve the harmonization between the different policies tackling pesticides in waters and the environment. For successful implementation of measures to reduce pesticide pollution, funding instruments are also a basis, and this could be a part of the next phase of the Common Agricultural Policy.

One goal of this technical report is to show possible uses of the Waterbase – Water Quality database set for further developments towards a pesticide indicator. Depending on the goal of any managing or monitoring action in surface or groundwater, different ways can be used to assess the risks due to pesticides. The historically developed and used way by regulatory bodies is the assessment of risk by using the single substance approach only. This means that EQS (or other threshold values) are used for risk assessment.

In human pharmacology and toxicology, the concept of mixture toxicity effects of many different substances which are applied at the same time is known. Adopting and applying this concept seems to be one possible solution to address contamination by pesticides in the environment. One published mixture approach is based on the Toxic Unit (TU) system. This TU is recommended to be used for risk assessment in the aquatic ecosystem. The TU is defined by the ratio of the concentration of a substance to its actual toxicity. Behind that concept stands the idea that the toxicity of a mixture of many similar acting substances can be assessed by adding up each substance effect concentration. This approach is most often known in scientific literature as the “concentration addition (CA)” approach.

Such an indicator also could for example combine toxicity risk assessment of monitored pesticide concentrations with agricultural area uses to identify the most problematic usages and pesticide types in specific European regions. With such assessments, countries could target management measures and thus decrease pesticide toxicity risk.