Assessment of Pesticide Contamination in the Water of the Santiago River, Mexico

Abstract

Introduction: In many regions of the world, the presence of pesticide residues and indications of active ingredients of organophosphates, organochlorines, carbamates, triazines and pyrethroids, among others, have been reported in surface and groundwater water near agricultural production areas, mainly in developing countries such as Mexico. In most cases, the concentrations found exceed the limits established by the national and international regulations established by the USEPA, EU and WHO. Many of these chemical compounds have been considered persistent organic pollutants and banned for more than 20 years. Through waterways, these toxic pollutants are transported away from the places where they are applied, contaminating other ecosystems and water sources which could be causing public health problems. Aims: The objective of this research is to evaluate the presence of pesticide residues or their metabolites in the water of the Santiago River and to inform about the ecological and health risks. Methodology: Sixty samples taken from 20 monitoring sites along the Santiago River basin in the state of Jalisco during 2024 were analyzed fifteen pesticides (acetachlor, 2,4-dichlorophenoxyacetic acid, ametrine, atrazine, carbendazine, carbofuran, cyalothrin, diazinon, glyphosate, malathion, oxandrolone, parathion, pyraclostrobin, picloram and thiabendazole) using liquid chromatography and mass spectrometry. Results: The results of the pesticide analysis in the Santiago River basin showed 13 pesticides with concentrations lower <10 μg/L. The pesticides glyphosate, malathion and picloram are those with concentrations >10 μg/L. The average concentrations of glyphosate were between 277 and 527 μg/L, those of malathion between 496 and 830 μg/L. and of plicoram between 26 and 68 μg/L. For the 3 pesticides, the analysis of variance (ANOVA) showed heterogeneous spatial and temporal concentrations throughout the Santiago River basin, the ANOVA and Tukey's DSH showed statistically significant differences between sites and months analyzed, with August being the highest level in 2024. Conclusion: According to the levels of pesticides, there is an ecological and health risk, due to the contact and use of the water of the Santiago River, with a high degree of contamination by pesticides, which represents ecological and health risks.