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1.  Annual Average Ambient Particulate Matter Exposure Estimates, Measured Home Particulate Matter, and Hair Nicotine are Associated with Respiratory Outcomes in Adults with Asthma 
Environmental research  2014;129:1-10.
Background
While exposure to outdoor particulate matter (PM) has been associated with poor asthma outcomes, few studies have investigated the combined effects of outdoor and indoor PM (including secondhand tobacco smoke).
Objective
To examine the associations between PM and asthma outcomes.
Methods
We analyzed data from a cohort of adults with asthma and rhinitis (n=302; 82% both conditions; 13% asthma only; 5% rhinitis alone) including measures of home PM, tobacco smoke exposure (hair nicotine and self-report), ambient PM from regional monitoring, distance to roadway, and season (wet or dry). The outcomes of interest were frequent respiratory symptoms and forced expiratory volume in 1 second (FEV1) below the lower limit of normal (NHANES reference values). Multivariable regression analyses examined the associations (Odds Ratio [OR] and 95% Confidence Interval [95%CI]) between exposures and these outcomes, adjusted by sociodemographic characteristics.
Results
In adjusted analyses of each exposure, the highest tertile of home PM and season of interview were associated with increased odds for more frequent respiratory symptoms (OR=1.64 95%CI: [1.00, 2.69] and OR = 1.66 95%CI: [1.09, 2.51]). The highest tertile of hair nicotine was significantly associated with FEV1 below the lower limit of normal (OR=1.80 95%CI: [1.00, 3.25]). In a model including home PM, ambient PM, and hair nicotine, and season, only two associations remained strong: hair nicotine with FEV1 below the lower limit of normal and season of measurement (dry, April-October) with increased respiratory symptoms (OR=1.85 95%CI: [1.00, 3.41] and OR = 1.54 95%CI: [1.0, 2.37]). When that model was stratified by sex, the highest tertiles of ambient PM and hair nicotine were associated with FEV1 below the lower limit of normal among women (OR=2.23 95%CI: [1.08, 4.61] and OR=2.90 95% CI: [1.32, 6.38]), but not men. The highest tertile of hair nicotine was also associated with increased respiratory symptoms in women but not men (OR=2.38 95% CI: [1.26, 4.49]). When stratified by age, the middle quartile of ambient PM and the highest hair nicotine tertile were associated with increased respiratory symptoms (OR=2.07 95%CI: [1.01, 4.24] and OR=2.55 95%CI: [1.21,5.36]) in those under 55 but not in the older stratum.
Conclusions
Exposure to PM from both home and ambient sources is associated with increased symptoms and lower lung function in adults with asthma, although these associations vary by type of PM, the respiratory outcome studied, sex and age.
doi:10.1016/j.envres.2013.12.007
PMCID: PMC4169238  PMID: 24528996
Particulate matter; indoor air quality; outdoor air quality; hair nicotine; asthma; respiratory symptoms; lung function
2.  Longitudinal Effects of Air Pollution on Exhaled Nitric Oxide: The Children’s Health Study 
OBJECTIVES
To assess the effects of long-term variations in ambient air pollutants on longitudinal changes in exhaled nitric oxide (FeNO), a potentially useful biomarker of eosinophilic airway inflammation, based on data from the southern California Children’s Health Study.
METHODS
Based on a cohort of 1,211 schoolchildren from 8 Southern California communities with FeNO measurements in 2006/07 and 2007/08, regression models adjusted for short-term effects of air pollution were fitted to assess the association between changes in annual long-term exposures and changes in FeNO.
RESULTS
Increases in annual average concentrations of 24-hr average NO2 and PM2.5 (scaled to the interquartile range (IQR) of 1.8 ppb and 2.4 μg/m3, respectively) were associated with a 2.29 ppb (CI=[0.36,4.21]; p =0.02) and a 4.94 ppb (CI=[1.44,8.47]; p = 0.005) increase in FeNO, respectively, after adjustments for short term effects of the respective pollutants. In contrast, changes in annual averages of PM10 and O3 were not significantly associated with changes in FeNO. These findings did not differ significantly by asthma status.
CONCLUSIONS
Changes in annual average exposure to current levels of ambient air pollutants are significantly associated with changes in FeNO levels in children, independent of short-term exposures and asthma status. Use of this biomarker in population-based epidemiologic research has great potential for assessing the impact of changing real world mixtures of ambient air pollutants on children’s respiratory health.
doi:10.1136/oemed-2013-101874
PMCID: PMC4310696  PMID: 24696513
Air pollution; chronic exposures; Children’s respiratory health; Environmental epidemiology; Exhaled nitric oxide; Airway inflammation
3.  Components of Air Pollution and Cognitive Function in Middle-aged and Older Adults in Los Angeles 
Neurotoxicology  2013;40:1-7.
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=1,496, 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 ug/m3 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.
doi:10.1016/j.neuro.2013.09.004
PMCID: PMC3946571  PMID: 24148924
air pollution; cognitive dysfunction; dementia; particulate matter; ozone; verbal learning
4.  Early-Life Air Pollution and Asthma Risk in Minority Children. The GALA II and SAGE II Studies 
Rationale: Air pollution is a known asthma trigger and has been associated with short-term asthma symptoms, airway inflammation, decreased lung function, and reduced response to asthma rescue medications.
Objectives: To assess a causal relationship between air pollution and childhood asthma using data that address temporality by estimating air pollution exposures before the development of asthma and to establish the generalizability of the association by studying diverse racial/ethnic populations in different geographic regions.
Methods: This study included Latino (n = 3,343) and African American (n = 977) participants with and without asthma from five urban regions in the mainland United States and Puerto Rico. Residential history and data from local ambient air monitoring stations were used to estimate average annual exposure to five air pollutants: ozone, nitrogen dioxide (NO2), sulfur dioxide, particulate matter not greater than 10 μm in diameter, and particulate matter not greater than 2.5 μm in diameter. Within each region, we performed logistic regression to determine the relationship between early-life exposure to air pollutants and subsequent asthma diagnosis. A random-effects model was used to combine the region-specific effects and generate summary odds ratios for each pollutant.
Measurements and Main Results: After adjustment for confounders, a 5-ppb increase in average NO2 during the first year of life was associated with an odds ratio of 1.17 for physician-diagnosed asthma (95% confidence interval, 1.04–1.31).
Conclusions: Early-life NO2 exposure is associated with childhood asthma in Latinos and African Americans. These results add to a growing body of evidence that traffic-related pollutants may be causally related to childhood asthma.
doi:10.1164/rccm.201302-0264OC
PMCID: PMC3778732  PMID: 23750510
air pollution; minority; children; asthma
5.  ASTHMA AND SCHOOL COMMUTING TIME 
Objectives
This study examined associations of asthma with school commuting time.
Methods
Time on likely school commute route was used as a proxy for on-road air pollution exposure among 4741 elementary school children at enrollment into the Children's Health Study. Lifetime asthma and severe wheeze (including multiple attacks, nocturnal or with shortness of breath) were reported by parents.
Results
In asthmatic children, severe wheeze was associated with commuting time (odds ratio (OR) 1.54 across the 9-minute 5%-95% exposure distribution; 95% confidence interval (CI) 1.01,2.36). The association was stronger in analysis restricted to asthmatic children with commuting times five minutes or longer (OR 1.97; 95% CI 1.02,3.77). No significant associations were observed with asthma prevalence.
Conclusions
Among asthmatics, severe wheeze was associated with relatively short school commuting times. Further investigation of effects of on-road pollutant exposure is warranted.
doi:10.1097/JOM.0b013e3181ebf1a9
PMCID: PMC4083079  PMID: 20657304
air pollution; asthma; child; epidemiology; traffic; commuting
6.  Traffic-related air pollution and obesity formation in children: a longitudinal, multilevel analysis 
Environmental Health  2014;13:49.
Background
Biologically plausible mechanisms link traffic-related air pollution to metabolic disorders and potentially to obesity. Here we sought to determine whether traffic density and traffic-related air pollution were positively associated with growth in body mass index (BMI = kg/m2) in children aged 5–11 years.
Methods
Participants were drawn from a prospective cohort of children who lived in 13 communities across Southern California (N = 4550). Children were enrolled while attending kindergarten and first grade and followed for 4 years, with height and weight measured annually. Dispersion models were used to estimate exposure to traffic-related air pollution. Multilevel models were used to estimate and test traffic density and traffic pollution related to BMI growth. Data were collected between 2002–2010 and analyzed in 2011–12.
Results
Traffic pollution was positively associated with growth in BMI and was robust to adjustment for many confounders. The effect size in the adjusted model indicated about a 13.6% increase in annual BMI growth when comparing the lowest to the highest tenth percentile of air pollution exposure, which resulted in an increase of nearly 0.4 BMI units on attained BMI at age 10. Traffic density also had a positive association with BMI growth, but this effect was less robust in multivariate models.
Conclusions
Traffic pollution was positively associated with growth in BMI in children aged 5–11 years. Traffic pollution may be controlled via emission restrictions; changes in land use that promote jobs-housing balance and use of public transit and hence reduce vehicle miles traveled; promotion of zero emissions vehicles; transit and car-sharing programs; or by limiting high pollution traffic, such as diesel trucks, from residential areas or places where children play outdoors, such as schools and parks. These measures may have beneficial effects in terms of reduced obesity formation in children.
doi:10.1186/1476-069X-13-49
PMCID: PMC4106205  PMID: 24913018
Childhood obesity; Air pollution; Traffic; California
8.  Traffic Related Air Pollution, Particulate Matter, and Autism 
JAMA psychiatry  2013;70(1):71-77.
Context
Autism is a heterogeneous disorder with genetic and environmental factors likely contributing to its origins. Examination of hazardous pollutants has suggested the importance of air toxics in autism etiology, yet little research has examined local level air pollution associations using residence-specific exposure assignments.
Objective
To examine the relationship between traffic-related air pollution (TRP), air quality, and autism.
Design, Setting and Population
This study includes data on 279 autism cases and 245 typically developing controls enrolled in the Childhood Autism Risks from Genetics and the Environment (CHARGE) Study in California. The mother’s address from the birth certificate and addresses reported from a residential history questionnaire were used to estimate exposure for each trimester of pregnancy and first year of life. TRP was assigned to each location using a line-source air-quality dispersion model. Regional air pollutant measures were based on the Environmental Protection Agency’s Air Quality System data. Logistic regression models compared estimated and measured pollutant levels for autism cases and typically developing controls.
Main Outcome Measures
Crude and multivariable-adjusted odds ratios (OR) for autism.
Results
Cases were more likely to live at residences in the highest quartile TRP exposure during pregnancy (OR=1.98, 95%CI 1.20–3.31) and the first year of life (OR=3.10, 1.76–5.57) compared to controls. Regional exposure measures of nitrogen dioxide (NO2) and particulate matter less than 2.5 and 10 microns in diameter (PM2.5 and PM10) were also associated with autism during gestation (NO2 OR=1.81/2SD, 95%CI 1.37–3.09; PM2.5 OR=2.08/2SD, 95%CI 1.93–2.25; PM10 OR=2.17/2SD, 95%CI 1.49–3.16) and the first year of life (NO2 OR=2.06, 95%CI 1.37–3.09; PM2.5 OR=2.12, 95%CI 1.45–3.10; PM10 OR=2.14, 95%CI 1.46–3.12).
Conclusions
Exposure to TRP, NO2, PM2.5, and PM10 during pregnancy and the first year of life was associated with autism. Further epidemiological and toxicological examination of likely biological pathways will help determine whether these associations are causal.
doi:10.1001/jamapsychiatry.2013.266
PMCID: PMC4019010  PMID: 23404082
9.  Interaction of the MET Receptor Tyrosine Kinase Gene and Air Pollution Exposure in Autism Spectrum Disorder 
Background
Independent studies report association of autism spectrum disorder with air pollution exposure and a functional promoter variant (rs1858830) in the MET receptor tyrosine kinase (MET) gene. Toxicologic data find altered brain Met expression in mice after prenatal exposure to a model air pollutant. Our objective was to investigate whether air pollution exposure and MET rs1858830 genotype interact to alter ASD risk.
Methods
We studied 252 cases of autism spectrum disorder and 156 typically developing controls the Childhood Autism Risk from Genetics and the Environment Study. Air pollution exposure was assigned for local traffic-related sources and regional sources (particulate matter, nitrogen dioxide and ozone). MET genotype was determined by direct re-sequencing.
Results
Subjects with both MET rs1858830 CC genotype and high air pollutant exposures were at increased risk of autism spectrum disorder compared with subjects who had both the CG/GG genotypes and lower pollutant exposures. A statistical test of multiplicative interaction identified a statistically significant effect between NO2 and MET CC genotype (p=0.03)
Conclusions
MET rs1858830 CC genotype and air pollutant exposure may interact to increase autism spectrum disorder risk.
doi:10.1097/EDE.0000000000000030
PMCID: PMC4019012  PMID: 24240654
10.  Childhood Obesity and Asthma Control in the GALA II and SAGE II Studies 
Rationale: Obesity is associated with increased asthma morbidity, lower drug responsiveness to inhaled corticosteroids, and worse asthma control. However, most prior investigations on obesity and asthma control have not focused on pediatric populations, considered environmental exposures, or included minority children.
Objectives: To examine the association between body mass index categories and asthma control among boys and girls; and whether these associations are modified by age and race/ethnicity.
Methods: Children and adolescents ages 8–19 years (n = 2,174) with asthma were recruited from the Genes-environments and Admixture in Latino Americans (GALA II) Study and the Study of African Americans, Asthma, Genes, and Environments (SAGE II). Ordinal logistic regression was used to estimate odds ratios (OR) and their confidence intervals (95% CI) for worse asthma control.
Measurements and Main Results: In adjusted analyses, boys who were obese had a 33% greater chance of having worse asthma control than their normal-weight counterparts (OR, 1.33; 95% CI, 1.04–1.71). However, for girls this association varied with race and ethnicity (P interaction = 0.008). When compared with their normal-weight counterparts, obese African American girls (OR, 0.65; 95% CI, 0.41–1.05) were more likely to have better controlled asthma, whereas Mexican American girls had a 1.91 (95% CI, 1.12–3.28) greater odds of worse asthma control.
Conclusions: Worse asthma control is uniformly associated with increased body mass index in boys. Among girls, the direction of this association varied with race/ethnicity.
doi:10.1164/rccm.201211-2116OC
PMCID: PMC3678111  PMID: 23392439
obesity; asthma control; race and ethnicity; age; sex
11.  Childhood Air Pollutant Exposure and Carotid Artery Intima-Media Thickness in Young Adults 
Circulation  2012;126(13):1614-1620.
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 2007–2009. Participants attended one 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 socio-demographic characteristics and a 12-hr 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 (AQS) 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) O3 exposure was associated with a 7.8 μm (95% CI −0.3, 15.9) or 10.1 μm (95% CI 1.8, 18.5) higher CIMT, respectively. Lifetime exposure to O3 showed similar but non-significant associations. No associations were observed for PM2.5, PM10 or NO2 although adjustment for these pollutants strengthened the childhood O3 associations.
Conclusion
Childhood exposure to O3 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.
doi:10.1161/CIRCULATIONAHA.112.096164
PMCID: PMC3474843  PMID: 22896588
atherosclerosis; cardiovascular diseases; carotid arteries; epidemiology; pediatrics
12.  The impact of secondhand smoke on asthma control among Black and Latino children 
Background
Among people with asthma, the clinical impact and relative contribution of maternal smoking during pregnancy (in utero smoking) and current secondhand smoke exposure on asthma control is poorly documented, and there is a paucity of research involving minority populations.
Objectives
To examine the association between poor asthma control and in utero smoking and current secondhand smoke exposure among Latino and Black children with asthma.
Methods
Case-only analysis of 2 multi-center case-control studies conducted from 2008–2010 using similar protocols. We recruited 2,481 Latinos and Blacks with asthma (ages 8–17) from the mainland United States and Puerto Rico. Ordinal logistic regression was used to estimate the effect of in utero smoking and current secondhand smoke exposures on National Heart Lung and Blood Institute-defined asthma control.
Results
Poor asthma control among children 8–17 years of age was independently associated with in utero smoking (odds ratio; 95% confidence interval = 1.5; 1.1–2.0). In utero smoking via the mother was also associated with secondary asthma outcomes, including early onset asthma (1.7; 1.1–2.4), daytime symptoms (1.6; 1.1–2.1), and asthma-related limitation of activities (1.6; 1.2–2.2).
Conclusions
Maternal smoking while in utero is associated with poor asthma control in Black and Latino subjects assessed at 8–17 years of age.
doi:10.1016/j.jaci.2012.03.017
PMCID: PMC3367092  PMID: 22552109
Secondhand smoke; prenatal exposure delayed effects; asthma; health status disparities
13.  Genetic and Epigenetic Variations in Inducible Nitric Oxide Synthase Promoter, Particulate Pollution and Exhaled Nitric Oxide in Children 
Background
Inducible nitric oxide synthase (iNOS, encoded by NOS2) is the major enzyme for nitric oxide synthesis in airways. As such, measurement of exhaled nitric oxide (FeNO) provides an in vivo assessment of iNOS activity. Short-term exposure to air pollution, haplotypes and DNA methylation in NOS2 promoter have been associated independently with iNOS expression and/or FeNO.
Objective
We aimed to examine the effects of ambient air pollutants, NOS2 promoter haplotypes and NOS2 promoter methylation on FeNO level in children.
Methods
We selected 940 participants in the Children’s Health Study who provided buccal samples and had undergone FeNO measurement on the same day. DNA methylation was measured using a bisulfite-polymerase chain reaction Pyrosequencing assay. Seven single nucleotide polymorphisms captured the haplotype diversity in the NOS2 promoter. Average particulate matter with aerodynamic diameter ≤2.5μm and ≤10μm (PM2.5 and PM10), ozone and nitrogen dioxide levels 7 days before FeNO measurement were estimated based on air pollution data obtained at central monitoring sites.
Results
We found interrelated effects of PM2.5, NOS2 promoter haplotypes and iNOS methylation on FeNO. Elevated 7-day average PM2.5 exposure was associated with lower iNOS methylation (P=.01). NOS2 promoter haplotypes were globally associated with NOS2 promoter methylation (P=6.2 × 10−8). There was interaction among one common promoter haplotype, iNOS methylation level and PM2.5 exposure on FeNO (Pinteraction=.00007).
Conclusion
Promoter variants in NOS2 and short term PM2.5 exposure affect iNOS methylation. This is one of the first studies showing contributions of genetic and epigenetic variations in air pollution mediated phenotype expression.
doi:10.1016/j.jaci.2011.09.037
PMCID: PMC3487398  PMID: 22055874
air pollution; biomarker; DNA methylation; epigenetics; genetics; gene-environment interaction; nitrosative stress
14.  Asthma Discordance in Twins Is Linked to Epigenetic Modifications of T Cells 
PLoS ONE  2012;7(11):e48796.
T cells mediate the inflammatory responses observed in asthma among genetically susceptible individuals and have been suspected to be prone to epigenetic regulation. However, these relationships are not well established from past clinical studies that have had limited capacity to control for the effects of variable genetic predisposition and early environmental exposures. Relying on a cohort of monozygotic twins discordant for asthma we sought to determine if epigenetic modifications in T cells were associated with current asthma and explored whether such modifications were associated with second hand smoke exposures. Our study was conducted in a monozygotic twin cohort of adult twin pairs (n = 21) all discordant for asthma. Regulatory T cell (Treg) and effector T cell (Teff) subsets were assessed for levels of cellular function, protein expression, gene expression and CpG methylation within Forkhead box P3 (FOXP3) and interferon gamma-γ (IFNγ) loci. Comparisons by asthma and current report of exposure to second hand smoke were made. Treg from asthmatic discordant twins demonstrated decreased FOXP3 protein expression and impaired Treg function that was associated with increased levels of CpG methylation within the FOXP3 locus when compared to their non-asthmatic twin partner. In parallel, Teff from discordant asthmatic twins demonstrated increased methylation of the IFNγ locus, decreased IFNγ expression and reduced Teff function when compared to Teff from the non-asthmatic twin. Finally, report of current exposure to second hand smoke was associated with modifications in both Treg and Teff at the transcriptional level among asthmatics. The results of the current study provide evidence for differential function of T cell subsets in monozygotic twins discordant for asthma that are regulated by changes in DNA methylation. Our preliminary data suggest exposure to second hand smoke may augment the modified T cell responses associated with asthma.
doi:10.1371/journal.pone.0048796
PMCID: PMC3511472  PMID: 23226205
15.  Near-Roadway Pollution and Childhood Asthma: Implications for Developing “Win–Win” Compact Urban Development and Clean Vehicle Strategies 
Environmental Health Perspectives  2012;120(11):1619-1626.
Background: The emerging consensus that exposure to near-roadway traffic-related pollution causes asthma has implications for compact urban development policies designed to reduce driving and greenhouse gases.
Objectives: We estimated the current burden of childhood asthma-related disease attributable to near-roadway and regional air pollution in Los Angeles County (LAC) and the potential health impact of regional pollution reduction associated with changes in population along major traffic corridors.
Methods: The burden of asthma attributable to the dual effects of near-roadway and regional air pollution was estimated, using nitrogen dioxide and ozone as markers of urban combustion-related and secondary oxidant pollution, respectively. We also estimated the impact of alternative scenarios that assumed a 20% reduction in regional pollution in combination with a 3.6% reduction or 3.6% increase in the proportion of the total population living near major roads, a proxy for near-roadway exposure.
Results: We estimated that 27,100 cases of childhood asthma (8% of total) in LAC were at least partly attributable to pollution associated with residential location within 75 m of a major road. As a result, a substantial proportion of asthma-related morbidity is a consequence of near-roadway pollution, even if symptoms are triggered by other factors. Benefits resulting from a 20% regional pollution reduction varied markedly depending on the associated change in near-roadway proximity.
Conclusions: Our findings suggest that there are large and previously unappreciated public health consequences of air pollution in LAC and probably in other metropolitan areas with dense traffic corridors. To maximize health benefits, compact urban development strategies should be coupled with policies to reduce near-roadway pollution exposure.
doi:10.1289/ehp.1104785
PMCID: PMC3556611  PMID: 23008270
air pollution; asthma; burden of disease; children; compact urban growth; risk assessment; vehicle emissions
16.  Parental Stress Increases the Detrimental Effect of Traffic Exposure on Children's Lung Function 
Rationale: Emerging evidence indicates that psychosocial stress enhances the effect of traffic exposure on the development of asthma.
Objectives: We hypothesized that psychosocial stress would also modify the effect of traffic exposure on lung function deficits.
Methods: We studied 1,399 participants in the Southern California Children's Health Study undergoing lung function testing (mean age, 11.2 yr). We used hierarchical mixed models to assess the joint effect of traffic-related air pollution and stress on lung function.
Measurements and Main Results: Psychosocial stress in each child's household was assessed based on parental response to the perceived stress scale (range, 0–16) at study entry. Exposures to nitric oxide, nitrogen dioxide, and total oxides of nitrogen (NOx), surrogates of the traffic-related pollution mixture, were estimated at schools and residences based on a land-use regression model. Among children from high-stress households (parental perceived stress scale >4) deficits in FEV1 of 4.5 (95% confidence interval, −6.5 to −2.4) and of 2.8% (−5.7 to 0.3) were associated with each 21.8 ppb increase in NOx at homes and schools, respectively. These pollutant effects were significantly larger in the high-stress compared with lower-stress households (interaction P value 0.007 and 0.05 for residential and school NOx, respectively). No significant NOx effects were observed in children from low-stress households. A similar pattern of association was observed for FVC. The observed associations for FEV1 and FVC remained after adjusting for sociodemographic factors and after restricting the analysis to children who do not have asthma.
Conclusions: A high-stress home environment is associated with increased susceptibility to lung function effects of air pollution both at home and at school.
doi:10.1164/rccm.201104-0720OC
PMCID: PMC3208647  PMID: 21700914
parental stress; traffic exposure; lung function; children
17.  Traffic exposure and incident venous thromboembolism in the Atherosclerosis Risk in Communities (ARIC) Study 
Summary
Background
Two recent case-control studies in Italy reported that long-term exposure to particulate air pollution or living near major traffic roads was associated with an increased risk of deep vein thrombosis (DVT). No prospective evidence exists about long-term traffic-related air pollution and incident venous thromboembolism (VTE).
Objectives
To examine the association between long-term traffic exposure and incident VTE in a population-based prospective cohort study.
Methods
We studied 13,143 middle-aged men and women in the Atherosclerosis Risk in Communities Study without history of DVT or pulmonary embolus (PE) at baseline examination (1987-1989). Geographical Information System (GIS)-mapped traffic density and distance to major roads in the four study communities served as measures of traffic exposure. We examined the association between traffic exposure and incident VTE using proportional hazards regression models.
Results
405 subjects developed VTE through 2005. Traffic density was not significantly associated with VTE. Relative to those in the lowest quartile of traffic density, the adjusted hazard ratios across increasing quartiles were 1.18 (95%CI 0.88-1.57), 0.99 (95%CI 0.74-1.34) and 1.14 (95%CI 0.86-1.51) (p for trend across quartiles = 0.64). For residents living within 150 meters of major roads compared to subjects living further away, the adjusted hazard ratio was 1.16 (95%CI 0.95-1.42, p=0.14).
Conclusions
This first prospective study in the general population does not support an association between air pollution exposure or traffic proximity and risk of DVT. More data may be needed to clarify whether traffic or air pollution influences the risk of VTE.
doi:10.1111/j.1538-7836.2011.04210.x
PMCID: PMC3071427  PMID: 21255249
traffic exposure; VTE; air pollution; cohort
18.  Residential Proximity to Freeways and Autism in the CHARGE Study 
Environmental Health Perspectives  2010;119(6):873-877.
Background
Little is known about environmental causes and contributing factors for autism. Basic science and epidemiologic research suggest that oxidative stress and inflammation may play a role in disease development. Traffic-related air pollution, a common exposure with established effects on these pathways, contains substances found to have adverse prenatal effects.
Objectives
We examined the association between autism and proximity of residence to freeways and major roadways during pregnancy and near the time of delivery, as a surrogate for air pollution exposure.
Methods
Data were from 304 autism cases and 259 typically developing controls enrolled in the Childhood Autism Risks from Genetics and the Environment (CHARGE) study. The mother’s address recorded on the birth certificate and trimester-specific addresses derived from a residential history obtained by questionnaire were geocoded, and measures of distance to freeways and major roads were calculated using ArcGIS software. Logistic regression models compared residential proximity to freeways and major roads for autism cases and typically developing controls.
Results
Adjusting for sociodemographic factors and maternal smoking, maternal residence at the time of delivery was more likely be near a freeway (≤ 309 m) for cases than for controls [odds ratio (OR) = 1.86; 95% confidence interval (CI), 1.04–3.45]. Autism was also associated with residential proximity to a freeway during the third trimester (OR = 2.22; CI, 1.16–4.42). After adjustment for socioeconomic and sociodemographic characteristics, these associations were unchanged. Living near other major roads at birth was not associated with autism.
Conclusions
Living near a freeway was associated with autism. Examination of associations with measured air pollutants is needed.
doi:10.1289/ehp.1002835
PMCID: PMC3114825  PMID: 21156395
autism; epidemiology; gene-environment interaction; roadway proximity; traffic emissions
19.  Traffic exposure and lung function in adults: the Atherosclerosis Risk in Communities study 
Thorax  2007;62(10):873-879.
Background
Traffic exposure is a major contributor to ambient air pollution for people living close to busy roads. The relationship between traffic exposure and lung function remains inconclusive in adults.
Methods
A cross‐sectional study was conducted to investigate the association between traffic exposure and lung function in the Atherosclerosis Risk in Communities (ARIC) study, a community based cohort of 15 792 middle aged men and women. Traffic density and distance to major roads were used as measures of traffic exposure.
Results
After controlling for potential confounders including demographic factors, personal and neighbourhood level socioeconomic characteristics, cigarette smoking and background air pollution, higher traffic density was significantly associated with lower forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) in women. Relative to the lowest quartile of traffic density, the adjusted differences across increasing quartiles were 5.1, −15.4 and −21.5 ml for FEV1 (p value of linear trend across the quartiles = 0.041) and 1.2, −23.4 and −34.8 ml for FVC (p trend = 0.010). Using distance from major roads as a simpler index of traffic related air pollution exposure, the FEV1 was −15.7 ml (95% CI −34.4 to 2.9) lower and the FVC was −24.2 ml (95% CI −46.2 to −2.3) lower for women living within 150 m compared with subjects living further away. There was no significant effect of traffic density or distance to major roads on lung function in men. The FEV1/FVC ratio was not significantly associated with traffic exposure in either men or women.
Conclusions
This is the largest published study of traffic exposure and pulmonary function in adults to date. These results add to growing evidence that chronic exposure to traffic related air pollution may adversely affect respiratory health.
doi:10.1136/thx.2006.073015
PMCID: PMC2094260  PMID: 17442705
20.  Childhood Incident Asthma and Traffic-Related Air Pollution at Home and School 
Environmental Health Perspectives  2010;118(7):1021-1026.
Background
Traffic-related air pollution has been associated with adverse cardiorespiratory effects, including increased asthma prevalence. However, there has been little study of effects of traffic exposure at school on new-onset asthma.
Objectives
We evaluated the relationship of new-onset asthma with traffic-related pollution near homes and schools.
Methods
Parent-reported physician diagnosis of new-onset asthma (n = 120) was identified during 3 years of follow-up of a cohort of 2,497 kindergarten and first-grade children who were asthma- and wheezing-free at study entry into the Southern California Children’s Health Study. We assessed traffic-related pollution exposure based on a line source dispersion model of traffic volume, distance from home and school, and local meteorology. Regional ambient ozone, nitrogen dioxide (NO2), and particulate matter were measured continuously at one central site monitor in each of 13 study communities. Hazard ratios (HRs) for new-onset asthma were scaled to the range of ambient central site pollutants and to the residential interquartile range for each traffic exposure metric.
Results
Asthma risk increased with modeled traffic-related pollution exposure from roadways near homes [HR 1.51; 95% confidence interval (CI), 1.25–1.82] and near schools (HR 1.45; 95% CI, 1.06–1.98). Ambient NO2 measured at a central site in each community was also associated with increased risk (HR 2.18; 95% CI, 1.18–4.01). In models with both NO2 and modeled traffic exposures, there were independent associations of asthma with traffic-related pollution at school and home, whereas the estimate for NO2 was attenuated (HR 1.37; 95% CI, 0.69–2.71).
Conclusions
Traffic-related pollution exposure at school and homes may both contribute to the development of asthma.
doi:10.1289/ehp.0901232
PMCID: PMC2920902  PMID: 20371422
air pollution; asthma; child; epidemiology; vehicular traffic
21.  An integrated model of environmental factors in adult asthma lung function and disease severity: a cross-sectional study 
Environmental Health  2010;9:24.
Background
Diverse environmental exposures, studied separately, have been linked to health outcomes in adult asthma, but integrated multi-factorial effects have not been modeled. We sought to evaluate the contribution of combined social and physical environmental exposures to adult asthma lung function and disease severity.
Methods
Data on 176 subjects with asthma and/or rhinitis were collected via telephone interviews for sociodemographic factors and asthma severity (scored on a 0-28 point range). Dust, indoor air quality, antigen-specific IgE antibodies, and lung function (percent predicted FEV1) were assessed through home visits. Neighborhood socioeconomic status, proximity to traffic, land use, and ambient air quality data were linked to the individual-level data via residential geocoding. Multiple linear regression separately tested the explanatory power of five groups of environmental factors for the outcomes, percent predicted FEV1 and asthma severity. Final models retained all variables statistically associated (p < 0.20) with each of the two outcomes.
Results
Mean FEV1 was 85.0 ± 18.6%; mean asthma severity score was 6.9 ± 5.6. Of 29 variables screened, 13 were retained in the final model of FEV1 (R2 = 0.30; p < 0.001) and 15 for severity (R2 = 0.16; p < 0.001), including factors from each of the five groups. Adding FEV1 as an independent variable to the severity model further increased its explanatory power (R2 = 0.25).
Conclusions
Multivariate models covering a range of individual and environmental factors explained nearly a third of FEV1 variability and, taking into account lung function, one quarter of variability in asthma severity. These data support an integrated approach to modeling adult asthma outcomes, including both the physical and the social environment.
doi:10.1186/1476-069X-9-24
PMCID: PMC2887801  PMID: 20487557
22.  Exposure to Traffic: Lung Function and Health Status in Adults with Asthma 
Background
Exposure to traffic has been associated with asthma outcomes in children, but its effect on asthma in adults has not been well studied.
Objective
To test the hypothesis that lung function and health status are associated with traffic exposures.
Methods
We measured forced expiratory volume in 1 second (FEV1) % predicted, general health status using the Physical Component Scale of the Short Form (SF-12 PCS) and quality of life (QoL) using the Marks Asthma Quality of Life questionnaire in a cohort of adults with asthma or rhinitis (n=176; 145 with asthma). We assessed exposures to traffic by geo-coding subjects’ residential addresses and assigning distance to roadways. Associations between distance to nearest roadway and distance to nearest major roadway and FEV1 % predicted or SF-12 PCS were studied using linear regression.
Results
FEV1 % predicted was positively associated with distance from nearest roadway (p=0.01) and major roadway (p=0.02). SF-12 PCS and QoL were not significantly associated with either traffic variable. Adjustment for income, smoking, and obesity did not substantively change the associations of the traffic variables with FEV1 % predicted (p=0.04 for nearest roadway and p=0.02 for nearest major roadway) and did not cause associations with either SF-12 PCS or OoL to become significant
Conclusions
Traffic exposure was associated with decreased lung function in adults with asthma.
doi:10.1016/j.jaci.2008.10.062
PMCID: PMC2785911  PMID: 19152968
asthma; traffic; heavy-duty vehicles; lung function; health status
23.  Prospective Analysis of Traffic Exposure as a Risk Factor for Incident Coronary Heart Disease: The Atherosclerosis Risk in Communities (ARIC) Study 
Environmental Health Perspectives  2008;116(11):1463-1468.
Background
For people living close to busy roads, traffic is a major source of air pollution. Few prospective data have been published on the effects of long-term exposure to traffic on the incidence of coronary heart disease (CHD).
Objectives
In this article, we examined the association between long-term traffic exposure and incidence of fatal and nonfatal CHD in a population-based prospective cohort study.
Methods
We studied 13,309 middle-age men and women in the Atherosclerosis Risk in Communities study, without previous CHD at enrollment, from 1987 to 1989 in four U.S. communities. Geographic information system–mapped traffic density and distance to major roads served as measures of traffic exposure. We examined the association between traffic exposure and incident CHD using proportional hazards regression models, with adjustment for background air pollution and a wide range of individual cardiovascular risk factors.
Results
Over an average of 13 years of follow-up, 976 subjects developed CHD. Relative to those in the lowest quartile of traffic density, the adjusted hazard ratio (HR) in the highest quartile was 1.32 [95% confidence interval (CI), 1.06–1.65; p-value for trend across quartiles = 0.042]. When we treated traffic density as a continuous variable, the adjusted HR per one unit increase of log-transformed density was 1.03 (95% CI, 1.01–1.05; p = 0.006). For residents living within 300 m of major roads compared with those living farther away, the adjusted HR was 1.12 (95% CI, 0.95–1.32; p = 0.189). We found little evidence of effect modification for sex, smoking status, obesity, low-density lipoprotein cholesterol level, hypertension, age, or education.
Conclusion
Higher long-term exposure to traffic is associated with incidence of CHD, independent of other risk factors. These prospective data support an effect of traffic-related air pollution on the development of CHD in middle-age persons.
doi:10.1289/ehp.11290
PMCID: PMC2592264  PMID: 19057697
air pollution; coronary disease; traffic
24.  Traffic-Related Air Pollution and Asthma Onset in Children: A Prospective Cohort Study with Individual Exposure Measurement 
Environmental Health Perspectives  2008;116(10):1433-1438.
Background
The question of whether air pollution contributes to asthma onset remains unresolved.
Objectives
In this study, we assessed the association between asthma onset in children and traffic-related air pollution.
Methods
We selected a sample of 217 children from participants in the Southern California Children’s Health Study, a prospective cohort designed to investigate associations between air pollution and respiratory health in children 10–18 years of age. Individual covariates and new asthma incidence (30 cases) were reported annually through questionnaires during 8 years of follow-up. Children had nitrogen dioxide monitors placed outside their home for 2 weeks in the summer and 2 weeks in the fall–winter season as a marker of traffic-related air pollution. We used multilevel Cox models to test the associations between asthma and air pollution.
Results
In models controlling for confounders, incident asthma was positively associated with traffic pollution, with a hazard ratio (HR) of 1.29 [95% confidence interval (CI), 1.07–1.56] across the average within-community interquartile range of 6.2 ppb in annual residential NO2. Using the total interquartile range for all measurements of 28.9 ppb increased the HR to 3.25 (95% CI, 1.35–7.85).
Conclusions
In this cohort, markers of traffic-related air pollution were associated with the onset of asthma. The risks observed suggest that air pollution exposure contributes to new-onset asthma.
doi:10.1289/ehp.10968
PMCID: PMC2569108  PMID: 18941591
air pollution; asthma onset; children; nitrogen dioxide
25.  Ambient Ozone Concentrations Cause Increased Hospitalizations for Asthma in Children: An 18-Year Study in Southern California 
Environmental Health Perspectives  2008;116(8):1063-1070.
Background
Asthma is the most important chronic disease of childhood. The U.S. Environmental Protection Agency has concluded that children with asthma continue to be susceptible to ozone-associated adverse effects on their disease.
Objectives
This study was designed to evaluate time trends in associations between declining warm-season O3 concentrations and hospitalization for asthma in children.
Methods
We undertook an ecologic study of hospital discharges for asthma during the high O3 seasons in California’s South Coast Air Basin (SoCAB) in children who ranged in age from birth to 19 years from 1983 to 2000. We used standard association and causal statistical analysis methods. Hospital discharge data were obtained from the State of California; air pollution data were obtained from the California Air Resources Board, and demographic data from the 1980, 1990, and 2000 U.S. Census. SoCAB was divided into 195 spatial grids, and quarterly average O3, sulfurdioxide, particulate matter with aerodynamic diameter ≤ 10 μm, nitrogen dioxide, and carbon monoxide were assigned to each unit for 3-month periods along with demographic variables.
Results
O3 was the only pollutant associated with increased hospital admissions over the study period. Inclusion of a variety of demographic and weather variables accounted for all of the non-O3 temporal changes in hospitalizations. We found a time-independent, constant effect of ambient levels of O3 and quarterly hospital discharge rates for asthma. We estimate that the average effect of a 10-ppb mean increase in any given mean quarterly 1-hr maximum O3 over the 18-year median of 87.7 ppb was a 4.6% increase in the same quarterly outcome.
Conclusions
Our data indicate that at current levels of O3 experienced in Southern California, O3 contributes to an increased risk of hospitalization for children with asthma.
doi:10.1289/ehp.10497
PMCID: PMC2516585  PMID: 18709165
air pollution; asthma; children; epidemiology; ozone

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