Impacts of urbanization on air quality and the related health risks in a city with complex terrain

[摘要] Urbanization affects air pollutants via urban expansion andemission growth, thereby inevitably changing the health risks involved with airpollutants. However, the health risks related to urbanization are rarelyestimated, especially for cities with complex terrain. In this study, ahighly urbanized city with severe air pollution and complex terrain(Chengdu) is selected to explore this issue. The effects of urban expansionare further compared with emission growth because air quality management isusually achieved by regulating anthropogenic emissions. Air pollution inChengdu was mainly caused by PM 2.5 and O 3 from 2015 to 2021.PM 2.5 pollution tended to appear in cold months (November to February)owing to the blocking of air and the stable atmospheric layer, whereas O 3 pollution was likely to occur in warm months (April to August) that experience high-temperature and strong-sunlight conditions and are dominated by high-pressure systems.From 2015 to 2021, the 7-year annual average of premature mortality fromall non-accidental causes (ANACs) due to PM 2.5 and O 3 was 9386(95 % confidence interval (CI) of 6542–11 726) and 8506 (95 % CI of4817–11 882), respectively. Based on the characteristics of PM 2.5 andO 3 , six numerical experiments were conducted to investigate the impactsof urban expansion and emission growth on the health risks related to air pollutants.The results show that urban land use led to an increase in the air temperatureand boundary layer height compared with cropland, which was conducive tothe diffusion of PM 2.5 . Thus, the monthly average surface PM 2.5 concentrations decreased by 10.8  µ g m −3 (7.6 %) in January.However, the monthly average daily maximum 8 h average (MDA8) O 3 concentrations increased by 10.6  µ g m −3 (6.0 %) in July owingto the stronger photochemical production and better vertical mixing duringdaytime. In this case, premature mortality from ANACs due to PM 2.5 decreased by 171 (95 % CI of 129–200, or about 6.9 %) in January, andthat due to O 3 increased by 203 (95 % CI of 122–268, or about 9.5 %)in July. As for the effects of emission growth, the monthly averagePM 2.5 and MDA8 O 3 concentrations increased by 23.9 (16.8 %) and 4.8  µ g m −3 (2.7 %), respectively, when anthropogenicemissions were taken into account. Premature mortality from ANACs due toPM 2.5 and O 3 then increased by 388 (95 % CI of 291–456, or about15.7 %) and 87 (95 % CI of 54–112, or about 4.1 %), respectively. From ahealth risk perspective, the effects of urban land use on the health risks related toPM 2.5 are about half that of anthropogenic emissions, whereas theeffects of urban land use on the health risks related to O 3 can be 2 times that ofanthropogenic emissions. This emphasizes that, in addition to regulatinganthropogenic emissions, urban planning is also important for urban airquality, especially for secondary pollutants like O 3 .

[学科分类] 医学（综合）