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EMI Questions & Answers

Q: What is EMI?

A: The EMI is a model that predicts individual exposures for multiple air pollutants from ambient concentrations, meteorology, and questionnaire information such as building characteristics, occupant behavior related to building operation, indoor sources, and time-activity patterns.

Q: Who is developing EMI?

A: The EMI is being developed, evaluated, and applied by National Exposure Research Laboratory (NERL) in coordination with EPA’s Office of Air Quality Planning and Standards, National Health and Environmental Effects Research Laboratory, National Center for Environmental Assessment, National Risk Management Research Laboratory; the University of Michigan, Harvard University, Applied Research Associates, the German Research Center for Environmental Health, and the National Children's Study.

Q: Who are the anticipated users of EMI?

A: The intended users of EMI include health scientists in government, academia, and industry who perform epidemiologic analysis for air pollution cohort health studies. The development and evaluation of EMI is being driven by the needs of the health studies. For this interdisciplinary research effort, several close collaborations have been established with health scientists performing cohort health studies both within and outside the EPA, including collaborators in the National Health and Environmental Effects Research Laboratory, University of Michigan, the National Children’s Study), and the German Research Center for Environmental Health.

Q: What does EMI provide its users?

A: Initially, EMI will provide exposure metrics for specific air pollutants associated with four cohort health studies that examine: (1) cardiovascular events for diabetics in central North Carolina, (2) development of asthma for children across the country (National Children’s Study), (3) exacerbation of asthma for children living near major roadways in Detroit, Michigan, and (4) respiratory effects for asthmatics in central North Carolina.

Q: Will users of EMI need specialized software?

A: No. EMI is being developed using software that will create standalone executables for royalty-free distribution to EMI users.

Q: Where does EMI fit in EPA's Research Goals?

A: This research supports the requirements under the Clean Air Act and recommendations by the National Research Council. Exit EPA Disclaimer The overall goal of this research is to provide a modeling tool to enhance the ability to conduct air pollution human exposure assessments with greater certainty. The EMI applications for client-specific needs will serve to strengthen the science behind regulatory decision-making on setting the National Ambient Air Quality Standards (NAAQS). This modeling effort will address significant challenges relating to:

Q: How will EMI estimates be evaluated?

A: The EMI estimates will be evaluated using questionnaires and measurements from data-rich exposure field studies. These field studies include (1) Research Triangle Park (RTP) Particulate Matter Panel Study, which is the same geographical location as some of the initial health studies planned for EMI application; (2) Detroit Exposure and Aerosol Research Study that is the same geographical location as other health studies planned for EMI application; (3) Boston Panel Study; Exit EPA Disclaimer (4) Los Angeles, Houston, Elizabeth NJ Panel Studies (RIOPA); Exit EPA Disclaimer (5) Milwaukee and Sacramento Panel Study. Exit EPA Disclaimer

Q: How does EMI relate to SHEDS-PM? (see References 2-4)

A: The algorithms for the indoor air quality models and dosimetry models used by EMI and SHEDS can be similar. However, there are several differences between EMI and SHEDS.

  1. The applications for EMI and SHEDS are different. The EMI is designed to support health studies with individual health outcomes, and requires sufficient questionnaire information from these individuals to provide the inputs for EMI. The SHEDS design provides population distributions of exposures for demographic groups (e.g., school-age children, elderly adults), not specific individuals, but can support health studies with health outcomes at census tract to county level resolution (e.g., emergency room visits, mortality).
  2. The input data and model‑predicted outputs of EMI and SHEDS are different. While both models predict exposures from a time-series of ambient air pollutant concentrations, EMI uses individual-level input data (e.g., questionnaires) to predict individual exposures for specific people in health studies, and SHEDS uses population-level input databases and parameter distributions (e.g., US Census and human activity databases) to estimate population variability in exposures.
  3. Since the goal of EMI is to estimate exposures for specific people rather than population variability, the time diary assembly algorithms used in the SHEDS are not appropriate for EMI. SHEDS uses a set of diaries selected from an activity database matched by age, gender, weekday/weekend, etc. EMI incorporates the individual time-location-activity diaries from the health study participants to assemble longitudinal time-location-activity profiles that are specific to each individual being assessed.

Q: How does EMI relate to other research within NERL and ORD?

A: Some EMI modules being developed and evaluated could be applied in other exposure models in NERL and ORD. For example, the air exchange rate model could be integrated into population-level exposure models such as SHEDS. Also, EMI can be coupled with other models such as air quality models and lung dosimetry models to improve understanding of the source to effects continuum.

Q: How does EMI relate to the National Children's Study? Exit EPA Disclaimer

A: We are coordinating with the National Children’s Study (NCS) Program Office to apply EMI for air pollutants related to the NCS asthma hypotheses, to help design NCS questionnaires to support EMI application and reduce participant burden, and to use EMI to help plan NCS pilot studies.

Q: How does EMI relate to other exposure research, specifically the C-FERST, that supports cumulative (multiple chemicals) exposure and risk assessments in communities research?

A: The NERL project to develop tools for community and environmental justice assessments is researching approaches for providing community-level human exposure assessments. The "communities" project is developing modeling and other exposure approaches to inform EPA Regional office and community assessments. The health studies where EMI is applied will evaluate the existing exposure science and either confirm its predictive abilities or suggest new hypotheses or approaches to characterize human exposure better. This information can then help to determine the most appropriate human exposure data needed for future community-level or environmental justice assessments.

Human Exposure and Atmospheric Sciences

Research & Development | National Exposure Research Laboratory

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