The level and distribution of heavy metals and changes in oxidative stress indices in humans from Lahore district, Pakistan

Human biomonitoring is a well-recognized tool for estimating the exposure of humans to environmental pollutants. However, heavy metals' pollution from anthropogenic origin is a cause for concern because of its potential accumulation in the environment and living organisms, leading to long-term toxic effects. This study was aimed to assess the concentrations of cadmium (Cd), chromium (Cr), lead (Pb), copper (Cu), nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), and zinc (Zn) in human biological samples (urine, whole blood, hair, and nails) and antioxidant response in blood samples from 48 individuals exposed to heavy metals and to compare them with different age classes and sites. The results indicated that there were metal-specific differences in concentration in exposure groups among the studied sites. The concentration of heavy metals in blood samples showed the following order : Pb > Cd > Ni > Co > Cr. In urine samples, the order was Cu > Pb > Cr > Ni > Co > Cd; in nails samples, the order was Pb > Ni > Cr > Co > Cd > Mn; and in hair samples, the trend was Pb > Ni > Cr > Mn > Cd > Co. A significant (p > 0.05) decrease in antioxidants enzymes activity was observed with increase in heavy metals concentrations. This is the first study reporting biological evidence of altered toxic metals' concentration in humans in Lahore, Pakistan, due to environmental exposure. Further research, including risk analysis studies, food chain contamination, and epidemiological and clinical investigations, are needed to assess optimal levels for dietary exposure in the study area and associated adverse health outcomes.