Health risk associated with heavy metal contamination of vegetables grown in agricultural soil of Siran valley, Mansehra, Pakistan—a case study

Monitoring of heavy metals in agricultural soils and the crops grown in them is essential to design mitigation strategies to reduce toxic heavy metals in diet and food chains. We determined chromium (Cr), arsenic (As), cadmium (Cd), and lead (Pb) concentrations in the soil–plant system from agricultural fields of Siran Valley, Mansehra, Pakistan, to assess their potential health risk. Although the concentrations of the heavy metals in soils were within the permissible limits for agricultural soils, heavy metal concentrations in many of the vegetables exceeded the recommended safe values. Among the six leafy vegetables tested, all had greater than safe limits for As, four also for Cr and two also for Cd. As level was greater than safe limits in all five fruit and flower vegetables, two had Cr, and one had Pb also at unsafe levels. Among the five tuber, bulb, and root vegetables, As was higher than safe limits in all and Cd in one. The transfer factor in all three categories of vegetables followed the descending order Cd > As > Cr > Pb. Daily intake of metals were within limit set by USEPA for all heavy metals except As. The health risk indices for Cr, As, Cd, and Pb indicated that values greater than 1 for As suggest that the vegetables studied here pose a risk of chronic arsenic poisoning, but other heavy metals do not pose such a risk. Our study reinforces the need for mitigation strategies to reduce unsafe levels of heavy metals in vegetables.