Health risk assessment of heavy metals in wheat using different water qualities: implication for human health

In the recent years, the use of sewage water for irrigation has attracted the attention of arid and semi-arid countries where the availability of fresh water is poor. Despite the potential use of sewage water in crop irrigation as effective and sustainable strategy, the environmental and human risks behind this use need to be deeply investigated. In this regard, an experiment was carried out under field conditions in Nursery, University College of Agriculture Sargodha, to evaluate the possible health risks of undesirable metals in wheat grains. Wheat variety Sarang was cultivated and irrigated with different combinations of ground (GW) and sewage water (SW). The concentrations of heavy metals (Cr, Cd, Ni, and Pb) and trace elements (Cu, Zn, and Fe) in wheat grains as well as in soil were determined. Moreover, the pollution load index (PLI), accumulation factor (AF), daily intake of metals (DIM), and health risk index (HRI) were calculated. Results showed that the concentration trend of heavy metals was Pb<Cr<Cu<Ni<Cd<Zn<Fe and Cr<Cu<Pb<Cd<Ni<Fe<Zn in soil and wheat, respectively. Among metals, Cd concentration in wheat exceeded the permissible limits regardless water quality, whereas Pb concentration in grain was within the acceptable levels as suggested by World Health Organization, when 100 % of SW was used for irrigation. Similar observation was reported for Cd concentration in the soil when wheat was irrigated with 100 % SW. In comparison to soil, the edible part of wheat presented lower concentration of all studied metals, except for Zn which was much higher compared to the tested soil samples. The higher concentration of Zn was responsible for increasing the DIM of Zn where, in average, the highest value was reported, particularly in 75 % SW treatment. This was reflected also in HRI where the maximum value was reported for Zinc under the same treatment. Higher value of HRI for wheat cultivated on polluted soils suggested that appropriate management of cultivated area is necessary for food safety and thus for public health. The results are expected to create awareness among the public on the safety of consuming food products grown in particular areas.