Evaluation of sources, spatial and temporal distribution, ecological and health risk associated with CAF (Caffeine) and DEET (N, N-diethyl-meta-toluamide) contamination in the urban groundwater parts of Vellore city, Tamilnadu, India.

Urban environments are heavily influenced by various activities, leading to contamination of water sources by emerging contaminants (ECs). Among these, caffeine (CAF) and N, N-diethyl-meta-toluamide (DEET) are notable ECs frequently found in domestic sewage due to human activities. Despite extensive research on emerging contaminants, limited studies have focused on the seasonal variations, human health and ecological risks of CAF and DEET in urban groundwater, particularly in Indian cities. This study aimed to analyze the occurrence, spatial distribution, ecological and health risks of CAF and DEET in groundwater in Vellore city, Tamil Nadu, India. A total of 96 groundwater samples were collected across four seasons in 2022 and analyzed using Hichrom HPLC in an 844 UV/VIS compact Ion Chromatography system. CAF and DEET were detected in 95% and 96% of samples, with mean concentrations of 34 μg/L and 30 μg/L, respectively. Contamination levels were higher during the Southwest Monsoon (SWM) and Northeast Monsoon (NEM) seasons. Health risk assessments for children, women, and men showed that CAF posed significant risks, particularly to children during the NEM season, followed by women and men. Although DEET exhibited lower health risks overall, children remained the most vulnerable group. Statistical analysis confirmed significant differences in exposure levels, with children showing the highest variations. Ecological risk assessment revealed that 96.88% of samples containing CAF posed moderate ecological risks, while 6.25% of DEET samples fell into the same category. This study highlights the widespread presence of CAF and DEET in urban groundwater and their associated health and ecological risks. The findings emphasize the need for effective strategies to monitor and mitigate EC contamination in urban water systems.