Current frameworks for the toxicological assessment of pesticide transformation products in drinking-water

Abstract

Despite the benefits of pesticides in agriculture, their widespread use contributes anthropogenic chemicals to the environment, sometimes resulting in the formation of pesticide transformation products. These transformation products may enter sources of drinking-water, potentially posing health risks when present at significant concentrations. Currently, there is no globally harmonized framework for the toxicological assessment of pesticide transformation products in drinking-water. The World Health Organization provides international guidance through the Guidelines for Drinking-water Quality. However, there remains a specific need for a more detailed framework addressing pesticide transformation products in drinking-water. This review was conducted under contract with the World Health Organization to support the development of a consistent and transparent global assessment framework for pesticide transformation products in drinking-water. The aim was to identify and compare relevant assessment schemes, particularly those focused on transformation products in drinking-water or its sources, to evaluate their strengths and limitations, and to formulate recommendations for future international frameworks. The analysis identified two primary guidance documents relevant to drinking-water: the European Commission's SANCO/221/2000 guidance, which varies in application across EU member states, and the ECHA/EFSA guidance focused on water treatment processes. Other frameworks, including those from the United States and the World Health Organization, lack provisions specific to transformation products in water. Common elements identified across frameworks include tiered assessment, comparison with parent pesticide toxicity, predictive modelling, aggregate exposure assessment, and consideration of treatment effects. The review highlights the need for an internationally harmonized approach to ensure consistent and effective management of transformation products in drinking-water.