Cleaner cars protect your health and future

When wildfires raged through Los Angeles at the start of the year, smoke filled the skies and evoked memories of the thick smog that blanketed the city decades ago. That level of smog is a thing of the past partly because of California’s pioneering clean car standards, which helped phase out leaded gasoline, introduced catalytic converters, and led to dramatic reductions in smog-forming pollutants. Today it’s the Advanced Clean Cars II (ACC II) regulations spearheaded by the state that are leading the way to clean vehicle technologies that bring substantial benefits for human health and the climate.

ACC II is a two-pronged regulation that applies to light-duty passenger cars, pickup trucks, and sport utility vehicles. It sets more stringent tailpipe emission standards and requires an increasing share of electric vehicles until they reach 100% of new sales in 2035. Under Section 177 of the Clean Air Act, other states have the authority to adopt California’s clean car and truck standards in lieu of federal standards to help meet their air quality standards.

After it was first adopted, the ICCT contracted Sonoma Technology Inc. to examine ACC II’s impacts. The analysis assessed emissions of nitrogen oxides (NO_x) and particulate matter (PM_2.5), both criteria pollutants, greenhouse gas (GHG) emissions in terms of carbon dioxide equivalent (CO₂e), and monetized health savings from avoided emissions in 11 states that have adopted ACC II as of 2025 and 5 additional states that have not. The results in Table 1, for the 11 states that have adopted ACC II, show that combined cumulative tank-to-wheel (TTW) NO_x emissions could be reduced by 81,000 tonnes and PM_2.5 emissions by 5,600 tonnes from 2025 to 2040. Well-to-wheel (WTW) CO₂e emissions could drop by close to 770 million tonnes during the same period and this would lead to an estimated $5 billion in net health benefits in 2040.

^a BAU is the absence of ACC II.

As you can see, New York is one of the states that stands to benefit most. It’s estimated to see a 45% reduction in NO_x emissions by 2040 alongside an 18% drop in PM_2.5 and an 89% decrease in CO₂e emissions. This translates to nearly 14,000 tonnes less NO_x, close to 1,250 tonnes less PM_2.5, and 190 million tonnes CO₂e emissions avoided, for close to $1.5 billion in net health benefits. Maryland is similarly projected to reap substantial net health benefits—an estimated $604 million. In states with lower population density such as New Mexico, Oregon, and Vermont, ACC II adoption would yield smaller-but-still-meaningful net health benefits ranging from $13 million to $106 million. If there’s any delay or retreat from the commitment to the ACC II regulations, which are among the most critical strategies for reaching attainment under the National Ambient Air Quality Standards, the states would be forfeiting some or all of these benefits and could face penalties if they fail to meet the standards.

This all shows that adopting and fully implementing clean vehicle standards isn’t just good for the climate—it’s a breath of fresh air for everyone. And while air pollution affects everyone, the health consequences are not evenly distributed. Low-income neighborhoods and communities of color are often located near highways, ports, and industrial zones and these areas are where vehicle emissions are highest. These communities consequently experience higher rates of asthma, respiratory diseases, and other pollution-related health issues. Without programs like ACC II, they will continue to bear the brunt of poor air quality. Investing in cleaner vehicle technologies is a matter of environmental justice.

A transition to zero-emission vehicles is also critical for the climate. Transportation remains the largest contributor to U.S. GHG emissions: In 2022, it was 28% of total GHGs—the largest share of any economic sector. Battery electric vehicles (BEVs) will play a critical role in reducing harmful pollutants and GHG emissions. As ICCT’s research shows, BEVs, which have zero tailpipe emissions, have significantly lower life-cycle GHG emissions than plug-in hybrid electric vehicles, hybrid electric vehicles, and traditional combustion engine vehicles. With the electricity grid expected to transition to renewable energy in the coming decades, the emissions advantage of BEVs will only grow larger. Already by 2020, in every U.S. state, the average BEV had lower well-to-wheel emissions than the average conventional gasoline vehicle.

The state-level leadership demonstrated by policies like ACC II is an important part of U.S. environmental stewardship. States that exercise the right to adopt California’s standards under the Clean Air Act by implementing leading-edge ACC II regulations are supporting clean air and environmental justice in their communities. This is especially powerful in the absence of strong federal leadership.