Ozone in urban China: Impact on mortalities and approaches for establishing indoor guideline concentrations

Abstract

Reducing indoor ozone levels may be an effective strategy to reduce total exposure and associated mortality. Here we estimate (a) premature mortalities attributable to ozone for China's urban population ≥25 years of age; (b) the fraction of total exposure occurring indoors; and (c) mortalities that can be potentially avoided through meeting current and more stringent indoor ozone standards/guidelines based on 1‐hour daily maxima. To estimate ozone‐attributable premature mortalities, we used hourly outdoor ozone concentrations measured at 1497 monitoring stations located in 339 Chinese cities and a published concentration‐response model. We proceeded to estimate province‐specific infiltration factors and co‐occurring hourly indoor ozone concentrations. For the year 2015, we estimated that indoor exposures accounted for 59% (95% confidence interval (CI): 26%‐79%) of the total ozone exposure that resulted in 70800 (95% CI: 35 900‐137 700) premature all‐cause mortalities in urban China. If the current Chinese indoor ozone standards (80 ppbv (160 µg/m3); 56 ppbv (112 µg/m3)) were met, the mean estimates of reduction in mortalities would be indistinguishable from zero. With stricter 1‐hour indoor ozone guidelines, the expected mortality reductions increase exponentially per unit decrease in indoor ozone. The analysis in this paper should help facilitate formulating present and future indoor ozone guidelines.

Effects of China’s current Air Pollution Prevention and Control Action Plan on air pollution patterns, health risks and mortalities in Beijing 2014–2018

“…At the city-level, PM 2.5 -related reported deaths were 20.9 thousands (Song et al, 2017) and 25.5 thousands , 17.7 thousands (Anenberg et al, 2019 and 18.2 thousands in 2016 (Maji et al, 2018), 25.8 thousands in 2017 (Ding et al, 2019b). Ozone-related total reported deaths were 2.98 thousands in 2015 (Xiang et al, 2019) and 2.1 thousands in 2016 (Maji et al, 2019). This difference in estimated pollution attributed deaths is mainly due to different methodologies for estimating death and ground-level ozone, and exposure-response coefficient.…”

Indoor ozone: Concentrations and influencing factors

“…26 Only recently has this terminology been extended to ozone, as introduced by Xiang et al, 27 who modeled the ozone infiltration factor for residences in Chinese cities. Xiang et al 27 displaying conditions more common in residences, with a combination of infiltration and natural ventilation. We note that Figure 1A does not account for penetration via infiltration, while Figure 1B does not account for ozone loss in central forced-air systems that are common in residences in the United States.…”

“…In Liu et al, 25 We also note that the term "infiltration factor" has a substantial history applied to indoor particulate matter. 26 Only recently has this terminology been extended to ozone, as introduced by Xiang et al, 27 who modeled the ozone infiltration factor for residences in Chinese cities. Xiang et al 27 displaying conditions more common in residences, with a combination of infiltration and natural ventilation.…”

How Do Indoor Environments Affect Air Pollution Exposure?

“…A compilation of empirical results studying the indoor/outdoor ratio for ozone in buildings without known indoor sources suggests a central tendency of about 0.25 with variation commonly spanning the range 0.1-0.6. 23,30 Important consequences ensue from the partial and variable protection provided by buildings against outdoor air pollution. In epidemiological studies, actual inhalation intake of outdoor air pollutants such as fine particles and ozone is lower than monitoring networks would indicate.…”