Occurrence of Some Heavy Metals in Drinking Water, Vegetables, and Urine in Rawalpindi and Islamabad, Pakistan—Human Health Risk Assessment

Food chain contamination with heavy metals is a severe environmental and health concern. The main aim of this study was to assess the occurrence of some heavy metals in water, vegetables, and urine and to explore the associated health risks. Selected vegetables were collected from four market centres (n = 96), i.e., Khana Pull (KP), Karachi Company (KC), Mandi Morh (MM), and Tramari (Tra), and four drinking water sources (Borehole, Khanpur Dam, Simly Dam, and Rawal Dam) (n = 16) were analysed for lead (Pb), zinc (Zn) and cadmium (Cd) by using atomic absorption spectroscopy in flame mode (AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The Combined Average Daily Intake (CADI), Target Hazard Quotient (THQ), and Hazard Index (HI) were assessed to estimate the human risk associated with both vegetables and drinking water. At the same time, Zn, Pb, and Cd concentrations in urine samples from healthy and unhealthy adults (n = 40) were evaluated. The mean concentration of Zn and Cd in all vegetables was below the allowable limit, but Pb exceeded the limit. The average mean concentration of Pb and Cd in water samples exceeded the WHO limit, while Zn was below the limit. The total CADI for Zn, Pb, and Cd in the four markets was lower than the acceptable limit set by FAO/WHO. The highest values for Zn, Pb, and Cd (mg/kg/day) were reported in KP, KC, and Tra, respectively. The THQ values of Zn and Cd were below the threshold value, except for Pb, and the HI of Zn, Pb, and Cd exceeded the limit. The concentrations of Pb and Zn in urine exceeded the healthy limits set by the WHO. The highest concentrations (mg/L) of Pb, Zn, and Cd were observed in smokers (0.124), kidney disease (1.079), and smokers (0.021), respectively. The findings highlight a significant risk to human health and warrant regulatory authorities taking measures to protect consumers from potential exposures.