Benefits and Impacts of Greenhouse Gas Limits on Disadvantaged Communities

Background

OEHHA conducts research to analyze the benefits and impacts of California’s climate actions on community air quality and health. We conduct analyses that are important to addressing communities’ concerns, use the best available data, and apply up-to-date methods. Our research represents successful collaboration between community-based organizations, the California Air Resources Board, and academic researchers.

On this webpage, you will find reports and publications summarizing our findings, as well as research tools that support equity-driven analyses.

Reports and Other Publications

Study: PM2.5 exposure disparities persist despite strict vehicle emissions controls in California

This study, published in 2024 in Science Advances, was conducted by UC Berkeley, University of Washington, and OEHHA. OEHHA provided technical and funding support for this work.

Study | Press Release

On-road mobile source PM2.5 exposure and relative disparity in exposure for each demographic group.

Fig. 1. On-road mobile source PM2.5 exposure and relative disparity in exposure for each demographic group.

Statewide population-weighted mean PM2.5 exposure concentrations (A) and relative disparity in exposure (B) attributable to on-road mobile sources for the four largest racial-ethnic groups and two policy-relevant environmental justice areas in California. See publication for full caption.

This publication’s major findings include the following:

1. There has been a 65% reduction in PM_2.5 exposure from vehicles over the last 20 years.
2. Communities of color and low-income communities have seen the biggest improvements. The largest reductions in air pollution levels over the past two decades (2000-2019) happened in Black, Hispanic, and Asian communities, narrowing disparities in exposure levels.
3. Despite these reductions, disparities remain. Communities of color are still exposed to higher levels of PM_2.5 than White Californians, a relative gap that did not change during the study period.
4. On average, cars and other light-duty vehicles caused greater disparities in PM_2.5 exposure levels than larger vehicles, such as trucks and buses, but there was significant variation by region.
5. The study found that most vehicular PM_2.5 exposure came from light-duty vehicles in the San Francisco Bay Area and the Los Angeles Area. But trucks, buses, and other heavy and medium-duty vehicles were responsible for most vehicular PM_2.5 exposure in the Central Valley.
6. Continued decreases in vehicle emissions will reduce PM_2.5 exposure for all Californians. Community- and equity-driven solutions are needed to narrow the gap in rate of exposure between racial/ethnic groups.

Report: Impacts of Greenhouse Gas Emission Limits Within Disadvantaged Communities: Progress toward Reducing Inequities

This report, released in 2022, focused on two significant contributors to greenhouse gas emissions in California, namely emissions from industrial facilities that were subject to the Cap-and-Trade Program and emissions from heavy-duty vehicles.

Executive Summary | Study | Press Release

This report’s major findings include the following:

1. Both HDVs and facilities subject to the Cap-and-Trade Program have reduced emissions of co-pollutants, with HDVs showing a clearer downward trend when compared to stationary sources. These emission reductions have major health benefits, including a reduction in premature pollution-related deaths.
2. The greatest beneficiaries of reduced emissions from both HDVs and facilities subject to the Cap-and-Trade Program have been in communities of color and in disadvantaged communities in California, as identified by CalEnviroScreen (CES). This has reduced the emission gap between communities with high and low CES scores, but a wide gap still remains.
3. The transition to zero-emission HDVs will expedite further emissions reductions.
4. While the progress observed is encouraging, inequities persist and federal, state, and local climate and air quality programs must do more to reduce emissions of GHGs and co-pollutants in order to reduce the burden of emissions on disadvantaged communities and communities of color.

Report: Tracking and Evaluation of Benefits and Impacts of Greenhouse Gas Limits in Disadvantaged Communities

This report, released in 2017, focused on facilities subject to the Cap-and-Trade Program. The report examines the location of these facilities with respect to communities identified as disadvantaged under Senate Bill 535 (SB535), and how facility emissions of greenhouse gases may relate to emissions of criteria and toxic air pollutants.

Report

This report’s major findings include the following:

1. A large fraction of facilities subject to the Cap-and-Trade Program are located in or near SB 535 disadvantaged communities.
2. Reductions in GHGs are likely to result in lower emissions of co-pollutants.

Research Tool to Support Equity-Driven Air Quality and Health Analyses: ECHO-AIR

OEHHA provided technical and funding support for the development of ECHO-AIR. ECHO-AIR can be used to evaluate disparities in PM_2.5 exposure and health outcomes. It was developed to support OEHHA's research and is available for public use on GitHub.

Intended Uses of ECHO-AIR

ECHO-AIR strikes a balance between the high spatial resolution required to assess PM_2.5 exposure disparities and the complexity of air quality modeling and was designed to support California Office of Environmental Health Hazard Assessment’s (OEHHA):

Analyses of the benefits and impacts of California’s climate policies in disadvantaged communities and to explore environmental justice disparities in PM_2.5 exposure and mortality. This includes evaluation of relative changes in PM_2.5 exposure and mortality between two or more timepoints or scenarios.
Estimates of PM_2.5 exposure using InMAP, a reduced complexity air quality model.

ECHO-AIR is well suited for projects investigating environmental justice issues, those requiring many modeling runs, or with limited resources to run complex air quality models. However, the ECHO-AIR tool is not a substitute for comprehensive chemical transport models; designed to evaluate absolute changes in PM_2.5 exposure and mortality; nor appropriate to apply to the neighborhood scale due to complexities in the modeling and the need for highly spatially resolved data sets.

For questions, please contact Álvaro Alvarado: Alvaro.Alvarado@oehha.ca.gov.