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

Ozone exposure and cardiovascular disease: A narrative review of epidemiology evidence and underlying mechanisms

Ozone (O3) poses a significant global public health concern as it exerts adverse effects on human cardiovascular health. Nevertheless, there remains a lack of comprehensive understanding regarding the relationships between O3 exposure and the risk of cardiovascular diseases (CVD), as well as the underlying biological mechanisms. To address this knowledge gap, this narrative review meticulously summarizes the existing epidemiological evidence, susceptibility, and potential underlying biological mechanisms linking O3 exposure with CVD. An increasing body of epidemiological studies has demonstrated that O3 exposure heightens the incidence and mortality of CVD, including specific subtypes such as ischemic heart disease, hypertension, and heart failure. Certain populations display heightened vulnerability to these effects, particularly children, the elderly, obese individuals, and those with pre-existing conditions. Proposed biological mechanisms suggest that O3 exposure engenders respiratory and systemic inflammation, oxidative stress, disruption of autonomic nervous and neuroendocrine systems, as well as impairment of coagulation function, glucose, and lipid metabolism. Ultimately, these processes contribute to vascular dysfunction and the development of CVD. However, some studies have reported the absence of associations between O3 and CVD, or even potentially protective effects of O3. Inconsistencies among the literature may be attributed to inaccurate assessment of personal O3 exposure levels in epidemiologic studies, as well as confounding effects stemming from co-pollutants and temperature. Consequently, our findings underscore the imperative for further research, including the development of reliable methodologies for assessing personal O3 exposure, exploration of O3 exposure's impact on cardiovascular health, and elucidation of its biological mechanisms. These endeavors will consolidate the causal relationship between O3 and cardiovascular diseases, subsequently aiding efforts to mitigate the risks associated with O3 exposure.

Impact of childhood exposure to traffic related air pollution on adult cardiometabolic health: Exploring the role of perceived stress

BACKGROUND

Little is known about how childhood exposure to traffic-related air pollution (TRAP) and stress interact to affect adults' cardiometabolic health. We examined this interaction and assessed the impact of over 10 years of childhood TRAP exposure on cardiometabolic health.

METHODS

From 2018 to 2023, 313 young adults from the Southern California Children's Health Study were enrolled in a follow-up assessment. Using CALINE4 line source dispersion model, average childhood TRAP exposures (from pregnancy to age 13) were estimated for nitrogen oxides (NOx) from all roads. Traffic density was calculated within a 300-m residential buffer. Cardiometabolic health was assessed in adulthood (mean age 24 ± 1.7) based on blood lipids (total cholesterol, high- and low-density lipoprotein [HDL, LDL], triglycerides), glucose metabolism (fasting glucose, fasting insulin, HbA1c), body composition (BMI, android/gynoid ratio [AG ratio], percent body fat), and blood pressure. A PDAY (Pathobiologic Determinants of Atherosclerosis in Youth) score was generated to evaluate overall cardiometabolic health. Participants' perceived stress was assessed in childhood and adulthood (ages 13 and 24 years, respectively).

RESULTS

Results of mixed effects linear models, adjusted for demographics and smoking status, suggested that each standard deviation increase in childhood exposure to traffic-related total NOx was associated with 0.62 increase in PDAY score (95% Confidence Interval [CI]:0.10,1.14), 0.09% increase in HbA1c (95%CI: 0.04, 0.15), 1.19% increase in percent body fat (95%CI: 0.18, 2.20), and 0.96 kg/m2 increase in BMI (0.11, 1.80) in adulthood. Among participants with higher childhood stress levels, we observed significant associations of traffic-related total NOx with total cholesterol, HDL, LDL, HbA1c, insulin, and BMI. None of these associations were significant among people with lower stress levels. We observed similar statistically significant associations of traffic density.

CONCLUSION

Long-term childhood exposure to TRAP in childhood may have lasting adverse impacts on cardiometabolic health, especially for children with higher stress levels.

Insights into elastic fiber fragmentation: Mechanisms and treatment of aortic aneurysm in Marfan syndrome

Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder caused by mutations in fibrillin 1 (FBN1) gene. These mutations result in defects in the skeletal, ocular, and cardiovascular systems. Aortic aneurysm is the leading cause of premature mortality in untreated MFS patients. Elastic fiber fragmentation in the aortic vessel wall is a hallmark of MFS-associated aortic aneurysms. FBN1 mutations result in FBN1 fragments that also contribute to elastic fiber fragmentation. Although recent research has advanced our understanding of MFS, the contribution of elastic fiber fragmentation to the pathogenesis of aneurysm formation remains poorly understood. This review provides a comprehensive overview of the molecular mechanisms of elastic fiber fragmentation and its role in the pathogenesis of aortic aneurysm progression. Increased comprehension of elastic fragmentation has significant clinical implications for developing targeted interventions to block aneurysm progression, which would benefit not only individuals with Marfan syndrome but also other patients with aneurysms. Moreover, this review highlights an overlooked connection between inhibiting aneurysm and the restoration of elastic fibers in the vessel wall with various aneurysm inhibitors, including drugs and chemicals. Investigating the underlying molecular mechanisms could uncover innovative therapeutic strategies to inhibit elastin fragmentation and prevent the progression of aneurysms.

Pollution from fine particulate matter and atherosclerosis: A narrative review

According to the WHO, the entire global population is exposed to air pollution levels higher than recommended for health preservation. Air pollution is a complex mixture of nano- to micro-sized particles and gaseous components that poses a major global threat to public health. Among the most important air pollutants, causal associations have been established between particulate matter (PM), mainly < 2.5 μm, and cardiovascular diseases (CVD), i.e., hypertension, coronary artery disease, ischemic stroke, congestive heart failure, arrhythmias as well as total cardiovascular mortality. Aim of this narrative review is to describe and critically discuss the proatherogenic effects of PM_2.5 that have been attributed to many direct or indirect effects comprising endothelial dysfunction, a chronic low-grade inflammatory state, increased production of reactive oxygen species, mitochondrial dysfunction and activation of metalloproteases, all leading to unstable arterial plaques. Higher concentrations of air pollutants are associated with the presence of vulnerable plaques and plaque ruptures witnessing coronary artery instability. Air pollution is often disregarded as a CVD risk factor, in spite of the fact that it is one of the main modifiable factors relevant for prevention and management of CVD. Thus, not only structural actions should be taken in order to mitigate emissions, but health professionals should also take care to counsel patients on the risks of air pollution.

Modern Concepts of the Role of Fine Particles (PM 2.5) in the Genesis of Atherosclerosis and Myocardial Damage: Clinical and Epidemiological Data, the Main Pathophysiological Mechanisms

Due to the fact that atherosclerotic cardiovascular diseases (CVDs) dominate in the structure of morbidity, disability and mortality of the population, the study of the risk factors for the development of atherosclerotic CVDs, as well as the study of the underlying pathogenetic mechanisms thereof, is the most important area of scientific research in modern medicine. Understanding these aspects will allow improving the set of treatment and preventive measures and activities. One of the important risk factors for the development of atherosclerosis, which has been actively studied recently, is air pollution with fine particulate matter (PM 2.5). According to clinical and epidemiological data, the level of air pollution with PM 2.5 exceeds the normative indicators in most regions of the world and is associated with subclinical markers of atherosclerosis and mortality from atherosclerotic CVDs. The aim of this article is to systematize and discuss in detail the role of PM 2.5 in the development of atherosclerosis and myocardial damage with the consideration of epidemiological and pathogenetic aspects. Materials and Methods: This narrative review is based on the analysis of publications in the Medline, PubMed, and Embase databases. The terms "fine particles" and "PM 2.5" in combination with "pathophysiological mechanisms," "cardiovascular diseases", "atherosclerosis", "cardiac troponins", "myocardial damage" and "myocardial injury" were used to search publications. Conclusion: According to the conducted narrative review, PM 2.5 should be regarded as the significant risk factor for the development of atherosclerotic CVDs. The pro-atherogenic effect of fine particulate matter is based on several fundamental and closely interrelated pathophysiological mechanisms: endothelial dysfunction, impaired lipid metabolism, increased oxidative stress and inflammatory reactions, impaired functioning of the vegetative nervous system and increased activity of the hemostatic system. In addition, PM 2.5 causes subclinical damage to cardiac muscle cells by several mechanisms: apoptosis, oxidative stress, decreased oxygen delivery due to coronary atherosclerosis and ischemic damage of cardiomyocytes. Highly sensitive cardiac troponins are promising markers for detecting subclinical myocardial damage in people living in polluted regions.

The Role of Fine Particles (PM 2.5) in the Genesis of Atherosclerosis and Myocardial Damage: Emphasis on Clinical and Epidemiological Data, and Pathophysiological Mechanisms

Due to the fact that atherosclerotic cardiovascular diseases (CVDs) dominate in the structure of morbidity, disability and mortality of the population, the study of the risk factors for the development of atherosclerotic CVDs, as well as the study of the underlying pathogenetic mechanisms thereof, is the most important area of scientific research in modern medicine. Understanding these aspects will allow to improve the set of treatment and preventive measures and activities. One of the important risk factors for the development of atherosclerosis, which has been actively studied recently, is air pollution with fine particulate matter (PM 2.5). According to clinical and epidemiological data, the level of air pollution with PM 2.5 exceeds the normative indicators in most regions of the world and is associated with subclinical markers of atherosclerosis and mortality from atherosclerotic CVDs. The aim of this article is to systematize and discuss in detail the role of PM 2.5 in the development of atherosclerosis and myocardial damage.

Urban Air Pollution and Subclinical Atherosclerosis in Adolescents and Young Adults

PURPOSE

The contribution of air pollution to subclinical atherosclerosis in a young population remains limited. This study aimed to assess whether long-term exposure to urban air pollutants increases carotid intima-media thickness (CIMT) in adolescents and young adults.

METHODS

This study included 789 subjects between the ages of 12 and 30 years who lived in the Taipei metropolis from a cohort of young Taiwanese individuals. Residential addresses were geocoded, and annual average concentrations of particulate matter (PM) of different diameters, e.g., PM₁₀, PM_2.5-10, PM_2.5, and nitrogen oxides (NO_X), were assessed using land use regression models. The generalized least squares strategy with error term to consider the cluster effect of living addresses between individuals was used to examine the associations between urban air pollution and CIMTs.

RESULTS

After adjusting for potential confounders, we found that interquartile range increases in PM_2.5 (8.2 μg/m³) and NO_X (17.5 μg/m³) were associated with 0.46% (95% CI: 0.02-0.90) and 1.00% (95% CI: 0.10-1.91) higher CIMTs, respectively. Stratified analyses showed that the relationships between CIMT and PM_2.5 and NO_X were more evident in subjects who were 18 years or older, female, nonsmoking, nonhypertensive, and nonhyperglycemic than in their respective counterparts.

DISCUSSION

Long-term exposure to PM_2.5 and NO_X is associated with subclinical atherosclerosis in a young population. Age, sex, and health status may influence the vulnerability of air pollution-associated subclinical atherosclerosis.

Long-term exposure to ozone and cardiovascular mortality in a large Chinese cohort

BACKGROUND

Evidence for the association between long-term exposure to ozone (O₃) and cause-specific cardiovascular disease (CVD) mortality is inconclusive, and this association has rarely been evaluated at high O₃ concentrations.

OBJECTIVES

We aim to evaluate the associations between long-term O₃ exposure and cause-specific CVD mortality in a Chinese population.

METHODS

From 2009 to 2018, 744,882 subjects (median follow-up of 7.72 years) were included in the CHinese Electronic health Records Research in Yinzhou (CHERRY) study. The annual average concentrations of O₃ and fine particulate matter (PM_2.5), which were estimated using grids with a resolution up to 1 × 1 km, were assigned to the community address for each subject. The outcomes were deaths from CVD, ischemic heart disease (IHD), myocardial infarction (MI), stroke, and hemorrhagic/ischemic stroke. Time-varying Cox model adjusted for PM_2.5 and individual-level covariates was used.

RESULTS

The mean of annual average O₃ concentrations was 68.05 μg/m³. The adjusted hazard ratio per 10 μg/m³ O₃ increase was 1.22 (95% confidence interval [CI]: 1.13-1.33) for overall CVD mortality, 1.08 (0.91-1.29) for IHD, 1.21 (0.90-1.63) for MI, 1.28 (1.15-1.43) for overall stroke, 1.39 (1.16-1.67) for hemorrhagic stroke and 1.22 (1.00-1.49) for ischemic stroke, respectively. The study showed that subjects without hypertension had a higher risk for CVD mortality associated with long-term O₃ exposure (1.66 vs. 1.15, p = 0.01).

CONCLUSIONS

We observed the association between long-term exposure to high O₃ concentrations and cause-specific CVD mortality in China, independent of PM_2.5 and other CVD risk factors. This suggested an urgent need to control O₃ pollution, especially in developing countries.

Urban Fine Particulate Matter and Elements Associated with Subclinical Atherosclerosis in Adolescents and Young Adults

The relationships between the elemental constituents of PM_2.5 and atherosclerosis remain limited, especially in young populations. This study included 755 subjects aged 12-30 years in the Taipei metropolis. A land use regression model was used to estimate residential annual mean concentrations of PM_2.5 and eight elemental constituents. We evaluated the percent differences in carotid intima-media thickness (CIMT) with PM_2.5 and elemental constituent exposures by linear regressions. Interquartile range increments for PM_2.5 (4.5 μg/m³), sulfur (108.6 ng/m³), manganese (2.0 ng/m³), iron (34.5 ng/m³), copper (3.6 ng/m³), and zinc (20.7 ng/m³) were found to associate with 0.92% (95% confidence interval (CI): 0.17-1.66), 0.51% (0.02-1.00), 0.36% (0.05-0.67), 0.98% (0.15-1.82), 0.74% (0.01-1.48), and 1.20% (0.33-2.08) higher CIMTs, respectively. Factor analysis identified four air pollution source-related factors, and the factors interpreted as traffic and industry sources were associated with higher CIMTs. Stratified analyses showed the estimates were more evident in subjects who were ≥18 years old, females, or who had lower household income. Our study results provide new insight into the impacts of source-specific air pollution, and future research on source-specific air pollution effects in young populations, especially in vulnerable subpopulations, is warranted.

Quantile regression to examine the association of air pollution with subclinical atherosclerosis in an adolescent population

BACKGROUND

Air pollution has been associated with carotid intima-media thickness test (CIMT), a marker of subclinical atherosclerosis. To our knowledge, this is the first study to report an association between ambient air pollution and CIMT in a younger adolescent population.

OBJECTIVE

To investigate the associations beyond standard mean regression by using quantile regression to explore if associations occur at different percentiles of the CIMT distribution.

METHODS

We measured CIMT cross-sectionally at the age of 16 years in 363 adolescents participating in the Dutch PIAMA birth cohort. We fit separate quantile regressions to examine whether the associations of annual averages of nitrogen dioxide (NO₂), fine particulate matter (PM_2.5), PM_2.5 absorbance (a marker for black carbon), PM_coarse and ultrafine particles up to age 14 assigned at residential addresses with CIMT varied across deciles of CIMT. False discovery rate corrections (FDR, p < 0.05 for statistical significance) were applied for multiple comparisons. We report quantile regression coefficients that correspond to an average change in CIMT (µm) associated with an interquartile range increase in the exposure.

RESULTS

PM_2.5 absorbance exposure at birth was statistically significantly (FDR < 0.05) associated with a 6.23 µm (95% CI: 0.15, 12.3) higher CIMT per IQR increment in PM_2.5 absorbance in the 10th quantile of CIMT but was not significantly related to other deciles within the CIMT distribution. For NO₂ exposure we found similar effect sizes to PM_2.5 absorbance, but with much wider confidence intervals. PM_2.5 exposure was weakly positively associated with CIMT while PM_coarse and ultrafine did not display any consistent patterns.

CONCLUSIONS

Early childhood exposure to ambient air pollution was suggestively associated with the CIMT distribution during adolescence. Since CIMT increases with age, mitigation strategies to reduce traffic-related air pollution early in life could possibly delay atherosclerosis and subsequently CVD development later in life.

Childhood traffic-related air pollution and adverse changes in subclinical atherosclerosis measures from childhood to adulthood

BACKGROUND

Chronic exposure to air pollutants is associated with increased risk of cardiovascular disease (CVD) among adults. However, little is known about how air pollution may affect the development of subclinical atherosclerosis in younger populations. Carotid artery intima-media thickness (CIMT) is a measure of subclinical atherosclerosis that provides insight into early CVD pathogenesis.

METHODS

In a pilot study of 70 participants from the Southern California Children's Health Study, we investigated CIMT progression from childhood to adulthood. Using carotid artery ultrasound images obtained at age 10 and follow-up images at age 21-22, we examined associations between childhood ambient and traffic-related air pollutants with changes in CIMT over time and attained adult CIMT using linear mixed-effects models adjusted for potential confounders. Average residential childhood exposures (i.e., birth to time of measurement at 10-11 years) were assigned for regional, ambient pollutants (ozone, nitrogen dioxide, particulate matter, interpolated from regulatory air monitoring data) and traffic-related nitrogen oxides (NO_x) by road class (modeled using the CALINE4 line source dispersion model). Traffic density was calculated within a 300-m residential buffer.

RESULTS

For each 1 standard deviation (SD) increase in childhood traffic-related total NO_x exposure, we observed greater yearly rate of change in CIMT from childhood to adulthood (β: 2.17 μm/yr, 95% CI: 0.78-3.56). Increases in annual rate of CIMT change from childhood to adulthood also were observed with freeway NO_x exposure (β: 2.24 μm/yr, 95% CI: 0.84-3.63) and traffic density (β: 2.11 μm/yr, 95% CI: 0.79-3.43). Traffic exposures were also related to increases in attained CIMT in early adulthood. No associations of CIMT change or attained level were observed with ambient pollutants.

CONCLUSIONS

Overall, we observed adverse changes in CIMT over time in relation to childhood traffic-related NO_x exposure and traffic density in our study population. While these results must be cautiously interpreted given the limited sample size, the observed associations of traffic measures with CIMT suggest a need for future studies to more fully explore this relationship.

Gradient-Based Colorimetric Array Sensor for Continuous Monitoring of Multiple Gas Analytes

Colorimetry is widely used in chemical sensing due to its high sensitivity and high selectivity. However, most colorimetric sensors are one-time use because the color-producing reactions or bindings are usually irreversible. In addition, traditional colorimetric sensors like the detection tubes are bulky and packed individually, making parallel sensing of multiple analytes difficult. Here, we demonstrate a gradient-based colorimetric array sensor (GCAS) to overcome these limitations. Different colorimetric sensing elements are inkjet-printed as parallel straight lines on a porous substrate. Lateral transport of analytes across the substrate creates color gradients on the sensing elements. The color gradients shift along the transport direction over time, and GCAS tracks the gradient shifts and converts them into analyte concentrations in real time. Using a low-cost complementary metal-oxide semiconductor imager, we show detection of three air pollutants using a single GCAS chip and 24 h continuous monitoring of ambient ozone.

The critical role of endothelial function in fine particulate matter-induced atherosclerosis

Ambient and indoor air pollution contributes annually to approximately seven million premature deaths. Air pollution is a complex mixture of gaseous and particulate materials. In particular, fine particulate matter (PM2.5) plays a major mortality risk factor particularly on cardiovascular diseases through mechanisms of atherosclerosis, thrombosis and inflammation. A review on the PM2.5-induced atherosclerosis is needed to better understand the involved mechanisms. In this review, we summarized epidemiology and animal studies of PM2.5-induced atherosclerosis. Vascular endothelial injury is a critical early predictor of atherosclerosis. The evidence of mechanisms of PM2.5-induced atherosclerosis supports effects on vascular function. Thus, we summarized the main mechanisms of PM2.5-triggered vascular endothelial injury, which mainly involved three aspects, including vascular endothelial permeability, vasomotor function and vascular reparative capacity. Then we reviewed the relationship between PM2.5-induced endothelial injury and atherosclerosis. PM2.5-induced endothelial injury associated with inflammation, pro-coagulation and lipid deposition. Although the evidence of PM2.5-induced atherosclerosis is undergoing continual refinement, the mechanisms of PM2.5-triggered atherosclerosis are still limited, especially indoor PM2.5. Subsequent efforts of researchers are needed to improve the understanding of PM2.5 and atherosclerosis. Preventing or avoiding PM2.5-induced endothelial damage may greatly reduce the occurrence and development of atherosclerosis.

Health Effects of Ozone on Respiratory Diseases

Ozone is known to cause bronchial inflammation and airway hyper-responsiveness via oxidative injury and inflammation. While other ambient air pollutants such as particulate matter (PM) and nitrogen dioxide showed decreasing trends in mean annual concentrations, ozone concentrations have not declined recently in most countries across the world. Short-term exposure to high concentrations of ozone has been associated with increased mortality and cardiovascular and respiratory morbidity in many regions of the world. However, the long-term effects of ozone have been less investigated than the short-term exposure due to the difficulty in modeling ozone exposure and linking between individual exposures and health outcome data. A recently developed model of ozone exposure enabled the investigation of long-term ozone effects on health outcomes. Recent findings suggested that long-term exposure to ozone was associated with an increased risk of cardiovascular and respiratory mortality. Longitudinal studies using large cohorts also revealed that long-term exposure to ozone was associated with a greater decline in lung function and the progression of emphysema. The development of long-term standards for ozone as well as PM should be considered to protect the respiratory health of the general population and people with chronic respiratory diseases.

Long-term exposure to air pollution and atherosclerosis in the carotid arteries in the Malmö diet and cancer cohort

BACKGROUND

Long-term exposure to air pollution increases the risk of cardiovascular morbidity and mortality, but the mechanisms are not fully known. Current evidence suggests that air pollution exposure contributes to the development of atherosclerosis. There are few studies investigating associations between air pollution and carotid plaques, a well-known precursor of cardiovascular disease.

METHODS

A Swedish population-based cohort (aged 45-64 years at recruitment) was randomly selected from the Malmö Diet and Cancer study between 1991 and 1994, of which 6103 participants underwent ultrasound examination of the right carotid artery to determine carotid plaque presence and carotid intima media thickness (CIMT). Participants were assigned individual residential air pollution exposure (source-specific PM_2.5, PM₁₀, NO_x, BC) at recruitment from Gaussian dispersion models. Logistic and linear regression models, adjusted for potential confounders and cardiovascular risk factors, were used to investigate associations between air pollutants and prevalence of carotid plaques, and CIMT, respectively.

RESULTS

The prevalence of carotid plaques was 35%. The mean levels of PM_2.5 and PM₁₀ at recruitment were 11 and 14 μg/m³, most of which was due to long range transport. The exposure contrast within the cohort was relatively low. PM_2.5 exposure was associated with carotid plaques in a model including age and sex only (OR 1.10 (95% CI 1.01-1.20) per 1 μg/m³), but after adjustment for cardiovascular risk factors and socioeconomic status (SES) the association was weak and not significant (OR 1.05 (95% CI 0.96-1.16) per 1 μg/m³). The pattern was similar for PM₁₀ and NO_x exposure. Associations between air pollutants and plaques were slightly stronger for long-term residents and in younger participants with hypertension. There was no clear linear trend between air pollution exposure and plaque prevalence. Non-significant slightly positive associations were seen between air pollution exposures and CIMT.

CONCLUSIONS

In this large, well-controlled cross-sectional study at low exposure levels we found no significant associations between air pollution exposures and subclinical atherosclerosis in the carotid arteries, after adjusting for cardiovascular risk factors and SES. Further epidemiological studies of air pollution and intermediate outcomes are needed to explain the link between air pollution and cardiovascular events.

Residential Exposure to PM2.5 and Ozone and Progression of Subclinical Atherosclerosis Among Women Transitioning Through Menopause: The Study of Women's Health Across the Nation

Objective: This article aims to examine the association between long-term ambient air pollution and progression of subclinical atherosclerosis with 2-year follow-up among midlife women from the Study of Women's Health Across the Nation (SWAN). Materials and Methods: Carotid duplex ultrasonography was performed in participants from a SWAN ancillary study carried out at the Pittsburgh and Chicago sites. Mean and maximum carotid intima-media thickness (CIMT) and plaque burden were assessed throughout the common, bulb, and internal carotid artery. The yearly mean exposure to PM2.5 (particulate matter) and ozone was generated based on monitors within 20 km of the participants' home. The effect of air pollutants during follow-up on progression of CIMT was estimated using linear mixed-effects models, and the effect on progression of plaque presence and plaque index, a measure of extent of plaque, was evaluated using logistic regression. Results: This study included 417 (257 White and 160 Black) women with a mean age of 51 years at baseline. A 1 μg/m3 higher yearly mean exposure to PM2.5 during follow-up was associated with a 4.28 (95% confidence interval [CI]: 0.02-8.54) μm/year increase in maximum CIMT, after adjusting for socioeconomic and traditional cardiovascular disease (CVD) risk factors. Exposure to PM2.5 contributed to a 30% (95% CI: 3%-65%) higher odds of plaque index progression adjusting for socioeconomic factors only. Conclusions: PM2.5 independently contributed to progression of subclinical atherosclerosis, among women transitioning through menopause, a time of increasing CVD risk. Yet no significant associations between ozone and subclinical atherosclerosis were observed.

Long-Term Exposure to Ambient Ozone and Progression of Subclinical Arterial Disease: The Multi-Ethnic Study of Atherosclerosis and Air Pollution

BACKGROUND

Long-term ozone ([Formula: see text]) exposure is associated with cardiovascular mortality, but little is known about the associations between [Formula: see text] and subclinical arterial disease.

OBJECTIVES

We studied the longitudinal association of exposure to [Formula: see text] and progression of key subclinical arterial markers in adults: intima-media thickness of common carotid artery ([Formula: see text]), carotid plaque (CP) burden, and coronary artery calcification (CAC).

METHODS

CAC was measured one to four times at baseline and at follow-up exams (1999–2012) by computed tomography (CT) in 6,619 healthy adults, recruited at age 45-84 y without cardiovascular disease (CVD), over a mean of 6.5 y (standard deviation: 3.5 y). [Formula: see text] and CP burden were quantified in 3,392 participants using carotid artery ultrasound imaging acquired over a mean of 9 y (1.7 y). Over 91% and 89% participants had at least one follow-up [Formula: see text] and CAC measurement, respectively. Residence-specific [Formula: see text] concentrations were estimated by a validated spatiotemporal model spanning from 1999 to 2012. This model relied on comprehensive monitoring data and geographical variables to predict individualized long-term average concentrations since baseline. Linear mixed models and logistic regression model were used to evaluate relationships of long-term average exposure to [Formula: see text] with longitudinal change in [Formula: see text], CAC, and CP formation, respectively.

RESULTS

Mean progression rates of [Formula: see text] and CAC were [Formula: see text] and [Formula: see text]. CP formation was identified in 55% of the subjects. A [Formula: see text] increase in long-term average [Formula: see text] exposure was associated with a [Formula: see text] [95% confidence interval (CI): 1.4, 9.7] greater increase in [Formula: see text] over 10 y. A [Formula: see text] increase in [Formula: see text] was also associated with new CP formation [odds ratio (OR): 1.2 (95% CI: 1.1, 1.4)] but not CAC progression [[Formula: see text] (95% CI: [Formula: see text], 2)]. Associations were robust in the analysis with extended covariate adjustment, including copollutants, i.e., nitrogen oxides ([Formula: see text]) and particulate matter with diameter [Formula: see text] ([Formula: see text]).

CONCLUSION

Over almost a decade of follow-up, outdoor [Formula: see text] concentrations were associated with increased rate of carotid wall thickness progression and risk of new plaque formation, suggesting arterial injury in this cohort. https://doi.org/10.1289/EHP3325.

Five-year exposure to PM2.5 and ozone and subclinical atherosclerosis in late midlife women: The Study of Women's Health Across the Nation

INTRODUCTION

Effects of more than one-year exposure to air pollution on atherosclerosis is seldom studied. This paper aims to examine the association between five-year exposure to particulate matter ≤2.5 μm (PM_2.5), ozone (O₃) and atherosclerosis observed about seven years later in late midlife women.

MATERIAL AND METHODS

This study was conducted among 1188 women of the Study of Women's Health Across the Nation (SWAN) from five sites, Detroit, MI; Oakland, CA; Pittsburgh, PA; Chicago, IL; and Newark, NJ, with available data on both air pollutant exposure and carotid ultrasound scans. Five-year mean annualized exposure levels of two air pollutants, PM_2.5 and ozone (O₃), were collected during 5 SWAN visits (1999-2005) from monitors 20 km within the participant's residential address. Linear regression models were used to estimate the association of prior five-year mean annualized exposure to PM_2.5 and O₃ with common carotid intima-media thickness (cIMT) and inter-adventitial diameter (IAD) examined approximately seven years later (2009-2013). Logistic and multinomial logistic regressions were applied to assess the associations of air pollutants with plaque presence and plaque index, respectively.

RESULTS

At time of carotid ultrasound scan, women were on average 59.6 (±2.7) years old and a majority was postmenopausal (88.4%). The women were White (48.4%), Black (31.2%), Chinese (13.3%) and Hispanic (7.1%). A 1 μg/m³ higher 5-year mean annualized exposure to PM_2.5 was associated with an 8.0 μm (95% CI: 1.0-15.1) greater maximum cIMT at a later mid-life, adjusting for cardiovascular disease risk factors; but was only related to IAD after adjusting for site. No association was found between either pollutant and plaque presence or plaque index.

CONCLUSIONS

Long-term exposure to PM_2.5 may contribute to elevated risk of atherosclerosis in the post-menopausal period.

Clinical effects of air pollution on the central nervous system; a review

The purpose of this review is to describe recent clinical and epidemiological studies examining the adverse effects of urban air pollution on the central nervous system (CNS). Air pollution and particulate matter (PM) are associated with neuroinflammation and reactive oxygen species (ROS). These processes affect multiple CNS pathways. The conceptual framework of this review focuses on adverse effects of air pollution with respect to neurocognition, white matter disease, stroke, and carotid artery disease. Both children and older individuals exposed to air pollution exhibit signs of cognitive dysfunction. However, evidence on middle-aged cohorts is lacking. White matter injury secondary to air pollution exposure is a putative mechanism for neurocognitive decline. Air pollution is associated with exacerbations of neurodegenerative conditions such as Alzheimer's and Parkinson's diseases. Increases in stroke incidences and mortalities are seen in the setting of air pollution exposure and CNS pathology is robust. Large populations living in highly polluted environments are at risk. This review aims to outline current knowledge of air pollution exposure effects on neurological health.

Integrated assessment of exposure to PM2.5 in South India and its relation with cardiovascular risk: Design of the CHAI observational cohort study

While there is convincing evidence that fine particulate matter causes cardiovascular mortality and morbidity, little of the evidence is based on populations outside of high income countries, leaving large uncertainties at high exposures. India is an attractive setting for investigating the cardiovascular risk of particles across a wide concentration range, including concentrations for which there is the largest uncertainty in the exposure-response relationship. CHAI is a European Research Council funded project that investigates the relationship between particulate air pollution from outdoor and household sources with markers of atherosclerosis, an important cardiovascular pathology. The project aims to (1) characterize the exposure of a cohort of adults to particulate air pollution from household and outdoor sources (2) integrate information from GPS, wearable cameras, and continuous measurements of personal exposure to particles to understand where and through which activities people are most exposed and (3) quantify the association between particles and markers of atherosclerosis. CHAI has the potential to make important methodological contributions to modeling air pollution exposure integrating outdoor and household sources as well as in the application of wearable camera data in environmental exposure assessment.

Ambient Air Pollutant Exposures and Hospitalization for Kawasaki Disease in Taiwan: A Case-Crossover Study (2000-2010)

BACKGROUND

Kawasaki disease (KD) is an acute and multi-systemic vasculitis that occurs predominantly in infants and young children. Although the etiological agent of KD remains unclear, limited studies have reported that windborne environmental factors may trigger KD.

OBJECTIVES

We conducted a time-stratified case-crossover study to assess the associations between air pollutants and KD in Taiwan.

METHODS

We identified children < 5 years old with a diagnosis of KD from the Longitudinal Health Insurance Database 2000 (LHID2000) between 2000 and 2010. We obtained data regarding carbon monoxide (CO), nitrogen dioxide (NO₂), ozone (O₃), particulate matter with aerodynamic diameter < 10 μm (PM₁₀), and sulfate dioxide (SO₂) from 70 monitoring stations and used inverse distance weighting to calculate average daily exposures for the residential postal code of each case. We performed conditional logistic regression to estimate associations between KD and each air pollutant according to interquartile range (IQR) increases and quartiles of exposure on the day of hospitalization versus 3-4 reference days during the same month for each case. Additionally, we estimated associations with single-day exposures lagged 1-2 days.

RESULTS

We identified 695 KD hospital admissions during the study period. An IQR increase (28.73 ppb) of O₃ was positively associated with KD after adjusting for temperature, humidity, northward wind, and eastward wind [adjusted odds ratio = 1.21; 95% confidence interval (CI): 1.01, 1.44]. There were no significant associations between KD and CO, NO₂, PM₁₀, or SO₂. The association with O₃ was limited to exposure on the day of hospitalization and to exposure during the summer months (June-August).

CONCLUSIONS

Our results provide new evidence that exposure to O₃ may increase the risk of KD in children. However, further investigation is needed to confirm the association and identify a potential biological mechanism.

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.

A hybrid model for spatially and temporally resolved ozone exposures in the continental United States

Ground-level ozone is an important atmospheric oxidant, which exhibits considerable spatial and temporal variability in its concentration level. Existing modeling approaches for ground-level ozone include chemical transport models, land-use regression, Kriging, and data fusion of chemical transport models with monitoring data. Each of these methods has both strengths and weaknesses. Combining those complementary approaches could improve model performance. Meanwhile, satellite-based total column ozone, combined with ozone vertical profile, is another potential input. The authors propose a hybrid model that integrates the above variables to achieve spatially and temporally resolved exposure assessments for ground-level ozone. The authors used a neural network for its capacity to model interactions and nonlinearity. Convolutional layers, which use convolution kernels to aggregate nearby information, were added to the neural network to account for spatial and temporal autocorrelation. The authors trained the model with the Air Quality System (AQS) 8-hr daily maximum ozone in the continental United States from 2000 to 2012 and tested it with left out monitoring sites. Cross-validated R² on the left out monitoring sites ranged from 0.74 to 0.80 (mean 0.76) for predictions on 1 km × 1 km grid cells, which indicates good model performance. Model performance remains good even at low ozone concentrations. The prediction results facilitate epidemiological studies to assess the health effect of ozone in the long term and the short term.

IMPLICATIONS

Ozone monitors do not provide full data coverage over the United States, which is an obstacle to assess the health effect of ozone when monitoring data are not available. This paper used a hybrid approach to combine satellite-based ozone measurements, chemical transport model simulations, land-use terms, and other auxiliary variables to obtain spatially and temporally resolved ground-level ozone estimation.

Prenatal Air Pollution Exposures, DNA Methyl Transferase Genotypes, and Associations with Newborn LINE1 and Alu Methylation and Childhood Blood Pressure and Carotid Intima-Media Thickness in the Children's Health Study

BACKGROUND

Although exposure to ambient air pollutants increases cardiovascular disease risk in adults little is known about the effects of prenatal exposure. Genetic variation and epigenetic alterations are two mechanisms that may influence the effects of early-life exposures on cardiovascular phenotypes.

OBJECTIVES

We investigated whether genetic and epigenetic variation modify associations between prenatal air pollution on markers of cardiovascular risk in childhood.

METHODS

We used linear regression analysis to investigate the associations between prenatal pollutants (PM2.5, PM10, NO2, O3), long interspersed nuclear elements (LINE1) and AluYb8 DNA methylation levels measured in newborn blood spot tests, and carotid intima-media thickness (CIMT) and blood pressure (BP) in 459 participants as part of the Children's Health Study. Interaction terms were also included to test for effect modification of these associations by genetic variation in methylation reprogramming genes.

RESULTS

Prenatal exposure to NO2 in the third trimester of pregnancy was associated with higher systolic BP in 11-year-old children. Prenatal exposure to multiple air pollutants in the first trimester was associated with lower DNA methylation in LINE1, whereas later exposure to O3 was associated with higher LINE1 methylation levels in newborn blood spots. The magnitude of associations with prenatal air pollution varied according to genotype for 11 SNPs within DNA methyltransferase 1 (DNMT1), DNA methyltransferase 3 Beta (DNMT3B), Tet methylcytosine dioxygenase 2 (TET2), and Thymine DNA glycosylase (TDG) genes. Although first-trimester O3 exposure was not associated with CIMT and systolic BP overall, associations within strata of DNMT1 or DNMT3B were observed, and the magnitude and the direction of these associations depended on DNMT1 genotypes.

CONCLUSIONS

Genetic and epigenetic variation in DNA methylation reprogramming genes and in LINE1 retrotransposons may play important roles in downstream cardiovascular consequences of prenatal air pollution exposure. Citation: Breton CV, Yao J, Millstein J, Gao L, Siegmund KD, Mack W, Whitfield-Maxwell L, Lurmann F, Hodis H, Avol E, Gilliland FD. 2016. Prenatal air pollution exposures, DNA methyl transferase genotypes, and associations with newborn LINE1 and Alu methylation and childhood blood pressure and carotid intima-media thickness in the Children's Health Study. Environ Health Perspect 124:1905-1912; http://dx.doi.org/10.1289/EHP181.

Effects of urban fine particulate matter and ozone on HDL functionality

BACKGROUND

Exposures to ambient particulate matter (PM) are associated with increased morbidity and mortality. PM2.5 (<2.5 μm) and ozone exposures have been shown to associate with carotid intima media thickness in humans. Animal studies support a causal relationship between air pollution and atherosclerosis and identified adverse PM effects on HDL functionality. We aimed to determine whether brief exposures to PM2.5 and/or ozone could induce effects on HDL anti-oxidant and anti-inflammatory capacity in humans.

METHODS

Subjects were exposed to fine concentrated ambient fine particles (CAP) with PM2.5 targeted at 150 μg/m(3), ozone targeted at 240 μg/m(3) (120 ppb), PM2.5 plus ozone targeted at similar concentrations, and filtered air (FA) for 2 h, on 4 different occasions, at least two weeks apart, in a randomized, crossover study. Blood was obtained before exposures (baseline), 1 h after and 20 h after exposures. Plasma HDL anti-oxidant/anti-inflammatory capacity and paraoxonase activity were determined. HDL anti-oxidant/anti-inflammatory capacity was assessed by a cell-free fluorescent assay and expressed in units of a HDL oxidant index (HOI). Changes in HOI (ΔHOI) were calculated as the difference in HOI from baseline to 1 h after or 20 h after exposures.

RESULTS

There was a trend towards bigger ΔHOI between PM2.5 and FA 1 h after exposures (p = 0.18) but not 20 h after. This trend became significant (p <0.05) when baseline HOI was lower (<1.5 or <2.0), indicating decreased HDL anti-oxidant/anti-inflammatory capacity shortly after the exposures. There were no significant effects of ozone alone or in combination with PM2.5 on the change in HOI at both time points. The change in HOI due to PM2.5 showed a positive trend with particle mass concentration (p = 0.078) and significantly associated with the slope of systolic blood pressure during exposures (p = 0.005).

CONCLUSIONS

Brief exposures to concentrated PM2.5 elicited swift effects on HDL anti-oxidant/anti-inflammatory functionality, which could indicate a potential mechanism for how particulate air pollution induces harmful cardiovascular effects.

Bayesian Maximum Entropy Integration of Ozone Observations and Model Predictions: A National Application

To improve ozone exposure estimates for ambient concentrations at a national scale, we introduce our novel Regionalized Air Quality Model Performance (RAMP) approach to integrate chemical transport model (CTM) predictions with the available ozone observations using the Bayesian Maximum Entropy (BME) framework. The framework models the nonlinear and nonhomoscedastic relation between air pollution observations and CTM predictions and for the first time accounts for variability in CTM model performance. A validation analysis using only noncollocated data outside of a validation radius rv was performed and the R(2) between observations and re-estimated values for two daily metrics, the daily maximum 8-h average (DM8A) and the daily 24-h average (D24A) ozone concentrations, were obtained with the OBS scenario using ozone observations only in contrast with the RAMP and a Constant Air Quality Model Performance (CAMP) scenarios. We show that, by accounting for the spatial and temporal variability in model performance, our novel RAMP approach is able to extract more information in terms of R(2) increase percentage, with over 12 times for the DM8A and over 3.5 times for the D24A ozone concentrations, from CTM predictions than the CAMP approach assuming that model performance does not change across space and time.

Prenatal Air Pollution Exposure and Early Cardiovascular Phenotypes in Young Adults

Exposure to ambient air pollutants increases risk for adverse cardiovascular health outcomes in adults. We aimed to evaluate the contribution of prenatal air pollutant exposure to cardiovascular health, which has not been thoroughly evaluated. The Testing Responses on Youth (TROY) study consists of 768 college students recruited from the University of Southern California in 2007–2009. Participants attended one study visit during which blood pressure, heart rate and carotid artery arterial stiffness (CAS) and carotid artery intima-media thickness (CIMT) were assessed. Prenatal residential addresses were geocoded and used to assign prenatal and postnatal air pollutant exposure estimates using the U.S. Environmental Protection Agency’s Air Quality System (AQS) database. The associations between CAS, CIMT and air pollutants were assessed using linear regression analysis. Prenatal PM₁₀ and PM_2.5 exposures were associated with increased CAS. For example, a 2 SD increase in prenatal PM_2.5 was associated with CAS indices, including a 5% increase (β = 1.05, 95% CI 1.00–1.10) in carotid stiffness index beta, a 5% increase (β = 1.05, 95% CI 1.01–1.10) in Young’s elastic modulus and a 5% decrease (β = 0.95, 95% CI 0.91–0.99) in distensibility. Mutually adjusted models of pre- and postnatal PM_2.5 further suggested the prenatal exposure was most relevant exposure period for CAS. No associations were observed for CIMT. In conclusion, prenatal exposure to elevated air pollutants may increase carotid arterial stiffness in a young adult population of college students. Efforts aimed at limiting prenatal exposures are important public health goals.

Causes of changes in carotid intima-media thickness: a literature review

Atherosclerosis causes significant morbidity and mortality. Carotid intima-media thickness (CIMT) predicts future cardiovascular and ischaemic stroke incidence. CIMT, a measure of atherosclerotic disease, can be reliably determined in vivo by carotid ultrasound. In this review, we determined that CIMT is associated with traditional cardiovascular risk factors such as age, sex, race, smoking, alcohol consumption, habitual endurance exercise, blood pressure, dyslipidemia, dietary patterns, risk-lowering drug therapy, glycemia, hyperuricemia, obesity-related anthropometric parameters, obesity and obesity-related diseases. We also found that CIMT is associated with novel risk factors, including heredity, certain genotypic indices, anthropometric cardiovascular parameters, rheumatoid arthritis, immunological diseases, inflammatory cytokines, lipid peroxidation, anthropometric hemocyte parameters, infectious diseases, vitamin D, matrix metalloproteinases, and other novel factors and diseases. However, the conclusions are inconsonant; the underlying causes of these associations remain to be further explored.

Development of Long-term Spatiotemporal Models for Ambient Ozone in Six Metropolitan regions of the United States: The MESA Air Study

BACKGROUND

Current epidemiologic studies rely on simple ozone metrics which may not appropriately capture population ozone exposure. For understanding health effects of long-term ozone exposure in population studies, it is advantageous for exposure estimation to incorporate the complex spatiotemporal pattern of ozone concentrations at fine scales.

OBJECTIVE

To develop a geo-statistical exposure prediction model that predicts fine scale spatiotemporal variations of ambient ozone in six United States metropolitan regions.

METHODS

We developed a modeling framework that estimates temporal trends from regulatory agency and cohort-specific monitoring data from MESA Air measurement campaigns and incorporates land use regression with universal kriging using predictor variables from a large geographic database. The cohort-specific data were measured at home and community locations. The framework was applied in estimating two-week average ozone concentrations from 1999 to 2013 in models of each of the six MESA Air metropolitan regions.

RESULTS

Ozone models perform well in both spatial and temporal dimensions at the agency monitoring sites in terms of prediction accuracy. City-specific leave-one (site)-out cross-validation R² accounting for temporal and spatial variability ranged from 0.65 to 0.88 in the six regions. For predictions at the home sites, the R² is between 0.60 and 0.91 for cross-validation that left out 10% of home sites in turn. The predicted ozone concentrations vary substantially over space and time in all the metropolitan regions.

CONCLUSION

Using the available data, our spatiotemporal models are able to accurately predict long-term ozone concentrations at fine spatial scales in multiple regions. The model predictions will allow for investigation of the long-term health effects of ambient ozone concentrations in future epidemiological studies.

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.

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.

Weight-of-evidence evaluation of long-term ozone exposure and cardiovascular effects

We conducted a weight-of-evidence (WoE) analysis to assess whether the current body of research supports a causal relationship between long-term ozone exposure (defined by EPA as at least 30 days in duration) at ambient levels and cardiovascular (CV) effects. We used a novel WoE framework based on the United States Environmental Protection Agency's National Ambient Air Quality Standards causal framework for this analysis. Specifically, we critically evaluated and integrated the relevant epidemiology and experimental animal data and classified a causal determination based on categories proposed by the Institute of Medicine's 2008 report, Improving the Presumptive Disability Decision-making Process for Veterans. We found that the risks of CV effects are largely null across human and experimental animal studies. The few positive associations reported in studies of CV morbidity and mortality are very small in magnitude, mainly reported in single-pollutant models, and likely attributable to bias, chance, or confounding. The few positive effects in experimental animal studies were observed mainly in ex vivo studies at high exposures, and even the in vivo findings are not likely relevant to humans. The available data also do not support a biologically plausible mechanism for the effects of ozone on the CV system. Overall, the current WoE provides no convincing case for a causal relationship between long-term exposure to ambient ozone and adverse effects on the CV system in humans, but the limitations of the available studies preclude definitive conclusions regarding a lack of causation; thus, we categorize the strength of evidence for a causal relationship between long-term exposure to ozone and CV effects as "below equipoise."

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.

Proximity of US schools to major roadways: a nationwide assessment

Long-term exposure to traffic pollution has been associated with adverse health outcomes in children and adolescents. A significant number of schools may be located near major roadways, potentially exposing millions of children to high levels of traffic pollution, but this hypothesis has not been evaluated nationally. We obtained data on the location and characteristics of 114,644 US public and private schools, grades prekindergarten through 12, and calculated their distance to the nearest major roadway. In 2005-2006, 3.2 million students (6.2%) attended 8,424 schools (7.3%) located within 100 m of a major roadway, and an additional 3.2 million (6.3%) students attended 8,555 (7.5%) schools located 100-250 m from a major roadway. Schools serving predominantly Black students were 18% (95% CI, 13-23%) more likely to be located within 250 m of a major roadway. Public schools eligible for Title I programs and those with a majority of students eligible for free/reduced price meals were also more likely to be near major roadways. In conclusion, 6.4 million US children attended schools within 250 m of a major roadway and were likely exposed to high levels of traffic pollution. Minority and underprivileged children were disproportionately affected, although some results varied regionally.

Components of air pollution and cognitive function in middle-aged and older adults in Los Angeles

While experiments in animals demonstrate neurotoxic effects of particulate matter (PM) and ozone (O3), epidemiologic evidence is sparse regarding the relationship between different constituencies of air pollution mixtures and cognitive function in adults. We examined cross-sectional associations between various ambient air pollutants [O3, PM2.5 and nitrogen dioxide (NO2)] and six measures of cognitive function and global cognition among healthy, cognitively intact individuals (n=1496, mean age 60.5 years) residing in the Los Angeles Basin. Air pollution exposures were assigned to each residential address in 2000-06 using a geographic information system that included monitoring data. A neuropsychological battery was used to assess cognitive function; a principal components analysis defined six domain-specific functions and a measure of global cognitive function was created. Regression models estimated effects of air pollutants on cognitive function, adjusting for age, gender, race, education, income, study and mood. Increasing exposure to PM2.5 was associated with lower verbal learning (β=-0.32 per 10 μg/m(3) PM2.5, 95% CI=-0.63, 0.00; p=0.05). Ambient exposure to NO2 >20 ppb tended to be associated with lower logical memory. Compared to the lowest level of exposure to ambient O3, exposure above 49 ppb was associated with lower executive function. Including carotid artery intima-media thickness, a measure of subclinical atherosclerosis, in models as a possible mediator did not attenuate effect estimates. This study provides support for cross-sectional associations between increasing levels of ambient O3, PM2.5 and NO2 and measures of domain-specific cognitive abilities.