Abstract
While PM2.5 (particles with aerodynamic diameter less than 2.5 µm) concentrations in China are beginning to decline because of pollution abatement measures, ozone (O3) concentrations continue to rise. In this study, we have used a Monte Carlo approach to estimate breathing-rate adjusted (BRA) population exposure to ozone and its oxidation products based on hourly O3 measurements collected in 2017 from monitoring stations in 333 Chinese cities. The median measured outdoor O3 concentration in these cities was 31 ppb, while the median calculated indoor concentrations of ozone and ozone-derived oxidation products were 7.5 ppb and 21 ppb, respectively. The median BRA O3 exposure concentration was 12 ppb, ranging from 2.2 ppb to 18 ppb among the cities. Eastern and central cities had higher exposure concentrations, while northeastern and western cities had lower. On average, the residents of these cities spent 88% of their time indoors. Consequently, even with breathing rate adjustments, indoor O3 exposure averaged 50% of the total O3 exposure nationwide. The median BRA exposure concentration for ozone-derived products was 18 ppb, ranging from 4.5 ppb to 32 ppb among the cities. On average, BRA exposure concentrations were 1.6 times larger for oxidation products than for ozone, while seasonal variations of exposure concentrations were smaller for oxidation products than for ozone. As many of the products of indoor ozone chemistry are toxic, the health consequences of exposure to such products should be further investigated.
Highlights
The evidence that ozone exposure results in significant adverse health effects continues to grow
Our Monte Carlo calculated exposures are based on hourly ozone measurements at the 1409 monitoring stations in 333 Chinese cities
The exposure concentrations have been adjusted for breathing rates while outdoors, indoors awake, and indoors asleep
Summary
The evidence that ozone exposure results in significant adverse health effects continues to grow. Humans themselves are covered with a thin layer of skin surface lipids containing squalene (~10%), sapienic acid (~6%), other unsaturated fatty acids, and unsaturated triglycerides (Nicolaides, 1974). Ozone reactions with these compounds generate oxidation products, some of which may adversely affect human health (Weschler, 2000; Weschler, 2004; Weschler, 2006; Weschler et al, 2006). Studies have found that the oxidation products of terpenes are potent contact allergens and might have inflammatory and respiratory sensitizing properties (Weschler, 2004; Wolkoff et al, 2013). Using a head out mouse bioassay, Wolkoff et al (2013) derived a human reference value (RF) for sensory irritation of
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