Bioavailable forms of heavy metals from rice samples and its potential health risk assessment

Abstract

Food crops grown in contaminated soils have a greater accumulation of heavy metals and the consumption of food crops grown in the contaminated soils are the source of metals that enters into the human body. Rice being a major food crop, the presence of heavy metals should be monitored regularly for reducing health risk. The analysis of total heavy metal always overestimates the content which leads to misinterpretation of results; however, bioaccessible heavy metal analysis projects the actual health risk. Hence, the present study aims to assess the bioavailable form of heavy metals in rice. The rice samples were collected from 20 different places and used for the inherent and bioavailable metal estimation. In vitro simulated digestion method was applied for bioaccessible metal analysis. Metal concentration in polished rice ranged from 0.10 to 0.82, 0.10 to 1.07, 0.11 to 0.56 and 0.23 to 1.09 mg kg-1 for Lead (Pb), Nickel (Ni), Cadmium (Cd) and Chromium (Cr), respectively. Twenty five percent of the samples recorded less than 0.028, 0.01, 0.01, and 0.03 mg kg-1 of bioaccessible Pb, Ni, Cd, and Cr, respectively. A significant negative correlation was observed between total metal concentration and bioaccessibility percentage. Targeted Hazard Quotient (THQ) of all the metals were less than one for adults indicating that there were no health risks, which undoubtedly reveals the importance of bioaccessible metal analysis. Hence, regular monitoring of heavy metals is essential to reduce the intensive accumulation in the human food chain. Also, the present study has opened up a wide scope on human health risk assessment using an in vitro digestion model.