On the nature of airborne aldehydes in a middle eastern megacity: Tehran, Iran

This work summarizes characteristics of acetaldehyde and formaldehyde in autumn 2018 in the ambient air of a major bus terminal in Tehran, Iran. The average (±standard deviation) concentration of formaldehyde/acetaldehyde was 109.99 ± 23.47/85.4 ± 17.17 μg m⁻³. Major sources of these species were traffic emissions, photochemical processes, and biogenic sources (e.g., deciduous-coniferous tree). The average inhalation lifetime cancer risk (ILTCR) values based on IRIS for both aldehydes were between 7.07 × 10^-5 and 5.09 × 10^-4, which surpass suggested EPA magnitudes. The mean ILTCR values based on the office of environmental health hazard assessment for these species ranged from 1.21 × 10^-4 to 1.02 × 10^-3, which exceed suggested values by EPA for eleven different age groups. Hazard quotient (HQ) values of formaldehyde were between 7.27 ± 1.61 to 1.34 ± 0.29, while those of acetaldehyde were between 6.68 ± 1.49 and 1.58 ± 0.355. Hence, the ILTCRs and HQs of these toxic species were higher than 1 × 10⁻⁶ and one, respectively, which is not at "an acceptable risk for humans". The results of the current work have relevance to the health of the general public close to ‘hot-spots’ like the study region where a large number of people are in contact with carcinogenic pollutants.