Integrated health risk assessment of ozone and nitrogen dioxide pollution during the cold and warm seasons in the Beijing–Tianjin–Hebei region

Understanding the risk trade-offs between nitrogen dioxide (NO₂) and ozone (O₃) pollution is crucial for ozone governance. The air quality health index (AQHI) provides a more comprehensive measure of air pollution mixtures. This study used environmental, meteorological, and health data of 13 cities in the Beijing–Tianjin–Hebei region for 2018–2020 to assess the health effects of pollutants during both cold and warm seasons. The study reveals that NO₂ pollution in the cold season (20.4–63.4 µg/m³) is more severe compared to warm season (18.3–49.7 µg/m³), and its concentrations have been decreasing annually in most cities. However, the study also highlights a concerning trend of increasing ozone concentrations during the cold season across all cities in the region (The average annual increase is 3.5 µg/m³). This increase may be linked to the abatement of nitrogen oxides (NO_X) and particulate matter (PM). The health benefit of reducing environmental air NO₂ concentrations maybe offset by the increase in O₃ concentrations. Emission control measures to reduce nitrogen dioxide, sulfur dioxide, and particulate matter levels have been effective in reducing the negative impacts on health caused by air pollution in various cities in the Beijing–Tianjin–Hebei region. It was necessary to construct the cold season AQHI (AQHI-C) and warm season AQHI (AQHI-W) separately in the Beijing–Tianjin–Hebei region, especially for the assessment of health risks during the cold season.