Heavy metals in agricultural cultivated products irrigated with wastewater in India: a review

Abstract

Abstract Indiscriminate industrialization and urbanization have negatively impacted our environment. One of the common environmental problems in semi-urban areas in India is the discharge of inefficiently treated municipal, industrial and domestic wastewater into the environment, resulting in the degradation of soil and water qualities. Depleting freshwater resources have led Indian farmers to look for easily available, cheaper, and nutrient-rich sources of irrigation water in the form of wastewater; however, this also led to increased pollutant transfer to the soils. Known as persistent pollutants, heavy metals such as cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), mercury (Hg), and a few others are potentially hazardous due to their non-biodegradable nature, extended biological half-lives, and biological interactions. These heavy metals can bind to soil surfaces and then be absorbed by plant tissues. Vegetables supply micronutrients, antioxidants, vitamins, and other nutrients essential for human growth. Therefore, the consumption of vegetables/crops grown in wastewater-irrigated land poses a potential threat to humans. Since wastewater irrigation cannot be eliminated in the Indian (semi-)urban areas because of the ever-increasing demand for irrigation water, it is important to assess the impact of wastewater irrigation. This review article congregates the findings of studies from India wherein heavy metal contaminations in vegetables have been reported. An attempt was made to estimate the risk to human health because of the long-term consumption of vegetables cultivated in wastewater-irrigated lands from the Indian sites.