Thermal Degradation and Health Risk Assessment of Dieldrin Residues in Grains and Legumes Consumed in Nigeria

Extensive application of pesticides in agriculture and food crop preservation has resulted in varying values of residual presence of pesticides in stored food products. This study investigated Dieldrin pesticide residue concentrations in legumes, grains and associated wastewater. 18 food crop types were collected from retail markets in Awka, Nigeria between May and August, 2024. They were washed, boiled at different degrees of temperature, extracted, cooled and screened for Dieldrin pesticides present in the boiled food crops and associated waste water after boiling and cooling using Gas Chromatography - Mass Spectrometry. Dieldrin residue was detected in some of the food samples, with concentrations ranging from 0.00 (Not detected) to 0.376 mg/kg. White iron beans had a Dieldrin concentration of 0.258 mg/kg at normal temperature but reduced slightly to 0.213 mg/kg upon heating to 100ºC, highlighting the limited effectiveness of heat in removing Dieldrin residues. A strong positive loading exists among local rice (r = 0.99), yellow corn (r = 1.00), red guinea corn (r = 1.67), pearl millet (r = 1.67), white soft wheat (r = 1.19), and white hard wheat (r = 1.46). The hazard index of Dieldrin in legume followed the decreasing order of Iron white beans (13.10) > brown beans (12.39) > pigeon pea (0.36), implying that Dieldrin in iron white beans and brown beans could cause significant health effects like neurological disorders and cancer. Evidence of the study shows that mere boiling as it is done in Nigeria cannot significantly reduce Dieldrin pesticide concentration in stored food crops. It is therefore recommended that Dieldrin should not be used for food preservation under any circumstance. Natural alternatives like diatomaceous earth and hermetic storage have shown effectiveness with minimal health risk.