Assessment of air pollution characteristics and population health risks during heating and non-heating seasons in Hohhot city from 2017 to 2022

ObjectiveTo understand the characteristics of air pollution and the associated population health risks during the heating season (October 15 to April 15 of the following year) and the non-heating season (April 16 to October 14 of the following year) in Hohhot city, Inner Mongolia, from 2017 to 2022, and to provide a reference for the development of scientific environmental protection policies in this region. MethodsData on monitored pollutants during the heating and non-heating seasons from January 1, 2017, to December 31, 2022, were collected from the Hohhot Ecological Environment Monitoring Station. Time series plots of pollutants were generated, and health risk values were calculated using the model recommended by the United States Environmental Protection Agency (USEPA) to assess the health risks posed by air pollutants to the population. ResultsFrom 2017 to 2022, there were 1 099 days in the heating season and 1 092 days in the non-heating season in Hohhot city. The exceedance rates of inhalable particulate matter (PM10), fine particulate matter (PM2.5), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and 8-hour ozone (O3-8 h) concentrations during the heating and non-heating seasons were 16.7% and 4.0%, 18.4% and 1.1%, 0 and 0, 2.2% and 0.1%, 0.1% and 0, and 0 and 12.5%, respectively. Compared with the non-heating season, the exceedance rates of PM10, PM2.5, and NO2 were higher during the heating season, while the exceedance rate of O3-8 h was lower during the heating season (all P<0.001). From 2017 to 2022, the annual average mass concentrations of PM10, PM2.5, SO2, NO2, and CO during both the heating and non-heating seasons showed a downward trend (all P<0.001). The annual average mass concentrations of PM10, PM2.5, SO2, NO2, and CO were higher during the heating season than during the non-heating season for each year, while the annual average mass concentration of O3-8 h was lower during the heating season (all P<0.001). Time series plots showed that the daily average concentrations of PM10, PM2.5, SO2, NO2, and CO in Hohhot city from 2017 to 2022 were higher during the heating season than during the non-heating season, while the daily average concentration of O3-8 h was lower during the heating season. Comparison of the daily average concentrations of air pollutants between the heating and non-heating seasons also showed that the daily average concentrations of PM10, PM2.5, SO2, NO2, and CO were higher during the heating season than during the non-heating season for each year from 2017 to 2022, while the daily average concentration of O3-8 h was lower during the heating season; these differences were all statistically significant (all P<0.001). From 2017 to 2022, the non-carcinogenic risk value of PM10 was > 1×10–6 during both the heating and non-heating seasons in Hohhot city. The non-carcinogenic risk value of PM2.5 was > 1×10–6 during the heating season and <1×10–6 during the non-heating season. The non-carcinogenic risk values of SO2 and NO2 were <1×10–6 during both the heating and non-heating seasons. ConclusionsFrom 2017 to 2022, air pollution in Hohhot city was more severe during the heating season than during the non-heating season. PM10 and PM2.5 pollution was particularly serious in this region, posing potential risks to human health.