Geospatial quality assessment of locally available ice for heavy metals and its potential risks for human health in the mega city Karachi, Pakistan

Extreme summers, high poverty rate and continuous electricity load shedding results in commercial manufacturing and sale of ice in many countries. The vendors prepared ice using untreated piped water, tanker water and ground water. These waters may contain hazardous pollutants and ice made from them can be a potential risk for human health. So, it is important to regularly monitor the ice quality in all populous cities. A contemporary examination was carried out to evaluate the physico-chemical properties and heavy metals in the ice sold in all the districts of Karachi. This study is one of the first efforts to assess the ice quality in relation to the metals' potential hazards to human health. Geospatial distribution of ice quality and major constituents among measured parameters were determined using GIS (Geographic Information Systems) and PCA (Principal Component Analysis) techniques. Results of physico-chemical properties showed that the ice quality was only marginally adequate and it was found that the total mean metal contents were in the sequence of Pb > Ni > Zn > Fe > Cr > As. These metals were above the upper allowed limit with reference to WHO guidelines. About 57.14% and 35.71% Ice samples had excellent and good physico-chemical properties in terms of Ice Quality Index (IQI), respectively. Similarly, IQI for metals showed that Ice was unsafe for human consumption. In terms of health risk assessment, the overall mean CDI (Chronic Daily intake) and HQ (Hazard Quotient) values were in the order of Pb(10.371) > Ni (3.156) > Zn(2.286) > Fe (2.101) > Cr(1.558) > As(0.519) and Pb(7.408) > As(1.729) > Cr(0.519) > Ni(0.405 > Zn (0.008) > Fe(0.003), respectively. This study suggests routine monitoring and evaluation of the water supplies available for making ice in order to protect public health.