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. , Lewis, Toby C. , Mukherjee, Bhramar , Dion, F , Robins, Thomas
Institution: University of Michigan
EPA Project Officer: Chung, Serena
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: Particulate Matter , Air
This proposal has the objectives of (1) investigating a diverse range of respiratory outcomes in children with asthma that are associated with near-road exposures to air pollutants, and (2) characterizing the pollutants and exposures associated with these outcomes. We will evaluate three respiratory health effect domains: asthma aggravation (lung function, symptoms), inflammation and oxidative stress responses (exhaled nitric oxide, nasal cytokines, urinary isoprostanes), and respiratory viral infections (frequency, severity, type) in order to address a number of important, unresolved questions: Which measures of traffic-associated pollution are most closely associated with asthma aggravation? Which characteristics of roadway-associated pollution are most strongly associated with markers of inflammation and oxidative stress in asthmatic children, and do these relationships vary by the type of traffic or characteristics of the child? Does traffic exposure influence the likelihood or severity of respiratory viral infections? What degree of exposure misclassification is attributable to the use of community monitoring as a surrogate for individual exposures, as compared to the use of indoor monitoring and individualized exposure modeling, and what impact does this have on point estimates and confidence intervals for measures of association between exposures and key health outcomes? These and other questions will be addressed in an observational study highly relevant to real world conditions, focusing on children with persistent asthma, a group which tends to be especially susceptible to adverse health effects from air pollutants.
The proposed epidemiological study will utilize a cohort of 105 children, ages 6 to 14 years, with persistent asthma living in Detroit, MI and recruited on the basis of the proximity of their residence to different types of roadways. We will examine three groups of 35 children each: (1) high traffic/high diesel (HD) homes, located within 150 m of roads with high volumes of both total (car plus truck) and commercial (diesel) truck traffic; (2) high total but low diesel (LD) traffic areas, i.e., again within 150 m of roads with a high volume of total traffic but low-to-moderate truck traffic, and; (3) low traffic (LT) areas, avoiding traffic corridors, i.e., homes more than 300 m from moderate-to-high traffic roads. All children will be drawn from the same neighborhoods and school catchment areas to help minimize possible confounding from unmeasured neighborhood-associated covariates. Community-based participatory research principles will be utilized, in part to aid participant enrollment and retention. A baseline health assessment will include review of the child’s medical history, asthma medications, health services utilization, a physical examination, spirometry, skin prick testing for common allergens, and a survey of the caregiver. Then, in 1-2 week periods conducted in most seasons over a nearly 2-year period, we will collect health measures and biomarkers relevant to pulmonary function, medication use, health care utilization, diary reports of upper respiratory infection (URI) symptoms; fraction of exhaled nitric oxide (FeNO), urinary F2-isoprostanes, and nasal lavage. Similar information will be collected when children report upper respiratory infections. Pollutant exposures will be monitored and modeled using a combination of indoor and ambient continuous and seasonal sampling. Covariate-adjusted generalized estimating equations (GEE) for repeated measure outcomes, and Poisson models for count outcomes, will be used to investigate exposure-health associations. The study design permits cross-validation of exposures and the ability to test effects from road-way exposures from four perspectives: (1) the three exposure groups, (2) direct measures of exposures closely associated with vehicular exhaust, e.g., PM2.5 and elemental carbon; (3) modeled exposures; and (4) source-apportioned vehicular and diesel exhaust. Through the use of study cohorts, baseline assessments, and other measurements and facilities provided through three currently funded, related epidemiological studies that the study team is conducting in Detroit, very significant efficiencies will be realized for achieving the objectives and addressing the hypotheses of the proposed study.
The proposed research addresses both the effects and the mechanisms by which traffic-associated exposures induce exaggerated airway responses in children with asthma, and how these exposures cause biologic responses on inflammatory pathways, oxidative stress, and the frequency and severity of respiratory outcomes. The linkages between air pollutants and several of the outcomes, e.g., oxidative stress and URI, are largely unexplored, and potentially very important in understanding the health significance of traffic-related air pollutants. Lastly, the combination of exposure assessment approaches used in the health studies should advance our understanding of those exposures that are most relevant to the health outcomes.