Evaluating seasonal health risks of copper, nickel, and chromium in airborne dust

Abstract

The primary objective of this study was to determine the concentration of heavy metals in atmospheric dust fallout and to evaluate their potential health risks to humans. Heavy metals are a significant concern in atmospheric dust as they can enter the human body through ingestion, inhalation, and dermal contact, potentially causing various health problems. This research specifically measured the quantities of dust fallout and the concentrations of copper (Cu), nickel (Ni), and chromium (Cr) in atmospheric dust across Tehran, from its western to eastern regions, during the period from winter 2018 to autumn 2019. Sampling sites were established at two points, one in the western area and one in the eastern area, particularly covering districts 11, 10, and 12 and the adjacent western regions. Monthly dust samples were collected over a year. A factorial experiment was conducted using a completely randomized design with three replications, considering sampling points (S.P.) and seasons as factors. The concentrations of Cu, Ni, and Cr were determined using a hydrochloric acid and concentrated nitric acid extraction method in a 3:1 ratio. Health risk assessments were calculated using the methodology provided by the U.S. Environmental Protection Agency (EPA). The results revealed that both the sampling location and the time of sampling significantly influenced the quantity of dust fallout and the concentrations of Cu, Ni, and Cr in the collected samples. The highest amount of atmospheric dust fallout was recorded during autumn at points 10E (Imam Khomeini Street), 11E (Vahdat Islami Street), and 12E (17th Shahrivar Street), with an average of 23.24 g·m⁻²·season⁻¹. Conversely, the lowest amount of dust fallout, 15.33 g·m⁻²·season⁻¹, was observed in winter at point 9 W, located in Tehransar. The highest amounts of Cu and Ni were measured in autumn at point 11E, reaching 11.22 and 4.45 mg·m⁻²·season⁻¹, respectively, while the highest Cr concentration, 52.3 mg·m⁻²·season⁻¹, was observed in autumn at points 10E, 11E, and 12E. In contrast, the lowest levels of Cu, Ni, and Cr—2.27, 1.4, and 0.96 mg·m⁻²·season⁻¹, respectively—were recorded during winter at point 9 W. Similarly, the lowest concentrations of Cu, Ni, and Cr in the dust (148.6, 91.83, and 62.86 mg·kg⁻¹, respectively) were found during winter at point 9 W. On the other hand, the highest concentrations of these metals were observed during autumn at point 11E (Vahdat Islami Street), with values of 646.46, 184.43, and 45.9 mg·kg⁻¹, respectively. Overall, the findings indicated that both the concentrations of heavy metals and the amount of atmospheric dust fallout tended to increase from west to east and from winter to autumn. The health risk assessment results demonstrated that ingestion of atmospheric dust fallout was the primary exposure route for heavy metals, accounting for over 90% of the non-cancerous disease risk associated with Cu, Ni, and Cr. For Cu and Ni, the highest levels of HQ_ingestion, HQ_inh, HQ_derm and HI were observed at point 11E, while for Cr, the highest levels were found at points 10E, 11E, and 12E. For Cu, the highest HQ_ing_values were 1.99E-02 for adults and 1.49E-01 for children. The highest HQ _inhalation values were 1.86E-06 for adults and 4.04E-06 for children, while Hq_dermal reached 2.02E-03 for adults and 7.91E-04 for children. The highest HI values for Cu were 2.19E-02 for adults and 0.149 for children. For Ni, the highest Hq_ing values were 1.58E-02 for adults and 1.17E-01 for children. HQ_inh peaked at 1.44E-06 for adults and 3.21E-06 for children, and Hq_derm reached 1.78E-03 for adults and 6.98E-04 for children. The highest HI values for Ni were 0.016 for adults and 0.118 for children, while the highest RI values for Ni were 2.5E-08 for adults and 5.56E-08 for children. For Cr, the highest Hq_ing values were 8.34E-02 for adults and 6.21E-01 for children. Hq_inh peaked at 8.33E-04 for adults and 1.83E-03 for children, while HQ reached 1.27E-01 for adults and 4.97E-02 for children. The highest HI values for Cr were 0.211 for adults and 0.673 for children, and the highest RI values for Cr were 9.89E-07 for adults and 2.19E-06 for children. Throughout all seasons, the Hazard Quotient (HQ) and Hazard Index (HI) for non-cancerous diseases from Cu, Ni, and Cr remained below the safe threshold for both adults and children, indicating no significant health risk. However, Cr’s cancer risk index (RI) consistently exceeded that of Ni across all seasons and regions, though it remained below concerning levels for adults.