Determination of Selected Heavy Metals in Air Samples and Human Health Risk Assessment in Tehran City, Iran

Heavy metal contamination has become a global issue. In this study, the concentrations of arsenic (As), lead (Pb), nickel (Ni), zinc (Zn), chromium (Cr), copper (Cu), and cadmium (Cd) in the air of the Tehran metropolis were measured. Also, cancer and non-cancer risk assessments were performed to quantify the rate and effect of infection on health. Sampling was done every month from April 2019 to March 2020 for one year. Sampling points in the whole city were determined based on Municipality 22 districts of Tehran. The concentrations of the studied heavy metals in nanogram per cubic meter ( /m3) showed the following order: Zn (106.22) > Pb (31.65) > Cu (16.38) > As (5.83) > Ni (5.77) > Cr (5.62) > Cd (5.36). The results indicate that in non-carcinogenic risk assessment, the hazard index (HQ) of As (8.20E+00), Ni (8.67E+00), Cr (1.14E+00), and Cd (1.13E+01), and the total hazard index (HI) of 2.94E+01 are above the safe level of 1, indicating the potential threat of non-carcinogenic diseases through the inhalation of air. According to USEPA guidelines, the risk of carcinogenicity is unacceptable for Cr, acceptable for As, Cd, and Ni, and without any significant health effects for Pb. The total carcinogenic risk of metals was 1.10E-02, being in the high-risk range. Therefore, exposure to heavy metals through air inhalation increases the risk of cancer and mortality, so 61 people annually suffer from various cancer types due to the inhalation of air. The Monte Carlo simulation uncertainty results also confirm those of non-carcinogenic and carcinogenic respiratory risk analysis of heavy metals in the air. The obtained results indicate the need for improving the air quality in Tehran needs and taking into account the health risks to humans via inhalation exposure to heavy atmospheric metals.