Pesticide mixtures in the Swedish streams: environmental risks, contributions of individual compounds and consequences of single-substance oriented risk mitigation
- Published
- Accepted
- Subject Areas
- Agricultural Science, Ecotoxicology, Environmental Contamination and Remediation, Environmental Sciences
- Keywords
- Kaplan-Meier method, mixture risk assessment, concentration addition, maximum cumulative ratio, chemical monitoring, mixture risk management
- Copyright
- © 2017 Gustavsson et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2017. Pesticide mixtures in the Swedish streams: environmental risks, contributions of individual compounds and consequences of single-substance oriented risk mitigation. PeerJ Preprints 5:e2779v2 https://doi.org/10.7287/peerj.preprints.2779v2
Abstract
This paper presents the ecotoxicological assessment and environmental risk evaluation of complex pesticide mixtures occurring in freshwater ecosystems in southern Sweden. The evaluation is based on exposure data collected between 2002 and 2013 by the Swedish pesticide monitoring program and includes 1308 individual samples, detecting mixtures of up to 53 pesticides (modal=8). Pesticide mixture risks were evaluated using three different scenarios for non-detects (best-case, worst-case and using the Kaplan-Meier method). The risk of each scenario was analyzed using Swedish Water Quality Objectives (WQO) and throphic-level specific environmental thresholds.
Using the Kaplan-Meier method the environmental risk of 73% of the samples exceeded acceptable levels, based on an assessment using Concentration-Addition and WQOs for the individual pesticides. Algae were the most sensitive organism group. However, analytical detection limits, especially for insecticides, were insufficient to analyze concentrations at or near their WQO’s. Thus, the risk of the analyzed pesticide mixtures to crustaceans and fish is systematically underestimated. Treating non-detects as being present at their individual limit of detection increased the estimated risk by a factor 100 or more, compared to the best-case or the Kaplan-Meier scenario.
Pesticide mixture risks are often driven by only 1-3 compounds. However, the risk-drivers (i.e., individual pesticides explaining the largest share of potential effects) differ substantially between sites and samples, and 83 of the 141 monitored pesticides need to be included in the assessment to account for 95% of the risk at all sites and years.
Single-substance oriented risk mitigation measures that would ensure that each individual pesticide is present at a maximum of 95% of its individual WQO, would also reduce the mixture risk, but only from a median risk quotient of 2.1 to a median risk quotient of 1.8. Also, acceptable total risk levels would still be exceeded in more than 70% of the samples.
Author Comment
This is an author-produced pre-copy-editing version of the manuscript, that was recently accepted for publication in Science of the Total Environment. Slight changes have been made in this version after the peer-reviewing process. This version contains some changes to tables and text. Further changes resulting from the publishing process, such as editing, corrections, structural formatting, and other quality control mechanisms are not reflected in this document. The definitive version is available online at https://doi.org/10.1016/j.scitotenv.2017.04.122