A novel method to construct an air quality index based on air pollution profiles

Background

Air quality indices based on the maximum of sub-indices of pollutants are easy to produce and help quantify the degree of air pollution. However, they discount the additive effects of multiple pollutants and are only sensitive to changes in highest sub-index.

Effects of coarse particulate matter on emergency hospital admissions for respiratory diseases: a time-series analysis in Hong Kong

Background: Many epidemiological studies have linked daily counts of hospital admissions to particulate matter (PM) with an aerodynamic diameter ≤ 10 μm (PM₁₀) and ≤ 2.5 μm (PM_2.5), but relatively few have investigated the relationship of hospital admissions with coarse PM (PM_c; 2.5–10 μm aerodynamic diameter).Objectives: We conducted this study to estimate the health effects of PM_c on emergency hospital admissions for respiratory diseases in Hong Kong after controlling for PM_2.5 and gaseous pollutants.Methods: We conducted a time-series analysis of associations between daily emergency hospital admissions for respiratory diseases in Hong Kong from January 2000 to December 2005 and daily PM_2.5 and PM_c concentrations. We estimated PM_c concentrations by subtracting PM_2.5 from PM₁₀ measurements. We used generalized additive models to examine the relationship between PM_c (single- and multiday lagged exposures) and hospital admissions adjusted for time trends, weather conditions, influenza outbreaks, PM_2.5, and gaseous pollutants (nitrogen dioxide, sulfur dioxide, and ozone).Results: A 10.9-μg/m³ (interquartile range) increase in the 4-day moving average concentration of PM_c was associated with a 1.94% (95% confidence interval: 1.24%, 2.64%) increase in emergency hospital admissions for respiratory diseases that was attenuated but still significant after controlling for PM_2.5. Adjusting for gaseous pollutants and altering models assumptions had little influence on PM_c effect estimates.Conclusion: PM_c was associated with emergency hospital admissions for respiratory diseases in Hong Kong independent of PM_2.5 and gaseous pollutants. Further research is needed to evaluate health effects of different components of PM_c.     

Air pollution and hospital admissions for respiratory and cardiovascular diseases in Hong Kong

OBJECTIVE: To investigate short term effects of concentrations of pollutants in ambient air on hospital admissions for cardiovascular and respiratory diseases in Hong Kong. METHODS: Retrospective ecological study. A Poisson regression was performed of concentrations of daily air pollutant on daily counts of emergency hospital admissions in 12 major hospitals. The effects of time trend, season, and other cyclical factors, temperature, and humidity were accounted for. Autocorrelation and overdispersion were corrected. Daily concentrations of nitrogen dioxide (NO2), sulphur dioxide (SO2), ozone (O3), and particulate matter < 10 microns in aerodynamic diameter (PM10) were obtained from seven air monitoring stations in Hong Kong in 1994 and 1995. Relative risks (RR) of respiratory and cardiovascular disease admissions (for an increase of 10 micrograms/m3 in concentration of air pollutant) were calculated. RESULTS: Significant associations were found between hospital admissions for all respiratory diseases, all cardiovascular diseases, chronic obstructive pulmonary diseases, and heart failure and the concentrations of all four pollutants. Admissions for asthma, pneumonia, and influenza were significantly associated with NO2, O3, and PM10. Relative risk (RR) for admissions for respiratory disease for the four pollutants ranged from 1.013 (for SO2) to 1.022 (for O3), and for admissions for cardiovascular disease, from 1.006 (for PM10) to 1.016 (for SO2). Those aged > or = 65 years were at higher risk. Significant positive interactions were detected between NO2, O3, and PM10, and between O3 and winter months. CONCLUSIONS: Adverse health effects are evident at current ambient concentrations of air pollutants. Further reduction in air pollution is necessary to protect the health of the community, especially that of the high risk group.

 

     

Spatial and temporal variations in criteria air pollutants in three typical terrain regions in Shaanxi,China, during 2015

Numerous studies have investigated air pollution in severely polluted plains, but the characteristics of pollutants are not well understood in other terrain regions. In this study, air pollution characteristics were analyzed in three typical terrain regions (plateau, plain, and mountain regions) in Shaanxi, based on hourly ambient monitoring of particulate matter with diameter less than 2.5 μm (PM_2.5) and less than 10 μm (PM₁₀), CO, SO₂, NO₂, and O₃ in 2015. PM_2.5 and PM₁₀ were the dominant pollutants in three regions, and their annual concentrations exceeded the Grade II standards by 9.4–68.6 and 6.0–73.9%, respectively. PM_2.5, PM₁₀, CO, SO₂, and NO₂ concentrations had similar seasonal trends with highest values in winter and lowest values in summer, whereas O₃ concentrations exhibited the opposite trend. Guanzhong Plain had higher PM_2.5, PM₁₀, NO₂, and SO₂ concentrations but lower CO, 1-h peak O₃, and 8-h peak O₃ (8 h-O₃) compared to other regions. PM_2.5, PM₁₀, and 8 h-O₃ were the three main dominant pollutants. The nonattainment rate was highest in winter and lowest in summer or autumn. Pollution also exhibited synergy, especially in the plateau region and Guanzhong Plain. PM_2.5 was significantly correlated with PM₁₀. NO₂ and SO₂ were positively correlated with PM_2.5 and PM₁₀, while 8 h-O₃ generally had significant negative correlations with other pollutants, especially in the winter. These results provide a comprehensive understanding of pollution status in the three typical terrain regions in Shaanxi and are helpful for improving air quality.     

Spatial and seasonal variations of gaseous and particulate matter pollutants in 31 provincial capital cities,China

In order to know air pollution situation and their health, environmental, and climate effects, the air quality data with high temporal and spatial resolutions are essential. The spatial and seasonal variations of six criteria pollutants were investigated in 31 provincial capital cities between April 2014 and March 2015 using hourly mean air quality monitoring data, and the cities were classified by cluster analysis based on annual variations of air pollutants. The annual mean concentrations of PM_2.5 (particulate matter with aerodynamic diameter less than 2.5 μm) and PM₁₀ (particulate matter with aerodynamic diameter less than 10 μm) were high for all cities, which exceeded Chinese Ambient Air Quality Standards (CAAQS) Grade I standards. Only Fuzhou, Haikou, Kunming, and Lasa met Grade II standards for PM_2.5 and PM₁₀. Additionally, elevated SO₂ concentration was observed in northern cities, especially in winter. However, the seasonal variation of O₃ was opposite to other pollutants with the lowest concentrations in the winter and the highest in the summer. Winter domestic heating has significant impact on urban air quality, especially SO₂ and PM₁₀.     

Association between daily mortality from respiratory and cardiovascular diseases and air pollution in Taiwan

Background

Many studies have investigated the effects of air pollutants on disease and mortality. However, the results remain inconsistent and inconclusive. We thought that the impact of different seasons or ages of people may explain these differences.

Methods

Measurement of the five pollutants (particulate matter <10 μm in aerodynamic diameter (PM₁₀), SO₂, NO₂, O₃, and CO) was monitored by automated measuring units at five different stations. Monitoring stations were provided by the Taiwan Environmental Protection Agency (EPA) from 1997 to 1999. The subjects in the study were classified in two groups: those 65 years of age and older, and those of all ages (including the subjects in the ?65 group). Data on daily mortality caused by respiratory disease, cardiovascular disease, and all other causes including the two aforementioned was collected by the Taiwan Department of Health (DOH). A time-series regression model was used to analyze the relative risk of respiratory and cardiovascular diseases due to air pollution in the summer and winter seasons.

Results

Risk of death from all causes and mortality from cardiovascular diseases during winter was significantly positively correlated with levels of SO₂, CO, and NO₂ for both groups of subjects and additionally with PM₁₀ for the elderly (?65 years old) group. There were significant positive correlations with respiratory diseases and levels of O₃ for both groups. However, the only significant positive correlation was with O₃ (RR=1.283) for the elderly group during summer. No other parameters showed significance for either group.

Conclusion

Our findings contribute to the evidence of an association between SO₂, CO, NO₂, and PM₁₀ and mortality from respiratory and cardiovascular diseases, especially among elderly people during the winter season.     

Spatio-seasonal variation in ambient air pollutants and influence of meteorological factors in Coimbatore,Southern India

Air quality is used worldwide to confirm the current status of air pollution level and associated health risks to the public. Several air pollutants reach very high concentrations in many regions across India. In this study, air pollutants were measured in an urban city of Coimbatore, Tamil Nadu, Southern India, during 2013 to 2014 based on season and location, and the influence of meteorological factors. Air pollutants (PM₁₀, PM_2.5, SO₂, NO₂, CO, and O₃) across eight locations including industrial, residential, traffic, and commercial areas were assessed. The results showed that PM₁₀, PM_2.5, and CO were the most serious pollutants and their average concentrations ranged from 65.5 to 98.6 μg/m³, 27.6 to 56.9 μg/m³, and 1.58 to 8.21 mg/m³, respectively, among various locations. Significantly higher concentration of air pollutants was recorded in industrial areas followed by traffic and commercial areas. Comparatively higher mean concentration of O₃ (2.22?±?0.75 μg/m³) and CO (7.73?±?1.86 mg/m³) was recorded during the summer season, whereas the concentration of PM₁₀ (80.3?±?24.4 μg/m³), PM_2.5 (45.1?±?17.7 μg/m³), SO₂ (7.86?±?1.55 μg/m³), and NO₂ (13?±?1.81 μg/m³) was higher in southwest monsoon. Ozone (O₃) and CO positively correlated with temperature and negatively correlated with relative humidity. The level of PM₁₀, PM_2.5, and CO concentrations exceeded the National Ambient Air Quality Standards (NAAQS) guidelines. The present study’s results emphasize the need of effective air pollution control in Coimbatore. Precautionary measures to be taken to avoid exposure of air pollutants to the public and minimize pollutants. This study further suggests an investigation on the adverse impact on human health and environment using appropriate risk analysis techniques.     

Short-term association between sulfur dioxide and daily mortality: The Public Health and Air Pollution in Asia (PAPA) study

Sulfur dioxide (SO₂) has been associated with increased mortality and morbidity, but only few studies were conducted in Asian countries. Previous studies suggest that SO₂ may have adverse health effects independent of other pollutants. In the Public Health and Air Pollution in Asia (PAPA) project, the short-term associations between ambient sulfur dioxide (SO₂) and daily mortality were examined in Bangkok, Thailand, and three Chinese cities: Hong Kong, Shanghai, and Wuhan. Poisson regression models incorporating natural spline smoothing functions were used to adjust for seasonality and other time-varying covariates. Effect estimates were obtained for each city and then for the cities combined. The impact of alternative model specifications, such as lag structure of pollutants and degree of freedom (df) for time trend, on the estimated effects of SO₂ were also examined. In both individual-city and combined analysis, significant effects of SO₂ on total non-accidental and cardiopulmonary mortality were observed. An increase of 10 μg/m³ of 2-day moving average concentrations of SO₂ corresponded to 1.00% [95% confidence interval (CI), 0.75-1.24], 1.09% (95% CI, 0.71-1.47), and 1.47% (95% CI, 0.85-2.08) increase of total, cardiovascular and respiratory mortality, respectively, in the combined analysis. Sensitivity analyzes suggested that these findings were generally insensitive to alternative model specifications. After adjustment for PM₁₀ or O₃, the effect of SO₂ remained significant in three Chinese cities. However, adjustment for NO₂ diminished the associations and rendered them statistically insignificant in all four cities. In conclusion, ambient SO₂ concentration was associated with daily mortality in these four Asian cities. These associations may be attributable to SO₂ serving as a surrogate of other substances. Our findings suggest that the role of outdoor exposure to SO₂ should be investigated further in this region.     

Respiratory health effects among schoolchildren and their relationship to air pollutants in Korea

The objective of this study is to investigate the relationship between five air pollutants (PM₁₀, SO₂, NO₂, O₃, CO) measured on the daily basis, and adverse health symptoms using epidemiological surveillance data. The generalized estimated equation (GEE) model, a logistic regression analysis model, was used to estimate the effects of air pollution on children's daily health symptoms, focusing on the morbidity including both respiratory and allergic symptoms in four different cities. Analysis of the effects of each pollutant on children's respiratory and allergic symptoms demonstrated that CO affected all symptoms in all the study areas. When the concentration of SO₂ and NO₂ was elevated, upper respiratory symptoms increased significantly. In contrast, when the concentration of O₃ rose, the symptoms decreased significantly. The relationship between measured concentrations and health symptoms was site-dependent for each pollutant.     

Respiratory Effects of Air Pollutants among Asthmatics in Central Taiwan

The authors investigated the relationship between respiratory effects and air pollutants among asthmatics in central Taiwan. A total of 12,926 subjects were selected from 8 junior high schools. Data about monthly hospital admissions for respiratory illnesses were collected over a period of 1 yr from the National Insurance Bureau. Data included how frequently subjects purchased medication and the respiratory symptoms recorded by clinic and hospital personnel. Pulmonary function tests were administered to 20% of the total study population, which was selected randomly. Data about monthly levels of air pollutants (i.e., particulate matter 10 μm and less [PM₁₀], ozone [O₃], sulfur dioxide [SO₂], and nitrogen dioxide [NO₂]) were provided by Taiwan's Environmental Protection Agency. The prevalence rates of asthma were correlated significantly with NO₂ (r = .63) and O₃ (r= .51) concentrations. Levels of NO₂ and PM₁₀ were correlated significantly with monthly hospital admissions. Forced vital capacity, forced expiratory volume in 1 sec, and peak expiratory flow for asthmatics in central Taiwan were 6–11 % lower than normal predicted values for the general Taiwanese student population, adjusted for age, height, and weight. In conclusion, the increased risk of asthma and the frequency of monthly hospital admissions among asthmatics may be correlated positively with pollution levels—especially NO₂ and PM₁₀.     

Ambient air pollution and emergency department visits among children and adults in Casablanca,Morocco

This study presents the relationships between ambient air pollutants and morbidity and emergency department visits among children and adults performed in Great Casablanca, the most populated and economic region in Morocco. This research was analyzed using conditional Poisson model for the period 2011–2013. In the period of study, the daily average concentrations of SO₂, NO₂, O₃ and PM₁₀ in Casablanca were 209.4 µg/m³, 61 µg/m³, 113.2 µg/m³ and 75.1 µg/m³, respectively. In children less than 5 years old, risk of asthma could be increased until 12% per 10 µg/m³ increase in NO₂, PM10, SO₂ and O₃. In children over 5 years and adults, an increase of 10 µg/m³ air pollutant can cause an increase until 3% and 4% in respiratory consultations and acute respiratory infection, respectively. Similarly, impact on emergency department visits due to respiratory and cardiac illness was established. Our results suggest a not negligible impact on morbidity of outdoor air pollution by NO₂, SO₂, O₃, and PM₁₀.     

Trend and status of air quality at three different monitoring stations in the Klang Valley,Malaysia

Over the last decades, the development of the Klang Valley (Malaysia), as an urban commercial and industrial area, has elevated the risk of atmospheric pollutions. There are several significant sources of air pollutants which vary depending on the background of the location they originate from. The aim of this study is to determine the trend and status of air quality and their correlation with the meteorological factors at different air quality monitoring stations in the Klang Valley. The data of five major air pollutants (PM₁₀, CO, SO₂, O₃, NO₂) were recorded at the Alam Sekitar Sdn Bhd (ASMA) monitoring stations in the Klang Valley, namely Petaling Jaya (S1), Shah Alam (S2) and Gombak (S3). The data from these three stations were compared with the data recorded at Jerantut, Pahang (B), a background station established by the Malaysian Department of Environment. Results show that the concentrations of CO, NO₂ and SO₂ are higher at Petaling Jaya (S1) which is due to influence of heavy traffic. The concentrations of PM₁₀ and O_3, however, are predominantly related to regional tropical factors, such as the influence of biomass burning and of ultra violet radiation from sunlight. They can, though, also be influenced by local sources. There are relatively stronger inter-pollutant correlations at the stations of Gombak and Shah Alam, and the results also suggest that heavy traffic flow induces high concentrations of PM₁₀, CO, NO₂ and SO₂ at the three sampling stations. Additionally, meteorological factors, particularly the ambient temperature and wind speed, may influence the concentration of PM₁₀ in the atmosphere.     

Socioeconomic disparities in air pollution-associated mortality

This study aimed to determine whether individuals with lower socioeconomic status (SES) were more susceptible to the acute effects of ambient air pollution than those with higher SES. We included 24,357 Hong Kong Chinese aged 30 or above who died of natural causes in 1998. Information on individual socioeconomic characteristics was obtained by interviewing proxy informants with a standardized questionnaire in all four death registries. Individual SES was indicated by three measures: type of housing, occupational group and education attainment. Poisson regression was performed to assess the short-term effects of ambient air pollution measured by PM₁₀, NO₂, SO₂ and O₃ on mortality for each SES group. The differences in the effects between SES groups were estimated by the interaction between air pollution and SES. We found that PM₁₀ and NO₂ were associated with greater risk of mortality on people living in public rental housing than in private housing. The effects of all four pollutants were significantly greater in blue-collar workers than the never-employed and white-collar groups (p<0.05). However, we found no compelling evidence of effect modification by education attainment. Our results provide new evidence on the role of individual's SES as effect modifiers of the short-term effects of air pollution on mortality. The reduction of risks associated with air pollution for socially disadvantaged populations should be a high priority in public health and environmental policies.     

Indoor air pollutant exposure and determinant factors controlling household air quality for elderly people in Hong Kong

This study investigated the levels and determinant factors of indoor air pollutants including fine particles (PM_2.5), nitrogen dioxide (NO₂), and formaldehyde (HCHO) in 55 households exclusively for the elderly in Hong Kong during summer and winter (Jul.–Sep. 2016 and Nov. 2016–Mar. 2017). The average concentrations of PM_2.5, NO₂, and formaldehyde were 25.3?±?15.0, 40.5?±?16.0, and 26.1?±?22.8 μg/m³ in summer and 34.2?±?19.0, 43.5?±?17.0, and 15.4?±?4.5 μg/m³ in winter, respectively. There were ~?50.3% of households exceeding the World Health Organization indoor air quality standard for PM_2.5 throughout the study, with ~?40.6 and ~61.0% of the households in summer and winter, respectively. The determinant factors for indoor PM_2.5 and NO₂ concentrations were identified as from incense burning and cooking. Cooking with suitable ventilation is an important factor to ease indoor pollutant concentrations. Both of PM_2.5 and NO₂ indoor concentrations showed good correlations with outdoor concentrations. Winter was observed with higher pollutant concentrations than summer except for formaldehyde concentrations. Major factors controlling indoor formaldehyde concentrations are temperature and humidity. The outcome will be useful for the development of future indoor air quality guidelines for Hong Kong.     

Study on ambient air quality in Beijing for the summer 2008 Olympic Games

With the coming/approaching of the Olympic Games in 2008, air pollution in Beijing attracts the attention of government and people. The objective of this study is to define the air quality during the Olympic Games; we conducted the observation of SO₂, NO, CO, NO₂, O₃, and PM₁₀ from August 7 to September 30 in 2007 in Beijing. The results showed that the average daily concentrations of SO₂, NO₂, CO, and PM₁₀ during observation were 0.024, 0.072, 2.25, and 0.19 mg m⁻³, respectively. Compared with the National Ambient Air Quality Standard II, the concentrations of SO₂ and CO in the observation were low, the concentration of NO₂ basically satisfied the National Ambient Air Quality Standard II, and the concentrations of O₃ and PM₁₀ were much higher than the values of the standard. The characteristics of diurnal variation of NO, NO₂, CO, and PM₁₀ were similar, and the lower concentrations of these pollutants were observed by day and the higher concentrations at night. The concentration of SO₂ in the daytime was a little higher than that at night. The highest 1-h concentration of O₃ occurred at 14:00 local time.     

Air pollution and admissions for acute lower respiratory infections in young children of Ho Chi Minh City

This study assessed the effects of exposure to air pollution on hospitalization for acute lower respiratory infection (ALRI) among children under 5 years of age in Ho Chi Minh City (HCMC) from 2003 to 2005. Case-crossover analyses with time-stratified selection of control periods were conducted using daily admissions for pneumonia and bronchiolitis and daily, citywide averages of PM₁₀, NO₂, SO₂, and O₃ (8-h maximum average) estimated from the local air quality monitoring network. Increased concentrations of NO₂ and SO₂ were associated with increased admissions in the dry season (November to April), with excess risks of 8.50% (95%CI 0.80–16.79) and 5.85% (95%CI 0.44–11.55), respectively. PM₁₀ could also be associated with increased admissions in the dry season, but high correlation between PM₁₀ and NO₂ (0.78) limits our ability to distinguish between PM₁₀ and NO₂ effects. In the rainy season (May–October), negative associations between pollutants and admissions were observed. Results of this first study of the health effects of air pollution in HCMC support the presence of an association between combustion-source pollution and increased ALRI admissions. ALRI admissions were generally positively associated with ambient levels of PM₁₀, NO₂, and SO₂ during the dry season, but not the rainy season. Negative results in the rainy season could be driven by residual confounding present from May to October. Preliminary exploratory analyses suggested that seasonal differences in the prevalence of viral causes of ALRI could be driving the observed differences in effects by season.     

Traffic related air pollution and acute hospital admission for respiratory diseases in Drammen, Norway 1995–2000

The aim of this study was to estimate the associations between seven ambient air pollutants [particulate matter (PM₁₀), nitrous dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), benzene, formaldehyde and toluene] and acute hospital admissions for respiratory diseases in Drammen, Norway 1995–2000. Time-series analysis of counts was performed by means of generalized additive models with log link and Poisson distribution. The results showed that benzene was the pollutant having the strongest association with respiratory diseases for the total study period, the relative risk of an interquartile increase of benzene was 1.095 with 95% confidence interval: 1.031–1.163. The corresponding results were 1.049 (0.990–1.112) for formaldehyde, 1.044 (1.000–1.090) for toluene, 1.064 (1.019–1.111) for NO₂, 1.043 (1.011–1.075) for SO₂, 0.990 (0.936–1.049) for O₃ and 1.022 (0.990–1.055) for PM₁₀. Dividing the total study period into two 3-year periods, there was a substantial reduction in the exposure levels of the volatile organic compounds (benzene, formaldehyde and toluene) from the first to the second period. Separate analyses for the second time period showed weaker association between these pollutants and the health outcome. This study provides further evidence for short-term respiratory health effects of traffic related air pollution.     

Seasonal effects of PM10 concentrations on mortality in Tianjin, China: a time-series analysis

Aim

There are uncertainties regarding the modification effects of season and temperature on the relationship between air pollution and mortality. This study aims to examine the effects of season and temperature on mortality associated with particulate matter less than 10 μm in diameter (PM₁₀) in Tianjin, China.

Methods

Time-series analysis was used to explore the modification effects of season and temperature on the association between PM₁₀ and cause-specific mortality in Tianjin between 2006 and 2009. The causes studied were overall non-accidental mortality and subcategories of cardiovascular, respiratory, cardiopulmonary, stroke, and ischemic heart diseases (IHD).

Results

The association between PM₁₀ and mortality showed a strong seasonal pattern and the effects of PM₁₀ on cause-specific mortalities were strongest for high temperature days. Generally, the adverse effects were stronger in summer than for other seasons, except for respiratory mortality. In the summer period, a 10 μg/m³ increase in PM₁₀ at 0–1 days was associated with an increase in mortality for non-accidental (0.95 %, 95 % confidence interval [CI]: 0.45, 1.45), cardiovascular (1.40 %, 95 %CI: 0.77, 2.03), cardiopulmonary (1.37 %, 95 %CI: 0.77, 1.98), IHD (1.55 %, 95 %CI: 0.73, 2.37), and stroke (1.27 %, 95 % CI: 0.37, 2.12) causes. The overall increase in mortality per 10 μg/m³ increase in PM₁₀ was 0.42 % (95 %CI: 0.26, 0.58) for non-accidental, 0.41 % (95 %CI: 0.21, 0.62) for cardiovascular, 0.46 % (95 %CI: 0.26,0.65) for cardiopulmonary, 0.57 % (95 %CI: 0.30, 0.84) for IHD, and 0.32 % (95 %CI: 0.03,0.61) for stroke. At high temperatures (≥23.8 °C), a 10 μg/m³ increase in PM₁₀ at 0–1 days was associated with an increase in mortality of 0.90 % (95 %CI: 0.61,1.19) for non-accidental, 1.01 % for cardiovascular, 1.40 % (95 %CI: 0.55, 2.27) for respiratory, 1.06 % (95 %CI: 0.71, 1.41) for cardiopulmonary, 1.47 % (95 %CI: 1.00, 1.94) for IHD, and 0.75 % (95 %CI: 0.24, 1.28) for stroke. In addition, the PM₁₀ effects of high temperature days were stronger for those aged 65 years and over.

Conclusion

Season and temperature could modify the adverse effects of PM₁₀. An increase in hot summer days caused by climate change may enhance the risks of air pollution on human health. More attention should be paid to older populations, especially in summer and days with high temperatures.     

The public health context for PM2.5 and ozone air quality trends

Tropospheric ozone (O₃) and particulate matter (PM_2.5) are associated with adverse health effects, including premature mortality. Regulation of these pollutants by the US Environmental Protection Agency has resulted in significant improvements in air quality over the last decade, as demonstrated by a national network of air quality monitors. However, ambient trends provide limited information regarding either the change in population exposure to these pollutants or how fluctuations in the levels of these pollutants might affect public health. We leverage the spatially and temporally extensive monitoring network in the US to estimate the improvements to public health associated with monitored air quality changes over a 7-year period. We estimate the impacts of monitored changes in ozone and PM_2.5 on premature mortality using health impact functions based on short-term relative risk estimates for O₃ and long-term relative risk estimates for PM_2.5. We spatially interpolate the O₃ and PM_2.5 data and utilize ozone air quality data that are adjusted for meteorological variability. We estimate that reductions in monitored PM_2.5 and ozone from 2000 to 2007 are associated with 22,000–60,000 PM_2.5 and 880–4,100 ozone net avoided premature mortalities. The change in estimated premature mortality can be highly variable from 1 year to the next, sometimes by thousands of deaths. The estimate of avoided ozone-related mortalities is sensitive to the use of meteorologically-adjusted air quality inputs. Certain locations, including Los Angeles and Houston see an opposing trend between mortality impacts attributable to ozone and PM_2.5.We find that improving air quality over the past 7 years has reduced premature mortality significantly.     

An Estimate of the Global Burden of Anthropogenic Ozone and Fine Particulate Matter on Premature Human Mortality Using Atmospheric Modeling

Background

Ground-level concentrations of ozone (O₃) and fine particulate matter [≤ 2.5 μm in aerodynamic diameter (PM_2.5)] have increased since preindustrial times in urban and rural regions and are associated with cardiovascular and respiratory mortality.

Objectives

We estimated the global burden of mortality due to O₃ and PM_2.5 from anthropogenic emissions using global atmospheric chemical transport model simulations of preindustrial and present-day (2000) concentrations to derive exposure estimates.

Methods

Attributable mortalities were estimated using health impact functions based on long-term relative risk estimates for O₃ and PM_2.5 from the epidemiology literature. Using simulated concentrations rather than previous methods based on measurements allows the inclusion of rural areas where measurements are often unavailable and avoids making assumptions for background air pollution.

Results

Anthropogenic O₃ was associated with an estimated 0.7 ± 0.3 million respiratory mortalities (6.3 ± 3.0 million years of life lost) annually. Anthropogenic PM_2.5 was associated with 3.5 ± 0.9 million cardiopulmonary and 220,000 ± 80,000 lung cancer mortalities (30 ± 7.6 million years of life lost) annually. Mortality estimates were reduced approximately 30% when we assumed low-concentration thresholds of 33.3 ppb for O₃ and 5.8 μg/m³ for PM_2.5. These estimates were sensitive to concentration thresholds and concentration–mortality relationships, often by > 50%.

Conclusions

Anthropogenic O₃ and PM_2.5 contribute substantially to global premature mortality. PM_2.5 mortality estimates are about 50% higher than previous measurement-based estimates based on common assumptions, mainly because of methodologic differences. Specifically, we included rural populations, suggesting higher estimates; however, the coarse resolution of the global atmospheric model may underestimate urban PM_2.5 exposures.