Size-fractioned particulate air pollution and cardiovascular emergency room visits in Beijing, China

Long-term exposure to particulate matter is associated with elevated blood pressure: Evidence from the Chinese plateau area

Background

Ambient air pollution could increase the risk of hypertension; however, evidence regarding the relationship between long-term exposure to particulate matter and elevated blood pressure in plateau areas with lower pollution levels is limited.

Methods

We assessed the associations of long-term exposure to particulate matter (PM, PM1, PM2.5, and PM10) with hypertension, diastolic blood pressure (DBP), systolic blood pressure (SBP) and pulse pressure (PP) in 4.235 Tibet adults, based on the baseline of the China multi-ethnic cohort study (CMEC) in Lhasa city, Tibet from 2018-19. We used logistic regression and linear regression models to evaluate the associations of ambient PM with hypertension and blood pressure, respectively.

Results

Long-term exposure to PM1, PM2.5, and PM10 is positively associated with hypertension, DBP, and SBP, while negatively associated with PP. Among these air pollutants, PM10 had the strongest effect on hypertension, DBP, and SBP, while PM2.5 had the strongest effect on PP. The results showed for hypertension odds ratio (OR) = 1.99; 95% confidence interval (CI) = 1.58, 2.51 per interquartile range (IQR) μg/m3 increase in PM1, OR = 1.93; 95% CI = 1.55, 2.40 per IQR μg/m3 increase in PM2.5, and OR = 2.12; 95% CI = 1.67, 2.68 per IQR μg/m3 increase in PM10.

Conclusions

Long-term exposure to ambient air pollution was associated with an increased risk of hypertension, elevated SBP and DBP levels, and decreased PP levels. To reduce the risk of hypertension and PP reduction, attention should be paid to air quality interventions in plateau areas with low pollution levels.

Source apportionment of fine and ultrafine particle number concentrations in a major city of the Eastern Mediterranean

Ultrafine particles (UFP) are recognized as an emerging pollutant able to induce serious health effects. However, quantitative information regarding the contributions of UFP sources is generally limited. This study evaluates statistical (k-means clustering) and receptor models (Positive Matrix Factorization - PMF) using particle number size distributions (PNSD), along with chemical speciation data, measured at an urban background supersite in Athens, Greece, aiming to characterize their sources. PNSD measurements (10-487 nm) were performed during three distinct periods (warm, cold, and lockdown cold). Traffic and residential biomass burning (BB) produced high UFP number concentrations (NUFP) in the cold period (+107 % compared to summer), while the lockdown restrictions reduced NUFP (-42 %). The five groups produced by cluster analysis that were common among periods were linked to high- and low-traffic, new particle formation (NPF), urban background and regional aerosols. PMF source apportionment identified 5 and 6 factors during warm and cold periods, respectively, indicating that traffic particles dominated NUFP (64-78 % in all periods), while accumulation-mode particles and volume concentrations were controlled by processed aerosol, and especially in the cold periods by BB emissions. A nucleation factor linked to NPF contributed 7-11 % to NUFP. Comparing the two cold periods (business-as-usual, lockdown), important lockdown reductions (-46 %) were seen for fresh traffic contributions to total number concentration (Ntotal). The impact of the source attributed to NPF also eroded (-41 % for Ntotal). Due to the large reduction (-47 % for Ntotal) observed also for the BB source during the lockdown (reduced wood usage due to a milder winter), the relative contributions of all sources did not change considerably (fractional reductions <7 % for Ntotal). The quantitative results, bolstered by source apportionment combining PNSD and online chemical composition measurements, indicate the potential to constrain UFP levels by regulating traffic and residential emissions, with a large upside for population exposure control.

Association Between Air Pollution and Cardiovascular Disease Hospitalizations in Lanzhou City, 2013-2020: A Time Series Analysis

Extensive evidence has shown that air pollution increases the risk of cardiovascular disease (CVD) admissions. We aimed to explore the short-term effect of air pollution on CVD admissions in Lanzhou residents and their lag effects. Meteorological data, air pollution data, and a total of 309,561 daily hospitalizations for CVD among urban residents in Lanzhou were collected from 2013 to 2020. Distributed lag non-linear model was used to analyze the relationship between air pollutants and CVD admissions, stratified by gender, age, and season. PM2.5, NO2, and CO have the strongest harmful effects at lag03, while SO2 at lag3. The relative risks of CVD admissions were 1.0013(95% CI: 1.0003, 1.0023), 1.0032(95% CI: 1.0008, 1.0056), and 1.0040(95% CI: 1.0024, 1.0057) when PM2.5, SO2, and NO2 concentrations were increased by 10 μg/m³, respectively. Each 1 mg/m3 increase in CO concentration was associated with a relative risk of cardiovascular hospitalization of risk was 1.0909(95% CI: 1.0367, 1.1479). We observed a relative risk of 0.9981(95% CI: 0.9972, 0.9991) for each 10 μg/m³ increase in O3 for CVD admissions at lag06. We found a significant lag effects of air pollutants on CVD admissions. NO2 and CO pose a greater risk of hospitalization for women, while PM2.5 and SO2 have a greater impact on men. PM2.5, NO2, and CO have a greater impact on CVD admissions in individuals aged <65 years, whereas SO2 affects those aged ≥65 years. Our research indicates a possible short-term impact of air pollution on CVD. Local public health and environmental policies should take these preliminary findings into account.

Short-term exposure to ultrafine particles and mortality and hospital admissions due to respiratory and cardiovascular diseases in Copenhagen, Denmark

Ultrafine particles (UFP; particulate matter <0.1 μm in diameter) may be more harmful to human health than larger particles, but epidemiological evidence on their health effects is still limited. In this study, we examined the association between short-term exposure to UFP and mortality and hospital admissions in Copenhagen, Denmark. Daily concentrations of UFP (measured as particle number concentration in a size range 11-700 nm) and meteorological variables were monitored at an urban background station in central Copenhagen during 2002-2018. Daily counts of deaths from all non-accidental causes, as well as deaths and hospital admissions from cardiovascular and respiratory diseases were obtained from Danish registers. Mortality and hospital admissions associated with an interquartile range (IQR) increase in UFP exposure on a concurrent day and up to six preceding days prior to the death or admission were examined in a case-crossover study design. Odds ratios (OR) with 95% confidence intervals (CI) per one IQR increase in UFP were estimated after adjusting for temperature and relative humidity. We observed 140,079 deaths in total, 236,003 respiratory and 342,074 cardiovascular hospital admissions between 2002 and 2018. Hospital admissions due to respiratory and cardiovascular diseases were significantly positively associated with one IQR increase in UFP (OR: 1.04 [95% CI: 1.01, 1.07], lag 0-4, and 1.02 [1.00, 1.04], lag 0-1, respectively). Among the specific causes, the strongest associations were found for chronic obstructive pulmonary disease (COPD) mortality and asthma hospital admissions and two-day means (lag 0-1) of UFP (OR: 1.13 [1.01, 1.26] and 1.08 [1.00, 1.16], respectively, per one IQR increase in UFP). Based on 17 years of UFP monitoring data, we present novel findings showing that short-term exposure to UFP can trigger respiratory and cardiovascular diseases mortality and morbidity in Copenhagen, Denmark. The strongest associations with UFP were observed with COPD mortality and asthma hospital admissions.

Impact of ultrafine particles and total particle number concentration on five cause-specific hospital admission endpoints in three German cities

INTRODUCTION

Numerous studies have shown associations between daily concentrations of fine particles (e.g., particulate matter with an aerodynamic diameter ≤2.5 µm; PM2.5) and morbidity. However, evidence for ultrafine particles (UFP; particles with an aerodynamic diameter of 10-100 nm) remains conflicting. Therefore, we aimed to examine the short-term associations of UFP with five cause-specific hospital admission endpoints for Leipzig, Dresden, and Augsburg, Germany.

MATERIAL AND METHODS

We obtained daily counts of (cause-specific) cardiorespiratory hospital admissions between 2010 and 2017. Daily average concentrations of UFP, total particle number (PNC; 10-800 nm), and black carbon (BC) were measured at six sites; PM2.5 and nitrogen dioxide (NO2) were obtained from monitoring networks. We assessed immediate (lag 0-1), delayed (lag 2-4, lag 5-7), and cumulative (lag 0-7) effects by applying station-specific confounder-adjusted Poisson regression models. We then used a novel multi-level meta-analytical method to obtain pooled risk estimates. Finally, we performed two-pollutant models to investigate interdependencies between pollutants and examined possible effect modification by age, sex, and season.

RESULTS

UFP showed a delayed (lag 2-4) increase in respiratory hospital admissions of 0.69% [95% confidence interval (CI): -0.28%; 1.67%]. For other hospital admission endpoints, we found only suggestive results. Larger particle size fractions, such as accumulation mode particles (particles with an aerodynamic diameter of 100-800 nm), generally showed stronger effects (respiratory hospital admissions & lag 2-4: 1.55% [95% CI: 0.86%; 2.25%]). PM2.5 showed the most consistent associations for (cardio-)respiratory hospital admissions, whereas NO2 did not show any associations. Two-pollutant models showed independent effects of PM2.5 and BC. Moreover, higher risks have been observed for children.

CONCLUSIONS

We observed clear associations with PM2.5 but UFP or PNC did not show a clear association across different exposure windows and cause-specific hospital admissions. Further multi-center studies are needed using harmonized UFP measurements to draw definite conclusions on the health effects of UFP.

Hydrocarbons in the atmospheric gas phase of a coastal city in Tunisia: Levels, gas-particle partitioning, and health risk assessment

Many studies have focused on aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (AHs and PAHs) in different environmental compartments, especially atmospheric particles (aerosols), due to their adverse effects on the environment and human health. However, much less information is currently available on the content of AHs and PAHs in the atmospheric gas phase, which is a major reservoir of volatile and photoreactive compounds. Here, for the first time, we assessed the levels, gas-particle partitioning, human health risks and seasonal variations of AHs and PAHs in the atmospheric gas-phase of Bizerte city (Tunisia, North Africa) over a one-year period (March 2015-January 2016). Σ₃₄PAH concentration in the gas phase over the period ranged from 6.7 to 90.6 ng m^-3 and on average was 2.5 times higher in the cold season than in the warm season. Σ₂₈AH concentration in the gas phase over the period ranged from 14.0 to 35.9 ng m^-3, with no clear seasonal variations. In the gas phase, hydrocarbons were dominated by low-molecular-weight (LMW) compounds, i.e. 3- and 4-ring for PAHs and < n-C₂₄ for AHs. Gas-phase concentrations of PAHs and AHs accounted for up to 80 % of the total (gas + particle phases) atmospheric concentrations of PAHs and AHs. Further analysis of gas-particle partitioning showed that LMW hydrocarbons preferential accumulated in the gas phase, and that gas-particle partitioning was not in equilibrium but dominated by absorption processes into the aerosol organic matter. Benzo[a]pyrene toxic equivalency quotient (BaP-TEQ) in the gas phase represented on average 37 % of the total atmospheric BaP-TEQ concentration, which was always higher in the cold season. Atmospheric gas is a significant factor in the risks of cancer associated with inhalation of ambient air. The Monte Carlo simulation-based exposure assessment model predicted that outdoor air exposure to PAHs does not pose a cancer risk to infants, but the children, adolescent, and adult populations may face a lower cancer risk during the warm season and a higher risk in the cold season.

Hourly Ultrafine Particle Exposure and Acute Myocardial Infarction Onset: An Individual-Level Case-Crossover Study in Shanghai, China, 2015-2020

Associations between ultrafine particles (UFPs) and hourly onset of acute myocardial infarction (AMI) have rarely been investigated. We aimed to evaluate the impacts of UFPs on AMI onset and the lag patterns. A time-stratified case-crossover study was performed among 20,867 AMI patients from 46 hospitals in Shanghai, China, between January 2015 and December 2020. Hourly data of AMI onset and number concentrations of nanoparticles of multiple size ranges below 0.10 μm (0.01-0.10, UFP/PNC_0.01-0.10; 0.01-0.03, PNC_0.01-0.03; 0.03-0.05, PNC_0.03-0.05; and 0.05-0.10 μm, PNC_0.05-0.10) were collected. Conditional logistic regressions were applied. Transient exposures to these nanoparticles were significantly associated with AMI onset, with almost linear exposure-response curves. These associations occurred immediately after exposure, lasted for approximately 6 h, and attenuated to be null thereafter. Each interquartile range increase in concentrations of total UFPs, PNC_0.01-0.03, PNC_0.03-0.05, and PNC_0.05-0.10 during the preceding 0-6 h was associated with increments of 3.29, 2.08, 2.47, and 2.93% in AMI onset risk, respectively. The associations were stronger during warm season and at high temperatures and were robust after adjusting for criteria air pollutants. Our findings provide novel evidence that hourly UFP exposure is associated with immediate increase in AMI onset risk.

Particle surface area, ultrafine particle number concentration, and cardiovascular hospitalizations

While the health impacts of larger particulate matter, such as PM₁₀ and PM_2.5, have been studied extensively, research regarding ultrafine particles (UFPs or PM_0.1) and particle surface area concentration (PSC) is lacking. This case-crossover study assessed the associations between exposure to PSC and UFP number concentration (UFPnc) and hospital admissions for cardiovascular diseases (CVDs) in New York State (NYS), 2013-2018. We used a time-stratified case-crossover design to compare the PSC and UFPnc levels between hospitalization days and control days (similar days without admissions) for each CVD case. We utilized NYS hospital discharge data to identify all CVD cases who resided in NYS. UFP simulation data from GEOS-Chem-APM, a state-of-the-art chemical transport model, was used to define PSC and UFPnc. Using a multi-pollutant model and conditional logistic regression, we assessed excess risk (ER)% per inter-quartile change of PSC and UFPnc after controlling for meteorological factors, co-pollutants, and time-varying variables. We found immediate and lasting associations between PSC and overall CVDs (lag0-lag0-6: ERs% (95% CI%) ranges: 0.4 (0.1,0.7) - 0.9 (0.7-1.2), and delayed and prolonged ERs%: 0.1-0.3 (95% CIs: 0.1-0.5) between UFPnc and CVDs (lag0-3-lag0-6). Exposure to larger PSC was associated with immediate ER increases in stroke, hypertension, and ischemic heart diseases (1.1%, 0.7%, 0.8%, respectively, all p < 0.05). The adverse effects of PSC on CVDs were highest among children (5-17 years old), in the fall and winter, and during cold temperatures. In conclusion, we found an immediate, lasting effects of PSC on overall CVDs and a delayed, prolonged impact of UFPnc. PSC was a more sensitive indicator than UFPnc. The PSC effects were higher among certain CVD subtypes, in children, in certain seasons, and during cold days. Further studies are needed to validate our findings and evaluate the long-term effects.

Ambient concentrations and dosimetry of inhaled size-segregated particulate matter during periods of low urban mobility in Bragança, Portugal

The restrictive measures in place during the COVID-19 pandemic provided a timely scenario to investigate the effects of human activities on air quality, and the extent to which mobility reduction strategies can impact atmospheric pollutant levels. Real-time concentrations of PM₁, PM_2.5 and PM₁₀ were measured using a mobile platform in a small city of Portugal, during morning and afternoon rush hours, in two distinct phases of the pandemic: emergency phase (cold period, lockdown) and calamity phase (warm period, less restricted). The Multiple-Path Particle Dosimetry Model (MPPD) was used to calculate the PM deposition for adults. Large spatio-temporal variabilities and pronounced changes in mean PM concentrations were observed, with lower concentrations in the calamity phase: PM₁ = 2.33 ± 1.61 μg m^-3; PM_2.5 = 5.15 ± 2.77 μg m^-3; PM₁₀ = 23.30 ± 21.53 μg m^-3 than in the emergency phase: PM₁ = 16.85 ± 31.80 μg m^-3; PM_2.5 = 30.92 ± 31.93 μg m^-3; PM₁₀ = 111.27 ± 104.53 μg m^-3. These changes are explained by a combination of meteorological factors and local emissions, mainly residential firewood burning. Regarding regional deposition, PM₁ was the main contributor to deposition in the tracheobronchial (5%) and pulmonary (12%) regions, and PM₁₀ in the head region (92%). In general, total deposition doses were higher for males than for females. This work quantitatively demonstrated that even with a 38% reduction in urban mobility during the lockdown, the use of firewood for residential heating is the main contributor to the high concentrations of PM and the respective inhaled dose.

Airborne particle number concentrations in China: A critical review

Particle number concentration (PNC) is an important parameter for evaluating the environmental health and climate effects of particulate matter (PM). A good understanding of PNC is essential to control atmospheric ultrafine particles (UFP) and protect public health. In this study, we reviewed the PNC studies in the literature aimed to gain a comprehensive understanding about the levels, trends, and sources of PNC in China. The PNC levels at the urban, suburban, rural, remote, and coastal sites in China were 8500-52,200, 8600-30,300, 8600-28,400, 2100-16,100, and 5700-19,600 cm^-3, respectively. The wide ranges of PNC indicate significant heterogeneity in the spatial distribution of PNC, but also are partly due to the different measurement techniques deployed in different studies. In general, it still can be concluded that the PNC levels at urban > suburban > rural > coastal > remote sites. Except for Mt. Waliguan (a remote site of 3816 m a.s.l.), other cities had the highest PNC in spring or winter and the lowest in summer or autumn. Long-term changes of PNCs in Beijing and Nanjing indicated that PNCs of Nucleation and Aitken modes had substantially declined following stricter emission controls in recent years, but more frequent new particle formation (NPF) events were observed due to reduction in coagulation sink. Overall, traffic emission was the most dominant source of PNC in more than 94.4% of the selected cities around the world, while combustion2 (the energy production and industry related combustion source), background aerosol, and nucleation sources were also important contributors to PNC. This study provides insights about PNC and its sources around the world, especially in China. A few recommendations were suggested to further improve the understanding of PNC and to develop effective PNC control strategies.

Smaller particular matter, larger risk of female lung cancer incidence? Evidence from 436 Chinese counties

BACKGROUND

Many studies have reported the effects of PM2.5 and PM10 on human health, however, it remains unclear whether particular matter with finer particle size has a greater effect.

OBJECTIVES

This work aims to examine the varying associations of the incidence rate of female lung cancer with PM1, PM2.5 and PM10 in 436 Chinese cancer registries between 2014 and 2016.

METHODS

The effects of PM1, PM2.5 and PM10 were estimated through three regression models, respectively. Mode l only included particular matter, while Model 2 and Model 3 further controlled for time and location factors, and socioeconomic covariates, respectively. Moreover, two sensitivity analyses were performed to investigate the robustness of three particular matte effects. Then, we examined the modifying role of urban-rural division on the effects of PM1, PM2.5 and PM10, respectively.

RESULTS

The change in the incidence rate of female lung cancer relative to its mean was 5.98% (95% CI: 3.40, 8.56%) for PM1, which was larger than the values of PM2.5 and PM10 at 3.75% (95% CI: 2.33, 5.17%) and 1.57% (95% CI: 0.73, 2.41%), respectively. The effects of three particular matters were not sensitive in the two sensitivity analyses. Moreover, urban-rural division positively modified the associations of the incidence rate of female lung cancer with PM1, PM2.5 and PM10.

CONCLUSIONS

The effect on the incidence rate of female lung cancer was greater for PM1, followed by PM2.5 and PM10. There were positive modifying roles of urban-rural division on the effects of three particular matters. The finding supports the argument that finer particular matters are more harmful to human health, and also highlights the great significance to develop guidelines for PM1 control and prevention in Chinese setting.

Ambient Ozone, PM1 and Female Lung Cancer Incidence in 436 Chinese Counties

Ozone air pollution has been increasingly severe and has become another major air pollutant in Chinese cities, while PM₁ is more harmful to human health than coarser PMs. However, nationwide studies estimating the effects of ozone and PM₁ are quite limited in China. This study aims to assess the spatial associations between ozone (and PM₁) and the incidence rate of female lung cancer in 436 Chinese cancer registries (counties/districts). The effects of ozone and PM₁ were estimated, respectively, using statistical models controlling for time, location and socioeconomic covariates. Then, three sensitivity analyses including the adjustments of smoking covariates and co-pollutant (SO₂) and the estimates of ozone, PM1 and SO₂ effects in the same model, were conducted to test the robustness of the effects of the two air pollutants. Further still, we investigated the modifying role of urban-rural division on the effects of ozone and PM₁. According to the results, a 10 μg/m³ increase in ozone and PM₁ was associated with a 4.57% (95% CI: 4.32%, 16.16%) and 4.89% (95% CI: 4.37%, 17.56%) increase in the incidence rate of female lung cancer relative to its mean, respectively. Such ozone and PM₁ effects were still significant in three sensitivity analyses. Regarding the modifying role of urban-rural division, the effect of PM₁ was greater by 2.98% (95% CI: 1.01%, 4.96%) in urban than in rural areas when PM1 changed by 10 μg/m³. However, there was no modification effect of urban-rural division for ozone. In conclusion, there were positive associations between ozone (and PM₁) and the incidence rate of female lung cancer in China. Urban-rural division may modify the effect of PM₁ on the incidence rate of female lung cancer, which is seldom reported. Continuous and further prevention and control measures should be developed to alleviate the situation of the two air pollutants.

Urban-rural differences in the association between long-term exposure to ambient air pollution and obesity in China

INTRODUCTION

Ambient air pollution might increase the risk of obesity; however, the evidence regarding the relationship between air pollution and obesity in comparable urban and rural areas is limited. Therefore, our aim was to contrast the effect estimates of varying air pollution particulate matter on obesity between urban and rural areas.

METHODS

Four obesity indicators were evaluated in this study, namely, body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR). Exposure to ambient air pollution (e.g., particulate matter with aerodynamic diameters 1.0 μm [PM₁], PM_2.5, and PM₁₀) was estimated using satellite-based random forest models. Linear regression and logistic regression models were used to assess the associations between air pollution particulate matter and obesity. Furthermore, the effect estimates of different air pollution particulates were contrasted between urban and rural areas.

RESULTS

A total of 36,998 participants in urban areas and 31, 256 in rural areas were included. We found positive associations between long-term exposure to PM₁, PM_2.5, and PM₁₀ and obesity. Of these air pollutants, PM_2.5 had the strongest association. The results showed that the odds ratios (ORs) for general obesity were 1.8 (95% CI, 1.64 to 1.98) per interquartile range (IQR) μg/m³ increase in PM₁, 1.89 (95% CI, 1.71 to 2.1) per IQR μg/m³ increase in PM_2.5, and 1.74 (95% CI, 1.58 to 1.9) per IQR μg/m³ increase in PM₁₀. The concentrations of air pollutants were lower in rural areas, but the effects of air pollution on obesity of rural residents were higher than those of urban residents.

CONCLUSION

Long-term (3 years average) exposure to ambient air pollution was associated with an increased risk of obesity. We observed regional disparities in the effects of particulate matter exposure from air pollution on the risk of obesity, with higher effect estimates found in rural areas. Air quality interventions should be prioritized not only in urban areas but also in rural areas to reduce the risk of obesity.

Different sized particles associated with all-cause and cause-specific emergency ambulance calls: A multicity time-series analysis in China

BACKGROUND

Compared with mortality and hospital admission, emergency ambulance calls (EACs) could be a more accurate outcome indicator to reflect the health effects of short-term air pollution exposure. However, such studies have been scarce, especially on a multicity scale in China.

METHODS

We estimated the associations of different diameter particles [i.e., inhalable particulate matter (PM₁₀), coarse particulate matter (PM_c), and fine particulate matter (PM_2.5)] with EACs for all-cause, cardiovascular, and respiratory diseases in seven Chinese cities. We collected data on EACs and air pollution from 2014 to 2019. We used generalized additive models and random-effects meta-analysis to examine the city-specific and overall associations. Stratified analyses were conducted to examine the effect modifications of gender, age, and season.

RESULTS

Significant associations of PM₁₀ and PM_2.5 with EACs were observed, while the PM_c associations were positive but not statistically significant in most analyses. Specifically, each 10 μg/m³ increase in 2-day moving average concentration of PM₁₀ was associated with a 0.25% [95% confidence interval (CI): 0.04%, 0.47%] increase in all-cause EACs, 0.13% (95% CI: -0.01%, 0.26%) in cardiovascular EACs, and 0.35% (95% CI: 0.04%, 0.66%) in respiratory EACs. The corresponding increases in daily EACs for PM_2.5 were 0.30% (95% CI, 0.03%, 0.57%), 0.13% (95% CI, -0.07%, 0.33%), and 0.46% (95% CI, 0.01%, 0.92%). Season of the year also modifies the association between particulate matter pollution and EACs.

CONCLUSIONS

Short-term exposure to PM₁₀ and PM_2.5 were positively associated with daily all-cause and respiratory-related EACs. The associations were stronger during warm season than cold season. Our findings suggest that the most harmful fraction of particulate matter pollution is PM_2.5, which has important implications for current air quality guidelines and regulations in China.

Evaluation of a Filtering Facepiece Respirator and a Pleated Particulate Respirator in Filtering Ultrafine Particles and Submicron Particles in Welding and Asphalt Plant Work Environments

Manufacturing sites, such as welding, casting, and asphalt production (fumes), generate vast numbers of ultrafine particles of <0.1 µm in size and submicron particles close to the ultrafine range (0.1-0.5 µm). Although cumulative masses of these particles are negligible in comparison to the larger particles, the health effects are more severe due to the higher penetration in the human lower respiratory tract, other body parts crossing the respiratory epithelial layers, and the larger surface area. This research investigates the effectiveness of two common commercially available N95 filtering facepieces and N95 pleated particulate respirator models against ultrafine and submicron particles. Two specific types of respirators, the N95 filtering facepiece and the N95 pleated particulate models, in both sealed and unsealed conditions to the manikin face, were tested at various commercial and academic manufacturing sites, a welding and foundry site, and an asphalt production plant. Two TSI Nanoscan SMPS nanoparticle counters were used simultaneously to collect data for particles of 10-420 nm in size from inside and outside of the respirators. While one of them represented the workplace exposure levels, the other one accounted for the exposure upon filtration through the respiratory surfaces. The results showed the particles generated by these manufacturing operations were mostly within the range of from 40 to 200 nm. Results also indicated that while the percentage of filtration levels varied based on the particle size, it remained mostly within the desired protection level of 95% for both of the N95 respirator models in sealed conditions and even for the N95 pleated particulate model in the unsealed condition. However, in the case of the N95 filtering facepiece model, unsealed respirators showed that the percentage of penetration was very high, decreasing the protection levels to 60% in some cases. Although the number of workplace airborne particle levels varied considerably, the filtration percentages were relatively consistent.

A Comparative Study on Air Pollution Characteristics in Four Key Cities during 2013 in Guangxi Province, China

Based on ambient air quality data of the four key cities (Nanning, Liuzhou, Guilin, and Beihai) in Guangxi, China, along with an analysis of the main emission sources, topographic features, weather conditions, and backward trajectories, the variation of main air pollutants and pollution episodes in the four cities were studied. Results showed that air pollution was most serious in Liuzhou and Guilin, followed by Nanning and Beihai. PM2.5 was the dominant pollutant in each city, followed by O3, PM10, and NO2. Concentrations of SO2 and CO did not exceed their National Ambient Air Quality Standard Grade II limit values. In the cities, the concentrations of PM2.5, PM10, NO2, and SO2 were high during fall and winter and low during spring and summer, while the concentrations of O3 were high during fall and low during the other seasons. Concentrations of CO were low during summer and high during the other seasons in Nanning and Liuzhou, while they were high during spring and winter and low during summer and fall in Guilin and Beihai. In these cities, pollution episodes resulted mainly from stagnant accumulation and showed characteristics of regional pollution. However, pollution levels and durations for each city were different due to differences in main pollution sources, local geography, and weather conditions. The influences of air masses on the four cities were similar. They were mainly influenced by local emission sources in the spring, while during autumn, long-distance transportation from Hunan and Hubei was significant. In winter, air pollution in Nanning and Beihai was mostly affected by local emission sources, and that in Liuzhou and Guilin was mainly affected by long-distance transportation from the south and northeast of Guangxi.

Chemical characterization and source apportionment of PM1 and PM2.5 in Tianjin, China: Impacts of biomass burning and primary biogenic sources

The submicron particulate matter (PM₁) and fine particulate matter (PM_2.5) are very important due to their greater adverse impacts on the natural environment and human health. In this study, the daily PM₁ and PM_2.5 samples were collected during early summer 2018 at a sub-urban site in the urban-industrial port city of Tianjin, China. The collected samples were analyzed for the carbonaceous fractions, inorganic ions, elemental species, and specific marker sugar species. The chemical characterization of PM₁ and PM_2.5 was based on their concentrations, compositions, and characteristic ratios (PM₁/PM_2.5, AE/CE, NO₃^-/SO₄^2-, OC/EC, SOC/OC, OM/TCA, K+/EC, levoglucosan/K⁺, V/Cu, and V/Ni). The average concentrations of PM₁ and PM_2.5 were 32.4 µg/m³ and 53.3 µg/m³, and PM₁ constituted 63% of PM_2.5 on average. The source apportionment of PM₁ and PM_2.5 by positive matrix factorization (PMF) model indicated the main sources of secondary aerosols (25% and 34%), biomass burning (17% and 20%), traffic emission (20% and 14%), and coal combustion (17% and 14%). The biomass burning factor involved agricultural fertilization and waste incineration. The biomass burning and primary biogenic contributions were determined by specific marker sugar species. The anthropogenic sources (combustion, secondary particle formation, etc) contributed significantly to PM₁ and PM_2.5, and the natural sources were more evident in PM_2.5. This work significantly contributes to the chemical characterization and source apportionment of PM₁ and PM_2.5 in near-port cities influenced by the diverse sources.

Unraveling the blood transcriptome after real-life exposure of Wistar-rats to PM2.5, PM1 and water-soluble metals in the ambient air

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Development of a “real-life” exposure system to ambient PM1 and PM2.5 particles for Wistar rats.

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Blood transcriptome analysis identified differentially expressed genes as candidate biomarkers in PM1 and PM2.5 groups.

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Pathway analysis revealed differentially regulated gene expression in inflammation signaling.

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Identification of candidate metals for possible correlation with the identified candidate genes leading to the development of AOPs.

Exposure to particulate matter (PM) is one of the most important environmental issues in Europe with major health impact. Various sizes of PM are suspended in the atmosphere and contributes to ambient air pollution. The current study aimed to explore the differential gene expression in blood, and the effect on the respective biological signaling pathways in Wistar rats, after exposure to PM2.5 and PM1 ambient air particles for an eight-week period. A control group was included with animals breathing non-filtered atmospheric air. In parallel, filtered PM2.5 and PM1 was collected in separate samplers. The results after whole genome microarray analysis showed 23 differentially expressed genes (DEGs) between control and PM2.5 group. In addition, pairwise comparison between control and PM1 group displayed 5635 DEGs linked to 69 biological pathways involved in inflammatory response, cell cycle and carcinogenicity. The smaller the size of the inhaled particles, the more gene alterations are triggered compared to non-filtered air group. More specifically, in inflammation signaling procedures differentially regulated gene expression was shown for interleukin-4 (IL-4), IL-7, IL-1, IL-5, IL-9, IL-6 and IL-2. We have identified that RASGFR1, TRIM65, TRIM33, PLEKHB1, CAR4, S100A8, S100A9, ALPL, NP4 and the PROK2 genes are potential targets for the development of adverse outcome pathways (AOPs) due to “real-life” exposure of Wistar rats. Particle measurements during the exposure period showed elevated concentrations of Fe, Mn and Zn in both PM1 and PM2.5 filter fractions, and of Cu in PM2.5. In addition, water-soluble concentration of metals showed significant differences between PM1 and PM2.5 fractions for V, Zn, As, Pb and Mn. In summary, in this study specific gene biomarkers of exposure to ambient air have been identified and heavy metals that are possibly linked to their altered regulation have been found. The results of this research will pave the way for the development of novel AOPs concerning the health effects of the environmental pollution.

Particulate matter pollution and hospital outpatient visits for endocrine, digestive, urological, and dermatological diseases in Nanjing, China

Clinical or pathological evidence demonstrated that air pollution could undermine other organ systems of human body besides respiratory and circulation systems. Investigations that directly relate hospital outpatient visits for endocrine (ENDO), digestive (DIGE), urological (UROL), and dermatological (DERM) diseases categories with ambient particulate matter (PM) are still lacking, particularly in heavily polluted cities. Here, we conducted a time-series analysis using 812,624, 1,111,342, 539,803, and 741,662 hospital visits for ENDO, DIGE, UROL, and DERM, respectively, in Nanjing, China from 2013 to 2019. A generalized additive model was applied to estimate the exposure-response associations. Results showed that a 10 μg/m³ increase in PM_2.5 concentration on lag 0 day was significantly associated with 0.59% (95% CI: 0.30%, 0.88%), 0.43% (0.15%, 0.70%), 0.36% (0.06%, 0.66%), and 0.65% (0.42%, 0.87%) increase for ENDO, DIGE, UROL, and DERM hospital visits, respectively. The estimated effects of PM₁₀ were slightly smaller but still statistically significant. The magnitude and significance of the associations between PM and four health outcomes were sensitive to additional adjustment for co-pollutants. Exposure-response relationships were linear for PM concentrations lower than 100 μg/m³ but the curves became nonlinear across the full range of exposures due to a flatten slope at higher concentrations. We also explored the effect modifications by season (cold or warm), age (5-18, 18-64, 65-74, or 75+ years), and sex (male or female). Results showed that the DERM-related population aged 65 years or older was more vulnerable to PM exposure, compared with the 5 to 17-year age group; the DERM-related population aged 75 years or older and 65 years or older was more vulnerable to PM_2.5 and PM₁₀ exposure, respectively, compared with the 18 to 64-year age group. Our study provided suggestive evidence that ambient PM pollution was associated with ENDO, DIGE, UROL, and DERM outpatient hospital visits in Nanjing, China.

Short-term effect of PM1 on hospital admission for ischemic stroke: A multi-city case-crossover study in China

This study aims to examine the association between short-term exposures to PM₁, PM_2.5 and PM₁₀ (particulate matter with aerodynamic diameters ≤1 μm, ≤2.5 μm and ≤10 μm, respectively) and hospital admission for ischemic stroke in China. Daily counts of hospital admission for ischemic stroke were collected in 5 hospitals in China during November 2013 to October 2015. Daily concentrations of PM₁, PM_2.5 and PM₁₀ were collected in 5 cities where the hospitals were located. A time-stratified case-crossover design was used to examine the hospital-specific PM-ischemic stroke association after controlling for potential confounders. Then the effect estimates were pooled using a random-effect meta-analysis. A total of 68,122 hospital admissions for ischemic stroke were identified from 5 hospitals during the study period. The pooled results showed that exposures to PM₁, PM_2.5 and PM₁₀ were significantly associated with increased hospital admission for ischemic stroke on the current day and previous 1 day. The RRs (relative risk associated with per 10 μg/m³ increase in each pollutant) and 95%CIs (confidence intervals) for the cumulative effects of PM₁, PM_2.5 and PM₁₀ on ischemic stroke during lag 0-1 days were 1.014 (1.005, 1.0023), 1.007 (1.000, 1.014) and 1.005 (1.001, 1.009), respectively. In total, 3.5%, 3.6% and 4.1% of hospital admissions for ischemic stroke could be attributable to PM₁, PM_2.5 and PM₁₀, respectively. Exposures to ambient PM₁, PM_2.5 and PM₁₀ pollution showed acute adverse effects on hospital admission for ischemic stroke. The health effects of PM₁ should be considered by policy-makers.

The health effects of ultrafine particles

Ultrafine particles (PM_0.1), which are present in the air in large numbers, pose a health risk. They generally enter the body through the lungs but translocate to essentially all organs. Compared to fine particles (PM_2.5), they cause more pulmonary inflammation and are retained longer in the lung. Their toxicity is increased with smaller size, larger surface area, adsorbed surface material, and the physical characteristics of the particles. Exposure to PM_0.1 induces cough and worsens asthma. Metal fume fever is a systemic disease of lung inflammation most likely caused by PM_0.1. The disease is manifested by systemic symptoms hours after exposure to metal fumes, usually through welding. PM_0.1 cause systemic inflammation, endothelial dysfunction, and coagulation changes that predispose individuals to ischemic cardiovascular disease and hypertension. PM_0.1 are also linked to diabetes and cancer. PM_0.1 can travel up the olfactory nerves to the brain and cause cerebral and autonomic dysfunction. Moreover, in utero exposure increases the risk of low birthweight. Although exposure is commonly attributed to traffic exhaust, monitored students in Ghana showed the highest exposures in a home near a trash burning site, in a bedroom with burning coils employed to abate mosquitos, in a home of an adult smoker, and in home kitchens during domestic cooking. The high point-source production and rapid redistribution make incidental exposure common, confound general population studies and are compounded by the lack of global standards and national reporting. The potential for PM_0.1 to cause harm to health is great, but their precise role in many illnesses is still unknown and calls for more research.

Tiny particles found in air pollution enter the body usually through the lungs and disperse to other organs, causing more inflammation and cellular toxicity than larger particles. Dean Schraufnagel from the University of Illinois at Chicago, USA, reviews the way by which nano-sized air pollutants threaten human health. He describes how ultrafine particles measuring less than 100 nanometres in diameter elicit greater inflammatory responses and stay in the lungs longer than larger particles. Repeated contact with extremely small particulate matter can trigger heart disease, diabetes, cancer, neurological disorders and respiratory ailments, especially among children and people with long-term occupational exposure. Much remains to be learned about the disease-causing properties of these nanoparticles and their long-term effects. Further developments in understanding remain handicapped by the lack of international standards and reporting measures.

Long-Term Exposure to Air Pollution and Survival After Ischemic Stroke

Background and Purpose- China bears a heavy burden of stroke because of its large population of elderly people and the propensity for stroke. Previous studies have examined the association between air pollution and stroke mortality or hospital admission. However, the global evidence for adverse effects of air pollution on survival after stroke is scarce. Methods- We used the first national hospital-based prospective registry cohort of stroke in China, which included 12 291 ischemic stroke patients who visited hospitals during 2007 to 2008. All patients were followed for 1-year poststroke. Deaths during the follow-up period were recorded. Participants' 3-year prestroke exposures to ambient PM₁, PM_2.5, PM₁₀ (particulate matter with aerodynamic diameters ≤1, ≤2.5, and ≤10 μm, respectively) and NO₂ (nitrogen dioxide) were estimated by machine learning algorithms with satellite remote sensing, land use information, and meteorological data. Cox proportional hazards models were used to examine the association between air pollution and survival after ischemic stroke. Results- In total, 1649 deaths were identified during the 1-year follow-up period. After controlling for potential confounders, significant associations were observed between exposure to PM₁ and PM_2.5 and incident fatal ischemic stroke. The corresponding hazard ratios and 95% CIs associated with 10 µg/m³ increase in PM₁ and PM_2.5 were 1.05 (1.02-1.09) and 1.03 (1.00-1.06), respectively. No significant association was observed for PM₁₀ or NO₂ (hazard ratios and 95% CIs, 1.01 [1.00-1.03] and 1.03 [0.99-1.06], respectively). Higher hazard ratios (and 95% CIs) were observed for male, elderly and obese individuals. Conclusions- Prestroke exposure to PM₁ and PM_2.5 was associated with increased incident fatal ischemic stroke in the year following an ischemic stroke in China. Improved air quality may be beneficial for people to recover from stroke.

Association of Long-Term Exposure to Fine Particulate Matter and Cardio-Metabolic Diseases in Low- and Middle-Income Countries: A Systematic Review

: Background: Numerous epidemiological studies indicated high levels of particulate matter less than2.5 μm diameter (PM2.5) as a major cardiovascular risk factor. Most of the studies have been conducted in high-income countries (HICs), where average levels of PM2.5 are far less compared to low- and middle- income countries (LMICs), and their socio-economic profile, disease burden, and PM speciation/composition are very different. We systematically reviewed the association of long-term exposure to PM2.5 and cardio-metabolic diseases (CMDs) in LMICs.

METHODS

Multiple databases were searched for English articles with date limits until March 2018. We included studies investigating the association of long-term exposure to PM2.5 (defined as an annual average/average measure for 3 more days of PM2.5 exposure) and CMDs, such as hospital admissions, prevalence, and deaths due to CMDs, conducted in LMICs as defined by World Bank. We excluded studies which employed exposure proxy measures, studies among specific occupational groups, and specific episodes of air pollution.

RESULTS

A total of 5567 unique articles were identified, of which only 17 articles were included for final review, and these studies were from Brazil, Bulgaria, China, India, and Mexico. Outcome assessed were hypertension, type 2 diabetes mellitus and insulin resistance, and cardiovascular disease (CVD)-related emergency room visits/admissions, death, and mortality. Largely a positive association between exposure to PM2.5 and CMDs was found, and CVD mortality with effect estimates ranging from 0.24% to 6.11% increased per 10 μg/m3 in PM2.5. CVD-related hospitalizations and emergency room visits increased by 0.3% to 19.6%. Risk factors like hypertension had an odds ratio of 1.14, and type 2 diabetes mellitus had an odds ratio ranging from 1.14-1.32. Diversity of exposure assessment and health outcomes limited the ability to perform a meta-analysis.

CONCLUSION

Limited evidence on the association of long-term exposure to PM2.5 and CMDs in the LMICs context warrants cohort studies to establish the association.

The impact of ambient particulate matter on hospital outpatient visits for respiratory and circulatory system disease in an urban Chinese population

There are limited evidence on the association between short-term exposure to ambient particulate matter (PM) and overall hospital outpatient visits for respiratory system disease (RESD) and cardio-cerebrovascular system disease (CCD) in high-polluted countries like China. Though previous epidemiological studies of RESD and CCD generally applied a linear relationship of the acute PM effects, it is unclear whether this linear exposure-response relationship holds in high pollution area. In this study, a time-series study during 2013 through 2016 was conducted to investigate 245,442 and 430,486 hospital visits for RESD and CCD respectively from Nanjing city, China. A combination of logistic generalized additive model (GAM) was used to evaluate the exposure-response associations. The results disclosed that a 10 μg/m³ increase in PM_2.5 and PM₁₀ concentration on the current day of exposure (lag 0) was associated with 0.36% (95% CI: -0.02%-0.73%) and 0.33% (0.07%-0.60%) increase in RESD; and 0.42% (0.00%-0.85%) and 0.37% (0.08%-0.67%) increase in CCD. The exposure-response association was approximately linear within 0-150 μg/m³ of PM concentration and non-linear across the full range of exposures. The effects of PM on RESD and CCD were sensitive to additional adjustment for co-pollutants, indicating the health effects of air pollution mixture in Nanjing city. There was no evidence of potential effect modification of RESD and CCD by season (cold and warm), age (5-64, 65-74, ≧75 years) and sex (male and female) groups. Though not statistically significant, the estimated risks in warm season were higher than those in cold season, suggesting potential synergistic effects of ambient PM pollution and temperature on triggering RESD and CCD.

Acute effect of ambient air pollution on hospitalization in patients with hypertension: A time-series study in Shijiazhuang, China

Although numerous studies have investigated the association between air pollution and hospitalization, few studies have focused on the health effect of air pollution on populations with hypertension. In this study, we conducted a time-series study to investigate the acute adverse effect of six criteria ambient air pollutants (fine particulate matter [PM_2.5], inhalable particulate matter [PM₁₀], nitrogen dioxide [NO₂], sulfur dioxide [SO₂], ozone [O₃], and carbon monoxide [CO]) on hospitalization of patients for hypertension in Shijiazhuang, China, from 2013 to 2016. An over-dispersed Poisson generalized addictive model adjusting for weather conditions, day of the week, and long-term and seasonal trends was used. In addition, we evaluated the effect of modification by season, sex, and age. A total of 650,550 hospitalization records were retrieved during the study period. A 10 μg/m³ increase of PM_2.5 (lag06), PM₁₀ (lag06), NO₂ (lag03), O₃ (lag6), and CO (lag04) corresponded to 0.56% (95% confidence interval [CI]: 0.28-0.83%), 0.31% (95% CI: 0.12-0.50%), 1.18% (95% CI: 0.49-1.87%), 0.40% (95% CI: 0.09-0.71%), and 0.03% (95% CI: 0.01-0.05%) increments in hospitalization of patients for hypertension, respectively. We observed statistically significant associations with PM_2.5, PM₁₀, NO₂, O₃, and CO, while positive but insignificant associations with SO₂. The effects of PM_2.5, PM₁₀, NO₂, O₃, and CO were robust when adjusted for co-pollutants. We found stronger associations in the cool season than in the warm season. Moreover, there were non-significant differences in the associations between air pollution and sex or age group. This study suggests that patients with hypertension had an increased risk of hospital admission when exposed to air pollution.

Association between short-term exposure to fine particulate matter and daily emergency room visits at a cardiovascular hospital in Dhaka, Bangladesh

BACKGROUND

It has been suggested that exposure to fine particulate matter (PM_2.5) adversely affects cardiovascular health. However, the effect modifications by individual characteristics and season have been less studied in developing countries where PM_2.5 levels are high.

OBJECTIVES

To estimate the risks of cardiovascular emergency room visits in relation to daily concentrations of PM_2.5 and to assess how these associations can be modified by age, sex, and nutritional status of patients and by season.

METHODS

The analytic sample was 6774 adults who visited the emergency room at a cardiovascular disease (CVD) hospital in Dhaka throughout one year (n = 364 days). A time-stratified case-crossover design with conditional Poisson regression analysis was used to estimate the relative risks (RRs) and 95% confidence intervals (CIs) of visits while adjusting for temperature. Stratification was performed by gender, age (<65 and ≥65 years), BMI (underweight, normal weight, overweight), and season (dry summer: February to April; wet summer: May to October; dry winter: November to January).

RESULTS

The mean concentration of PM_2.5 was 86.1 μg/m³. An IQR increase (103 μg/m³) in PM_2.5 at lag 3 was significantly associated with a 12% (RR: 1.12; 95% CI: 1.01-1.23) increase in CVD emergency room visits. No evidence of association was found for the other lags. Underweight and overweight patients showed evidence of increased risk at lag 2 (RR: 1.31; 95% CI: 1.02-1.67) and lag 4 (RR: 1.20; 95% CI: 1.04-1.39), respectively.

CONCLUSION

Increases in the daily concentrations of PM_2.5 may lead to more cardiovascular emergency room visits in Dhaka, Bangladesh. Response times from ambient exposure to CVD emergency visits may differ by season and the nutritional status of susceptible individuals, necessitating further research.

Insight into the critical factors determining the particle number concentrations during summer at a megacity in China

To identify the critical factors impacting the number concentration of particles with the aerodynamic diameters less than 2.5μm (PNC_2.5), the continuous measurement of PNC_2.5, chemical components in PM_2.5, gaseous pollutants and meteorological conditions were conducted at an urban site in Tianjin in June 2015. Results indicated that the average PNC_2.5 was 2839±2430 dN/dlogDp 1/cm³ during the campaign. Compared to other meteorological parameters, the relative humidity (RH) had the strongest relationship with PNC_2.5, with a Pearson's correlation coefficient of 0.53, and RH larger than 30% influenced strongly PNC_2.5. The important influence of secondary reactions on PNC_2.5 was inferred due to higher correlation coefficients between PNC_2.5 and SO₄^2-, NO₃^-, NH₄⁺ (r=0.78-0.89; p<0.01) and between PNC_2.5 and ratios that represent the conversion of nitrogen and sulfur oxides to particulate matter (r=0.42-0.49; p<0.01). Under specific RH conditions, there were even stronger correlations between PNC_2.5 and NO₃^-, SO₄^2-, NH₄⁺, while those between PNC_2.5 and EC, OC were relatively weak, especially when RH exceeded 50%. Principal component analysis (PCA) and Pearson's correlation analysis indicated that secondary sources, vehicle emission and coal combustion might be major contributors to PNC_2.5. Backward trajectory and potential source contribution function (PSCF) analysis suggested that the transport of air masses originated from these regions around Tianjin (Liaoning, Hebei, Shandong and Jiangsu) influenced critically PNC_2.5. The north of Jiangsu, the west of Shandong, and the east of Hebei were distinguished as major potential source-areas of PNC_2.5 by PSCF model.

Short-term effects of particulate matter in metro cabin on heart rate variability in young healthy adults: Impacts of particle size and source

BACKGROUND

Metro system has become popular in urban areas. However, short-term effects of size-fractionated particulate matter (PM) on cardiac autonomic function in metro system remain unexplored.

OBJECTIVES

To explore the contribution of ambient PM to in-cabin PM and investigate the short-term effects of exposure to size-fractionated PM and black carbon (BC) in metro system on cardiac autonomic function in young healthy adults.

METHODS

Thirty nine young healthy adults were asked to travel in metro system during 9:00-13:00 on a weekends between March and May 2017. We performed continuous ambulatory electrocardiogram monitoring for each of them, and measured real-time size-fractionated PM, BC, nitrogen dioxide, nitric oxide, carbon dioxide, ozone, noise, temperature and relative humidity in metro cabin. We also collected the data of ambient PM_2.5 (aerodynamic diameter < 2.5 µm) concentrations in Beijing. Linear regression model was used to estimate the infiltration factor of ambient PM_2.5 to assess the relationship between metro cabin PM and ambient PM. Mixed-effects model was used to estimate the associations between changes in HRV parameters and PM_0.5 (aerodynamic diameter < 0.5 µm), PM_0.5-2.5 (aerodynamic diameter between 0.5 µm and 2.5 µm), PM_2.5-10 (aerodynamic diameter between 2.5 µm and 10 µm), and BC, respectively.

RESULTS

We found that size-fractionated PM in metro systems were significantly associated with HRV parameters. Per IQR (interquartile range) increase in PM_0.5 (1.6*10⁷/m³) in 1-h moving average concentration was associated with a 13.96% (95% CI: - 18.99%, - 8.61%) decrease in SDNN (standard deviation of normal-to-normal intervals). Similar inverse associations were found between size-fractionated PM exposure and LF (low frequency power), HF (high frequency power), respectively, and smaller particles had greater effects on HRV parameters at shorter lag time. Sex of participants modified the adverse associations between size-fractionated PM and HRV. An IQR of 1-h PM_0.5 increasing was associated with a decrease of 6.05% (95% CI: - 22.87%, - 14.44%) in males and a 34.87% (95% CI: - 49.59%, - 15.85%) in females in LF (P for interaction = 0.026). The infiltration factor of ambient PM_2.5 was 0.39 (95% CI: 0.33, 0.45). It is estimated that PM_2.5 originated from ambient air may account for 20.2% of the PM measured in metro cabin. Per IQR increase in BC (5.5 μg/m³) in 5-min, 1-h, and 2-h moving averages, a primary tracer for ambient PM from combustion source, was associated with decreases of 0.84% (95% CI: - 1.20%, - 0.47%), 2.22% (95% CI: - 3.20%, - 1.22%), and 4.44% (95% CI: - 6.28%, - 2.56%) in SDNN, respectively.

CONCLUSIONS

Short-term exposure to PM may disturb metro commuter's cardiac autonomic function, and the potential effects depend on the size of PM and the sex of commuters. Ambient PM from combustion source may have adverse effects on the cardiac autonomic function of passengers in cabin.

Association of size-fractionated indoor particulate matter and black carbon with heart rate variability in healthy elderly women in Beijing

Associations between size-fractionated indoor particulate matter (PM) and black carbon (BC) and heart rate variability (HRV) and heart rate (HR) in elderly women remain unclear. Twenty-nine healthy elderly women were measured for 24-hour HRV/HR indices. Real-time size-fractionated indoor PM and BC were monitored on the same day and on the preceding day. Mixed-effects models were applied to investigate the associations between pollutants and HRV/HR indices. Increases in size-fractionated indoor PM were significantly associated with declines in power in the high-frequency band (HF), power in the low-frequency band (LF), and standard deviation of all NN intervals (SDNN). The largest decline in HF was 19% at 5-minute moving average for an interquartile range (IQR) increase (24 μg/m³ ) in PM_0.5 . The results showed that smaller particles could lead to greater reductions in HRV indices. The reported associations were modified by body mass index (BMI): Declines in HF at 5-minute average for an IQR increase in PM_0.5 were 34.5% and 1.0% for overweight (BMI ≥25 kg/m² ) and normal-weight (BMI <25 kg/m² ) participants, respectively. Moreover, negative associations between BC and HRV indices were found to be significant in overweight participants. Increases in size-fractionated indoor PM and BC were associated with compromised cardiac autonomic function in healthy elderly women, especially overweight ones.

Considering spatial heterogeneity in the distributed lag non-linear model when analyzing spatiotemporal data

The distributed lag non-linear (DLNM) model has been frequently used in time series environmental health research. However, its functionality for assessing spatial heterogeneity is still restricted, especially in analyzing spatiotemporal data. This study proposed a solution to take a spatial function into account in the DLNM, and compared the influence with and without considering spatial heterogeneity in a case study. This research applied the DLNM to investigate non-linear lag effect up to 7 days in a case study about the spatiotemporal impact of fine particulate matter (PM_2.5) on preschool children's acute respiratory infection in 41 districts of northern Taiwan during 2005 to 2007. We applied two spatiotemporal methods to impute missing air pollutant data, and included the Markov random fields to analyze district boundary data in the DLNM. When analyzing the original data without a spatial function, the overall PM_2.5 effect accumulated from all lag-specific effects had a slight variation at smaller PM_2.5 measurements, but eventually decreased to relative risk significantly <1 when PM_2.5 increased. While analyzing spatiotemporal imputed data without a spatial function, the overall PM_2.5 effect did not decrease but increased in monotone as PM_2.5 increased over 20 μg/m³. After adding a spatial function in the DLNM, spatiotemporal imputed data conducted similar results compared with the overall effect from the original data. Moreover, the spatial function showed a clear and uneven pattern in Taipei, revealing that preschool children living in 31 districts of Taipei were vulnerable to acute respiratory infection. Our findings suggest the necessity of including a spatial function in the DLNM to make a spatiotemporal analysis available and to conduct more reliable and explainable research. This study also revealed the analytical impact if spatial heterogeneity is ignored.

Inhalation exposure to three-dimensional printer emissions stimulates acute hypertension and microvascular dysfunction

Fused deposition modeling (FDM™), or three-dimensional (3D) printing has become routine in industrial, occupational and domestic environments. We have recently reported that 3D printing emissions (3DPE) are complex mixtures, with a large ultrafine particulate matter component. Additionally, we and others have reported that inhalation of xenobiotic particles in this size range is associated with an array of cardiovascular dysfunctions. Sprague-Dawley rats were exposed to 3DPE aerosols via nose-only exposure for ~3h. Twenty-four hours later, intravital microscopy was performed to assess microvascular function in the spinotrapezius muscle. Endothelium-dependent and -independent arteriolar dilation were stimulated by local microiontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP). At the time of experiments, animals exposed to 3DPE inhalation presented with a mean arterial pressure of 125±4mmHg, and this was significantly higher than that for the sham-control group (94±3mmHg). Consistent with this pressor response in the 3DPE group, was an elevation of ~12% in resting arteriolar tone. Endothelium-dependent arteriolar dilation was significantly impaired after 3DPE inhalation across all iontophoretic ejection currents (0-27±15%, compared to sham-control: 15-120±21%). Endothelium-independent dilation was not affected by 3DPE inhalation. These alterations in peripheral microvascular resistance and reactivity are consistent with elevations in arterial pressure that follow 3DPE inhalation. Future studies must identify the specific toxicants generated by FDM™ that drive this acute pressor response.

Size-resolved aerosol water-soluble ions during the summer and winter seasons in Beijing: Formation mechanisms of secondary inorganic aerosols

Size-segregated water-soluble ionic species (WSIs) were measured using an Anderson cascade impactor from Jul. to Aug. 2008 and from Dec. 2009 to Feb. 2010 in urban Beijing. The results showed that fine particles (PM_2.1, Dp < 2.1 μm) accounted for ∼49% (summer) and ∼34% (winter) of the total particulate mass, and WSIs accounted for 23-82% of the mass concentration of PM_2.1. Secondary inorganic aerosols (SIAs, the sum of SO₄^2-, NO₃^- and NH₄⁺) accounted for more than 30% of the fine particles, which were greatly elevated during particle pollution events (PM events), thereby leading to an alteration of the size distributions of SO₄^2- and NO₃^- to nearly single fine-mode distributions peaking at 0.65-2.1 μm. This finding suggests that heterogeneous aqueous reactions were enhanced at high RH values. SIAs also increased during dust events, particularly for coarse mode SO₄^2-, which indicated enhanced heterogeneous reactions on the dust surface. The positive matrix factorization (PMF) model was used to resolve the bulk mass size distributions into condensation, droplet, and coarse modes, representing the three major sources of the particles. The formation of SO₄^2- was attributed primarily to in-cloud or aerosol droplet processes during summer (45%), and the heterogeneous reaction of SO₂ on mineral dust surfaces was an important formation pathway during winter (45%). The formation pathways of NO₃^- in fine particles were similar to those of SO₄^2-, where over 30% were formed by in-cloud processes. This work provides important field measurement-based evidence for understanding the formation pathway of secondary inorganic aerosols in the megacity of Beijing.

Effects of ambient PM1 air pollution on daily emergency hospital visits in China: an epidemiological study

BACKGROUND

China is experiencing severe ambient air pollution. However, few studies anywhere have examined the health effects of PM₁ (particulate matter with aerodynamic diameter <1 μm), which are a major part of PM_2·5 (particulate matter with aerodynamic diameter <2·5 μm) and even potentially more harmful than PM_2·5. We aimed to estimate the effects of ambient daily PM₁ and PM_2·5 concentrations on emergency hospital visits in China.

METHODS

In this epidemiological study, we collected daily counts of emergency hospital visits from the 28 largest hospitals in 26 Chinese cities from Sept 9, 2013, to Dec 31, 2014. Ground-based monitoring data for PM₁ and PM_2·5 and meteorological data were also collected. Hospital-specific emergency hospital visits associated with PM₁ or PM_2·5 were evaluated with a time-series Poisson regression. The effect estimates were then pooled at the country level using a random-effects meta-analysis.

FINDINGS

The mean daily concentration of PM₁ in all cities was 42·5 μg/m³ (SD 34·6) and of PM_2·5 was 51·9 μg/m³ (41·5). The mean daily number of emergency hospital visits in all hospitals was 278 (SD 173). PM₁ and PM_2·5 concentrations were significantly associated with an increased risk of emergency hospital visits at lag 0-2 days (cumulative relative risk [RRs] 1·011 [95% CI 1·006-1·017] for a 10 μg/m³ increase in PM₁ and 1·010 [1·005-1·016] for a 10 μg/m³ increase in PM_2·5). Slightly higher RRs of ambient PM₁ and PM_2·5 pollution were noted among women and children than among men and adults, respectively, but without statistical significance. Given a cause-effect association, 4·47% (95% CI 2·05-6·79) and 5·05% (2·23-7·75) of daily emergency hospital visits in China could be attributed to ambient PM₁ and PM_2·5 pollution, respectively.

INTERPRETATION

Exposure to both ambient PM₁ and PM_2·5 were significantly associated with increased emergency hospital visits. The results suggest that most of the health effects of PM_2·5 come from PM₁.

FUNDING

None.

A Laboratory Comparison of Emission Factors, Number Size Distributions, and Morphology of Ultrafine Particles from 11 Different Household Cookstove-Fuel Systems

Ultrafine particle (UFP) emissions and particle number size distributions (PNSD) are critical in the evaluation of air pollution impacts; however, data on UFP number emissions from cookstoves, which are a major source of many pollutants, are limited. In this study, 11 fuel-stove combinations covering a variety of fuels and different stoves are investigated for UFP emissions and PNSD. The combustion of LPG and alcohol (∼10¹¹ particles per useful energy delivered, particles/MJ_d), and kerosene (∼10¹³ particles/MJ_d), produced emissions that were lower by 2-3 orders of magnitude than solid fuels (10¹⁴-10¹⁵ particles/MJ_d). Three different PNSD types-unimodal distributions with peaks ∼30-40 nm, unimodal distributions with peaks <30 nm, and bimodal distributions-were observed as the result of both fuel and stove effects. The fractions of particles smaller than 30 nm (F₃₀) varied among the tested systems, ranging from 13% to 88%. The burning of LPG and alcohol had the lowest PM_2.5 mass emissions, UFP number emissions, and F₃₀ (13-21% for LPG and 35-41% for alcohol). Emissions of PM_2.5 and UFP from kerosene were also low compared with solid fuel burning but had a relatively high F₃₀ value of approximately 73-80%.

Environmental Exposures and Cardiovascular Disease: A Challenge for Health and Development in Low- and Middle-Income Countries

Environmental exposures in low- and middle-income countries lie at the intersection of increased economic development and the rising public health burden of cardiovascular disease. Increasing evidence suggests an association of exposure to ambient air pollution, household air pollution from biomass fuel, lead, arsenic, and cadmium with multiple cardiovascular disease outcomes, including hypertension, coronary heart disease, stroke, and cardiovascular mortality. Although populations in low- and middle-income countries are disproportionately exposed to environmental pollution, evidence linking these exposures to cardiovascular disease is derived from populations in high-income countries. More research is needed to further characterize the extent of environmental exposures.

Ambient Air Pollution and Morbidity in Chinese

The rapid economic growth in China is coupled with a severe ambient air pollution, which poses a huge threat to human health and the sustainable development of social economy. The rapid urbanization and industrialization over the last three decades have placed China as one of countries with the greatest disease burden in world. Notably, the prevalence rate of chronic noncommunicable diseases (CND), including respiratory diseases, CVD, and stroke, in 2010 reaches 16.9%. The continuous growth of the incidence of CND urgent needs for effective regulatory action for health protection. This study aims to evaluate the impact of rapid urbanization on status of ambient air pollution and associated adverse health effects on the incidence and the burden of CND and risk assessment. Our findings would be greatly significant in the prediction of the risk of ambient air pollution on CND and for evidence-based policy making and risk management in China.

Health benefits from improved outdoor air quality and intervention in China

China is at its most critical stage of outdoor air quality management. In order to prevent further deterioration of air quality and to protect human health, the Chinese government has made a series of attempts to reduce ambient air pollution. Unlike previous literature reviews on the widespread hazards of air pollution on health, this review article firstly summarized the existing evidence of human health benefits from intermittently improved outdoor air quality and intervention in China. Contents of this paper provide concrete and direct clue that improvement in outdoor air quality generates various health benefits in China, and confirm from a new perspective that it is worthwhile for China to shift its development strategy from economic growth to environmental economic sustainability. Greater emphasis on sustainable environment design, consistently strict regulatory enforcement, and specific monitoring actions should be regarded in China to decrease the health risks and to avoid long-term environmental threats.

Effects of Air Pollution on Hospital Emergency Room Visits for Respiratory Diseases: Urban-Suburban Differences in Eastern China

A study on the relationships between ambient air pollutants (PM_2.5, SO₂ and NO₂) and hospital emergency room visits (ERVs) for respiratory diseases from 2013 to 2014 was performed in both urban and suburban areas of Jinan, a heavily air-polluted city in Eastern China. This research was analyzed using generalized additive models (GAM) with Poisson regression, which controls for long-time trends, the “day of the week” effect and meteorological parameters. An increase of 10 μg/m³ in PM_2.5, SO₂ and NO₂ corresponded to a 1.4% (95% confidence interval (CI): 0.7%, 2.1%), 1.2% (95% CI: 0.5%, 1.9%), and 2.5% (95%: 0.8%, 4.2%) growth in ERVs for the urban population, respectively, and a 1.5% (95%: 0.4%, 2.6%), 0.8% (95%: −0.7%, 2.3%), and 3.1% (95%: 0.5%, 5.7%) rise in ERVs for the suburban population, respectively. It was found that females were more susceptible than males to air pollution in the urban area when the analysis was stratified by gender, and the reverse result was seen in the suburban area. Our results suggest that the increase in ERVs for respiratory illnesses is linked to the levels of air pollutants in Jinan, and there may be some urban-suburban discrepancies in health outcomes from air pollutant exposure.

Particle size and chemical constituents of ambient particulate pollution associated with cardiovascular mortality in Guangzhou, China

Though significant associations between particulate matter (PM) air pollution and cardiovascular diseases have been widely reported, it remains unclear what characteristics, such as particle size and chemical constituents, may be responsible for the effects. A time-series model was applied to examine the cardiovascular effects of particle size (for the period of 2009-2011) and chemical constituents (2007-2010) in Guangzhou, we controlled for potential confounders in the model, such as time trends, day of the week, public holidays, meteorological factors and influenza epidemic. We found significant associations of cardiovascular mortality with PM10, PM2.5 and PM1; the excess risk (ER) was 6.10% (95% CI: 1.76%, 10.64%), 6.11% (95% CI: 1.76%, 10.64%) and 6.48% (95% CI: 2.10%, 11.06%) for per IQR increase in PM10, PM2.5 and PM1 at moving averages for the current day and the previous 3 days (lag03), respectively. We did not find significant effects of PM2.5-10 and PM1-2.5. For PM2.5 constituents, we found that organic carbon, elemental carbon, sulfate, nitrate and ammonium were significantly associated with cardiovascular mortality, the corresponding ER for an IQR concentration increase at lag03 was 1.13% (95% CI: 0.10%, 2.17%), 2.77% (95% CI: 0.72%, 4.86%), 2.21% (95% CI: 1.05%, 3.38%), 1.98% (95% CI: 0.54%, 3.44%), and 3.38% (95% CI: 1.56%, 5.23%), respectively. These results were robust to adjustment of other air pollutants and they remained consistent in various sensitivity analyses by changing model parameters. Our study suggests that PM1 and constituents from combustion and secondary aerosols might be important characteristics of PM pollution associated with cardiovascular mortality in Guangzhou.

Particulate air pollution and circulating biomarkers among type 2 diabetic mellitus patients: the roles of particle size and time windows of exposure

BACKGROUND

Short-term associations between size-fractionated particulate matter (PM) air pollution and circulating biomarkers are not well established, especially among diabetes patients.

METHODS

We conducted a longitudinal panel study involving 6 repeated measurements of 12 circulating biomarkers among 35 diabetes patients from April to June, 2013 in Shanghai, China. Real-time number and mass concentrations of PM with multiple size fractions between 0.25 and 10 μm were measured. Linear mixed-effect models were used to explore the associations between size-fractionated PM concentrations and blood biomarkers at different time windows.

RESULTS

Short-term exposure to PM was significantly associated with elevated levels of 5 biomarkers of inflammation, 3 biomarkers of coagulation and 1 vasoconstrictor. The effects varied considerably by particle size and time windows. Overall, PM with smaller size had stronger associations, and the most significant size fractions were 0.25-0.40 μm. Even 2 h exposure to PM can lead to a significant increase in biomarkers. The effects on biomarkers of inflammation and vasoconstriction were restricted to the first 12h after exposure, but the effects on coagulation persisted for 24-72 h. For example, an interquartile range increase in 2h average exposure to PM(0.25-0.40) was associated with 6-20% increase in biomarkers of inflammation, 19-38% in coagulation and 17% in vasoconstriction. PM had a stronger effect among male patients than female patients.

CONCLUSIONS

Our results provided important evidence on the roles of the size and time windows of exposure in the PM-mediated effects on circulating biomarkers of inflammation, coagulation and vasoconstriction in diabetes patients in China.

Differential effects of particulate matter upwind and downwind of an urban freeway in an allergic mouse model

Near-road exposure to air pollutants has been associated with decreased lung function and other adverse health effects in susceptible populations. This study was designed to investigate whether different types of near-road particulate matter (PM) contribute to exacerbation of allergic asthma. Samples of upwind and downwind coarse, fine, and ultrafine PM were collected using a wind direction-actuated ChemVol sampler at a single site 100 m from Interstate-96 in Detroit, MI during winter 2010/2011. Upwind PM was enriched in crustal and wood combustion sources while downwind PM was dominated by traffic sources. Control and ovalbumin (OVA)-sensitized BALB/cJ mice were exposed via oropharyngeal (OP) aspiration to 20 or 100 μg of each PM sample 2 h prior to OP challenge with OVA. In OVA-allergic mice, 100 μg of downwind coarse PM caused greater increases than downwind fine/ultrafine PM in bronchoalveolar lavage neutrophils, eosinophils, and lactate dehydrogenase. Upwind fine PM (100 μg) produced greater increases in neutrophils and eosinophils compared to other upwind size fractions. Cytokine (IL-5) levels in BAL fluid also increased markedly following 100 μg downwind coarse and downwind ultrafine PM exposures. These findings indicate coarse PM downwind and fine PM upwind of an interstate highway promote inflammation in allergic mice.

Multi-site time series analysis of acute effects of multiple air pollutants on respiratory mortality: a population-based study in Beijing, China

In large cities in China, the traffic-related air pollution has become the focus of attention, and its adverse effects on health have raised public concerns. We conducted a study to quantify the association between exposure to three major traffic-related pollutants - particulate matter < 10 μm in aerodynamic diameter (PM10), carbon monoxide (CO) and nitrogen dioxide (NO2) and the risk of respiratory mortality in Beijing, China at a daily spatiotemporal resolution. We used the generalized additive models (GAM) with natural splines and principal component regression method to associate air pollutants with daily respiratory mortality, covariates and confounders. The GAM analysis adjusting for the collinearity among pollutants indicated that PM10, CO and NO2 had significant effects on daily respiratory mortality in Beijing. An interquartile range increase in 2-day moving averages concentrations of day 0 and day 1 of PM10, CO and NO2 corresponded to 0.99 [95% confidence interval (CI): 0.30, 1.67], 0.89 (95% CI: 0.27, 1.51) and 0.95 (95% CI: 0.29, 1.61) percent increase in daily respiratory mortality, respectively. The effects were varied across the districts. The strongest effects were found in two rural districts and one suburban district but significant in only one district. In conclusion, high level of several traffic-related air pollutants is associated with an increased risk of respiratory mortality in Beijing over a short-time period. The high risk found in rural areas suggests a potential susceptible sub-population with undiagnosed respiratory diseases in these areas. Although the rural areas have relatively lower air pollution levels, they deserve more attention to respiratory disease prevention and air pollution reduction.

Beyond black lung: scientific evidence of health effects from coal use in electricity generation

While access to electricity affects health positively, combustion of coal in power plants causes well-documented adverse health effects. We review respiratory, cardiovascular, reproductive, and neurologic health outcomes associated with exposure to coal-fired power plant emissions. We also discuss population-level health effects of coal combustion and its role in climate change. Our review of scientific studies suggests that those we present here can be used to inform energy policy.

Health risks caused by short term exposure to ultrafine particles generated by residential wood combustion: a case study of Temuco, Chile

Temuco is one of the most highly wood smoke polluted cities in Chile; however, there is scarce evidence of respiratory morbidity due to fine particulate matter. We aimed to estimate the relationship between daily concentration of ultrafine particles (UFP), with an aerodynamic diameter ≤ 0.1 μm, and outpatient visits for respiratory illness at medical care centers of Temuco, Chile, from August the 20th, 2009 to June the 30th, 2011. The Air Pollution Health Effects European Approach (APHEA2) protocol was followed, and a multivariate semi-parametric Poisson regression model was fitted with GAM techniques using R-Project statistical package; controlling for trend, seasonality, and confounders. The daily UFP were measured by a MOUDI NR-110 sampler. We found that results of the statistical analyses show significant associations between UFP and respiratory outpatient visits, with the elderly (population ≥ 65 years), being the group that presented the greatest risk. An interquartile increase of 4.73 μg/m(3) in UFP (lag 5 days) was associated with respiratory outpatient visits with a relative risk (RR) of 1.1458 [95% CI (1.0497-1.2507)] for the elderly. These results show novel findings regarding the relevance of daily UFP concentrations and health risk, especially for susceptible population in a wood smoke polluted city.

Multiple exposures to airborne pollutants and hospital admissions due to diseases of the circulatory system in Santiago de Chile

BACKGROUND

High concentrations of various air pollutants have been associated with hospitalization due to development and exacerbation of cardiovascular diseases.

OBJECTIVES

We aimed to assess associations between airborne exposures by particulate matter as well as gaseous air pollutants and hospital admissions due to different cardiovascular disease groups in Santiago de Chile.

METHODS

The study was performed in the metropolitan area of Santiago de Chile during 2004-2007. We applied a time-stratified case-crossover analysis taking temporal variation, meteorological conditions and autocorrelation into account. We computed associations between daily ambient concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), particulate matter (PM10 and PM2.5--particulate matter with aerodynamic diameters less than 10 or 2.5 μm, respectively) or ozone (O3) and hospital admissions for cardiovascular illnesses.

RESULTS

We found for CO, NO2, PM10 and PM2.5 adverse relationships to cardiovascular admissions while effect strength and lag depended on the pollutant and on the disease group. By trend, in 1-pollutant models most adverse pollutants were NO2 and particulate matter (PM10 and PM2.5) followed by CO, while in 2-pollutant models effects of PM10 persisted in most cases whereas other effects weakened. In addition the strongest effects seemed to be immediate or with a delay of up to 2 days. Adverse effects of ozone could not be detected.

CONCLUSIONS

Our results provided evidence for adverse health effects of combined exposure to airborne pollutants. Different pollutants accounted for varying adverse effects within different cardiovascular disease groups. Taking case numbers and effect strength of all cardiovascular diseases into account, mitigation measures should address all pollutants but especially NO2, PM10, and CO.

The burden of air pollution on years of life lost in Beijing, China, 2004-08: retrospective regression analysis of daily deaths

OBJECTIVES

To better understand the burden of air pollution on deaths, we examined the effects of air pollutants on years of life lost (YLL) in Beijing, China.

DESIGN

Retrospective regression analysis using daily time series.

SETTING

8 urban districts in Beijing, China.

PARTICIPANTS

80 515 deaths (48 802 male, 31 713 female) recorded by the Beijing death classification system during 2004-08.

MAIN OUTCOME MEASURES

Associations between daily YLL and ambient air pollutants (particulate matter with aerodynamic diameter <2.5 µm (PM2.5), PM10, SO2, and NO2), after adjusting for long term trends, seasonality, day of the week, and weather conditions. We also examined mortality risk related to air pollutants.

RESULTS

Mean concentrations of daily PM2.5, PM10, SO2 and NO2 were 105.1 μg/m(3), 144.6 μg/m(3), 48.6 μg/m(3), and 64.2 μg/m(3), respectively. All air pollutants had significant effects on years of life lost when we used single pollutant models. An interquartile range (IQR) increase in PM2.5, PM10, SO2, and NO2 was related to YLL increases of 15.8, 15.8, 16.2, and 15.1 years, respectively. The effects of air pollutants on YLL appeared acutely and lasted for two days (lag 0-1); these effects associated with an IQR increase in PM2.5 were greater in women than men (11.1 (95% confidence interval 4.7 to 17.5) v 4.7 (-2.9 to 12.3) YLL) and in people aged up to 65 years than those older than 65 years (12.0 (2.9 to 21) v 3.8 (-0.9 to 8.6) YLL). The mortality risk associated with an IQR increase in PM2.5 was greater for people older than 65 years (2.5% (95% confidence interval 0.6% to 4.5%) increase of mortality) than those aged up to 65 years (0.7% (-0.8% to 2.2%)).

CONCLUSIONS

YLL provides a complementary measure for examining the effect of air pollutants on mortality. Increased YLL are associated with increased air pollution. This study highlights the need to reduce air pollution in Beijing, China, to protect the health of the population.