Final Report: Near Roadways Exposure to Urban Air Pollutants Study (NEXUS)

EPA Grant Number: R834117
Title: Near Roadways Exposure to Urban Air Pollutants Study (NEXUS)
Investigators: Batterman, Stuart A. , Dion, F , Lewis, Toby C. , Mukherjee, Bhramar , Robins, Thomas
Institution: University of Michigan
EPA Project Officer: Ilacqua, Vito
Project Period: March 1, 2009 through February 29, 2012 (Extended to February 28, 2014)
Project Amount: $1,399,973
RFA: Health Effects of Near-Roadway Exposures to Air Pollution (2008) RFA Text |  Recipients Lists
Research Category: Health Effects , Particulate Matter , Air

Objective:

The Near Roadways Exposure to Urban Air Pollutants Study (NEXUS) has the objectives of understanding the types and severity of respiratory and cardiovascular outcomes in children with asthma that are associated with near-road exposures to air pollutants, and characterizing the pollutants and exposures associated with these outcomes. NEXUS derived a tiered set of exposure metrics and collected information on a diverse and innovative set of respiratory health outcomes and interactions that have been hypothesized to be associated with near-road exposures to air pollutants. This information was used to investigate a number of hypotheses: Which measures of traffic-associated pollution are most closely associated with asthma aggravation? Do children with asthma who are highly exposed to traffic, particularly diesel exhaust, exhibit more inflammation and oxidative stress? Does traffic exposure influence the likelihood of respiratory viral infections? How much error (exposure misclassification) is caused by the use of community monitoring versus indoor monitoring and exposure modeling, and what impact does this have on the effect size and statistical confidence of odds ratios relating exposures to health outcomes? To approach these questions, NEXUS used an observational approach, which is highly relevant to real-world conditions, and focused on children with persistent asthma, who tend to be highly susceptible to air pollutants. 

Summary/Accomplishments (Outputs/Outcomes):

Using a community-based participatory research approach, the NEXUS study recruited and enrolled 141 children with asthma in Detroit, Michigan, on the basis of the proximity of the child's residence to major roads. Exposure measures were developed in tiers that layered increasing levels of spatial and temporal detail on factors that affect exposure, ultimately resulting in child-specific estimates of hourly and daily air pollution exposure from sources including diesel exhaust particulate matter. Activities supporting the exposure measures conducted as part of NEXUS included determination of air exchange rates in each residence, collection and analysis of dust samples for mold in children's homes, development and analysis of a hybrid dispersion model system, analyses of spatial resolution and geocoding errors, comparison of alternative exposure measures, and collection of time activity information for children. A wide set of health-related measures was collected for each child, caregiver and household. Health measures collected on a seasonal basis included respiratory symptoms, lung function, medication use and exhaled nitric oxide concentrations. Additional measures were collected when children reported colds. Urine specimens and nasal lavage samples for viral identification were collected and archived. Statistical analyses tested for differences between exposure groups, and multivariate models using generalized estimating equation (GEE) models and generalized additive mixed models (GAMM) were used to evaluate relationships with exposure variables and to adjust for covariates and potential confounders (e.g., age, gender, race, season of data collection, caregiver education and depression score, and household tobacco smoke exposure). These analyses were completed for outcome measures using categorical exposure measures initially used to recruit the children. 

Conclusions:

As noted earlier, this report has summarized a subset of findings from NEXUS. This section summarizes key findings from the analysis. Ambient pollutant concentrations measured in typical urban scale monitoring networks do not reflect the levels and patterns of traffic-related air pollutant concentrations, although they may reflect temporal variations that result from meteorological factors. More refined exposure measures that capture the spatial and temporal resolution of traffic-related air pollutants are needed. A tier of increasingly detailed exposure metrics was developed. Comparisons of selected metrics, including geographic measures (e.g., proximity to major roadways), traffic data, emission inventory information, and dispersion modeling showed substantial differences and the potential for exposure misclassification. Spatially and temporally refined exposure metrics are needed, ideally matching the location and time spent in different locations (home, school, near roadways, etc.) To accurately estimate exposures of traffic-related pollutants, a high degree of spatial resolution is needed, and geocoding errors can be significant. Air quality modeling provided detailed spatial and temporal coverage of air pollutant concentrations across the study area, from which subject-specific exposure metrics were derived for use in the epidemiology (health) models. As noted, such resolved exposure information is difficult or infeasible to obtain using air quality monitoring or statistical models (e.g., land use regression models). While data and computational demands for dispersion modeling of traffic emissions at the urban scale are non-trivial, once established, dispersion modeling systems can provide exposure information for both on- and near-road environments that benefit exposure assessments of traffic-related air pollutants. NEXUS focused on children with symptoms or diagnoses of asthma. Health effect domains focused on asthma aggravation (e.g., lung function, symptoms), inflammation and oxidative stress (e.g., exhaled nitric oxide), and respiratory viral infections (e.g., frequency, severity, type). Health information collected on the 141 children enrolled have a high degree of temporal and spatial coverage and resolution, for example, we have repeated health measurements on the children through multiple seasons. Results of the children's baseline pulmonary function tests indicate that a substantial fraction of the children enrolled in NEXUS have obstructive lung function, frequent symptoms, and elevated exhaled nitric oxide levels consistent with poorly controlled asthma. While rates of asthma in portions of Detroit are known to exceed state and regional averages, NEXUS was not designed to investigate health disparities. In analyses using adjustments for the child’s age, gender, race, season of data collection, duration of time in study, caregiver education, caregiver depression score, and household tobacco smoke exposure, proximity of the child's home to large highways, and to highways with considerable diesel traffic, appears to be risk factors for airways obstruction in children, as based on pulmonary function tests. Ongoing analyses are testing more refined exposure metrics. 


Journal Articles on this Report : 12 Displayed | Download in RIS Format

Other project views: All 39 publications 12 publications in selected types All 12 journal articles
Type Citation Project Document Sources
Journal Article Arunachalam S, Valencia A, Akita Y, Serre ML, Omary M, Garcia V, Isakov V. A method for estimating urban background concentrations in support of hybrid air pollution modeling for environmental health studies. International Journal of Environmental Research and Public Health 2014;11(10):10518-10536. R834117 (Final)
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  • Journal Article Batterman S. The near-road ambient monitoring network and exposure estimates for health studies. EM 2013(7):24-30. R834117 (Final)
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  • Journal Article Batterman S, Burke J, Isakov V, Lewis T, Mukherjee B, Robins T. A comparison of exposure metrics for traffic-related air pollutants: application to epidemiology studies in Detroit, Michigan. International Journal of Environmental Research and Public Health 2014;11(9):9553-9577. R834117 (Final)
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  • Journal Article Batterman S, Chambliss S, Isakov V. Spatial resolution requirements for traffic-related air pollutant exposure evaluations. Atmospheric Environment 2014:94:518-528. R834117 (Final)
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  • Journal Article Batterman S, Ganguly R, Isakov V, Burke J, Arunachalam S, Snyder M, Robins T, Lewis T. Dispersion modeling of traffic-related air pollutant exposures and health effects among children with asthma in Detroit, Michigan. Transportation Research Record 2014;2452:105-112. R834117 (Final)
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  • Journal Article Batterman S, Ganguly R, Harbin P. High resolution spatial and temporal mapping of traffic-related air pollutants. International Journal of Environmental Research and Public Health 2015;12(4):3646-3666. R834117 (Final)
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  • Journal Article Breen MS, Burke JM, Batterman SA, Vette AF, Godwin C, Croghan CW, Schultz BD, Long TC. Modeling spatial and temporal variability of residential air exchange rates for the Near-Road Exposures and Effects of Urban Air Pollutants Study (NEXUS). International Journal of Environmental Research and Public Health 2014;11(11):11481-11504. R834117 (Final)
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  • Journal Article Breen M, Long T, Schultz B, Crooks J, Breen M, Langstaff J, Isaacs K, Tan Y-M, Williams R, Cao Y, Geller A, Devlin R, Batterman S, Buckley T. GPS-based Microenvironment Tracker (MicroTrac) Model to estimate time-location of individuals for air pollution exposure assessments: model evaluation in central North Carolina. Journal of Exposure Science and Environmental Epidemiology 2014;24:412-420. R834117 (Final)
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  • Journal Article Ganguly R, Batterman S, Isakov V, Snyder M, Breen M, Brakefield-Caldwell W. Effect of geocoding errors on traffic-related air pollutant exposure and concentration estimates. Journal of Exposure Science and Environmental Epidemiology 2015;25(5):490-498. R834117 (Final)
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  • Journal Article Isakov V, Arunachalam S, Batterman S, Bereznicki S, Burke J, Dionisio K, Garcia V, Heist D, Perry S, Snyder M, Vette A. Air quality modeling in support of the Near-Road Exposures and Effects of Urban Air Pollutants Study (NEXUS). International Journal of Environmental Research and Public Health 2014;11(9):8777-8793. R834117 (Final)
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  • Journal Article Kamal A, Burke J, Vesper S, Batterman S, Vette A, Godwin C, Chavez-Camarena M, Norris G. Applicability of the environmental relative moldiness index for quantification of residential mold contamination in an air pollution health effects study. Journal of Environmental and Public Health 2014;2014:261357 (7 pp.). R834117 (Final)
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  • Journal Article Vette A, Burke J, Norris G, Landis M, Batterman S, Breen M, Isakov V, Lewis T, Gilmour MI, Kamal A, Hammond D, Vedantham R, Bereznicki S, Tian N, Croghan C, Community Action Against Asthma Steering Committee. The Near-Road Exposures and Effects of Urban Air Pollutants Study (NEXUS): study design and methods. Science of the Total Environment 2013;448:38-47. R834117 (2012)
    R834117 (Final)
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  • Supplemental Keywords:

    Air pollution, asthma, diesel, traffic, Detroit, RFA, Health, Scientific Discipline, PHYSICAL ASPECTS, Air, HUMAN HEALTH, particulate matter, Health Risk Assessment, Health Effects, Physical Processes, Allergens/Asthma, asthma, children's health, asthma triggers, air toxics, exposure, air pollution, children, air pollutant, human exposure, airborne pollutants, PM

    Relevant Websites:

    Detroit Community-Academic Urban Research Center and CAAA

    http://www.detroiturc.org/

    EPA fact sheet:

    https://www.epa.gov/nerl/download_files/documents/NearRoadwayTechnical_external_fact_she

    et_071910.pdf

    Air quality:

    2010: http://www.youtube.com/watch?v=0107SLVY0oU

    2011: http://www.youtube.com/watch?v=5vZ0lG5T7wc Exit

    Progress and Final Reports:

    Original Abstract
  • 2009 Progress Report
  • 2010 Progress Report
  • 2011 Progress Report
  • 2012 Progress Report