Human health risk assessment on pesticide residues in fishes of kuttanad wetland, a globally important agricultural heritage system

Kuttanad is a unique wetland agriculture system featuring polder-based rice cultivation below sea level. Facing increasing pollution threats from agrochemicals, this FAO-recognized Globally Important Agricultural Heritage System (GIAHS) needs constant monitoring and risk assessment. The present study investigated the seasonal dynamics of agricultural pesticide residues in fish cultured in the wetland system. A total of 217 fish samples were analyzed, spanning three different sampling stations of Kuttanad, viz., Vaikom, Ramankari, and Edathua, during pre-monsoon, monsoon, and post-monsoon seasons. The results revealed the presence of 14 pesticides across locations and seasons. The pesticides found in the highest concentrations were propetamphos (54.64 mg L −1 ), thiacloprid (46.78 mg L −1 ), and diphenylamine (24.70 mg L −1 ). The most frequently detected pesticides were propoxur, fenuron, and thiacloprid. Contaminants were detected more frequently during the post-monsoon season (49%) compared to the monsoon (38%) and pre-monsoon (13%) seasons, with imidacloprid being present in all three seasons. The target hazard quotients (THQ) for propetamphos, thiacloprid, and diphenylamine were determined to be 0.04, 0.004, and 0.0002, respectively. The hazard index (HI) calculated as the sum of THQ of quantified pesticides was 0.056, indicating a low to moderate risk. However, consistent monitoring of pesticides in the Kuttanad wetland agriculture system is important to ensure timely intervention to protect biodiversity and human health.