A Quantitative Approach for Ranking Human Health Risks from Pesticides in Irish Groundwater

This study aims to quantitatively assess the risk of pesticides (used in Irish agriculture) and their degradation products to groundwater and human health. This assessment uses a human health Monte-Carlo risk-based approach that includes the leached quantity combined with an exposure estimate and the No Observed Adverse Effect Level (NOAEL) as a toxicity ranking endpoint, resulting in a chemical intake toxicity ratio statistic (R) for each pesticide. A total of 34 active substances and their metabolites registered and used in the agricultural field were evaluated. MCPA obtained the highest rank (i.e., in order of decreasing human health risk), followed by desethly-terbuthylazine and deethylatrazine (with risk ratio values of 1.1 x 10(-5), 9.5 x 10(-6), and 5.8 x 10(-6), respectively). A sensitivity analysis revealed that the soil organic carbon content and soil sorption coefficient were the most important parameters that affected model predictions (correlation coefficient of -0.60 and -0.58, respectively), highlighting the importance of soil and pesticide properties in influencing risk estimates. The analysis highlights the importance of taking a risk-based approach when assessing pesticide risk. The model can help to prioritize pesticides, with potentially negative human health effects, for monitoring programs as opposed to traditional approaches based on pesticide leaching potential.