Long-term exposure to air pollution and vascular damage in young adults

Endogenous Sulfur Dioxide: A New Member of Gasotransmitter Family in the Cardiovascular System

Sulfur dioxide (SO2) was previously regarded as a toxic gas in atmospheric pollutants. But it has been found to be endogenously generated from metabolism of sulfur-containing amino acids in mammals through transamination by aspartate aminotransferase (AAT). SO2 could be produced in cardiovascular tissues catalyzed by its synthase AAT. In recent years, studies revealed that SO2 had physiological effects on the cardiovascular system, including vasorelaxation and cardiac function regulation. In addition, the pathophysiological effects of SO2 were also determined. For example, SO2 ameliorated systemic hypertension and pulmonary hypertension, prevented the development of atherosclerosis, and protected against myocardial ischemia-reperfusion (I/R) injury and isoproterenol-induced myocardial injury. These findings suggested that endogenous SO2 was a novel gasotransmitter in the cardiovascular system and provided a new therapy target for cardiovascular diseases.

Evaluation of atherosclerosis as a potential mode of action for cardiovascular effects of particulate matter

Epidemiology studies have consistently reported associations between PM2.5 exposure and cardiovascular (CV) morbidity and mortality, but the epidemiology evidence for associations between PM2.5 and subclinical measures of atherosclerosis is unclear. We critically reviewed the experimental studies of PM2.5 and effects associated with acceleration and exacerbation of atherosclerosis and evaluated whether they support a biologically plausible, human-relevant mode of action (MoA) for the associations between PM2.5 exposure and adverse CV outcomes reported in epidemiology studies. We focused on outcomes related to atherosclerotic plaque development, thrombosis, and coagulation, and we examined whether these outcomes were correlated with measures of oxidative stress and systemic or pulmonary inflammation, to evaluate whether these processes are likely to be key early events for atherogenic effects of PM. While the current experimental evidence indicates that the acceleration and exacerbation of atherosclerosis is a biologically plausible MoA in experimental animal models, we found that the human relevance of the key events in the proposed MoA is unclear and not well supported by the existing data. Further studies are needed to fill several important data gaps before the human relevance of this MoA can be established.

Association of Exposure to particular matter and Carotid Intima-Media Thickness: A Systematic Review and Meta-Analysis

Background: Long time exposure to particular matter has been linked to myocardial infarction, stroke and blood pressure, but its association with atherosclerosis is not clear. This meta-analysis was aimed at assessing whether PM_2.5 and PM₁₀ have an effect on subclinical atherosclerosis measured by carotid intima-media thickness (CIMT). Methods: Pubmed, Ovid Medline, Embase and NICK between 1948 and 31 March 2015 were searched by combining the keywords about exposure to the outcome related words. The random-effects model was applied in computing the change of CIMT and their corresponding 95% confidence interval (95% CI). The effect of potential confounding factors was assessed by stratified analysis and the impact of traffic proximity was also estimated. Results: Among 56 identified studies, 11 articles satisfied the inclusion criteria. In overall analysis increments of 10 μg/m³ in PM_2.5 and PM₁₀ were associated with an increase of CIMT (16.79 μm; 95% CI, 4.95–28.63 μm and 4.13 μm; 95% CI, −5.79–14.04 μm, respectively). Results shown in subgroup analysis had reference value for comparing with those of the overall analysis. The impact of traffic proximity on CIMT was uncertain. Conclusions: Exposure to PM_2.5 had a significant association with CIMT and for women the effect may be more obvious.

Long-term ambient air pollution exposure and risk of high blood pressure among citizens in Nis, Serbia

Epidemiological studies suggest that long-term exposure to air pollution increases the risk for high blood pressure (BP). The aim of our study is to evaluate any effects in BP in citizens exposed to long-term ambient air pollution. The subjects are 1136 citizens, aged 18-70 years, living for more than 5 years in the same home in the areas with a different level of air pollution. The air concentrations of black smoke and sulfur dioxide were determined in the period from 2001 to 2011. We measured systolic and diastolic BP and heart rate. Multivariate methods were used in the analysis. Alcohol consumption had the greatest influence on the incidence of hypertension as a risk factor (RR: 3.461; 95% CI: 1.72-6.93) and age had the least (RR: 1.23; 95% CI: 1.183-1.92). Exposure to air pollution increases risk for developing hypertension 2.5 times (95% CI: 1.46-4.49). Physical activity has proved to be statistically significant protective factor for the development of hypertension. Long-term exposure to low levels of main air pollutants is significantly associated with elevated risk of hypertension.

Carotid Intima-Media Thickness and Long-Term Exposure to Traffic-Related Air Pollution in Middle-Aged Residents of Taiwan: A Cross-Sectional Study

BACKGROUND

Associations between long-term exposure to air pollution and carotid intima-media thickness (CIMT) have inconsistent findings.

OBJECTIVES

In this study we aimed to evaluate association between 1-year average exposure to traffic-related air pollution and CIMT in middle-aged adults in Asia.

METHODS

CIMT was measured in Taipei, Taiwan, between 2009 and 2011 in 689 volunteers 35-65 years of age who were recruited as the control subjects of an acute coronary heart disease cohort study. We applied land-use regression models developed by the European Study of Cohorts for Air Pollution Effects (ESCAPE) to estimate each subject's 1-year average exposure to traffic-related air pollutants with particulate matter diameters ≤ 10 μm (PM10) and ≤ 2.5 μm (PM2.5) and the absorbance levels of PM2.5 (PM2.5abs), nitrogen dioxide (NO2), and nitrogen oxides (NOx) in the urban environment.

RESULTS

One-year average air pollution exposures were 44.21 ± 4.19 μg/m3 for PM10, 27.34 ± 5.12 μg/m3 for PM2.5, and (1.97 ± 0.36) × 10-5/m for PM2.5abs. Multivariate regression analyses showed average percentage increases in maximum left CIMT of 4.23% (95% CI: 0.32, 8.13) per 1.0 × 10-5/m increase in PM2.5abs; 3.72% (95% CI: 0.32, 7.11) per 10-μg/m3 increase in PM10; 2.81% (95% CI: 0.32, 5.31) per 20-μg/m3 increase in NO2; and 0.74% (95% CI: 0.08, 1.41) per 10-μg/m3 increase in NOx. The associations were not evident for right CIMT, and PM2.5 mass concentration was not associated with the outcomes.

CONCLUSIONS

Long-term exposures to traffic-related air pollution of PM2.5abs, PM10, NO2, and NOx were positively associated with subclinical atherosclerosis in middle-aged adults.

Air pollution and atherosclerosis: a cross-sectional analysis of four European cohort studies in the ESCAPE study

BACKGROUND

In four European cohorts, we investigated the cross-sectional association between long-term exposure to air pollution and intima-media thickness of the common carotid artery (CIMT), a preclinical marker of atherosclerosis.

METHODS

Individually assigned levels of nitrogen dioxide, nitrogen oxides, particulate matter ≤ 2.5 μm (PM2.5), absorbance of PM2.5 (PM2.5abs), PM10, PMcoarse, and two indicators of residential proximity to highly trafficked roads were obtained under a standard exposure protocol (European Study of Cohorts for Air Pollution Effects-ESCAPE study) in the Stockholm area (Sweden), the Ausburg and Ruhr area (Germany), and the Girona area (Spain). We used linear regression and meta-analyses to examine the association between long-term exposure to air pollution and CIMT.

RESULTS

The meta-analysis with 9,183 individuals resulted in an estimated increase in CIMT (geometric mean) of 0.72% (95% CI: -0.65%, 2.10%) per 5-μg/m3 increase in PM2.5 and 0.42% (95% CI: -0.46%, 1.30%) per 10-5/m increase in PM2.5abs. Living in proximity to high traffic was also positively but not significantly associated with CIMT. Meta-analytic estimates for other pollutants were inconsistent. Results were similar across different adjustment sets and sensitivity analyses. In an extended meta-analysis for PM2.5 with three other previously published studies, a 0.78% (95% CI: -0.18%, 1.75%) increase in CIMT was estimated for a 5-μg/m3 contrast in PM2.5.

CONCLUSIONS

Using a standardized exposure and analytical protocol in four European cohorts, we found that cross-sectional associations between CIMT and the eight ESCAPE markers of long-term residential air pollution exposure did not reach statistical significance. The additional meta-analysis of CIMT and PM2.5 across all published studies also was positive but not significant.

Association between fine particulate matter exposure and subclinical atherosclerosis: A meta-analysis

BACKGROUND

Epidemiological studies in humans that have evaluated the association between fine particulate matter (PM2.5) and atherosclerosis have yielded mixed results.

DESIGN

In order to further investigate this relationship, we conducted a comprehensive search for studies published through May 2014 and performed a meta-analysis of all available observational studies that investigated the association between PM2.5 and three noninvasive measures of clinical and subclinical atherosclerosis: carotid intima media thickness, arterial calcification, and ankle-brachial index.

METHODS AND RESULTS

Five reviewers selected studies based on predefined inclusion criteria. Pooled mean change estimates and 95% confidence intervals were calculated using random-effects models. Assessment of between-study heterogeneity was performed where the number of studies was adequate. Our pooled sample included 11,947 subjects for carotid intima media thickness estimates, 10,750 for arterial calcification estimates, and 6497 for ankle-brachial index estimates. Per 10 µg/m(3) increase in PM2.5 exposure, carotid intima media thickness increased by 22.52 µm but this did not reach statistical significance (p = 0.06). We did not find similar associations for arterial calcification (p = 0.44) or ankle-brachial index (p = 0.85).

CONCLUSION

Our meta-analysis supports a relationship between PM2.5 and subclinical atherosclerosis measured by carotid intima media thickness. We did not find a similar relationship between PM2.5 and arterial calcification or ankle-brachial index, although the number of studies was small.

Carotid intima-media thickness, a marker of subclinical atherosclerosis, and particulate air pollution exposure: the meta-analytical evidence

Introduction

Studies on the association between atherosclerosis and long-term exposure to ambient air pollution suggest that carotid intima-media thickness (CIMT), a marker of subclinical atherosclerosis, is positively associated with particulate matter (PM) exposure. However, there is heterogeneity between the different studies concerning the magnitude of this association. We performed a meta-analysis to determine the strength of the association between CIMT and particulate air pollution.

Methods

We queried PubMed citation database and Web of Knowledge up to March 2015 in order to identify studies on CIMT and particulate air pollution. Two investigators selected and computerized all relevant information, independently. Eight of the reviewed epidemiological publications provided sufficient details and met our inclusion criteria. Descriptive and quantitative information was extracted from each selected study. The meta-analysis included 18,349 participants from eight cohorts for the cross-sectional association between CIMT and PM and 7,268 participants from three cohorts for the longitudinal analysis on CIMT progression and PM exposure.

Results

The average exposure to PM_2.5 in the different study populations ranged from 4.1 to 20.8 µg/m³ and CIMT averaged (SD) 0.73 (0.14) mm. We computed a pooled estimate from a random-effects model. In the combined cross-sectional studies, an increase of 5 µg/m³ PM_2.5 was associated with a 1.66% (95% CI: 0.86 to 2.46; P<0.0001) thicker CIMT, which corresponds to an average increase of 12.1 µm. None of the studies moved the combined estimate outside the confidence interval of the overall estimate. A funnel plot suggested absence of publication bias. The combined longitudinal estimate showed for each 5 µg/m³ higher PM_2.5 exposure, a 1.04 µm per year (95% CI: 0.01 to 2.07; P=0.048) greater CIMT progression.

Conclusion

Our meta-analysis supports the evidence of a positive association between CIMT, a marker of subclinical atherosclerosis, and long-term exposure to particulate air pollution.

Long-term particulate matter exposure: Attributing health effects to individual PM components

While most in the scientific community are of the opinion that the composition of fine particulate matter (PM2.5) is an important driver of resultant health effects, there is still some degree of uncertainty regarding those components considered to be most harmful. Reviews of the subject from several perspectives have been published, but to our knowledge a comprehensive review of the epidemiological and toxicological literature related to long-term exposure to PM2.5 components does not exist. We reviewed published epidemiological studies that were of a cohort design, included at least one PM component as well as PM2.5 mass, and included quantitative analysis to relate health outcomes to individual components. Toxicological studies were included if they were ≥5 months in duration and either included at least one PM component as well as PM mass or focused on a specific PM or emissions type. Overall, we find that epidemiological and toxicological evidence for long-term effects of PM components is limited, in contrast to the short-term literature, which is more plentiful. Epidemiological literature suggests that a number of components are associated with health effects, and that no component is unequivocally not so associated. Toxicological studies that can more easily identify potentially causal components are generally limited to long-term studies using concentrated ambient particles (CAPs), of which few long-term studies exist. Epidemiological study designs that utilize existing monitoring data routinely collected by the U.S. Environmental Protection Agency would be valuable additions to the literature, as would novel toxicological studies that incorporate innovative designs to separate components or groups of components, such as denuders, filtration, or other approaches. From a policy perspective, it is important to more comprehensively investigate this issue so that if particular constituents are determined to be more potent in inducing health effects, their sources can be controlled.

IMPLICATIONS

Understanding the components of PM2.5 that are most harmful to human health is a critical policy issue. This review examined the epidemiological and toxicological literature related to long-term exposure to PM components and found that, unlike the literature on short-term health effects, there is insufficient information to make clear inferences about causal components. There is a need for further research in this area to exploit existing PM monitoring data in epidemiological studies and to design experimental studies that are able to tease out the effects of multiple constituents.

Residential exposure to urban traffic is associated with increased carotid intima-media thickness in children

Chronic exposure to urban traffic pollution is documented to promote atherosclerosis in adults but little is known about its potential effects in children. Our study examined the association of long-term exposure to traffic with carotid intima-media thickness (cIMT) in 287 healthy children. Residential proximity and distance-weighted traffic density (DWTD) were used as proximity markers for traffic-related air pollution exposure. The multivariable analyses revealed that children residing <100 meters from the nearest heavily trafficked road had cIMT mean and maximum measurements that were increased by 15% and 11% compared to those living ≥ 200 meters away (P = 0.0001). Similar increases in cIMT were identified for children in the highest versus lowest DWTD tertile. Children who resided 100–199 meters from traffic or in the middle DWTD tertile also exhibited increased cIMT but these differences were not statistically significant. No statistically significant differences were identified between residential distance to traffic or DWTD and systemic inflammation indicators (CRP, IL-6). The study results suggest that exposure to urban traffic promotes arterial remodeling in children. This finding is important since even small increases in cIMT over time can potentially lead to earlier progression to atherosclerosis. It is also important because traffic-related pollution is potentially modifiable.

Long-term exposure to traffic-related air pollution and cardiovascular health in a Greek cohort study

Our objective is to evaluate the association of exposure to traffic-related air pollution with the incidence of fatal and non-fatal ischemic heart disease (IHD), stroke and total cardiovascular disease (CVD) events in a Greek cohort. We used data from the European Prospective Investigation on Nutrition and Cancer (EPIC) for 2752 subjects followed from 1997 to 2011, whose residence was in 10 municipalities of the Greater Athens area. Air pollution exposure estimation was based on a spatio-temporal land use regression model linking geo-coded residential addresses to long-term average NO2 and PM10 concentrations. We conducted Cox proportional hazards regression analysis, adjusting for potential confounders. Hazard ratios (HR) above 1 (not all statistically significant) were associated with higher PM10 exposure for all outcomes. Weaker associations were found with NO2 exposure. Specifically, the estimated HR for a CVD event associated with 10 μg/m(3) increase in long-term exposure to PM10 was 1.50 (1.05-2.16, p-value: 0.027). The relationship was more evident for subjects ≤50 years old at recruitment. Associations of PM10 and NO2 exposure with IHD events were found only among women with HRs respectively of 2.24 (0.89-5.64, p-value: 0.086) and 1.54 (1.01-2.37, p-value: 0.046) associated with 10 μg/m(3) increase in the corresponding pollutant. In conclusion, the present study suggests that long-term exposure to traffic-related air pollution has an impact on CVD and IHD morbidity, particularly among women and younger subjects.

Long-term exposure to traffic-related air pollution and progression of carotid artery atherosclerosis: a prospective cohort study

OBJECTIVES

Epidemiological studies have demonstrated associations between long-term exposure to traffic-related air pollution and coronary heart disease (CHD). Atherosclerosis is the principal pathological process responsible for CHD events, but effects of traffic-related air pollution on progression of atherosclerosis are not clear. This study aimed to investigate associations between long-term exposure to traffic-related air pollution and progression of carotid artery atherosclerosis.

SETTING

Healthy volunteers in metropolitan Vancouver, Canada.

PARTICIPANTS AND OUTCOME MEASURES

509 participants aged 30-65 years were recruited and followed for approximately 5 years. At baseline and end of follow-up, participants underwent carotid artery ultrasound examinations to assess atherosclerosis severity, including carotid intima-media thickness, plaque area, plaque number and total area. Annual change of each atherosclerosis marker during the follow-up period was calculated as the difference between these two measurements divided by years of follow-up. Living close to major roads was defined as ≤150 m from a highway or ≤50 m from a major road. Residential exposures to traffic-related air pollutants including black carbon, fine particles, nitrogen dioxide and nitric oxide were estimated using high-resolution land-use regression models. The data were analysed using general linear models adjusting for various covariates.

RESULTS

At baseline, there were no significant differences in any atherosclerosis markers between participants living close to and those living away from major roads. After follow-up, the differences in annual changes of these markers between these two groups were small and not statistically significant. Also, no significant associations were observed with concentrations of traffic-related air pollutants including black carbon, fine particles, nitrogen dioxide and nitric oxide.

CONCLUSIONS

This study did not find significant associations between traffic-related air pollution and progression of carotid artery atherosclerosis in a region with lower levels and smaller contrasts of ambient air pollution.

Associations between short-term changes in air pollution and correlates of arterial stiffness: The Veterans Affairs Normative Aging Study, 2007-2011

We investigated associations between short-term exposure to air pollution and central augmentation index and augmentation pressure, correlates of arterial stiffness, in a cohort of elderly men in the Boston, Massachusetts, metropolitan area. This longitudinal analysis included 370 participants from the Veterans Affairs Normative Aging Study with up to 2 visits between 2007 and 2011 (n = 445). Augmentation index (as %) and augmentation pressure (in mmHg) were measured at each visit by using radial artery applanation tonometry for pulse wave analysis and modeled in a mixed effects regression model as continuous functions of moving averages of air pollution exposures (over 4 hours and 1, 3, 7, and 14 days). The results suggest that short-term changes in air pollution were associated with augmentation index and augmentation pressure at several moving averages. Interquartile range (IQR) increases in 3-day average exposure to particles with aerodynamic diameter less than 2.5 μm (3.6-μg/m(3) IQR increase) and sulfate (1.4-μg/m(3) IQR increase) and 1-day average exposure to particle number counts (8,741-counts/cm(3) IQR increase) were associated with augmentation index values that were 0.8% (95% confidence interval (CI): 0.2, 1.4), 0.6% (95% CI: 0.1, 1.2), and 1.7% (95% CI: 0.4, 2.9) higher, respectively. Overall, the findings were similar for augmentation pressure. The findings support the hypothesis that exposure to air pollution may affect vascular function.

Changes in traffic exposure and the risk of incident myocardial infarction and all-cause mortality

BACKGROUND

Traffic-related exposures, such as air pollution and noise, have been associated with increased cardiovascular morbidity and mortality. Few studies, however, have been able to examine the effects of changes in exposure on changes in risk. Our objective was to explore the associations of changes in traffic exposure with changes in risk between 1990 and 2008 in the Nurses' Health Study.

METHODS

Incident myocardial infarction (MI) and all-cause mortality were prospectively identified. As a proxy for traffic exposure, we calculated residential distance to roads at all residential addresses 1986-2006 and considered addresses to be "close" or "far" based on distance and road type. To examine the effect of changes in exposure, each consecutive pair of addresses was categorized as: (1) consistently close, (2) consistently far, (3) change from close to far, and (4) change from far to close. We also examined the change in NO2 levels between address pairs.

RESULTS

In time-varying Cox proportional hazards models adjusted for a variety of risk factors, women living at residences consistently close to traffic were at a higher risk of an incident MI (hazard ratio [HR] = 1.11; 95% confidence interval [CI] = 1.01-1.22) and a higher risk of all-cause mortality (1.05; 1.00-1.10), compared with those consistently far. The highest risks were seen among women who moved from being far from traffic to close (incident MI: HR = 1.50 [95% CI = 1.11-2.03]; all-cause mortality: HR = 1.17 [95% CI = 1.00-1.37]). Each 1 ppb increase in NO2 compared with the previous address was associated with a HR = 1.22 for incident MI (95% CI = 0.99-1.50) and 1.03 for all-cause mortality (95% CI = 0.92-1.15).

CONCLUSIONS

Our results suggest that changes in traffic exposure (measured as roadway proximity or change in NO2 levels) are associated with changes in risk of MI and all-cause mortality.

Acute and subacute effects of urban air pollution on cardiopulmonary emergencies and mortality: time series studies in Austrian cities

Daily pollution data (collected in Graz over 16 years and in the Linz over 18 years) were used for time series studies (GAM and case-crossover) on the relationship with daily mortality (overall and specific causes of death). Diagnoses of patients who had been transported to hospitals in Linz were also available on a daily basis from eight years for time series analyses of cardiopulmonary emergencies. Increases in air pollutant levels over several days were followed by increases in mortality and the observed effects increased with the length of the exposure window considered, up to a maximum of 15 days. These mortality changes in Graz and Linz showed similar patterns like the ones found before in Vienna. A significant association of mortality could be demonstrated with NO₂, PM_2.5 and PM₁₀ even in summer, when concentrations are lower and mainly related to motor traffic. Cardiorespiratory ambulance transports increased with NO₂/PM_2.5/PM₁₀ by 2.0/6.1/1.7% per 10 µg/m³ on the same day. Monitoring of NO₂ (related to motor traffic) and fine particulates at urban background stations predicts acute effects on cardiopulmonary emergencies and extended effects on cardiopulmonary mortality. Both components of urban air pollution are indicators of acute cardiopulmonary health risks, which need to be monitored and reduced, even below current standards.

Association between long-term exposure to traffic-related air pollution and subclinical atherosclerosis: the REGICOR study

BACKGROUND

Epidemiological evidence of the effects of long-term exposure to air pollution on the chronic processes of atherogenesis is limited.

OBJECTIVE

We investigated the association of long-term exposure to traffic-related air pollution with subclinical atherosclerosis, measured by carotid intima media thickness (IMT) and ankle-brachial index (ABI).

METHODS

We performed a cross-sectional analysis using data collected during the reexamination (2007-2010) of 2,780 participants in the REGICOR (Registre Gironí del Cor: the Gerona Heart Register) study, a population-based prospective cohort in Girona, Spain. Long-term exposure across residences was calculated as the last 10 years' time-weighted average of residential nitrogen dioxide (NO2) estimates (based on a local-scale land-use regression model), traffic intensity in the nearest street, and traffic intensity in a 100 m buffer. Associations with IMT and ABI were estimated using linear regression and multinomial logistic regression, respectively, controlling for sex, age, smoking status, education, marital status, and several other potential confounders or intermediates.

RESULTS

Exposure contrasts between the 5th and 95th percentiles for NO2 (25 µg/m3), traffic intensity in the nearest street (15,000 vehicles/day), and traffic load within 100 m (7,200,000 vehicle-m/day) were associated with differences of 0.56% (95% CI: -1.5, 2.6%), 2.32% (95% CI: 0.48, 4.17%), and 1.91% (95% CI: -0.24, 4.06) percent difference in IMT, respectively. Exposures were positively associated with an ABI of > 1.3, but not an ABI of < 0.9. Stronger associations were observed among those with a high level of education and in men ≥ 60 years of age.

CONCLUSIONS

Long-term traffic-related exposures were associated with subclinical markers of atherosclerosis. Prospective studies are needed to confirm associations and further examine differences among population subgroups.

Fine particulate air pollution and the progression of carotid intima-medial thickness: a prospective cohort study from the multi-ethnic study of atherosclerosis and air pollution

BACKGROUND

Fine particulate matter (PM2.5) has been linked to cardiovascular disease, possibly via accelerated atherosclerosis. We examined associations between the progression of the intima-medial thickness (IMT) of the common carotid artery, as an indicator of atherosclerosis, and long-term PM2.5 concentrations in participants from the Multi-Ethnic Study of Atherosclerosis (MESA).

METHODS AND RESULTS

MESA, a prospective cohort study, enrolled 6,814 participants at the baseline exam (2000-2002), with 5,660 (83%) of those participants completing two ultrasound examinations between 2000 and 2005 (mean follow-up: 2.5 years). PM2.5 was estimated over the year preceding baseline and between ultrasounds using a spatio-temporal model. Cross-sectional and longitudinal associations were examined using mixed models adjusted for confounders including age, sex, race/ethnicity, smoking, and socio-economic indicators. Among 5,362 participants (5% of participants had missing data) with a mean annual progression of 14 µm/y, 2.5 µg/m(3) higher levels of residential PM2.5 during the follow-up period were associated with 5.0 µm/y (95% CI 2.6 to 7.4 µm/y) greater IMT progressions among persons in the same metropolitan area. Although significant associations were not found with IMT progression without adjustment for metropolitan area (0.4 µm/y [95% CI -0.4 to 1.2 µm/y] per 2.5 µg/m(3)), all of the six areas showed positive associations. Greater reductions in PM2.5 over follow-up for a fixed baseline PM2.5 were also associated with slowed IMT progression (-2.8 µm/y [95% CI -1.6 to -3.9 µm/y] per 1 µg/m(3) reduction). Study limitations include the use of a surrogate measure of atherosclerosis, some loss to follow-up, and the lack of estimates for air pollution concentrations prior to 1999.

CONCLUSIONS

This early analysis from MESA suggests that higher long-term PM2.5 concentrations are associated with increased IMT progression and that greater reductions in PM2.5 are related to slower IMT progression. These findings, even over a relatively short follow-up period, add to the limited literature on air pollution and the progression of atherosclerotic processes in humans. If confirmed by future analyses of the full 10 years of follow-up in this cohort, these findings will help to explain associations between long-term PM2.5 concentrations and clinical cardiovascular events.

Prospective study of particulate air pollution exposures, subclinical atherosclerosis, and clinical cardiovascular disease: The Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air)

The Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air) was initiated in 2004 to investigate the relation between individual-level estimates of long-term air pollution exposure and the progression of subclinical atherosclerosis and the incidence of cardiovascular disease (CVD). MESA Air builds on a multicenter, community-based US study of CVD, supplementing that study with additional participants, outcome measurements, and state-of-the-art air pollution exposure assessments of fine particulate matter, oxides of nitrogen, and black carbon. More than 7,000 participants aged 45-84 years are being followed for over 10 years for the identification and characterization of CVD events, including acute myocardial infarction and other coronary artery disease, stroke, peripheral artery disease, and congestive heart failure; cardiac procedures; and mortality. Subcohorts undergo baseline and follow-up measurements of coronary artery calcium using computed tomography and carotid artery intima-medial wall thickness using ultrasonography. This cohort provides vast exposure heterogeneity in ranges currently experienced and permitted in most developed nations, and the air monitoring and modeling methods employed will provide individual estimates of exposure that incorporate residence-specific infiltration characteristics and participant-specific time-activity patterns. The overarching study aim is to understand and reduce uncertainty in health effect estimation regarding long-term exposure to air pollution and CVD.

Vascular responses to long- and short-term exposure to fine particulate matter: MESA Air (Multi-Ethnic Study of Atherosclerosis and Air Pollution)

OBJECTIVES

This study evaluated the association of long- and short-term air pollutant exposures with flow-mediated dilation (FMD) and baseline arterial diameter (BAD) of the brachial artery using ultrasound in a large multicity cohort.

BACKGROUND

Exposures to ambient air pollution, especially long-term exposure to particulate matter <2.5 μm in aerodynamic diameter (PM(2.5)), are linked with cardiovascular mortality. Short-term exposure to PM(2.5) has been associated with decreased FMD and vasoconstriction, suggesting that adverse effects of PM(2.5) may involve endothelial dysfunction. However, long-term effects of PM(2.5) on endothelial dysfunction have not been investigated.

METHODS

FMD and BAD were measured by brachial artery ultrasound at the initial examination of the Multi-Ethnic Study of Atherosclerosis. Long-term PM(2.5) concentrations were estimated for the year 2000 at each participant's residence (n = 3,040) using a spatio-temporal model informed by cohort-specific monitoring. Short-term PM(2.5) concentrations were based on daily central-site monitoring in each of the 6 cities.

RESULTS

An interquartile increase in long-term PM(2.5) concentration (3 μg/m(3)) was associated with a 0.3% decrease in FMD (95% confidence interval [CI] of difference: -0.6 to -0.03; p = 0.03), adjusting for demographic characteristics, traditional risk factors, sonographers, and 1/BAD. Women, nonsmokers, younger participants, and those with hypertension seemed to show a greater association of PM(2.5) with FMD. FMD was not significantly associated with short-term variation in PM(2.5) (-0.1% per 12 μg/m(3) daily increase [95% CI: -0.2 to 0.04] on the day before examination).

CONCLUSIONS

Long-term PM(2.5) exposure was significantly associated with decreased endothelial function according to brachial ultrasound results. These findings may elucidate an important pathway linking air pollution and cardiovascular mortality.

Ischaemic heart disease mortality and years of work in trucking industry workers

OBJECTIVES

Evidence from general population-based studies and occupational cohorts has identified air pollution from mobile sources as a risk factor for cardiovascular disease. In a cohort of US trucking industry workers, with regular exposure to vehicle exhaust, the authors previously observed elevated standardised mortality ratios for ischaemic heart disease (IHD) compared with members of the general US population. Therefore, the authors examined the association of increasing years of work in jobs with vehicle exhaust exposure and IHD mortality within the cohort.

METHODS

The authors calculated years of work in eight job groups for 30,758 workers using work records from four nationwide companies. Proportional hazard regression was used to examine relationships between IHD mortality, 1985-2000, and employment duration in each job group.

RESULTS

HRs for at least 1 year of work in each job were elevated for dockworkers, long haul drivers, pick-up and delivery drivers, combination workers, hostlers, and shop workers. There was a suggestion of an increased risk of IHD mortality with increasing years of work as a long haul driver, pick-up and delivery driver, combination worker, and dockworker.

CONCLUSION

These results suggest an elevated risk of IHD mortality in workers with a previous history of regular exposure to vehicle exhaust.

Childhood air pollutant exposure and carotid artery intima-media thickness in young adults

BACKGROUND

Exposure to ambient air pollutants increases risk for cardiovascular health outcomes in adults. The contribution of childhood air pollutant exposure to cardiovascular health has not been thoroughly evaluated.

METHODS AND RESULTS

The Testing Responses on Youth study consists of 861 college students recruited from the University of Southern California in 2007 to 2009. Participants attended 1 study visit during which blood pressure, heart rate, and carotid artery intima-media thickness (CIMT) were assessed. Self-administered questionnaires collected information about health and sociodemographic characteristics, and a 12-hour fasting blood sample was drawn for lipid and biomarker analyses. Residential addresses were geocoded and used to assign cumulative air pollutant exposure estimates based on data derived from the U.S. Environmental Protection Agency's Air Quality System database. The associations between CIMT and air pollutants were assessed using linear regression analysis. Mean CIMT was 603 μm (±54 SD). A 2 standard deviation (SD) increase in childhood (aged 0-5 years) or elementary school (aged 6-12 years) O(3) exposure was associated with a 7.8-μm (95% confidence interval, -0.3-15.9) or 10.1-μm (95% confidence interval, 1.8-18.5) higher CIMT, respectively. Lifetime exposure to O(3) showed similar but nonsignificant associations. No associations were observed for PM(2.5), PM(10), or NO(2), although adjustment for these pollutants strengthened the childhood O(3) associations.

CONCLUSIONS

Childhood exposure to O(3) may be a novel risk factor for CIMT in a healthy population of college students. Regulation of air pollutants and efforts that focus on limiting childhood exposures continue to be important public health goals.

Investigating the association of cardiovascular effects with personal exposure to particle components and sources

BACKGROUND

Few studies included information on components and sources when exploring the cardiovascular health effects from personal exposure to particulate matters (PM). We previously reported that exposure to PM between 1.0 and 2.5 μm (PM(2.5-1)) was associated with increased cardio-ankle vascular index (CAVI, an arterial stiffness index), while exposure to PM smaller than 0.25 μm (PM(0.25)) decreased the heart rate variability (HRV) indices. The purpose of this study was to investigate the association between PM elements and cardiovascular health effects and identify responsible sources.

METHODS

In a panel study of seventeen mail carriers, the subjects were followed for 5-6 days while delivering mail outdoors. Personal filter samples of PM(2.5-1) and PM(0.25) were analyzed for their elemental concentrations. The source-specific exposures were further estimated by using absolute principal factor analysis. We analyzed the component- and source-specific health effects on HRV indices and CAVI using mixed models.

RESULTS

Several elements in PM(2.5-1) (e.g., cadmium and strontium) were associated with the CAVI. Subsequent analyses showed that an interquartile range increase in exposure to PM from regional sources was significantly associated with a 3.28% increase in CAVI (95% confidence interval (CI), 1.47%-5.13%). This significant effect remained (3.35%, CI: 1.62%-5.11%) after controlling for the ozone exposures. For exposures to PM(0.25), manganese, calcium, nickel, and chromium were associated with the CAVI and/or the HRV indices.

CONCLUSIONS

Our study suggests that PM(2.5-1) and PM(0.25) components may be associated with different cardiovascular effects. Health risks from exposure to PM from sources other than vehicle exhaust should not be underappreciated.

Development of outcome-based, multipollutant mobile source indicators

Multipollutant indicators of mobile source impacts are developed from readily available CO, NOx, and elemental carbon (EC) data for use in air quality and epidemiologic analysis. Two types of outcome-based Integrated Mobile Source Indicators (IMSI) are assessed. The first is derived from analysis of emissions of EC, CO, and NOx such that pollutant concentrations are mixed and weighted based on emission ratios for both gasoline and diesel vehicles. The emission-based indicators (IMSI(EB)) capture the impact of mobile sources on air quality estimated from receptor models and their uncertainty is comparable to measurement and source apportionment uncertainties. The IMSI(EB) have larger correlation between two different receptor sites impacted by traffic than single pollutants, suggesting they are better indicators of the local impact ofmobile sources. A sensitivity analysis of fractions of pollutants in a two-pollutant mixture and the inclusion in an epidemiologic model is conducted to develop a second set of indicators based on health outcomes. The health-based indicators (IMSI(HB)) are weighted combinations of CO, NOx, and EC pairs that have the lowest P value in their association with cardiovascular disease emergency department visits, possibly due to their better spatial representativeness. These outcome-based, multipollutant indicators can provide support for the setting of multipollutant air quality standards and other air quality management activities.

Differential effects of inhalation exposure to PM2.5 on hypothalamic monoamines and corticotrophin releasing hormone in lean and obese rats

Acute exposure to airborne pollutants, especially particulate matter (PM2.5) is known to increase hospital admissions for cardiovascular conditions, increase cardiovascular related mortality and predispose the elderly and obese individuals to cardiovascular conditions. The mechanisms by which PM2.5 exposure affects the cardiovascular system is not clear. Since the autonomic system plays an important role in cardiovascular regulation, we hypothesized that PM2.5 exposure most likely activates the paraventricular nucleus (PVN) of the hypothalamus to cause an increase in sympathetic nervous system and/or stress axis activity. We also hypothesized that these changes may be sustained in obese rats predisposing them to higher cardiovascular risk. To test this, adult male Brown Norway (BN) rats were subjected to one day or three days of inhalation exposures to filtered air (FA) or concentrated air particulate (CAP) derived from ambient PM2.5. Corpulent JCR-LA rats were exposed to FA or CAP for four days. Animals were sacrificed 24h after the last inhalation exposure. Their brains were removed, frozen and sectioned. The PVN and median eminence (ME) were microdissected. PVN was analyzed for norepinephrine (NE), dopamine (DA) and 5-hydroxy-indole acetic acid (5-HIAA) levels using HPLC-EC. ME was analyzed for corticotrophin releasing hormone (CRH) levels by ELISA. One day exposure to CAP increased NE levels in the PVN and CRH levels in the ME of BN rats. Repeated exposures to CAP did not affect NE levels in the PVN of BN rats, but increased NE levels in JCR/LA rats. A similar pattern was observed with 5-HIAA levels. DA levels on the other hand, were unaffected in both BN and JCR/LA strains. These data suggest that repeated exposures to PM2.5 continue to stimulate the PVN in obese animals but not lean rats.

Investigating air pollution and atherosclerosis in humans: concepts and outlook

Although ambient particulate matter contributes to atherosclerosis in animal models, its role in atherogenesis in humans needs to be established. This article discusses concepts, study design, and choice of health outcomes to efficiently investigate the atherogenic role of ambient air pollution, with an emphasis on early preclinical biomarkers of atherosclerosis that are unaffected by short-term exposure to air pollution (eg, carotid intima-media thickness [CIMT] and functional performance of the vessel). Air pollution studies using these end points are summarized. The CIMT is currently the most frequently used outcome in this field (6 studies). The continuous nature of CIMT, the lack of short-term variation, its relationship to atherosclerotic changes in the artery wall, its predictive value for coronary heart disease, and the noninvasiveness of the assessment make it a useful candidate for cross-sectional and longitudinal studies investigating the role of air pollution in atherogenesis.

Urban particulate matter air pollution is associated with subclinical atherosclerosis: results from the HNR (Heinz Nixdorf Recall) study

OBJECTIVES

The aim of this study was to investigate the association of long-term residential exposure to fine particles with carotid intima-media thickness (CIMT).

BACKGROUND

Experimental and epidemiological evidence suggest that long-term exposure to air pollution might have a causal role in atherogenesis, but epidemiological findings are still inconsistent. We investigate whether urban particulate matter (PM) air pollution is associated with CIMT, a marker of subclinical atherosclerosis.

METHODS

We used baseline data (2000 to 2003) from the HNR (Heinz Nixdorf Recall) study, a population-based cohort of 4,814 participants, 45 to 75 years of age. We assessed residential long-term exposure to PM with a chemistry transport model and measured distance to high traffic. Multiple linear regression was used to estimate associations of air pollutants and traffic with CIMT, adjusting for each other, city of residence, age, sex, diabetes, and lifestyle variables.

RESULTS

Median CIMT of the 3,380 analyzed participants was 0.66 mm (interquartile range 0.16 mm). An interdecile range increase in PM(2.5) (4.2 μg/m(3)), PM(10) (6.7 μg/m(3)), and distance to high traffic (1,939 m) was associated with a 4.3% (95% confidence interval [CI]: 1.9% to 6.7%), 1.7% (95% CI: -0.7% to 4.1%), and 1.2% (95% CI: -0.2% to 2.6%) increase in CIMT, respectively.

CONCLUSIONS

Our study shows a clear association of long-term exposure to PM(2.5) with atherosclerosis. This finding strengthens the hypothesized role of PM(2.5) as a risk factor for atherogenesis.

Hazard identification of particulate matter on vasomotor dysfunction and progression of atherosclerosis

The development and use of nanoparticles have alerted toxicologists and regulators to issues of safety testing. By analogy with ambient air particles, it can be expected that small doses are associated with a small increase in risk of cardiovascular diseases, possibly through oxidative stress and inflammatory pathways. We have assessed the effect of exposure to particulate matter on progression of atherosclerosis and vasomotor function in humans, animals, and ex vivo experimental systems. The type of particles that have been tested in these systems encompass TiO(2), carbon black, fullerene C(60), single-walled carbon nanotubes, ambient air particles, and diesel exhaust particles. Exposure to ambient air particles is associated with accelerated progression of atherosclerosis and vasomotor dysfunction in both healthy and susceptible animal models and humans at risk of developing cardiovascular diseases. The vasomotor dysfunction includes increased vasoconstriction as well as reduced endothelium-dependent vasodilatation; endothelium-independent vasodilatation is often unaffected indicating mainly endothelial dysfunction. Pulmonary exposure to TiO(2), carbon black, and engineered nanoparticles generate vasomotor dysfunction; the effect size is similar to that generated by combustion-derived particles, although the effect could depend on the exposure period and the administered dose, route, and mode. The relative risk associated with exposure to nanoparticles may be small compared to some traditional risk factors for cardiovascular diseases, but superimposed on these and possible exposure to large parts of the population it is a significant public health concern. Overall, assessment of vasomotor dysfunction and progression of atherosclerosis are promising tools for understanding the effects of particulate matter.

The relationship of air pollution and surrogate markers of endothelial dysfunction in a population-based sample of children

Background

This study aimed to assess the relationship of air pollution and plasma surrogate markers of endothelial dysfunction in the pediatric age group.

Methods

This cross-sectional study was conducted in 2009-2010 among 125 participants aged 10-18 years. They were randomly selected from different areas of Isfahan city, the second large and air-polluted city in Iran. The association of air pollutants' levels with serum thrombomodulin (TM) and tissue factor (TF) was determined after adjustment for age, gender, anthropometric measures, dietary and physical activity habits.

Results

Data of 118 participants was complete and was analyzed. The mean age was 12.79 (2.35) years. The mean pollution standards index (PSI) value was at moderate level, the mean particular matter measuring up to 10 μm (PM₁₀) was more than twice the normal level. Multiple linear regression analysis showed that TF had significant relationship with all air pollutants except than carbon monoxide, and TM had significant inverse relationship with ozone. The odds ratio of elevated TF was significantly higher in the upper vs. the lowest quartiles of PM₁₀, ozone and PSI. The corresponding figures were in opposite direction for TM.

Conclusions

The relationship of air pollutants with endothelial dysfunction and pro-coagulant state can be an important factor in the development of atherosclerosis from early life. This finding should be confirmed in future longitudinal studies. Concerns about the harmful effects of air pollution on children's health should be considered a top priority for public health policy; it should be underscored in primordial and primary prevention of chronic diseases.