EPAReal-time and historical ground-level air quality measurements from EPA's nationwide monitoring network. Incorporates PM2.5, ozone, CO, and NO₂ with IMPROVE and CASTNet quality flags.
EPA
EPA National Emissions Inventory (NEI)
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The National Emissions Inventory (NEI) is EPA's comprehensive estimate of air pollutant emissions from all source categories in the United States, published every three years. The NEI covers criteria pollutants (PM2.5, PM10, SO₂, NOx, CO, VOCs, ammonia), hazardous air pollutants, and greenhouse gases from point, area, mobile, and natural sources.
NEI data is the primary input to EPA's air quality modeling systems and provides the foundation for state and regional implementation plans under the Clean Air Act. The inventory is compiled from state and local agency reports, EPA emission factors, and sector-specific data collected through the National Emission Inventory Combined Air Emissions Reporting (CAER) system.
Learn more
Documentation, algorithm details, and background reading for NEI.
Download data
Access NEI through the provider portal or download it directly.
Tutorials
Self-paced tutorials to help you get started with NEI.
Getting started with NEI
An introduction to the NEI dataset — what it measures, how it is produced, and when to use it.
Accessing and downloading NEI dataFind, subset, and download NEI data, with tips for common file formats and access tools.
Exploring NEI in the AIR4US visualization toolLoad NEI layers in the AIR4US visualization tool and interpret them alongside other air quality data.
Cite this dataset
US EPA. EPA National Emissions Inventory (NEI). 1990 – Present. Accessed via the AIR4US Portal, https://www.epa.gov/air-emissions-inventories/national-emissions-inventory-nei.
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