Wastewater surveillance for assessing human exposure to pesticides: investigating populations living near flower bulb fields

Wastewater-based surveillance (WBS) is a complementary approach that overcomes some of the limitations of human biomonitoring, such as sampling biases, invasiveness, high costs and ethical issues. This study explores WBS to assess the spatial differences in human exposure in areas with relatively high use of pesticides versus reference areas. Societal concerns have been raised related to reported exposure to pesticides of residents near flower bulb fields. To this aim, several specific human metabolites of triazines, pyrethroids and organophosphates authorized for bulb cultivation have been selected as pesticide exposure biomarkers, investigating their presence in wastewater samples collected near flower bulb fields and areas where those pesticides are less – or not – applied i.e., control areas. In this unique study a total of 71 influent wastewater samples were analyzed during the period of pesticide application on flower cultivation, 31 originated from flower bulb areas and 40 from control areas. Higher population normalized mass loads were found in the flower areas for 2-methyl-6-ethylaniline (up to 21 µg/day/1000 inh.) and hydroxytebuconazole (up to 6 µg/day/1000 inh.), metabolites corresponding to the pesticides metolachlor-S and tebuconazole, respectively. Our findings illustrate the need for wide WBS monitoring campaigns for assessing exposure of populations living near flower bulb fields. Where WBS provides additional data input for further risk assessment. WBS can be further employed in areas of other crops that are relevant such as potatoes, other vegetables and fruit trees, where pesticides are also widely applied.