Health risk assessment of heavy metals and metalloids in atmospheric PM_2.5 from Inner Mongolia Autonomous Region in 2023

Background The Inner Mongolia Autonomous Region is a vast area with a wide array of ecological environments, resulting in considerable regional variations in air pollution characteristics. Current research is limited by a scarcity of systematic, region-wide studies and risk assessments.

Objective To assess the health risks associated with inhalation exposure to nine heavy metal and metalloid elements in atmospheric fine particulate matter (PM_2.5) for the population of the Inner Mongolia Autonomous Region.

Methods From the 10th to the 16th of each month throughout 2023, atmospheric PM_2.5 samples were collected at designated monitoring sites in 12 leagues (cities) across the Inner Mongolia Autonomous Region to analyze the characteristics and trends in concentration. The health risk assessment model developed by the United States Environmental Protection Agency was employed to evaluate both the non-carcinogenic and carcinogenic risks associated with the heavy metal elements beryllium (Be), cadmium (Cd), chromium (Cr), hydrargyrum (Hg), plumbum (Pb), manganese (Mn), and nickel (Ni) and the metalloid elements stibium (Sb) and arsenic (As).

Results In 2023, a total of 1206 valid PM_2.5 samples were analyzed from the Inner Mongolia Autonomous Region. The annual average PM_2.5 concentrations in Inner Mongolia, as well as in the cities of Ordos, Wuhai, and the Alxa League, all exceeded the national limit of 35 μg·m⁻³. The PM_2.5 concentrations across the leagues (cities) exhibited a clear seasonal variation, peaking in winter, followed by spring, and reaching a minimum in summer and autumn. The median PM_2.5 concentration in Ordos throughout the year was higher than that in the other leagues (cities) of the region. Concerning health risks, the non-carcinogenic risks associated with the 9 elements detected in each league (city) were all below 1, indicating acceptable levels. However, the non-carcinogenic risk values for Mn, Cr, and As were relatively high; specifically, Ordos City displayed the highest non-carcinogenic risk values for Mn (7.74×10⁻¹) and Cr (2.97×10⁻²), while Chifeng City recorded the highest value for As (2.34×10⁻³). The carcinogenic risk values for As, Cd, Cr, and Ni fell within the range of 1×10⁻⁹ to 1×10⁻⁵, representing an acceptable level. The health risks varied with age, and the elderly residents faced the highest non-carcinogenic and carcinogenic health risks.

Conclusion While the carcinogenic and non-carcinogenic risks from heavy metals and metalloids within atmospheric PM_2.5 in the Inner Mongolia Autonomous Region are generally within acceptable limits, the potential risks that Mn, As, and Cr pose to the health of elderly people warrants particular attention, and Ordos and Chifeng cities exhibit notably higher health risks among other areas. It is recommended that regular, long-term monitoring be conducted, taking into account the specific conditions at monitoring sites across each league (city), and that targeted air quality management strategies be implemented to protect public health.