Current Ambient Air Quality Standards Research Articles

Particulate matter pollution and asthma mortality in China: A nationwide time-stratified case-crossover study from 2015 to 2020

BackgroundA national and comprehensive evaluation is lacking on the relationship between short-term exposure to submicron particulate matter (PM1) pollution and asthma mortality. MethodsData was obtained from 29,553 asthma deaths from the China National Mortality Surveillance System from 2015 to 2020. We used a bilinear interpolation approach to estimate each participant's daily ambient particulate matter pollution and meteorological variables exposure based on their geocoded residential address and a 10 km × 10 km grid from China High Air Pollutants and the fifth generation of European ReAnalysis-Land reanalysis data set. The associations were estimated using a time-stratified case-crossover design and conditional logistic regressions. ResultsOur results revealed significant associations between short-term exposure to various particulate matter and asthma mortality. The 5-day moving average of particulate matter exposure produced the most pronounced effect. Compared to fine particulate matter (PM2.5) and inhalable particulate matter (PM10), significantly stronger effects on asthma mortality related to PM1 pollution were noted. The ERs% for asthma mortality associated with each interquartile range (IQR) increase of exposures to PM1 (IQR: 19.2 μg/m3) was 5.59% (95% CI: 2.11–9.19), which is 14% and 22% higher than that for PM2.5 (IQR: 32.0 μg/m3, 4.82% (95% CI: 1.84–7.90)) and PM10 (IQR: 52.2 μg/m3, 4.37% (95% CI: 1.16–7.69)), respectively. The estimates remained consistent in various sensitivity analyses. ConclusionsOur study provided national evidence that acute exposures to various ambient particulate matter pollution can increase mortality due to asthma in China, highlighting stronger associations with ambient PM1 than PM2.5 and PM10. China needs to adjust the current ambient air quality standards urgently and pay greater attention to the adverse health effects of PM1.

Air Pollution, Student Health, and School Absences: Evidence from China

Little is known about the impact of air pollution on school children in developing countries. This paper aims to fill this gap by quantifying the causal effects of air pollution on the health status and the school attendance of the Chinese students. We relate the arguably exogenous daily variation in air pollution-instrumented by the occurrence of temperature inversion-with student illnesses and absences from more than 3000 schools in Guangzhou City. We find a sizable deleterious effect of air pollution on school attendance through the health channel. The impact persists for at least four days and displays a monotonically increasing pattern. Notably, this harmful effect is non-negligible even when pollution levels are below the official standards for air quality in China, suggesting that the current ambient air quality standards in China are not low enough to protect students.

Air Pollution, Student Health, and School Absences: Evidence from China

Little is known about the impact of air pollution on school children in developing countries. This paper aims to fill this gap by quantifying the causal effect of air pollution on the health status and the school attendance of the Chinese students. We relate the arguably exogenous daily variation in air pollution-instrumented by the occurrence of temperature inversion-with student illnesses and absences from more than 3,000 schools in Guangzhou City. We find a sizable deleterious effect of air pollution on school attendance through the health channel. The impact persists for at least four days and displays a monotonically increasing pattern. Notably, this harmful effect is non-negligible even when pollution levels are below the official standard for air quality in China, suggesting that the current ambient air quality standards in China are not low enough to protect students.

Optimal design and impact analysis of urban traffic regulations under ambient uncertainty

Decision-making in traffic regulations is challenging with uncertainty in the environment. In this research we extend probabilistic engineering design concepts to policy decision-making for urban traffic with variability from field data. City traffic is simulated using user equilibrium and cellular automata. A cellular automata (CA) model is developed by combing existing CA models with tailored rules for local traffic behaviors in Tainan, Taiwan. Both passenger sedans and motorcycles are considered with the possibility of passing between different types of vehicles. The tailpipe emissions from all mobile sources are modeled as Gaussian dispersion with finite line sources. Speed limits of all roads are selected as independent policy design variables, resulting in a problem with 50 dimensions. We first study the impacts of a particular policy-setting on traffic behaviors and on the environment under various sources of uncertainties. The genetic algorithm, combined with probabilistic analysis, is then used to obtain the optimal regulations with the minimal cost to the environment in compliance to the current ambient air quality standards.

Modality in ambient particle size distributions and its potential as a basis for developing air quality regulation

Current ambient air quality standards are mass-based and restricted to PM 2.5 and PM 10 fractions. The major contribution to both PM 2.5 and PM 10 fractions is from particles belonging to the coarse mode and generated by mechanical processes. These standards are thus unable to effectively control particle concentrations from combustion sources, such as motor vehicles and power plants, which tend to emit very small particles that are almost entirely respirable and in the submicron range, and dominate the nucleation and accumulation modes, which contribute much less to particle mass concentration. The aim of this work was to examine whether PM 1 and PM 10 would be a more effective combination of mass standards than PM 2.5 (dominant in the nucleation and accumulation modes) and PM 10 (dominant in the coarse mode) in controlling combustion-related ambient particles, as well as those originating from mechanical processes. First, a large body of data on particle size distributions in a range of environments in South East Queensland, Australia, was analysed, with an aim of identifying the relation between modality in the distributions and sources of particles belonging to different modes. The analyses included a matrix of the following elements: particle volume and number distributions, type of environment and locations of the modes in the range of PM 1, PM 2.5 and PM 10 fractions. Second, with the same aim, 600 published modal location values relating to number, surface area, volume and mass size distributions for a range of environments worldwide were analysed. The analysis identified a clear and distinct separation between the location of the modes for a substantial number of environments worldwide and particle metrics, which suggests that modality in particle size distributions may be a parameter that has potential to be used in the development of PM 1 air quality guidelines and standards. Based on these analyses, implications for choosing different mass standards for airborne particulate matter are discussed in the paper.

Interaction Between Ambient Air Pollution and Typical Asthma Medication Regimens on Exhaled Nitric Oxide

P-111 Abstract: Airway inflammation is considered one of the major mechanisms by which air pollution affects respiratory health. Exhaled nitric oxide (NO), a non-invasive measure of airway inflammation, has only been used as an outcome variable in limited air pollution epidemiological studies. This study is designed to examine the association between ambient air pollution and exhaled NO in patients with moderate asthma, and to examine the modifications of asthma medications on the associations. We compared airway inflammation response to ambient air pollution in 119 asthmatics who were enrolled in a controlled clinical trial of three therapies from the Salmeterol Off Corticosteroids Study (SOCS) within the Asthma Clinical Research Network (ACRN). The three therapies were an inhaled corticosteroid alone, an inhaled long-acting beta-agonist alone, and placebo. The participants were non-smokers aged 12 through 63 years recruited from six university-based ambulatory care centers from February 1997 to January 1999. The ambient pollutant data was derived from the U.S. Environmental Protection Agency (EPA) Aerometric Information Retrieval System (AIRS) which provides average daily measured concentrations of NO2, PM10, O3, and SO2. An increase of 10 ppb of ambient NO2 daily concentrations was associated with an increase in exhaled NO of 0.13 ppb (95% confidence interval (CI) 0.06 to 0.19) in models adjusted for age, sex, race/ethnicity, asthma clinical center, season, week, daily average temperature, and daily average relative humidity. Similarly, an increase in the daily average PM10 concentration of 10 μg/m3 was associated with an increase in exhaled NO of 0.07 ppb (95% CI 0.02 to 0.12). A negative association was observed for a maximum 8- hour average O3 concentration of 10 ppb with exhaled NO (-0.09 ppb, 95% CI −0.13 to −0.05). In general, there was a trend of a more pronounced association between exhaled NO with NO2, PM10 and O3, respectively in the group of asthmatics on the beta-agonist. Ambient air pollution at levels below the current ambient air quality standards may still enhance airway inflammation on patients with moderate asthma even on typical asthma medication regimens. An inhaled long-acting beta-agonist may enhance the effects of air pollution on airway inflammation.

Effects of Ambient Ozone Exposure on Mail Carriers’ Peak Expiratory Flow Rates

The extent to which occupational exposure to ozone in ambient air can affect lung function remains unclear. We conducted a panel study in 43 mail carriers by measuring their peak expiratory flow rates (PEFRs) twice daily for 6 weeks in 2001. The daily exposure of each mail carrier to O3, particulate matter < 10 μm in aerodynamic diameter (PM10), and nitrogen dioxide was estimated by one air monitoring station in the center of the mail carrier’s delivery area. Hourly concentrations of air pollutants during their exposure periods were 6–96 ppb for O3, 11–249 μg/m3 for PM10, and 14–92 ppb for NO2. Linear mixed-effects models were used to estimate the association between air pollution exposures and PEFR after adjusting for subject’s sex, age, and disease status and for temperature and humidity. We found that night PEFR and the deviation in night PEFR were significantly decreased in association with 8-hr O3 exposures with a lag 0–2 days and by daily maximum O3 exposures with a lag of 0–1 day in our multipollutant models. By contrast, neither PM10 nor NO2 was associated with a PEFR reduction. Daily 8-hr mean concentrations of O3 had greater reduction effects on PEFR than did daily maximum concentrations. For a 10-ppb increase in the 8-hr average O3 concentration, the night PEFR was decreased by 0.54% for a 0-day lag, 0.69% for a 1-day lag, and 0.52% for a 2-day lag. We found that an acute lung function reduction occurs in mail carriers exposed to O3 concentrations below current ambient air quality standards and occupational exposure limits.

Air Pollution and Daily Mortality in Seven Major Cities of Korea, 1991–1997

The relationship between ambient air pollution and daily mortality in seven major cities of Korea for the period 1991–1997 was examined. These cities account for half of the Korean population (about 22 million). The observed concentrations of sulfur dioxide (SO2, mean=23.3 ppb), ozone (O3, mean=23.7 ppb), and total suspended particulates (TSP, mean=77.9 μg/m3) during the study period were at levels below Korea's current ambient air quality standards. Generalized additive models were applied to allow for the highly flexible fitting of seasonal and long-term time trends in air pollution as well as nonlinear associations with weather variables, such as air temperature and relative humidity. In city-specific analyses, an increase of 50 ppb of SO2 corresponded to 1–12% more deaths, given constant weather conditions. The risk of all-cause mortality was estimated to increase by 0.5–4%, with an increase in the 2-day moving average of TSP levels equal to 100 μg/m3. In multipollutant models with pooled data, we found that the estimated risk of death by SO2 was notably unaffected by adding the other two pollutants (TSP and O3) to the model and was statistically significant in various regression models. The rate ratio (RR) for SO2 remained elevated, indicating an excess mortality of 3% 50 ppb (RR=1.03; 95% CI, 1.01–1.05). TSP's effect on mortality maintained its significance with O3, but not with SO2. This implies that there may be collinearity problems where TSP and SO2 are included in the same model or that TSP may function less than SO2 as a surrogate for fine particles in the ambient air of Korea. In conclusion, increased mortality was associated with air pollution at SO2 levels below the current recommendation for air quality. Further research is needed to clarify the relationship between SO2 and fine particles in Korea.

Air Pollution and Daily Mortality in Seoul and Ulsan, Korea

The relationship between air pollution and daily mortality for the period 1991-1995 was examined in two Korean cities, Seoul and Ulsan. The observed concentrations of sulfur dioxide (SO2; mean = 28.7 ppb), ozone (O3; mean = 29.2 ppb), and total suspended particulates (TSP; mean = 82.3 microg/m3) during the study period were at levels below Korea's current ambient air quality standards. Daily death counts were regressed separately in the two cities, using Poisson regression on SO2, O3, and/or TSP controlling for variability in the weather and seasons. When considered singly in Poisson regression models controlling for seasonal variations and weather conditions, the nonaccidental mortality associated with a 50-ppb increment in a 3-day moving average of SO2 concentrations, including the concurrent day and the preceding 2 days, was 1.078 [95% confidence interval (CI), 1.057-1.099] for Seoul and 1.051 (CI, 0.991-1.115) for Ulsan. The rate ratio was 1.051 (CI, 1.031-1.072) in Seoul and 0.999 (CI, 0. 961-1.039) in Ulsan per 100 microg/m3 for TSP, and 1.015 (CI, 1. 005-1.025) in Seoul and 1.020 (0.889-1.170) in Ulsan per 50 ppb for 1-hr maximum O3. When TSP was considered simultaneously with other pollutants, the TSP association was no longer significant. We observed independent pollution effects on daily mortality even after using various approaches to control for either weather or seasonal variables in the regression model. This study demonstrated increased mortality associated with air pollution at both SO2 and O3 levels below the current World Health Organization recommendations.

Air pollution and daily mortality in Seoul and Ulsan, Korea.

The relationship between air pollution and daily mortality for the period 1991-1995 was examined in two Korean cities, Seoul and Ulsan. The observed concentrations of sulfur dioxide (SO2; mean = 28.7 ppb), ozone (O3; mean = 29.2 ppb), and total suspended particulates (TSP; mean = 82.3 microg/m3) during the study period were at levels below Korea's current ambient air quality standards. Daily death counts were regressed separately in the two cities, using Poisson regression on SO2, O3, and/or TSP controlling for variability in the weather and seasons. When considered singly in Poisson regression models controlling for seasonal variations and weather conditions, the nonaccidental mortality associated with a 50-ppb increment in a 3-day moving average of SO2 concentrations, including the concurrent day and the preceding 2 days, was 1.078 [95% confidence interval (CI), 1.057-1.099] for Seoul and 1.051 (CI, 0.991-1.115) for Ulsan. The rate ratio was 1.051 (CI, 1.031-1.072) in Seoul and 0.999 (CI, 0. 961-1.039) in Ulsan per 100 microg/m3 for TSP, and 1.015 (CI, 1. 005-1.025) in Seoul and 1.020 (0.889-1.170) in Ulsan per 50 ppb for 1-hr maximum O3. When TSP was considered simultaneously with other pollutants, the TSP association was no longer significant. We observed independent pollution effects on daily mortality even after using various approaches to control for either weather or seasonal variables in the regression model. This study demonstrated increased mortality associated with air pollution at both SO2 and O3 levels below the current World Health Organization recommendations.

Particulate Air Pollution and Hospital Emergency Room Visits for Asthma in Seattle

Recent studies have associated short-term exposure to respirable particulate matter (PM10) exposure with peak flow decrements, increased symptoms of respiratory irritation, increased use of asthma medications, and increased hospitalization for asthma. Increased mortality from chronic respiratory disease has also been reported. To help confirm whether PM10 exposure is a risk factor for the exacerbation of asthma, we compiled daily records of asthma emergency room visits from eight hospitals in the Seattle area. In Poisson regressions controlling for weather, season, time trends, age, hospital, and day of the week, the daily counts of emergency room visits for persons under age 65 were significantly associated with PM10 exposure on the previous day. The mean of the previous 4 days' PM10 was a better predictor (p < 0.005). The relative risk for a 30 micrograms/m3 increase in PM10 was 1.12 (95% confidence interval 1.20 to 1.04). Daily PM10 concentrations never exceeded 70% of the current ambient air quality standards during the period. The consistency of investigations of the health effects of PM10 suggest that increased attention should be given to the control of particulate matter air pollution.

Daily air pollution effects on children's respiratory symptoms and peak expiratory flow.

To identify acute respiratory health effects associated with air pollution due to coal combustion, a subgroup of elementary school-aged children was selected from a large cross-sectional study and followed daily for eight months. Children were selected to obtain three equal-sized groups: one without respiratory symptoms, one with symptoms of persistent wheeze, and one with cough or phlegm production but without persistent wheeze. Parents completed a daily diary of symptoms from which illness constellations of upper respiratory illness (URI) and lower respiratory illness (LRI) and the symptom of wheeze were derived. Peak expiratory flow rate (PEFR) was measured daily for nine consecutive weeks during the eight-month study period. Maximum hourly concentrations of sulfur dioxide, nitrogen dioxide, ozone, and coefficient of haze for each 24-hour period, as well as minimum hourly temperature, were correlated with daily URI, LRI, wheeze, and PEFR using multiple regression models adjusting for illness occurrence or level of PEFR on the immediately preceding day. Respiratory illness on the preceding day was the most important predictor of current illness. A drop in temperature was associated with increased URI and LRI but not with increased wheeze or with a decrease in level of PEFR. No air pollutant was strongly associated with respiratory illness or with level of PEFR, either in the group of children as a whole, or in either of the symptomatic subgroups; the pollutant concentrations observed, however, were uniformly lower than current ambient air quality standards. Moreover, since exposure estimation based on monitoring of ambient air likely results in misclassification of the true exposure, the negative findings of this study must be interpreted cautiously.