Ambient particulate air pollution and circulating C-reactive protein level: A systematic review and meta-analysis

BackgroundAmbient particulate air pollution is a major threat to the cardiovascular health of people. Inflammation is an important component of the pathophysiological process that links air pollution and cardiovascular disease (CVD). A classical marker of inflammation—C-reactive protein (CRP), has been recognized as an independent predictor of CVD risk. Exposure to ambient particulate matter (PM) may cause systemic inflammatory response but its association with CRP has been inconsistently reported.ObjectivesTo estimate the potential effects of short-term and long-term exposures to ambient particulate air pollution on circulating CRP level based on previous epidemiological studies.MethodsA systematic literature search of PubMed, Web of Science, Embase, and Scopus databases for publications up to January 2018 was conducted for studies reporting the association between ambient PM (PM_2.5 or PM₁₀, or both) and circulating CRP level. We performed a meta-analysis for the associations reported in individual studies using a random-effect model and evaluated the effect modification by major potential modifiers.ResultsThis meta-analysis comprised data from 40 observational studies conducted on 244,681 participants. These included 32 (27 PM_2.5 studies and 13 PM₁₀ studies) and 11 (9 PM_2.5 studies and 5 PM₁₀ studies) studies that investigated the associations of CRP with short-term and long-term exposure to particulate air pollution, respectively. A 10 μg/m³ increase in short-term exposure to PM_2.5 and PM₁₀ was associated with increases of 0.83 % (95% CI: 0.30%, 1.37%) and 0.39% (95% CI: -0.04%, 0.82%) in CRP level, respectively, and a 10 μg/m³ increase in long-term exposure to PM_2.5 and PM₁₀ was associated with much higher increases of 18.01% (95% CI: 5.96%, 30.06%) and 5.61% (95% CI: 0.79%, 10.44%) in CRP level, respectively. The long-term exposure to particulate air pollution was more strongly associated with CRP level than short-term exposure and PM_2.5 had a greater effect on CRP level than PM₁₀.ConclusionExposure to ambient particulate air pollution is associated with elevated circulating CRP level suggesting an activated systemic inflammatory state upon exposure, which may explain the association between particulate air pollution and CVD risk.     

Is particulate air pollution associated with health and health inequalities in New Zealand?

Air pollution can increase mortality risk and may also exacerbate socioeconomic inequalities in health outcomes. This New Zealand study investigated whether exposure to particulate air pollution (PM₁₀) was associated with mortality and health inequalities. Annual mean PM₁₀ estimates for urban Census Area Units (CAUs) were linked to cause-specific mortality data. A dose-response relationship was found between PM₁₀ and respiratory disease mortality, including at concentrations below the existing annual average guideline value of 20 μg m⁻³. Establishing and enforcing a lower guideline value is likely to have population health benefits. However, socioeconomic inequalities in respiratory disease mortality were not significantly elevated with PM₁₀ exposure.     

Daily Mortality and PM10 Pollution in Utah Valley

The association between daily mortality and respirable particulate pollution (PM₁₀) in Utah County was assessed from April 1985 through December 1989. Poisson regression analysis was used to regress daily death counts on PM₁₀ pollution levels, controlling for variability in the weather. A significant positive association between nonaccidental mortality and PM₁₀ pollution was observed. The strongest association was with 5-d moving average PM₁₀ levels, including the concurrent day and the preceding 4 d. An increase in 5-d moving average PM₁₀ levels, equal to 100 μg/m², was associated with an estimated increase in deaths per day equal to 16%. The association with mortality and PM₁₀ was largest for respiratory disease deaths, next largest for cardiovascular deaths, and smallest for all other deaths. Mean PM₁₀ concentrations during the study period equaled 47 μg/m². The maximum 24-h and 5-d moving average PM₁₀ levels equaled 365 and 297 μg/m³, respectively. Relatively low levels of sulfur dioxide, aerosol acidity, and ozone suggested an independent association between mortality and PM₁₀. The relative risk of death increased monotonically with PM₁₀, and the relationship was observed at PM₁₀ levels that were well below the current National Ambient Air Quality Standard of 150 μg/m³.     

Acute health effects of urban fine and ultrafine particles on children with atopic dermatitis

Although ambient particulate pollutants have been shown to exacerbate existing allergic symptoms of mucous membranes including rhinitis and asthma, the effects on skin such as atopic dermatitis in childhood deserve further study. We investigated the effects of urban particulate pollutants including ultrafine particles on atopic severity in children with atopic dermatitis. We included 41 schoolchildren, 8–12 years old, who had been diagnosed with atopic dermatitis. For 67 consecutive days, all of them measured their symptoms in a diary. To assess exposure, the daily ambient mass concentrations of particulate matter less than 10, 2.5 and 1 μm (PM₁₀, PM_2.5 and PM₁, respectively) and concentrations of submicron particles (0.01–1 μm) were measured at a local school. The mean mass concentrations of PM₁₀, PM_2.5 and PM₁ were 74.0, 57.8 and 50.8 μg/m³, respectively. The mean concentrations were 41,335/cm³ ultrafine particles (UFPs) and 8577/cm³ accumulation mode (0.1–1 μm) particles. Significant associations were found between the concentrations of ultrafine particles and the itchiness symptom in children with atopic dermatitis. An interquartile range (IQR) increase in previous day ultrafine particles concentration (IQR: 28–140/m³) was significantly associated with a 3.1% (95% confidence interval, 0.2–6.1) increase in the itch symptom score for children with atopic dermatitis. The results suggested that the concentration of ambient ultrafine particles may exacerbate skin symptoms in children with atopic dermatitis.     

Elemental composition and source characterization of airborne PM10 at residences with relative proximities to metal-industrial complex

Objectives: Exposure estimates based solely on proximity to air pollution sources are not robust and require confirmation. Consequently, the present study was designed to scientifically evaluate the atmospheric particulate pollution in residences relative to their proximity to a Korean major metal-industrial complex (MIC). Methods: This purpose was achieved by concurrently measuring the concentrations and elemental composition of particulate matter with aerodynamic diameters equal to or less than 10 μm (PM₁₀) and characterizing the PM₁₀ source types in industrial ambient air from MIC and residential ambient air with relative proximities to MIC. Trace metals were analyzed using an inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The elemental composition data were employed to calculate enrichment factors and statistically analyzed using a principal component analysis (PCA) to characterize the PM₁₀ source types. The source contributions were quantitatively analyzed using an absolute PCA (APCA). Results: The most enriched elements for which a significant anthropogenic origin can be suggested were Cd, Cu, Pb, Sb, Tl, and Zn. For PCA, four or five factors with eigenvalues greater than unity were obtained for each sampling site, and those having high loadings with the same variables represented similar source types. The APCA result yielded significant regression coefficients, explaining 74–85% of the variability in the PM₁₀, which depends on the sampling site. The industrial mean values exceeded the Korean year/70 μg/m³ standard for PM₁₀, whereas the residential mean values did not. However, the maximum residential values did exceed or were close to the Korean PM₁₀ year standard. For individual elements, the ambient concentrations ranged widely from values in the order of a few ng/m³ to thousands of ng/m³. The residential mean mass concentrations in the PM₁₀ measured in the present study were higher than or similar to those reported in earlier studies. Conclusions: The present study confirmed that residents in neighborhoods near the MIC are exposed to elevated particulate and metal levels compared to residents living further away from such a source, thereby supporting that proximity to air pollution sources can be employed to indicate environmental exposure.     

Air Pollution and Mortality in Elderly People: A Time-Series Study in Sao Paulo,Brazil

The relationship between daily mortality of elderly (65 + y) persons and air pollution in the metropolitan area of Sao Paulo, Brazil, for the period May 1990 to April 1991 was evaluated by time series regression, controlling for season, weather, and other factors. Mortality was associated with respirable particles (PM₁₀), nitrogen oxides (NO_x), sulfur dioxide (SO₂), and carbon monoxide (CO). The association with PM₁₀ was most statistically significant, robust, and independent of other air pollutants. An increase in PM₁₀ equal to 100 μg/m³ was associated with an increase in overall mortality equal to approximately 13%. This association was consistent across various model specifications and estimation techniques. The dose-response relationship between mortality and respirable particulate pollution was almost linear, with no evidence of a “safe” threshold level. The results were similar to those observed in London and several U.S. cities. The results were also supportive of recent animal studies that have observed adverse health outcomes in experimental animals exposed to air pollution in Sao Paulo.     

Exposure to particulate air pollution at different living locations and respiratory symptoms in Hong Kong – an application of satellite information

Respiratory ill-health effects due to particulate air exposure at different geographical locations in Hong Kong that aggregate individual living locations were estimated based on satellite information. We assessed the presence of respiratory symptoms of a frequent cough or sputum in school students aged 11–20 years old (n = 9,881). Daily particulate air pollution levels at students' living locations were derived from the surface extinction coefficients measured by satellite and measurements from the air pollutant monitoring stations at ground level. Adjusted odds ratio (OR) [95% CI] of respiratory symptoms was 1.047 [1.005, 1.091] per 10 μg m^?3 increase in PM₁₀ concentration. Specificity tests showed that adjusted OR of having other symptoms is not significant (p = 0.20–0.94). Exposures to PM₁₀ at different geographical locations is associated with increased odds of having respiratory symptoms (cough or sputum) but not with other symptoms unrelated to air pollution.     

Ambient air pollution the risk of stillbirth: A prospective birth cohort study in Wuhan,China

Background

Recent studies suggest that ambient air pollution exposure during pregnancy is associated with stillbirth occurrence. However, the results on the associations between ambient air pollutants and stillbirths are inconsistent and little is known about the gestational timing of sensitive periods for the effects of ambient air pollutants exposure on stillbirth.

Daily variation in fine and ultrafine particulate air pollution and urinary concentrations of lung Clara cell protein CC16

Background: Daily variations in ambient particulate air pollution have been associated with respiratory mortality and morbidity.

Aims: To assess the associations between urinary concentration of lung Clara cell protein CC16, a marker for lung damage, and daily variation in fine and ultrafine particulate air pollution.

Methods: Spot urinary samples (n = 1249) were collected biweekly for six months in subjects with coronary heart disease in Amsterdam, Netherlands (n = 37), Erfurt, Germany (n = 47), and Helsinki, Finland (n = 47). Ambient particulate air pollution was monitored at a central site in each city.

Results: The mean 24 hour number concentration of ultrafine particles was 17.3x10³ cm^–3 in Amsterdam, 21.1x10³ cm^–3 in Erfurt, and 17.0x10³ cm^–3 in Helsinki. The mean 24 hour PM_2.5 concentrations were 20, 23, and 13 µg/m³, respectively. Daily variation in ultrafine particle levels was not associated with CC16. In contrast, CC16 concentration seemed to increase with increasing levels of PM_2.5 in Helsinki, especially among subjects with lung disorders. No clear associations were observed in Amsterdam and Erfurt. In Helsinki, the CC16 concentration increased by 20.2% (95% CI 6.9 to 33.5) per 10 µg/m³ increase in PM_2.5 concentration (lag 2). The respective pooled effect estimate was 2.1% (95% CI –1.3 to 5.6).

Conclusion: The results suggest that exposure to particulate air pollution may lead to increased epithelial barrier permeability in lungs.

     

Long-term Exposure to PM2.5 and Incidence of Acute Myocardial Infarction

Background: A number of studies have shown associations between chronic exposure to particulate air pollution and increased mortality, particularly from cardiovascular disease, but fewer studies have examined the association between long-term exposure to fine particulate air pollution and specific cardiovascular events, such as acute myocardial infarction (AMI).Objective: We examined how long-term exposure to area particulate matter affects the onset of AMI, and we distinguished between area and local pollutants.Methods: Building on the Worcester Heart Attack Study, an ongoing community-wide investigation examining changes over time in myocardial infarction incidence in greater Worcester, Massachusetts, we conducted a case–control study of 4,467 confirmed cases of AMI diagnosed between 1995 and 2003 and 9,072 matched controls selected from Massachusetts resident lists. We used a prediction model based on satellite aerosol optical depth (AOD) measurements to generate both exposure to particulate matter ≤ 2.5 μm in diameter (PM_2.5) at the area level (10 × 10 km) and the local level (100 m) based on local land use variables. We then examined the association between area and local particulate pollution and occurrence of AMI.Results: An interquartile range (IQR) increase in area PM_2.5 (0.59 μg/m³) was associated with a 16% increase in the odds of AMI (95% CI: 1.04, 1.29). An IQR increase in total PM_2.5 (area + local, 1.05 μg/m³) was weakly associated with a 4% increase in the odds of AMI (95% CI: 0.96, 1.11).Conclusions: Residential exposure to PM_2.5 may best be represented by a combination of area and local PM_2.5, and it is important to consider spatial gradients within a single metropolitan area when examining the relationship between particulate matter exposure and cardiovascular events.     

Short-term association between exposure to ozone and mortality in Oporto, Portugal

Exposures to air pollution in developed countries have generally decreased over the last two decades. However, many recent epidemiological studies have consistently shown positive associations between low-level exposure to air pollutants and health outcomes. In Portugal, very few studies have analysed the acute effect of air pollutants on health.The present study evaluates the association between exposure to air pollution and daily mortality in the Oporto Metropolitan Area, Portugal. Generalised additive models were used for this analysis. Pollutants assessed were ozone, nitrogen dioxide, and particulate matter (PM₁₀). Models were adjusted for time trend, seasonality, and weather.We report that an increase of 10 μg/m³ in the daily ozone 8-h maximum moving-average corresponds to an increase of 0.95% (95%CI: 0.30, 1.60) and 1.58% (95%CI: 0.45, 2.73) in non-accidental mortality and cardiovascular mortality, respectively, in the summer season. A significant effect of 0.67% (95% CI: 0.03:1.32) was also found for the association between PM₁₀ and non-accidental mortality in the summer season. Associations with ozone and PM₁₀ exposures were higher in the elderly people. No significant effects on mortality were observed during the summer season with nitrogen dioxide exposures.Our analyses provide the first significant evidence in Oporto that exposures to O₃ and PM₁₀ have adverse effects on the health of the general population in the summer months.     

Does Air Pollution Trigger Infant Mortality in Western Europe? A Case-Crossover Study

Background: Numerous studies show associations between fine particulate air pollutants [particulate matter with an aerodynamic diameter ≤ 10 μm (PM₁₀)] and mortality in adults.Objectives: We investigated short-term effects of elevated PM₁₀ levels on infant mortality in Flanders, Belgium, and studied whether the European Union (EU) limit value protects infants from the air pollution trigger.Methods: In a case-crossover analysis, we estimated the risk of dying from nontraumatic causes before 1 year of age in relation to outdoor PM₁₀ concentrations on the day of death. We matched control days on temperature to exclude confounding by variations in daily temperature.Results: During the study period (1998–2006), PM₁₀ concentration averaged 31.9 ± 13.8 μg/m³. In the entire study population (n = 2,382), the risk of death increased by 4% [95% confidence interval (CI), 0–8%; p = 0.045] for a 10-μg/m³ increase in daily mean PM₁₀. However, this association was significant only for late neonates (2–4 weeks of age; n = 372), in whom the risk of death increased by 11% (95% CI, 1–22%; p = 0.028) per 10-μg/m³ increase in PM₁₀. In this age class, infants were 1.74 (95% CI, 1.18–2.58; p = 0.006) times more likely to die on days with a mean PM₁₀ above the EU limit value of 50 μg/m³ than on days below this cutoff.Conclusions: Even in an affluent region in Western Europe, where infant mortality is low, days with higher PM air pollution are associated with an increased risk of infant mortality. Assuming causality, the current EU limit value for PM₁₀, which may be exceeded on 35 days/year, does not prevent PM₁₀ from triggering mortality in late neonates.     

The effects of particulate and ozone pollution on mortality in Moscow,Russia

The objectives of this study were (1) to evaluate how acute mortality responds to changes in particulate and ozone (O₃) pollution levels, (2) to identify vulnerable population groups by age and cause of death, and (3) to address the problem of interaction between the effects of O₃ and particulate pollution. Time-series of daily mortality counts, air pollution, and air temperature were obtained for the city of Moscow during a 3-year period (2003–2005). To estimate the pollution-mortality relationships, we used a log-linear model that controlled for potential confounding by daily air temperature and longer term trends. The effects of 10 μg/m³ increases in daily average measures of particulate matter ≤10 μm in aerodynamic diameter (PM₁₀) and O₃ were, respectively, (1) a 0.33% [95% confidence interval (CI) 0.09–0.57] and 1.09% (95% CI 0.71–1.47) increase in all-cause non-accidental mortality in Moscow; (2) a 0.66% (0.30–1.02) and 1.61% (1.01–2.21) increase in mortality from ischemic heart disease; (3) a 0.48% (0.02–0.94) and 1.28% (0.54–2.02) increase in mortality from cerebrovascular diseases. In the age group >75 years, mortality increments were consistently higher, typically by factor of 1.2 – 1.5, depending upon the cause of death. PM₁₀-mortality relationships were significantly modified by O₃ levels. On the days with O₃ concentrations above the 90th percentile, PM₁₀ risk for all-cause mortality was threefold greater and PM₁₀ risk for cerebrovascular disease mortality was fourfold greater than the unadjusted risk estimate.     

Maternal Exposure to Particulate Air Pollution and Term Birth Weight: A Multi-Country Evaluation of Effect and Heterogeneity

Background: A growing body of evidence has associated maternal exposure to air pollution with adverse effects on fetal growth; however, the existing literature is inconsistent.Objectives: We aimed to quantify the association between maternal exposure to particulate air pollution and term birth weight and low birth weight (LBW) across 14 centers from 9 countries, and to explore the influence of site characteristics and exposure assessment methods on between-center heterogeneity in this association.Methods: Using a common analytical protocol, International Collaboration on Air Pollution and Pregnancy Outcomes (ICAPPO) centers generated effect estimates for term LBW and continuous birth weight associated with PM₁₀ and PM_2.5 (particulate matter ≤ 10 and 2.5 µm). We used meta-analysis to combine the estimates of effect across centers (~ 3 million births) and used meta-regression to evaluate the influence of center characteristics and exposure assessment methods on between-center heterogeneity in reported effect estimates.Results: In random-effects meta-analyses, term LBW was positively associated with a 10-μg/m³ increase in PM₁₀ [odds ratio (OR) = 1.03; 95% CI: 1.01, 1.05] and PM_2.5 (OR = 1.10; 95% CI: 1.03, 1.18) exposure during the entire pregnancy, adjusted for maternal socioeconomic status. A 10-μg/m³ increase in PM₁₀ exposure was also negatively associated with term birth weight as a continuous outcome in the fully adjusted random-effects meta-analyses (–8.9 g; 95% CI: –13.2, –4.6 g). Meta-regressions revealed that centers with higher median PM_2.5 levels and PM_2.5:PM₁₀ ratios, and centers that used a temporal exposure assessment (compared with spatiotemporal), tended to report stronger associations.Conclusion: Maternal exposure to particulate pollution was associated with LBW at term across study populations. We detected three site characteristics and aspects of exposure assessment methodology that appeared to contribute to the variation in associations reported by centers.     

Associations between ambient air pollution and bone turnover markers in 10-year old children: Results from the GINIplus and LISAplus studies

Negative associations between bone turnover markers and bone mineral density have been reported. In order to study the association between ambient air pollution and bone turnover markers, as indicators of bone loss, we investigated associations between land-use regression modeled air pollution (NO₂, PM_2.5 mass, PM_{2.5 – 10} [coarse particles], PM₁₀ mass and PM_2.5 absorbance) and bone turnover markers in 2264 children aged 10 years. Serum osteocalcin and C-terminal telopeptide of type I collagen (CTx), measured by Modular-System (Roche), were the two bone turnover markers considered in this analysis. In total population, NO₂, PM_{2.5 – 10} and PM₁₀ mass exposure were positively and significantly associated with both osteocalcin and CTx. A 2.5 (95% CI: 0.6, 4.4) ng/ml increase in osteocalcin and a 24.0 (95% CI: 6.7, 41.3) ng/L increase in CTx were observed per IQR (6.7 μg/m³) increase in NO₂, independent of socioeconomic status, sex, age, pubertal status, fasting status and total physical activity. The estimated coefficients were 3.0 (95% CI: 0.1, 5.8) for osteocalcin and 32.3 (95% CI: 6.1, 58.5) for CTx with PM_{2.5 – 10}; 3.2 (95% CI: 0.0, 6.4) for osteocalcin and 30.7 (95% CI: 1.7, 59.7) for CTx with PM₁₀. Children living close to a major road (≤ 350 m) had higher levels of both osteocalcin (1.4 [−1.2, 4.0] ng/ml) and CTx (16.2 [−7.4, 39.8] ng/L). The adverse impact of ambient air pollution on bone turnover rates observed in one of the study areas showed stimulation of more such studies.     

A preliminary assessment of PM10 and TSP concentrations in Tuticorin, India

The respirable particulate matter (RPM; PM₁₀) and total suspended particulate matter (TSP) concentrations in ambient air in Tuticorin, India, were preliminarily estimated. Statistical analyses on so-generated database were performed to infer frequency distributions and to identify dominant meteorological factor affecting the pollution levels. Both the RPM and TSP levels were well below the permissible limits set by the US Environmental Protection Agency. As expected, lognormal distribution always fit the data during the study period. However, fit with the normal was also acceptable except for very few seasons. The RPM concentrations ranged between 20.9 and 198.2 μg/m³, while the TSP concentrations varied from 51.5 to 333.3 μg/m³ during the study period. There was a better correlation between PM_10–100 and TSP concentrations than that of PM₁₀ (RPM) and TSP concentrations, but the correlation of RPM fraction was also acceptable. It was found that wind speed was the most important meteorological factor affecting the concentrations of the pollutants of present interest. Significant seasonal variations in the pollutant concentrations of present interest were found at 5% significance level except for TSP concentrations in the year 2006.     

Characterization of coarse particulate matter in school gyms

We investigated the mass concentration, mineral composition and morphology of particles resuspended by children during scheduled physical education in urban, suburban and rural elementary school gyms in Prague (Czech Republic). Cascade impactors were deployed to sample the particulate matter. Two fractions of coarse particulate matter (PM_10−2.5 and PM_2.5−1.0) were characterized by gravimetry, energy dispersive X-ray spectrometry and scanning electron microscopy. Two indicators of human activity, the number of exercising children and the number of physical education hours, were also recorded. Lower mass concentrations of coarse particulate matter were recorded outdoors (average PM_10−2.5 4.1–7.4 μg m⁻³ and PM_2.5−1.0 2.0–3.3 μg m⁻³) than indoors (average PM_10−2.5 13.6–26.7 μg m⁻³ and PM_2.5−1.0 3.7–7.4 μg m⁻³). The indoor concentrations of coarse aerosol were elevated during days with scheduled physical education with an average indoor–outdoor (I/O) ratio of 2.5–16.3 for the PM_10−2.5 and 1.4–4.8 for the PM_2.5−1.0 values. Under extreme conditions, the I/O ratios reached 180 (PM_10−2.5) and 19.1 (PM_2.5−1.0). The multiple regression analysis based on the number of students and outdoor coarse PM as independent variables showed that the main predictor of the indoor coarse PM concentrations is the number of students in the gym. The effect of outdoor coarse PM was weak and inconsistent. The regression models for the three schools explained 60–70% of the particular dataset variability. X-ray spectrometry revealed 6 main groups of minerals contributing to resuspended indoor dust. The most abundant particles were those of crustal origin composed of Si, Al, O and Ca. Scanning electron microscopy showed that, in addition to numerous inorganic particles, various types of fibers and particularly skin scales make up the main part of the resuspended dust in the gyms. In conclusion, school gyms were found to be indoor microenvironments with high concentrations of coarse particulate matter, which can contribute to increased short-term inhalation exposure of exercising children.     

Acute respiratory inflammation in children and black carbon in ambient air before and during the 2008 Beijing Olympics

Background: Epidemiologic evidence for a causative association between black carbon (BC) and health outcomes is limited.Objectives: We estimated associations and exposure–response relationships between acute respiratory inflammation in schoolchildren and concentrations of BC and particulate matter with an aerodynamic diameter of ≤ 2.5 μm (PM_2.5) in ambient air before and during the air pollution intervention for the 2008 Beijing Olympics.Methods: We measured exhaled nitric oxide (eNO) as an acute respiratory inflammation biomarker and hourly mean air pollutant concentrations to estimate BC and PM_2.5 exposure. We used 1,581 valid observations of 36 subjects over five visits in 2 years to estimate associations of eNO with BC and PM_2.5 according to generalized estimating equations with polynomial distributed-lag models, controlling for body mass index, asthma, temperature, and relative humidity. We also assessed the relative importance of BC and PM_2.5 with two-pollutant models.Results: Air pollution concentrations and eNO were clearly lower during the 2008 Olympics. BC and PM_2.5 concentrations averaged over 0–24 hr were strongly associated with eNO, which increased by 16.6% [95% confidence interval (CI), 14.1–19.2%] and 18.7% (95% CI, 15.0–22.5%) per interquartile range (IQR) increase in BC (4.0 μg/m³) and PM_2.5 (149 μg/m³), respectively. In the two-pollutant model, estimated effects of BC were robust, but associations between PM_2.5 and eNO decreased with adjustment for BC. We found that eNO was associated with IQR increases in hourly BC concentrations up to 10 hr after exposure, consistent with effects primarily in the first hours after exposure.Conclusions: Recent exposure to BC was associated with acute respiratory inflammation in schoolchildren in Beijing. Lower air pollution levels during the 2008 Olympics also were associated with reduced eNO.     

Prospective evaluation of respiratory health benefits from reduced exposure to airborne particulate matter

We aimed to investigate if short-term exposure to reduced particulate matter (PM) air pollution would affect respiratory function in healthy adults. We followed a cohort of 42 healthy participants from a community afflicted with severe PM air pollution to a substantially less polluted area for nine days. We measured daily airborne PM [with an aerodynamic diameter of less than 2.5 μm (PM_2.5) and 10 μm (PM₁₀)] and PM_2.5 carbon component concentrations. Five repeated respiratory function measurements and fractional exhaled nitric oxide test were made for each participant. Associations between respiratory health and PM exposure were assessed using linear mixed models. Each 10 μg/m³ decrease in same-day PM_2.5 was associated with small but consistent increase in the forced expiratory volume in 1 s (FEV₁) (9.00 mL) and forced vital capacity (14.35 mL). Our observations indicate that respiratory health benefits can be achieved even after a short-term reduction of exposure to PM. Our results provide strong evidence for more rigorous air pollution controls for the health benefit of populations.