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

Real-Time Monitoring of Air Pollution Health Impacts Using Breath-Borne Gaseous Biomarkers from Rats

Offline techniques are adopted for studying air pollution health impacts, thus failing to provide in situ observations. Here, we have demonstrated their real-time monitoring by online analyzing an array of gaseous biomarkers from rats' exhaled breath using an integrated exhaled breath array sensor (IEBAS) developed. The biomarkers include total volatile organic compounds (TVOC), CO2, CO, NO, H2S, H2O2, O2, and NH3. Specific breath-borne VOCs were also analyzed by a gas chromatography-ion mobility spectrometer (GC-IMS). After real-life ambient air pollution exposures (2 h), the pollution levels of PM2.5 and O3 were both found to significantly affect the relative levels of multiple gaseous biomarkers in rats' breath. Eleven biomarkers, especially NO, H2S, and 1-propanol, were detected as significantly correlated with PM2.5 concentration, while heptanal was shown to be significantly correlated with O3. Likewise, significant changes were also detected in multiple breath-borne biomarkers from rats under lab-controlled O3 exposures with levels of 150, 300, and 1000 μg/m3 (2 h), compared to synthetic air exposure. Importantly, heptanal was experimentally confirmed as a reliable biomarker for O3 exposure, with a notable dose-response relationship. In contrast, conventional biomarkers of inflammation and oxidative stress in rat sera exhibited insignificant differences after the 2 h exposures. The results imply that breath-borne gaseous biomarkers can serve as an early and sensitive indicator for ambient pollutant exposure. This work pioneered a new research paradigm for online monitoring of air pollution health impacts while obtaining important candidate biomarker information for PM2.5 and O3 exposures.

Mortality Burden of Cardiovascular Disease Attributable to Ozone in China: 2019 vs 2050

Due to a combination of lifestyle risk factors, the burden of cardiovascular disease (CVD) has been increasing in China, affecting an estimated 330 million people. Environmental risk factors can exacerbate these risks or independently contribute to CVD. Ozone is an overlooked and invisible risk factor, and it plays a significant role in the development of CVD. Our study provides a novel quantification of the ozone-attributable CVD mortality burden based on daily maximum 8-h average ozone concentration during May to October (6mDMA8) in Chinese adults in 2050, projected under Shared Socioeconomic Pathways 585 and 126, and using the updated WHO air quality guideline level. The study also considers the contributions made by changes in ozone exposure, population aging, population size, and baseline death rates of CVD between 2019 and 2050. While adopting a sustainable and green pathway (SSP 126) can reduce the projected magnitude of premature CVD deaths to 359,200 in 2050, it may not be sufficient to reduce the CVD mortality burden significantly. Therefore, it is crucial to implement strategies for stricter ozone control and reducing the baseline death rate of CVD to mitigate the impacts of ozone on Chinese adults.

A novel hollow microsphere composite MnOx/PAA: effective catalyst for ozone decomposition at high humidity

Ozone air pollution poses a serious threat to human health and ecological environment. Manganese oxide (MnOx) is a popular material for ozone decomposition with excellent catalytic performance. However, the catalytic activity may be reduced under high-humidity conditions because of oxygen vacancy of MnOx from the water evaporation. In this paper, a new type of MnOx/poly(acrylic acid-co-divinylbenzene) (PAA) catalyst with MnOx supported on hollow PAA was successfully prepared, which greatly improved the ozone decomposition efficiency under high humidity. It was shown that when the acrylic acid (AA) content was more than 50%, the PAA polymer layer was hydrophilic and the ozone decomposition efficiency would keep high activity for both the low- and high-humidity conditions. The best performance of ozone decomposition was identified for the methanol reduction and AA content of 60%, in which the efficiencies reached 94.5% and 85% at 50% and 90% humidity levels, respectively. It is the synergetic effect of the hydrophilic PAA support and hollow structure that retains and improves the decomposition activity, which can absorb the water vapor molecules and increase the ozone retention time. Therefore, the hollow microsphere catalyst prepared in this paper has great potential in solving the problem of ozone air pollution.

Wearable Sensor-Based Monitoring of Environmental Exposures and the Associated Health Effects: A Review

Recent advances in sensor technology have facilitated the development and use of personalized sensors in monitoring environmental factors and the associated health effects. No studies have reviewed the research advancement in examining population-based health responses to environmental exposure via portable sensors/instruments. This study aims to review studies that use portable sensors to measure environmental factors and health responses while exploring the environmental effects on health. With a thorough literature review using two major English databases (Web of Science and PubMed), 24 eligible studies were included and analyzed out of 16,751 total records. The 24 studies include 5 on physical factors, 19 on chemical factors, and none on biological factors. The results show that particles were the most considered environmental factor among all of the physical, chemical, and biological factors, followed by total volatile organic compounds and carbon monoxide. Heart rate and heart rate variability were the most considered health indicators among all cardiopulmonary outcomes, followed by respiratory function. The studies mostly had a sample size of fewer than 100 participants and a study period of less than a week due to the challenges in accessing low-cost, small, and light wearable sensors. This review guides future sensor-based environmental health studies on project design and sensor selection.

Reactions and Products of Squalene and Ozone: A Review

This critical review describes the squalene-ozone (SqOz) reaction, or squalene ozonolysis. Ambient ozone penetrates indoors and drives indoor air chemistry. Squalene, a component of human skin oil, contains six carbon-carbon double bonds and is very reactive with ozone. Bioeffluents from people contribute to indoor air chemistry and affect the indoor air quality, resulting in exposures because people spend the majority of their time indoors. The SqOz reaction proceeds through various formation pathways and produces compounds that include aldehydes, ketones, carboxylic acids, and dicarbonyl species, which have a range of volatilities. In this critical review of SqOz chemistry, information on the mechanism of reaction, reaction probability, rate constants, and reaction kinetics are compiled. Characterizations of SqOz reaction products have been done in laboratory experiments and real-world settings. The effect of multiple environmental parameters (ozone concentration, air exchange rate (AER), temperature, and relative humidity (RH)) in indoor settings are summarized. This critical review concludes by identifying the paucity of available exposure, health, and toxicological data for known reaction products. Key knowledge gaps about SqOz reactions leading to indoor exposures and adverse health outcomes are provided as well as an outlook on where the field is headed.

Indoor ozone: Concentrations and influencing factors

Because people spend most of their time indoors, much of their exposure to ozone occurs in buildings, which are partially protective against outdoor ozone. Measurements in approximately 2000 indoor environments (residences, schools, and offices) show a central tendency for average indoor ozone concentration of 4-6 ppb and an indoor to outdoor concentration ratio of about 25%. Considerable variability in this ratio exists among buildings, as influenced by seven building-associated factors: ozone removal in mechanical ventilation systems, ozone penetration through the building envelope, air-change rates, ozone loss rate on fixed indoor surfaces, ozone loss rate on human occupants, ozone loss by homogeneous reaction with nitrogen oxides, and ozone loss by reaction with gas-phase organics. Among these, the most important are air-change rates, ozone loss rate on fixed indoor surfaces, and, in densely occupied spaces, ozone loss rate on human occupants. Although most indoor ozone originates outdoors and enters with ventilation air, indoor emission sources can materially increase indoor ozone concentrations. Mitigation technologies to reduce indoor ozone concentrations are available or are being investigated. The most mature of these technologies, activated carbon filtration of mechanical ventilation supply air, shows a high modeled health-benefit to cost ratio when applied in densely occupied spaces.

Spatio-temporal variations and trends of major air pollutants in China during 2015-2018

The Chinese government, as a policy response, has continued to invest efforts and resources to implement cost-effective air pollution control technologies and stringent regulation to reduce emissions from the most contributing sectors to protect the environment and public health. The higher density of monitoring stations (> 1600) distributed across China provides a timely opportunity to use them to study in detail the national pollution trends in light of more stringent air pollution control policies. In the present study, air quality datasets comprising hourly concentrations of PM2.5, O3, NO2, and SO2 collected across 1309, 1341, 1289, and 1347 monitoring stations respectively were obtained from the National Environmental Monitoring Centre over 4 years (2015-2018) and trend analysis was performed. Results indicate that the overall annual trends for PM2.5 and SO2 were - 2.9 ± 2.7 and - 3.2 ± 3.2 μg/m3/year, while the winter trends were - 4.8 ± 5.8 and - 6.9 ± 8.4 μg/m3/year respectively across China. The daily maximum 8-h average (DMA8) ozone concentration showed a significant positive trend of 2.4 ± 4.6 μg/m3/year, which was comparatively higher in summer at 4.4 ± 9.0 μg/m3/year. On the other side, NO2 trend is not great in number (- 0.45 ± 2.0 μg/m3/year). Overall, 62.2%, 61.8%, and 20.9% of PM2.5, SO2, and NO2 monitoring stations were associated with a negative trend of ≥ - 2 μg/m3/year. For O3 DMA8 concentrations, 50.7% of the monitoring stations showed a significant positive trend of ≥ 2 μg/m3/year. In light of the Chinese government's increasing impetus on combating air pollution and climate change via new policy regulations, it is important to understand the spatio-temporal distributions and relative contributions of the spectrum of gaseous pollutants to the pollution loads as well as identify changing emission loads across sectors. The results of this study will facilitate the formulation of evidence-based air pollution reduction strategies and policies.

Substantial changes in PM2.5 pollution and corresponding premature deaths across China during 2015-2019: A model prospective

Long-term exposure to the ambient fine particulate matter (PM_2.5) is the major public health risk factor in China. Several past studies have assessed premature mortalities associated with PM_2.5 in China at varying levels of temporal and spatial scales using different methodological approaches. However, recently developed global exposure mortality model [GEMM NCD + LRI and GEMM 5-COD] provides a much more sophisticated methodology in capturing mortality due to PM_2.5-exposure than the commonly accepted integrated exposure-response (IER) model, which this study applied to China. This study provides a comparative assessment of the excess long-term PM_2.5-attributed nonaccidental deaths as well as cause-specific deaths for 349 cities in mainland China during five years (from 2015 to 2019) and compares the results with the spatial resolution scale of 0.1° × 0.1° across overall China. The results demonstrate that the national annual average PM_2.5 concentration declined from 51.9 ± 18.2 μg/m³ in 2015 to 39.0 ± 13.2 μg/m³ in 2019, and the overall annual negative trend was around -3.1 ± 2.2 μg/m³/year [-5.6 ± 3.4%/year] across China. Consequently, the number of PM_2.5-related deaths decreased by 383 thousand [95% CI: 331-429] to 1755 thousand [95% Confidence Interval: 1470-2025; GEMM NCD + LRI]; 315 thousand [95% CI: 227-370] to 1380 thousand [95% CI: 948-1740; GEMM 5-COD] and 125 thousand [95% CI: 64-140] to 876 thousand [95% CI: 394-1262; IER] in 2019, derived from the pre-established models (GEMM and IER). The estimate PM_2.5-attributed death with a spatial resolution of 0.1° × 0.1° was 2419 thousand [95% CI: 2041-2771; GEMM NCD + LRI], 1918 thousand [95% CI: 1333-2377; GEMM 5-COD] and 1162 thousand [95% CI: 534-1611; IER] in 2015, which is about 11-16% higher value than the city-level health risk assessment study. The estimated deaths by GEMM NCD + LRI and GEMM 5-COD were 104% and 61% higher than the estimated by IER, highlighting that total premature mortalities associated with PM_2.5 were substantially left behind based on the pre-existing model. The "other noncommunicable diseases" mortality, which IER method doesn't account for, was 375 thousand in 2019, 68 thousand less than in 2015. Such significant mortality was previously overlooked in estimation methods, which should now be considered for the air pollution-related policy development in China. The high number of premature deaths in central and northern parts of China, calls for the need for the Government to quickly impose even more stringent and effective pollution control measures.