Assessment of Nitrate Contamination in Groundwater and Dietary Nitrate Exposure in Farming Communities in Plateau State, North Central Nigeria

Nitrate contamination of groundwater is a significant environmental health concern in agricultural communities, with potential health consequences including methemoglobinemia in infants and carcinogenic N-nitroso compound formation in adults. This study assessed nitrate contamination in groundwater sources and estimated dietary nitrate exposure among farming communities in Shendam Local Government Area, Plateau State, North Central Nigeria. Forty-five groundwater samples from boreholes, springs, and hand-dug wells were analyzed for nitrate, nitrite, ammonium, and microbial indicators. Dietary nitrate intake was assessed through a twenty-four-hour dietary recall in 320 farming households, with emphasis on leafy vegetable and drinking water contributions. Agricultural practice data, including fertilizer type, application rates, and irrigation water use, were collected to identify contamination sources. Results showed that thirty-six percent of groundwater samples exceeded the WHO nitrate guideline of 50 mg/L, with concentrations ranging up to 148 mg/L. The highest nitrate levels were associated with intensive vegetable farming plots using nitrogen fertilizers without adherence to safe application rates. Dietary nitrate intake estimates revealed that forty-two percent of adults exceeded the acceptable daily intake, primarily through consumption of home-grown vegetables irrigated with contaminated water. Infants in affected communities were identified as being at risk of methemoglobinemia. The study fills a critical local data gap on the agricultural-groundwater-dietary nitrate pathway in Plateau State. Recommendations include fertilizer use guidelines, groundwater protection zone demarcation, and infant dietary counseling. Keywords: nitrate, groundwater contamination, dietary exposure, Plateau State, farming communities.