A modular system for source-to-dose exposure modeling of co-occurring air pollutants: recent developments and computational implementation
S. Isukapalli1, S.W. Wang1, P.G. Georgopoulos1, T. Pierce, J. Ching2
1Environmental and Occupational Health Sciences Institute, UMDNJ - R.W. Johnson Medical School and Rutgers University, Piscataway, NJ; 2National Exposure Research Laboratory (NERL), USEPA, Research Triangle Park, NC
The probabilistic source-to-dose modeling system, MENTOR/SHEDS-1A [Modeling ENvironment for TOtal Risk studies (MENTOR) using the Stochastic Human Exposure and Dose Simulation (SHEDS) approach in a One Atmosphere (1A) setting] characterizes cumulative exposures to co-occurring air pollutants by taking into account their physical and chemical interactions, and calculates exposure and dose profiles, while providing the ability to focus on time scales and subpopulations of interest. This is achieved through a sequence of steps involving (1) calculation of ambient outdoor concentrations using multiscale photochemical modeling, (2) spatiotemporal interpolation for developing census-tract level outdoor concentration fields, (3) calculation of microenvironmental concentrations that match activity patterns of the individuals in the population of each census tract considered, and (4) population-based dosimetry modeling that accounts for activity and physiological variability. The implementation of MENTOR/SHEDS-1A presented here improves upon previous versions by explicitly characterizing contributions of indoor sources, as well as effects of commuting patterns. A case study is presented focusing on modeling hourly resolved exposures over one year to ozone, formaldehyde, benzene, xylene, and toluene, for the urban Philadelphia, PA, and Camden, NJ areas. This case study utilizes the Models-3/CMAQ-AT (CMAQ-Air Toxics), which explicitly models a number of gas-phase air toxic compounds. Population exposures and doses are characterized with special focus on susceptible population groups such as the children and the elderly. The presentation focuses on methodological and computational issues relevant to implementing and optimizing the MENTOR/SHEDS-1A system for long-term population exposures.
This work is funded in part by a University Partnership Agreement between USEPA and EOHSI. Viewpoints expressed here do not necessarily reflect the views of USEPA or its contractors.