IMPACT OF CLIMATE CHANGES ON PESTICIDE LEVELS IN DRINKING WATER: THE FLOODING CASE IN THE STATE OF RIO GRANDE DO SUL.

Resumo

INTRODUCTION: Pesticides constitute a grave public health concern globally, in Latin
America and in Brazil. The environmental exposure to these substances has been
associated degenerative deceases. In this context, drinking water represents a critical
matrix, where the presence of pesticides can compromise its safety. OBJECTIVE:
Evaluate the potential impact of the Rio Grande do Sul (RS) floods on pesticide
dynamics. MATERIALS AND METHODS: A comparative analysis of pesticide
residues in drinking water was conducted before (March/24) and after (June/24) rainfall
events in RS State, Brazil. Water samples (250 or 500 mL) were collected from various
sources, including rivers, wells, and the public water supply, by the State Sanitary
Surveillance, sent and analysed in the Tox Lab/CESTEH/ENSP/FIOCRUZ. The
method, validated according to the INMETRO DOQ-CGCRE-008 norma, employed
solid-phase extraction (SPE), followed by gas chromatography-triple quadrupole mass
spectrometry (GC-MS/MS), to identify/quantify 99 pesticides. The sample was positive
if its analytical response exceeded the limit of quantification (LOQ) for each analyte of
the method, coupled with CG-MS/MS-identification criteria. The study evaluated the
frequency of quantified samples, detected target analytes, concentrations, and sample
source origin. RESULTS: From a total of 54 analysed samples (23 in March/24 and 31
in June/24), 11 (47,8%) were considered positive before the rainfall event, whereas 6
(19,4%) were positive afterwards, following the climate disaster. Atrazine, metolachlor
and tebuconazole, were the pesticides that showed detections increased (ranging from
6.1 to 24.2%). Azoxystrobin exhibited decreased positivity frequencies, which ranged
from 1.5% CONCLUSION: These findings suggest that the floods in RS interfered with
the availability of pesticides in water for human consumption.