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Science Question Box:

Do community-based ambient air monitors accurately represent what people are exposed to every day?

Understanding this is critical to understanding the impacts of specific ambient pollution sources – such as factories, power plants, and traffic – on human health. It is also crucial to understanding the ability of community-based monitors to represent potential human exposures.

DEARS was designed to investigate a wide range of environmental pollutants (including particulate matter, criteria gases, semi-volatile organics and volatile organic compounds) across multiple seasons. The wealth of data collected during the project has proven extremely useful for scientists in and outside EPA.

Researchers and stakeholders from Health Canada, Environment Canada, University of Michigan, the Michigan Department of Environmental Quality, Detroit Department of Environmental Affairs, and the Detroit public school system have all used DEARS data to either conduct or supplement air quality studies of their own. DEARS data captures the variations in air quality experienced across many distinctive Detroit neighborhoods, and includes both residential and personal air quality monitoring measurements.

Data from more than 1,300 measurements of particulate matter and other pollutants in outdoor air were obtained during the DEARS data collection. A similar number of measurements were collected from personal monitoring devices, as well as from home indoor air quality monitors.

These measurements provided the means to investigate select human cardiovascular health effects in the DEARS study population (University of Michigan and Health Canada). The data also provided the means to investigate U.S.-Canadian border air quality, and to explore the origin and transport of air pollutants of interest to the United States and Canada (Health Canada, Environment Canada).

DEARS additionally supported EPA’s investigations into the role of air pollutants’ impact on asthmatic children’s health, and the toxicological properties of these pollutants.

Research Goals

EPA and its collaborators have conducted a series of research studies targeting the Detroit Metropolitan area. These include:

The overarching goal of these related efforts has been to use community, residential indoor, residential outdoor, and personal exposure monitoring data (such as that collected in DEARS) to assess the impact of ambient-based particulate matter (PM) and air toxic sources on human populations and the neighborhoods in which they live.

Assessing ambient source impacts to local neighborhoods and observed health effects has provided valuable information on the current uncertainty of using ambient-based monitors as a surrogate for human exposures.

The Studies

DEARS - Detroit Exposure and Aerosol Research Study (DEARS)
DEARS collected ambient, personal, residential indoor, and residential outdoor data on 136 residents in Wayne County, Mich., over a three-year period from 2004-2007. Researchers identified the ambient source impact of component PM materials and certain air toxics. This source information, along with air pollution concentrations (personal, residential indoor, residential outdoor) is being used to determine the human and environmental exposure factors that influenced the study population. The impact of these air pollutants on select cardiovascular health effects, such as arterial dilation, is currently being studied. For preliminary research findings see DEARS Research Findings.

Researchers have completed all the DEARS field data collections. Source apportionment and modeling applications are being pursued and an extensive number of peer-reviewed publications and reports have been published. A recent report (EPA/600/R-11/048) found in the Publication section summarizes progress DEARS has achieved concerning its primary study objectives and ongoing research efforts.

Contact: Ron Williams, 1-866-EPA-DEAR

Detroit Children's Health Study (DCHS)
Using measurements and modeled environmental data for pollution collected by DEARS, the Detroit Children’s Health Study compared certain pollutants against data on asthma symptoms in children (ages 7-12) living in the Detroit and Dearborn areas. One of the main priorities of the DCHS, which was led by EPA scientists, was to learn more about the relationship between asthma symptoms in children and their exposure to automotive emissions. School-based exposure monitoring was conducted and then linked to the collection of approximately 11,000 health surveys collected from children in the specified age range. Preliminary findings have been published and additional DCHS data analyses are being pursued.

Contact: Dr. Lucas Neas. 919-966-9961 or Dr. Shaibal Mukerjee at 919-541-1865

Mechanistic Indicators of Childhood Asthma (MICA)
A number of environmental and personal factors have been associated with the development and exacerbation of childhood asthma, but many aspects of this association require further research. The Mechanistic Indicators of Childhood Asthma study (MICA) was an epidemiologic study conducted by EPA in 2006-2009 to advance understanding of risk factors and triggers of childhood asthma.

This study gathered information on biological markers of exposure, early effect, and susceptibility (including gene expression data) from approximately 100 asthmatic and 100 non-asthmatic children recruited from the Detroit, Michigan Metropolitan area.

MICA study participants provided questionnaire data, exhaled nitric oxide and lung function measurements, and indoor dust, blood, urine and other biological specimens. These are being analyzed for various markers of exposure to volatile organic compounds (VOCs), metals and polycyclic aromatic hydrocarbons (PAHs).

The air monitoring component of MICA (MICA-air) used a participant-based approach in which passive air samplers were deployed by parents to collect indoor and outdoor measurements of nitrogen dioxide, VOCs, PAHs and naphthalene. The novel participant-based strategy was found to provide a cost-effective approach to exposure assessment that might be useful in other future epidemiological studies.

Contact: Dr. Jane Gallagher, 919-966-0638

Detroit Cardiovascular Health Study

The Detroit Cardiovascular Health Study was conducted by the University of Michigan as a parallel study to DEARS. Novel in-home measurements of cardiovascular function and extensive human exposure monitoring were conducted during the Detroit Cardiovascular Health Study. This data was combined with personal exposure data from DEARS to explore the human health impacts of exposure to particulate matter. Several epidemiological findings have now been published and are listed in the Publication section on the DEARS home page.

Field data collections for the study have been completed. Information gained from real-world collection of circulatory vessel constriction as a function of pollutant exposure has been integrated with DEARS exposure data. This integration has resulted in a number of epidemiological-based publications identifying the impact of particulate matter exposures on select human health effects. Ongoing efforts are attempting to identify the sources of the air pollutants and the role human activity has on human health.

Contact: Dr. Rob Brook, University of Michigan Department of Internal Medicine, 734-998-5627

Detroit PM Toxicology Study
The Detroit PM Toxicology Study is designed to link data about pollutant sources collected in DEARS to specific sizes of particulate matter. Using state of the art equipment, EPA scientists collected samples of PM in the Detroit area during two seasons of monitoring, and are currently running toxicological assessments of the material. Combining this information with the DEARS source data will give scientists a better understanding of the toxic properties of PM that comes from specific sources in the Detroit area.

Contact: Dr. Ian Gilmour, 919-541-0015

Canadian Windsor, Ontario Exposure Assessment Study (WOEAS)
The Canadian Windsor Ontario Exposure Assessment Study (WOEAS) was conducted simultaneously with DEARS and used a similar study design. Field data collections for WOEAS were completed in 2005. Integration of data from DEARS was conducted by EPA scientists to assist Canadian researchers in investigating the impact of regional air pollution sources on WOEAS study participants.

Data from both DEARS and WOEAS are being used to establish border air quality findings of interest to the United States and Canada. Data collected in WOEAS has the potential for extending exposure model development to a larger geographical area than what DEARS alone will provide. Potentially, this combined data could help scientists’ efforts to build spatial models of pollutant concentrations.

Preliminary findings have now been published on select air pollutants. A publication describing the WOEAS design and preliminary environmental findings may be found in the Publication section of the DEARS home page. A large number of additional analyses are ongoing and are expected to be publically available between 2011-2015.

Contact: Dr. Amanda Wheeler, 613 948-3686

Impact and Outcomes

The Detroit studies show the impact of collaborative inter-and intra-laboratory efforts across EPA to fully leverage resources on the complex issue of PM, air toxics, and observed toxicological and human health effects. EPA is collaborating with EPA’s Region 5, the state of Michigan, local environmental community action groups, local governmental organizations, academia, Health Canada and Environment Canada in this process. The outcome of these efforts is a database being used by a large number of partners to understand PM and air toxics source impacts on local populations, and the reduction of the uncertainty of using ambient-based monitors to assess source impacts for epidemiological studies.

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