COBRA Revision History

This page describes the revisions and updates made to the CO-Benefits Risk Assessment (COBRA) Screening Model since October 2017.

June 7, 2024

EPA released version 5.1 in the Desktop Edition, which includes:

Bug fixes in the code to run batch files. Batch files can be used to submit emissions data representing multiple years or scenarios so that scenarios can run in succession without additional input from the user. This update fixed an issue where COBRA was not using the correct population and incidence input files for batch runs. This update also added an input for valuation files for batch runs, which was not included in previous versions. In addition, the format of the outputs from the batch files have been updated to match the format of the desktop model. See Appendix G of the User’s Manual for more information on running batch files for COBRA.
Updated valuation for asthma onset for 2028. The default 2028 valuation file included in COBRA had an incorrect dollar value for asthma onset from particulate matter, which was causing COBRA to underestimate the economic value of avoiding asthma onset for scenarios using the 2028 analysis year. This has been updated to the correct value of $80,211.96 per case avoided.
Updated interface for Advanced Options. This update removed the radio buttons for Model Year to select SR Matrix and Adjustments by year, which is no longer used in COBRA starting with version 5.0.

This update did not impact the Web Edition of COBRA.

April 23, 2024

EPA released version 5.0 in the Desktop Edition and Web Edition of COBRA, which includes:

Updated air quality model. Both the Desktop and Web Editions now use an updated air quality model (Source-Receptor (SR) matrix) that can estimate changes in annual ambient concentrations of both ozone (O₃) and particulate matter (PM_2.5). The previous S-R matrix version, which had been used in COBRA up through version 4.1., could only estimate changes in PM_2.5concentrations. Please see the updated COBRA User’s Manual for more information on the updated S-R matrix.
Health impacts of O₃ formation. Both the Desktop and Web Editions can now estimate the health impacts of O₃ formation as a result of changes in NO_x and VOC emissions. These are 12 health endpoints that describe O₃ health impacts, including the following new health endpoints: School loss days and asthma symptoms, including cough, wheeze, chest tightness, and shortness of breath.
Revised health impact functions for PM_2.5. The new health impact functions for PM_2.5 match those used in the regulatory impact analysis of the Particulate Matter National Ambient Air Quality Standards. These new functions also include new health effects not previously included in COBRA, including hospital admissions for Alzheimer’s disease and Parkinson’s Disease, incidence of stroke and lung cancer, asthma onset, and incidence of hay fever/rhinitis.
Results in 2023 dollars. The monetized health benefits result from COBRA Desktop and Web Edition are now presented in 2023 U.S. dollars.
Updated discount rate. Based on guidance from OMB Circular A-4, COBRA now uses a 2% discount rate by default. Users have the option to enter a custom discount rate in both the desktop and web editions of the tool.
Population and incidence input data for 2030-2050. EPA has developed inputs for 2030, 2035, 2040, 2045, and 2050, which can be uploaded to the COBRA Desktop Edition to estimate health impacts for years beyond what is preloaded.

November 23, 2021

EPA released version 4.1 in the Desktop Edition and Web Edition of COBRA, which includes improved connectivity EPA’s AVoided Emissions and geneRation Tool (AVERT) tool:

The COBRA Desktop Edition can now accept the full suite of pollutants estimated by AVERT, which now includes ammonia (NH₃) and volatile organic compounds (VOCs) in addition to fine particulate matter (PM_2.5), nitrogen oxides (NO_x), and sulfur dioxide (SO₂).
The COBRA Web Edition can now accept outputs directly from EPA’s AVERT Web Edition. Simply run a scenario in the AVERT Web Edition and click the button labeled “Submit Results to COBRA.” The changes in PM_2.5, NO_x, SO₂, NH₃, and VOCs estimated by AVERT will be pre-loaded and ready for you to run in the COBRA Web Edition.
Both the Desktop and Web Editions include an improved approach for the rare instances when AVERT estimates greater changes in emissions than the emissions in the COBRA baseline. In these rare instances, COBRA now accounts for the full impact of emissions reductions. See the COBRA User Manual for more details.

April 11, 2021

EPA released the COBRA Web Edition, a cloud-based version of COBRA, using version 4.0. The Web Edition of COBRA offers much of the same analytics as the Desktop Edition of COBRA, but in a format that users can run directly in their internet browsers. The methodology and process for running the Web Edition is the same as the Desktop Edition of COBRA, with some differences that are explained in more detail in the COBRA FAQs.

June 22, 2020

EPA released version 4.0 which includes a new set of analysis year options. Users can now choose among 2016, 2023, and 2028 for each COBRA run. Sources of the new 2016, 2023, and 2028 data include:

Emissions data: The COBRA 2016, 2023, and 2028 emissions baselines use emissions data from EPA’s 2016 Version 1 Air Emissions Modeling Platform (2016v1 platform), including reported emissions data for 2016 and forecast emissions for 2023 and 2028.
Population data: COBRA uses 2016, 2023, and 2028 population projections based on US Census of Population and Housing 2010 and economic forecasting models developed by Woods & Poole (2015).
Incidence data: COBRA 2016, 2023, and 2028 baseline mortality incidence is based on the US Centers for Disease Control’s mortality rate projections for 2015, 2025, and 2030.
Valuation data: All unit values were adjusted for historical/projected growth in real U.S. income between the year of the original unit value estimate and the COBRA evaluation year – either 2016, 2023, or 2028. The health values for each of these three years are expressed in terms of 2017 U.S. dollars.

May 30, 2018

EPA released version (3.2) which includes a new feature and minor enhancements, including:

A function to import results from EPA’s AVERT tool. EPA’s AVoided Emissions and geneRation Tool (AVERT) provides estimates of air pollution emission reductions from energy efficiency and renewable energy projects, programs, and policies. The latest version of AVERT (v2.0) allows users to export the results of the tool in a format that can easily be imported into COBRA. The newly released version of COBRA (v3.2) now includes a button that users can click to import the county-level emissions results from AVERT directly into COBRA. This new feature will allow easier screening-level analyses of the public health benefits of emission reductions from energy efficiency or renewable energy projects, programs, and policies.
Results in 2017 U.S. dollars. The monetized health benefits results from COBRA are now presented in 2017 U.S. dollars. In the previous version of COBRA (v.3.1), the results had been presented in 2010 U.S. dollars.

March 9, 2018

EPA released version (3.1) which includes a correction and minor enhancements, including:

A corrected set of calibration factors for 2017. COBRA 3.0 included incorrect factors that calibrate modeled data to actual monitored data for 2017 and, as a result, the estimated change in air quality was lower than it should have been for runs using the 2017 baseline. This also means that the estimated health benefits were lower than they should have been. The difference varies for different parts of country, but in some areas the benefits could be half of what they should be. Previous versions of COBRA (e.g., COBRA v2.71) did not have this error.
Minor user enhancements to the interface and for batch mode operation. Minor adjustments were made to the interface, including rearranging the “Create Emissions Scenario” screen so that all of the user options are displayed on the screen without having to scroll to see them, and a bug was fixed that was causing COBRA to crash for some users when running in “batch mode.”

October 2, 2017

EPA released version (3.0) which includes several enhancements, including:

An improved user interface with more flexible mapping functionality. With this version of COBRA, users can: customize the map color scheme, modify map interval breaks, explore data geospatially by selecting for specific attributes, and export maps for use in GIS programs.
New features that enable advanced users to import custom baseline and scenario emissions files, population datasets, incidence datasets, health effect functions, and valuation functions. This functionality makes it possible to use COBRA for years other than the preloaded 2025 baseline.
An additional analysis year, 2025, so for each COBRA run, users can now select the previously available 2017 baseline or the newly added 2025 baseline. Sources of the new 2025 data include:
- Emissions data: The COBRA 2025 emissions baseline uses emissions data from EPA’s 2011 Version 6.2 Air Emissions Modeling Platform (2011v6.2 platform) to forecast ambient 2025 PM_2.5 levels.
- Population data: COBRA uses 2025 population projections based on US Census of Population and Housing 2010 and economic forecasting models developed by Woods & Poole (2012).
- Incidence data: COBRA 2025 baseline mortality incidence is based on 2025 national-level Census mortality rate projections.
- Valuation data: For consistency with the 2025 COBRA emissions baseline year, all unit values were adjusted for historical/projected growth in real U.S. income between the year of the original unit value estimate and 2025. The 2025 health values, like the 2017 values, are expressed in terms of 2010 U.S. dollars.

(Note: the 2017 baseline remains unchanged from version 2.71)