Cancer and non-cancer risk assessment of fluoride and nitrate in water samples from selected Niger Delta communities.

Abstract

Nitrate (NO₃^-) and fluoride (F^-) are beneficial in trace amounts but pose health risks at high concentrations. This study evaluated their contamination and associated health risks in water from Niger Delta communities, focusing on infants, children, teenagers, and adults through oral ingestion and dermal exposure pathways. Analysis of 113 samples revealed fluoride concentrations (3.55-7.50 mg/L) consistently exceeded the WHO guidelines (1.5 mg/L) with dietary intake mostly exceeding tolerable upper intake levels across life stage groups with a few exceptions in Communities such as Evboehighae, Ikobi, Jadawa By EPZ, Obubra and Maternity. Nitrate levels (3.55-13.10 mg/L) were below the WHO guideline (50 mg/L), with a low Nitrate Pollution Index. Human Health Risk Assessment identified oral ingestion as the main exposure pathway. Fluoride posed a pervasive non-carcinogenic risk, with its Hazard Quotient (HQ) exceeding the safety threshold for all age groups in every community. Nitrate, while low, presented a critical carcinogenic threat. The Mean Cancer Risk (MCR) for nitrate surpassed acceptable limits by several orders of magnitude for all ages, with infants most vulnerable. These findings indicate a public health crisis involving widespread fluorosis and a latent carcinogenic risk from nitrate, necessitating immediate interventions like defluoridation, pollution control, and health education.