Resource Type: Model
GEOS-Chem is an open?source global 3?D chemical transport model used to simulate atmospheric composition, including gases and aerosols, and their chemistry, transport, and deposition. The website provides documentation, installation and run instructions, tutorials, model version information, input datasets, and links to the user community and developer resources. Researchers use it to run simulations for air quality, climate, and biogeochemical cycling studies, and to contribute improvements back to the shared codebase.
EPA’s HAPEM (Hazardous Air Pollutant Exposure Model) is a human exposure model that estimates how people are exposed to outdoor-origin hazardous air pollutants as they move through different microenvironments (home, work, in transit, outdoors). Using ambient concentration inputs, population and activity-pattern data, and microenvironmental factors (e.g., infiltration indoors), HAPEM produces distributions of exposure for various population groups and is used in national? and regional?scale risk assessments such as the National Air Toxics Assessment.
EPA’s Human Exposure Model (HEM) is a probabilistic exposure assessment tool used to estimate how people are exposed to contaminants (often air pollutants, but not limited to them) through different pathways and microenvironments. It is designed to support human health risk assessments by translating environmental concentrations into population exposure distributions for specific pollutants, locations, and demographic groups. HEM uses information on contaminant levels, population characteristics, and time–activity patterns to produce quantitative estimates of average and high-end exposures suitable for regulatory analyses and comparative policy evaluations.
EPA’s MOtor Vehicle Emission Simulator (MOVES) is a state-of-the-science emission modeling system that estimates emissions for mobile sources at the national, county, and project level for criteria air pollutants, greenhouse gases, and air toxics.
Repository for the Simple Interactive Models for better air quality set of tools. These tools demonstrate fundamental equations to calculate, visualize, and interpret air emissions and pollution. The tools are intended to make links between emissions, pollution dispersion, impacts, and potential solutions more accessible to a wider set of stakeholders. The tools include models as well as primers on different air quality topics.
The HARP Air Dispersion Modeling and Risk Tool, developed by the California Air Resources Board, is Windows-based software that allows users to run air dispersion models and calculate associated health risks from toxic air pollutants. Used primarily in the state’s Hot Spots Analysis & Reporting Program, it integrates modeled concentration outputs with built?in health effect values and demographic data (including a dedicated census database and health database) to support standardized health risk assessments for stationary emission sources in California.
The CACES data portal provides publicly available, high?resolution estimates of air pollution exposures and related metrics developed by the Center for Air, Climate, and Energy Solutions. It offers gridded and geographically linked datasets (e.g., by census tract, county, or other units) for pollutants like fine particulate matter (PM?.?), ozone, and nitrogen dioxide over multiple years, along with documentation and code. Researchers, agencies, and advocates can download these modeled exposure surfaces to analyze trends, assess health and equity impacts, and link air quality estimates to demographic, health, and policy data.
Estimate of surface-level nitrogen dioxide (NO2) concentrations for the continental US at ~ 1km × 1km derived from TROPOMI data from a land-use regression model. The development of this dataset is documented in a manuscript in ES&T Air by Nawaz et al. and was originally developed for a time period of 2019-2022. This dataset estimates surface-level NO2 by combining satellite derived data (TROPOMI) with OpenStreetMaps and Google Earth Engine land-use information and ERA5 meteorology reanalysis data.
The ECHO-AIR website documents an open-source modeling tool that converts changes in emissions into estimates of PM2.5 concentration and health impacts using the InMAP Source Receptor Matrix. Developed initially for California, it provides code, setup instructions, and methodological details for running scenario analyses that quantify how incremental emission changes affect population exposure and excess mortality, with an emphasis on environmental justice and climate policy evaluation.
EPA’s Community Multiscale Air Quality (CMAQ) modeling system is an open-source, regional air quality model used to simulate how pollutants such as ozone, PM2.5, and air toxics form and move in the atmosphere. It combines detailed atmospheric chemistry, emissions, and meteorology to estimate pollutant concentrations and deposition over time and space. The CMAQ website provides the model code, documentation, tutorials, input datasets, and example applications, supporting researchers and agencies in evaluating air quality policies, health and ecosystem impacts, and interactions between air quality and climate.
