Health risk assessment of heavy metals via dietary intake of wheat grown in Tianjin sewage irrigation area

The possible health risks from heavy metal (Zn, Cu, Cr, Ni, Pb, and Cd) contamination to the local population through the food chain were evaluated in Tianjin, China, a city with a long history of sewage irrigation. Results showed that the continuous application of wastewater has led to an accumulation of heavy metals in the soil, and 54.5 and 18.25 % soil samples accumulated Cd and Zn in concentrations exceeding the permissible limits in China. Concentrations of heavy metals in wheat grain decreased in the order of Zn > Cu > Cr > Ni > Pb > Cd, and transfer factors for the six heavy metals showed the trend as Zn > Cd > Cu > Pb > Cr > Ni. The risk assessment for the six heavy metals through wheat consumption suggests that concentrations of Cr and Cd in some wheat samples exceed their reference oral dose for adults and children. In general, no target hazard quotient value of any individual element was greater than one, which means they are within the safe interval. However, 36.4 and 63.6 % hazard index values for adults and children were greater than one, respectively. The health risk due to the added effects of heavy metals was significant for children and adults, and more attention should be paid tothe potential added threat fromheavy metals to the health of children via dietary intake of wheat in Tianjin.