Use of post-registration monitoring data to evaluate the ecotoxicological risks of pesticides to surface waters: a case study with chlorpyrifos in the Iberian Peninsula.

Chemical monitoring datasets such as those provided by the implementation of the Water Framework Directive (WFD) offer opportunities to evaluate the ecological risks of pesticides under large spatio-temporal scales and to evaluate the protectiveness of the current prospective risk assessment framework. As a case study, we used the monitoring dataset for the insecticide chlorpyrifos (CPF) to perform a probabilistic risk assessment for Iberian surface water ecosystems. The specific objectives of the study were: (1) to assess the occurrence of CPF in relation to different agricultural production land uses, (2) to assess the spatio-temporal variation in the exceedance of the European WFD short- and long-term environmental quality standards (MAC-EQS and AA-EQS), and (3) to perform a probabilistic risk assessment for freshwater invertebrates. A database was analysed that contains CPF concentrations from 14600 surface water samples taken between 2012 and 2017 in the Iberian Peninsula (Spain and Portugal). CPF was detected in 21% of these samples. The MAC-EQS was exceeded in 2% of the cases, while the AA-EQS was exceeded in 18% of the cases. The majority of the exceedances took place in the littoral areas of the east and south-east part of the Iberian Peninsula, particularly in areas with dominant citrus production during late-spring, late-summer and autumn. Our study indicates unacceptable risks posed by chlorpyrifos to Iberian surface waters over the study period, while it was approved for use in Europe. This study supports the need to perform further post-registration monitoring assessments with other pesticides following similar approaches, which can help to identify possible pesticide misuse practices and improvements of the prospective risk assessment framework. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.