The spatial variation in the effects of air pollution on cardiovascular mortality in Beijing, China

Geospatial analysis of short-term exposure to air pollution and risk of cardiovascular diseases and mortality-A systematic review

The cardiovascular risk associated with short-term ambient air pollution exposure is well-documented. However, recent advancements in geospatial techniques have provided new insights into this risk. This systematic review focuses on short-term exposure studies that applied advanced geospatial pollution modelling to estimate cardiovascular disease (CVD) risk and accounted for additional unconventional neighbourhood-level confounders to analyse their modifier effect on the risk. Four databases were investigated to select publications between 2018 and 2023 that met the inclusion criteria of studying the effect of particulate matter (PM2.5 and PM10), SO2, NOx, CO, and O3 on CVD mortality or morbidity, utilizing pollution modelling techniques, and considering spatial and temporal confounders. Out of 3277 publications, 285 were identified for full-text review, of which 34 satisfied the inclusion criteria for qualitative analysis, and 12 of them were chosen for additional quantitative analysis. Quality assessment revealed that 28 out of 34 included articles scored 4 or above, indicating high quality. In 30 studies, advanced pollution modelling techniques were used, while in 4 only simpler methods were applied. The most pertinent confounders identified were socio-demographic variables (e.g., socio-economic status, population percentage by race or ethnicity) and neighbourhood-level built environment variables (e.g., urban/rural area, percentage of green space, proximity to healthcare), which exhibited varying modifier effects depending on the context. In the quantitative analysis, only PM 2.5 showed a significant positive association to all-cause CVD-related hospitalisation. Other pollutants did not show any significant effect, likely due to the high inter-study heterogeneity and a limited number of cases. The application of advanced geospatial measurement and modelling of air pollution exposure, as well as its risk, is increasing. This review underscores the importance of accounting for unconventional neighbourhood-level confounders to enhance the understanding of the CVD risk associated with short-term pollution exposure.

Short-term association of CO and NO2 with hospital visits for glomerulonephritis in Hefei, China: a time series study

Objective

Recent studies suggest air pollution as an underlying factor to kidney disease. However, there is still limited knowledge about the short-term correlation between glomerulonephritis (GN) and air pollution. Thus, we aim to fill this research gap by investigating the short-term correlation between GN clinical visits and air pollution exposure.

Methods

Between 2015 and 2019, daily GN visit data from two grade A tertiary hospitals in Hefei City were collected, along with corresponding air pollution and meteorological data. A generalized linear model integrated with a distributed lag nonlinear model was employed to analyze the relationship between GN visits and air pollutants. Moreover, we incorporated a dual pollutant model to account for the combined effects of multiple pollutants. Furthermore, subgroup analyses were performed to identify vulnerable populations based on gender, age, and season.

Results

The association between 23,475 GN visits and air pollutants was assessed, and significant positive associations were found between CO and NO2 exposure and GN visit risk. The single-day lagged effect model for CO showed increased risks for GN visits from lag0 (RR: 1.129, 95% CI: 1.031-1.236) to lag2 (RR: 1.034, 95% CI: 1.011-1.022), with the highest risk at lag0. In contrast, NO2 displayed a more persistent impact (lag1-lag4) on GN visit risk, peaking at lag2 (RR: 1.017, 95% CI: 1.011-1.022). Within the dual-pollutant model, the significance persisted for both CO and NO2 after adjusting for each other. Subgroup analyses showed that the cumulative harm of CO was greater in the cold-season and older adult groups. Meanwhile, the female group was more vulnerable to the harmful effects of cumulative exposure to NO2.

Conclusion

Our study indicated that CO and NO2 exposure can raise the risk of GN visits, and female and older adult populations exhibited greater susceptibility.

Climatology and landscape determinants of AOD, SO2 and NO2 over Indo-Gangetic Plain

Indo-Gangetic Plains (IGP) experiences high loading of particulate and gaseous pollutants all year around and is considered to be the most polluted regions of India. Understanding the effect of landscape determinants on air pollution in IGP regions is crucial to make its environment sustainable. We examined satellite retrievals of OMI NO₂ and SO₂, and MODIS AOD to analyse the long-term trend, spatio-seasonal pattern and dynamics of aerosols, NO₂ and SO₂ over three IGP regions, namely Upper Indo-Gangetic plain (UIGP), Middle Indo-Gangetic plain (MIGP) and Lower Indo-Gangetic plain (LIGP) over the period 2005-2019. IGP experienced an overall increment in AOD (R² = 0.63) and SO₂ (R² = 0.67) values, with LIGP (AOD, R² = 0.8 & SO₂, R² = 0.8) experiencing the largest rate of enhancement. The levels of NO₂ (R² = 0.2) experienced a decrement after 2012 (owing to implementation of vehicle emission policy) except in MIGP, with UIGP (R² = 0.23) exhibiting the largest rate of decrement. Seasonal heterogeneity in the nature of sources was observed over IGP regions. AOD (0.61 ± 0.1) and NO₂ value (3.82 ± 0.98 × 10¹⁵ molecules/cm²) were found highest during post-monsoon in UIGP owing to crop residue burning activity. The value of NO₂ (3.8 ± 1.4 × 10¹⁵ molecules/cm²) in MIGP was found highest during pre-monsoon due to high consumption of coal in power plants for summer cooling demand. The highest SO₂ level (0.09 ± 0.06 DU) was observed during post-monsoon in UIGP, as a large number of brick kilns are fired during this period. Correlations among landscape determinants and pollutants revealed that topography is the dominant variable that affect the spatial pattern of AOD compared to vegetation and land use. Lower elevation tends to have high AOD values compared to higher elevation. Vegetation-AOD relationship showed an inverse association in IGP regions and is influenced by factors such as seasonal meteorology and size of the airborne particles. Vegetation possesses positive relationship with SO₂ and NO₂, implying no pollution abatement effect on SO₂ and NO₂ pollutants. Built-up change has deteriorating effect as well as quenching effect on pollutants. Increase in built terrain have deteriorated the air quality in UIGP whereas it favored in suppressing the aerosol level in LIGP.

Research on Mobile Machinery NOx Emission Control Based on a Physical Model and Closed-Loop Control

Mobile machinery means a power-driven vehicle that is specifically designed and constructed to perform work on or off the road. To reduce the nitrogen oxide (NOx) emissions that come from mobile machinery, a combination of a physical model and closed-loop control is applied to the selective catalytic reduction (SCR) system. Based on the design of the variable cross-section extended exhaust structure, the differential pressure measurement was achieved, and the physical model of the exhaust flow based on the differential pressure was established. Based on the analysis of the heat and mass transfer process of the SCR catalyst, a prediction model for the internal temperature field of the catalyst was established by combining the upstream and downstream exhaust temperature sensors. Using the SCR downstream nitrogen oxides signal and the proportional–integral–derivative (PID) closed-loop control algorithm, segmented PID closed-loop control under the large hysteresis response of the SCR system was realized. The above algorithms were used to form the control code through MATLAB/Simulink and downloaded to the embedded microprocessor. The test results show that the established model can realize the real-time calculation of the exhaust gas flow rate and the internal temperature of the catalyst. Under steady-state conditions, the calculation error of the exhaust flow rate is less than ±3%, and the calculation error of the catalyst temperature is less than ±5%. Under transient conditions, the calculation error of the exhaust flow rate is less than ±9%, and the calculation error of the catalyst temperature is less than ±8%. The nitrogen–oxygen signal-based PID closed-loop algorithm can improve the nitrogen–oxygen conversion efficiency and control accuracy of the model.

Increasing mortality caused by chronic obstructive pulmonary disease (COPD) in relation with exposure to ambient fine particulate matters: an analysis in Southeastern China

The objective of this study was to investigate the association between ambient particulate matters (PMs) and chronic obstructive pulmonary disease (COPD) mortality. generalized additive mixed model was employed to investigate the effects of ambient fine and coarse PMs on COPD mortality using 13,066 deaths from 2014 to 2016 among six cities in Zhejiang Province in Southeastern China. The daily average death count due to COPD was 3, varying from 1 to 7 among six cities. The daily 24-h mean concentrations were diverse among cities, from 29.7 to 56.8 μg/m³ for PM_2.5, 16.7 to 30.3 μg/m³ for PM_2.5-10, and 50.3 to 87.1 μg/m³ for PM₁₀, respectively. The analysis showed that daily exposure to PM_2.5 and PM₁₀ was associated with increased mortality due to COPD and that weak effects were observed between PM_2.5-10 and COPD mortality. Our results provided solid evidence that the fine particles in air pollution have stronger functions on adverse health effects other than coarser particles in Southeastern China, which may be considered as a potential clinic target in PM-associated COPD.

Association between short-term exposure to sulfur dioxide and carbon monoxide and ischemic heart disease and non-accidental death in Changsha city, China

Background

To investigate the effects of short-term exposure to sulfur dioxide (SO₂) and carbon monoxide (CO) in the central and southern China areas on ischemic heart disease (IHD) and non-accidental deaths.

Method

We investigated the associations between short-term exposure to SO₂ and CO in a city in south-central China and IHD and non-accidental death using a time-series design and generalized additive models with up to a 5-day lag adjusting for day of the week, temperature, air pressure, wind speed, and relative humidity. The relative risks of IHD and non-accidental death per 10-unit increase in SO₂ and CO were derived from zero to five days in single-pollutant models.

Results

Between 2016 and 2018, a total of 10,507 IHD and 44,070 non-accidental deaths were identified. The largest significant relative risk for IHD death was lag 02 for both SO₂ (1.080; 95% confidence interval: 1.075–1.084) and CO (5.297; 95% confidence interval: 5.177–5.418) in single-pollutants models. A significant association was shown at all lag multiple-day moving averages. Two-pollutant models identified an association between SO₂ and mortality when adjusting for CO. In stratified analyses, SO₂ exhibited a stronger association with death during the cold season, while CO exhibited a stronger association with mortality from IHD during the warm season. The risk of death was more robust in the elderly for both pollutants, but was greater in men for CO and in women for SO₂.

Conclusions

Overall, we found an association between short-term exposure to low-level SO₂ and CO and the risk of IHD and non-accidental death.

The Short-Term Effects of Ambient Air Pollutants are Associated With Daily Mortality in Northeast China From 2014 to 2018: A Time Series Analysis

OBJECTIVE

We aimed to examine the associations between ambient air pollutants and daily mortality in Northeast China from 2014 to 2018.

METHODS

A two-stage approach was used to estimate particulate matter with an aerodynamic diameter of 10 μm (PM10), nitrogen dioxide (NO2), and sulfur dioxide (SO2) exposure and daily mortality.

RESULTS

An increase of 10 μg/m3 of PM10 exposure and NO2 at lag of 0 to16 days was associated with the cumulative relative risk of 1.011 (95% confidence interval [CI]: 1.004, 1.019) and 1.026 (95% CI: 1.004, 1.049), respectively, in non-accident mortality. Meanwhile, significant association was observed in people aged under 60 years between SO2 exposure and respiratory mortality at lag of 0 to 9 days.

CONCLUSIONS

Our findings strengthen the evidence of PM10 and NO2 exposures were independent risk for daily mortality.

Adverse Birth Outcomes Related to NO2 and PM Exposure: European Systematic Review and Meta-Analysis

There is a growing number of international studies on the association between ambient air pollution and adverse pregnancy outcomes, and this systematic review and meta-analysis has been conducted focusing on European countries, to assess the crucial public health issue of this suspected association on this geographical area. A systematic literature search (based on Preferred Reporting Items for Systematic reviews and Meta-Analyses, PRISMA, guidelines) has been performed on all European epidemiological studies published up until 1 April 2020, on the association between maternal exposure during pregnancy to nitrogen dioxide (NO₂) or particular matter (PM) and the risk of adverse birth outcomes, including: low birth weight (LBW) and preterm birth (PTB). Fourteen articles were included in the systematic review and nine of them were included in the meta-analysis. Our meta-analysis was conducted for 2 combinations of NO₂ exposure related to birth weight and PTB. Our systematic review revealed that risk of LBW increases with the increase of air pollution exposure (including PM₁₀, PM_2.5 and NO₂) during the whole pregnancy. Our meta-analysis found that birth weight decreases with NO₂ increase (pooled beta = −13.63, 95% confidence interval (CI) (−28.03, 0.77)) and the risk of PTB increase for 10 µg/m3 increase in NO₂ (pooled odds ratio (OR) = 1.07, 95% CI (0.90, 1.28)). However, the results were not statistically significant. Our finding support the main international results, suggesting that increased air pollution exposure during pregnancy might contribute to adverse birth outcomes, especially LBW. This body of evidence has limitations that impede the formulation of firm conclusions. Further studies, well-focused on European countries, are called to resolve the limitations which could affect the strength of association such as: the exposure assessment, the critical windows of exposure during pregnancy, and the definition of adverse birth outcomes. This analysis of limitations of the current body of research could be used as a baseline for further studies and may serve as basis for reflection for research agenda improvements.

The 10-Year Study of the Impact of Particulate Matters on Mortality in Two Transit Cities in North-Eastern Poland (PL-PARTICLES)

The detrimental influence of air pollution on mortality has been established in a series of studies. The majority of them were conducted in large, highly polluted cities-there is a lack of studies from small, relatively clean regions. The aim was to analyze the short-term impact of particulate matters (PMs) on mortality in north-eastern Poland. Time-stratified case-crossover design was performed for mortality in years 2008-2017. Daily concentrations of PM_2.5 (28.4 µg/m³, interquartile range (IQR) = 25.2) vs. (12.6 µg/m³, IQR = 9.0) and PM₁₀ (29.0 µg/m³, IQR = 18.0) vs. (21.7 µg/m³, IQR = 14.5) were higher in Łomża than Suwałki (p < 0.001). Impact of PM_2.5 on mortality was recorded in Łomża (odds ratio (OR) for IQR increase 1.061, 1.017-1.105, p = 0.06, lag 0) and Suwałki (OR for IQR increase 1.044, 1.001-1.089, p = 0.004, lag 0). PM₁₀ had an impact on mortality in Łomża (OR for IQR increase 1.028, 1.000-1.058, p = 0.049, lag 1). Cardiovascular mortality was affected by increase of PM_2.5 in Łomża (1.086, 1.020-1.156, p = 0.01) and Suwałki (1.085, 1.005-1.171, p = 0.04). PM_2.5 had an influence on respiratory mortality in Łomża (1.163, 1.021-1.380, p = 0.03, lag 1). In the whole studied region, despite differences in the air quality, the influence of PMs on mortality was observed.

Short-term effects of air pollutants on daily mortality in the Stockholm county - A spatiotemporal analysis

Short-term exposure to air pollutants has been extensively related to daily mortality, however most of the evidence comes from studies conducted in major cities, and little is known on the extent of the spatial heterogeneity in the effects within areas including both urban and non-urban settings. We aimed to investigate the short-term association of air pollutants with daily cause-specific mortality in the Stockholm county, and to test whether an association exists also outside the metropolitan area. We used a spatiotemporal random forest model to predict daily concentrations of fine and inhalable particulate matter (PM_2.5 and PM₁₀), nitrogen dioxide (NO₂) and ozone (O₃) at 1-km spatial resolution over Sweden for 2005-2016. We collected data on daily mortality for each small area for market statistics (SAMS) of the Stockholm county, to which we matched daily exposures to air pollutants and air temperature. We applied a case-crossover design to investigate the short-term association between the four pollutants and mortality from non-accidental, cardiovascular and respiratory causes. We compared the associations in and out the Stockholm urban area, by SAMS population density and across the 26 municipalities of the county. We found weak effects of most air pollutants on cause-specific mortality in the full year analysis, with estimates much larger and significant only during the warmer months (April to September): non-accidental mortality increased by 4.58% (95% confidence interval - 95% CI: 0.89%, 8.41%) and by 2.21% (95% CI: 0.71%, 3.73%) per 10 μg/m³ increase in lag 0-1 PM_2.5 and O₃, respectively. Associations were in general higher in the Stockholm city and in SAMS with high population density. When comparing the 26 municipalities, we didn't detect a significant heterogeneity in the short-term associations with air pollutants. In conclusion, we found a suggestion of a harmful role of air pollution also in non-urban areas, but the study was underpowered to draw firm conclusions. We consider this study as a pilot to investigate the spatial heterogeneity of the association between daily air pollution and mortality at the national level in Sweden.

Associations between daily air quality and hospitalisations for acute exacerbation of chronic obstructive pulmonary disease in Beijing, 2013-17: an ecological analysis

BACKGROUND

Air pollution in Beijing has been improving through implementation of the Air Pollution Prevention and Control Action Plan (2013-17), but its implications for respiratory morbidity have not been directly investigated. We aimed to assess the potential effects of air-quality improvements on respiratory health by investigating the number of cases of acute exacerbations of chronic obstructive pulmonary disease (COPD) advanced by air pollution each year.

METHODS

Daily city-wide concentrations of PM10, PM2·5, PMcoarse (particulate matter >2·5-10 μm diameter), nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO), and ozone (O3) in 2013-17 were averaged from 35 monitoring stations across Beijing. A generalised additive Poisson time-series model was applied to estimate the relative risks (RRs) and 95% CIs for hospitalisation for acute exacerbation of COPD associated with pollutant concentrations.

FINDINGS

From Jan 18, 2013, to Dec 31, 2017, 161 613 hospitalisations for acute exacerbation of COPD were recorded. Mean ambient concentrations of SO2 decreased by 68% and PM2·5 decreased by 33% over this 5-year period. For each IQR increase in pollutant concentration, RRs for same-day hospitalisation for acute exacerbation of COPD were 1·029 (95% CI 1·023-1·035) for PM10, 1·028 (1·021-1·034) for PM2·5, 1·018 (1·013-1·022) for PMcoarse, 1·036 (1·028-1·044) for NO2, 1·019 (1·013-1·024) for SO2, 1·024 (1·018-1·029) for CO, and 1·027 (1·010-1·044) for O3 in the warm season (May to October). Women and patients aged 65 years or older were more susceptible to the effects of these pollutants on hospitalisation risk than were men and patients younger than 65 years. In 2013, there were 12 679 acute exacerbations of COPD cases that were advanced by PM2·5 pollution above the expected number of cases if daily PM2·5 concentrations had not exceeded the WHO target (25 μg/m3), whereas the respective figure in 2017 was 7377 cases.

INTERPRETATION

Despite improvement in overall air quality, increased acute air pollution episodes were significantly associated with increased hospitalisations for acute exacerbations of COPD in Beijing. Stringent air pollution control policies are important and effective for reducing COPD morbidity, and long-term multidimensional policies to safeguard public health are indicated.

FUNDING

UK Medical Research Council.

Exhaled carbon monoxide levels correlate with incidence of oral mucosal lesions independent of smoking status

Carbon monoxide (CO) is an important component of tobacco smoke, but also environmental toxicity. This study analyzed possible correlation between exhaled CO level and oral health indicators in two geographically distributed populations during health-promoting public events organized for local communities in cities with high and low environmental pollution in Poland (907 patients). Self-reported, instructor-led, oral health questionnaire was developed to monitor current and previous mucosal lesion incidence. Exhaled CO correlated with subjects smoking status and environmental CO exposure: highest in smoking inhabitants of Krakow (12 ppm), with lower levels in smokers from Kozienice (6.5 ppm) and non-smokers from Krakow (6 ppm), and lowest for Kozienice non-smokers (2 ppm) (p < 0.001). After propensity score matching and adjustment for smoking status, demography and comorbidities odds ratio for mucosal lesion incidence was 1.46 (1.31-1.63), p < 0.001) per 1 ppm increase of exhaled CO level. This result might implicate a possible role of environmental pollution factors in oral health pathology.

Air pollution may affect the assessment of smoking habits by exhaled carbon monoxide measurements

BACKGROUND

While European air quality policies reduce ambient carbon monoxide (CO) concentrations in general, there are still areas affected by high environmental CO exposure from transportation, industry and burning low-quality fossil fuels. We investigated, how these CO amounts might influence exhaled CO measurements used to monitor the smoking status of healthy subjects.

METHODS

A cross-sectional study of healthy adults living in areas of high air pollution (N = 742) and low air pollution (N = 197) in Poland. They completed a survey regarding their smoking habits and underwent necessary body measurements including exhaled CO concentration levels.

RESULTS

Ambient CO levels were much higher in highly pollutes cities. Also exhaled CO levels in subjects from high pollution areas were significantly higher, independent of subject smoking status (8.25 ppm vs. 3.26 ppm). Smokers exhaled more CO than non-smokers. Although the duration of smoking did not affect the CO levels, they were proportional to the number of cigarettes smoked during the day, especially for higher amounts of cigarettes and in unpolluted areas. It was possible to differentiate active from passive smokers in all areas, but the difference for passive smokers vs. non-smokers was significant only in low pollution city inhabitants.

CONCLUSIONS

Exhaled CO levels were confirmed to be a good indicator of smoking status and smoking pattern in healthy subjects. However, high environmental CO levels both increase baseline exhaled CO concentrations in non-smokers affecting their discrimination from passive smokers, and obscure categorizing cigarette consumption in heavy smokers. These findings add important evidence on both understanding of exhaled CO monitoring results and a significance of environmental CO exposure in areas with high pollution.

Short-term PM10 and emergency department admissions for selective cardiovascular and respiratory diseases in Beijing, China

BACKGROUND

Few studies have explored PM₁₀'s connection with specific respiratory and cardiovascular emergency department admissions (EDAs). This study aimed to examine the overall effects of PM₁₀ on EDAs for cardiovascular and respiratory diseases, including specifically, cerebrovascular events (CVE), ischemic heart disease (IHD), arrhythmia, heart failure (HF), upper respiratory tract infection (URTI), lower respiratory tract infection (LRTI), chronic obstructive pulmonary disease (COPD) and asthma.

METHODS

We collected daily data for EDAs from the 10 largest hospitals in Beijing, between January 2013 and December 2013 as well as daily measurements of PM₁₀ from 17 stations in Beijing. The generalized-additive model was utilized to evaluate the associations between daily PM₁₀ and cardio-pulmonary disease admissions. Differences in gender, age, and season groups were also examined by models. Relative risks (RR) with 95% confidence interval (CI) were calculated based on subtype, age, gender and seasonal groups. In all, there were approximately 56,212 cardiovascular and 92,464 respiratory emergency admissions presented in this study.

RESULTS

The largest estimate effects in EDAs of total cardiovascular disease, CVE, IHD, total respiratory diseases, URTI, LRTI and COPD were found for PM₁₀ at day 4 (accumulative) moving average, were 0.29% (95% CI:0.12%, 0.46%), 0.36% (95% CI:0.11%, 0.61%), 0.68% (95% CI:0.25%, 1.10%), 0.34% (95% CI:0.22%, 0.47%), 0.35% (95% CI:0.18%, 0.51%), 0.34% (95% CI:0.14%, 0.55%), 2.75% (95% CI:1.38%, 4.12%) respectively. In two-pollutant models and full-pollutant model modified confounding factors, the positive correlation remained unchanged. The elderly (age ≥ 65 years) and male subjects were more susceptible to specific respiratory diseases. PM₁₀'s impact on EDAs for HF was found higher during the hot season however, EDAs for COPD peaked during the cold season.

CONCLUSION

The study markedly informed that PM₁₀ pollution was strongly associated with EDAs for cardio-pulmonary diseases. The effects of PM₁₀ pollution on COPD and heart failure EDAs were clearly determined by seasonal-temperatures.

Effects of ambient carbon monoxide on daily hospitalizations for cardiovascular disease: a time-stratified case-crossover study of 460,938 cases in Beijing, China from 2013 to 2017

BACKGROUND

Evidence focused on exposure to ambient carbon monoxide (CO) and the risk of hospitalizations for cardiovascular diseases (CVD) is lacking in developing countries. This study aimed to examine the effect of CO exposure on hospitalizations for CVD in Beijing, China.

METHODS

A total of 460,938 hospitalizations for cardiovascular diseases were obtained from electronic hospitalization summary reports from 2013 to 2017. A time-stratified case-crossover design was conducted to investigate the association between CO exposure and hospitalizations for total and cause-specific CVD, including coronary heart disease (CHD), atrial fibrillation (AF), and heart failure (HF). Stratified analysis was also conducted by age group (18-64 years and ≥ 65 years) and sex.

RESULTS

Linear exposure-response curves for the association between ambient CO exposure and hospitalizations for CVD was observed. Ambient CO was positively associated with hospitalizations for total CVD and CHD. However, the observed increased risk was not statistically significant for hospitalizations for AF and HF. The strongest effect of CO concentration was observed on the current- and previous-day of exposure (lag _0-1 day). For a 1 mg/m³ increase in a 2-day moving average CO concentration, an increase of 2.8% [95% confidence interval (CI): 2.2 to 3.3%] and 3.0% (95% CI: 2.4 to 3.6%) in daily hospital admissions for CVD and CHD were estimated, respectively. This association was robust after adjusting for other copollutants and did not vary by age group and sex.

CONCLUSIONS

Ambient CO exposure increased the risk of hospitalizations for CVD, especially for CHD in Beijing. Further studies are warranted to explore the association between ambient CO and hospitalizations for AF and HF.