Carcinogenic and non-carcinogenic risk assessment of heavy metals in PM_2.5 air pollutant in Ulaanbaatar, Mongolia during the wintertime

In recent decades, fine particulate matter air pollution has increased due to coal combustion, resulting in detrimental effects on public health. This study aimed to assess the health risk associated with fine particulate matter (PM_2.5) using the US EPA risk assessment method and to determine which variable exerts a stronger influence. Eight heavy metals were measured from Ulaanbaatar city center and ger area within the scope of the project “Capacity development project for air pollution control in Ulaanbaatar Mongolia” funded by JICA (Japan International Cooperation Agency), and the processed results were disseminated. The concentration of heavy metals in the city center, from highest to lowest, were Cu > Cr > Mn > Ni > Zn > Ba > Pb > Mo > As, while in the ger area they were Cu > Zn > Mn > Ni > Cr > Pb > Ba > As > Mo. In both the city center and the ger area, 6 heavy metals, namely Zn, Cu, Pb, Ni, As and Mo, had values of less than 1 and exhibited no non-carcinogenic effects. Among the two other heavy metals, Cr (VI) and Mn, values were higher than 1 and demonstrated non-carcinogenic effects. As Ni and Cr (VI) are considered carcinogenic heavy metals and their assessment results exceeded the safe level, this implies a potential risk for cancer.

In addition, Hazard Quotient has been calculated on each age groups, and among children under the age of 11, exposure to heavy metals is relatively higher than elder citizens, above the age of 11, HQ decreases gradually. Monte Carlo Simulation has been used for the probability distribution of Hazard Quotient (HQ), and its result showed that HQ is generally higher in the Ger area. Sensitivity coefficient analysis has resulted Exposure Time (h/d) affects more stronger than other variables.

This research concludes that heavy metals in PM2.5 pollution have carcinogenic and non-carcinogenic risk effects. Regarding spatial distribution, the Ger area exhibits a higher risk level, and with respect to age groups, children under the age of 11 are more exposed to heavy metals. Furthermore, this study suggests that limiting outdoor exposure to less than 30 min per day may mitigate health risks for individuals.