Heavy Metals Contamination of Agricultural Soil and Vegetables, and Human Health Risk Assessment Through Vegetable Consumption in Nagaland, Northeast India

We investigated the heavy metal (HM) concentration in agricultural soil—viz., lead (Pb), copper (Cu), cadmium (Cd), zinc (Zn), nickel (Ni), and chromium (Cr)—and vegetables (14 different varieties) from two districts (Dimapur and Wokha) of Nagaland in northeast India. The soil presented 0.15–0.19 mg Cd/kg, 49.65–78.8 mg Cr/kg, 8–10 mg Cu/kg, 8.6–14 mg Pb/kg, 22–25 mg Ni/kg, and 50.6–71 mg Zn/kg. In vegetables, Cr, Pb, and Ni ranged between 4.9–15.16 mg/kg, 0.29–2.68 mg/kg, and 5.78–14.58 mg/kg, correspondingly. Multivariate statistical analysis indicated that most heavy metals (HMs) were contributed by human activities. The evaluation of health hazards to humans as per the risk assessment model by the United States Environmental Protection Agency (USEPA) for adults (≥24 years) and children (≤6 years) showed that vegetable ingestion induced non-carcinogenic risk, estimated via the hazard quotient (HQ) and hazard index (HI). HI ranged from 1.06 to 2.18 in adults and 3.3 to 6.83 in children. The total carcinogenic risk (TCR) from all HMs (ranged: 2.34 × 10⁻³ to 3.94 × 10⁻³ in adults and 1.83 × 10⁻³ to 3.09 × 10⁻³ in children) was >10⁻⁴, the stipulated minima for causing substantial carcinogenic threat. In general, children are highly vulnerable to non-carcinogenic risks and adults are more susceptible to carcinogenic risks. Soil and vegetables from the Wokha district posed a greater hazard to consumers’ health. The results of this research give recent underlying information on HM concentrations, which may be utilized to establish prospective risk reduction and management measures. This study thereby suggested that proper monitoring, maintenance, and remediation methods must be taken up to preserve soil and vegetable quality and protect the health of humans.