Risk Assessment on Organochlorine Pesticides in Agricultural Soils of Eastern City, China

To explore how organochlorine pesticides (OCPs) are perpetual in soils and the risk they may bring, Ningbo, a city with an extensive usage history of OCPs, was selected as a case to investigate. Sixty-nine agriculture soils were taken from 0–20 cm layers, then OCPs were analyzed, and a risk assessment was performed. Results indicate five OCPs were detected in agricultural soils, with total concentrations ranging from below detection limits to 43.08 µg·kg−1 and an average value of 15.58 µg·kg−1. Among them, δ-Hexachlorocyclohexane (δ-HCH) and p, p’-Dichlorodiphenyltrichloroethane (p, p’-DDT) were the primary contributors to the residual contamination levels. The health risk assessment indicates that even at maximum exposure levels, the non-carcinogenic risk (1.71 × 10−4) and carcinogenic risk (5.97 × 10−8) of OCPs in the study area are significantly below the risk thresholds of 1 and 10−6, respectively. Monte Carlo simulation further confirms that the 95th percentile values for non-carcinogenic and carcinogenic risks (3.39 × 10−4 and 1.23 × 10−7) remain well below these limits, suggesting that the health risks posed by OCPs to adults are negligible. Subsequent ecological risk assessment revealed that the vast majority (73.91%) of soil samples exhibited medium-low ecological risk, with dichlorodiphenyltrichloroethane (DDTs) being the primary contributor to ecological risk. Our findings strengthen the view that although OCPs have been banned for a long time, the ecological risks of residuals in the soil remain a concern, and more effective control methods should be used to mitigate them.