The American Lung Association’s Year of Air Pollution and Health seeks to raise awareness of the health impacts of air pollution, and to generate support for the solutions needed to provide healthy air for every American. This month’s theme is “Where does Air Pollution Come From?”

In California, where I live and work, transportation sources dominate our harmful air pollution burdens. According to the California Air Resources Board, burning fossil fuels for transportation causes approximately 80 percent of the nitrogen oxide (NOx) pollutants that form ozone (AKA “smog”) that threatens the health of tens of millions of our residents (and lands us at the top of the “State of the Air” most-polluted cities list). Ozone is an air pollutant that causes essentially a “sunburn” in the lungs and can be deadly. Transportation emissions are also responsible for roughly half of California’s climate pollution, and transportation is the leading source of climate pollution across the United States.1 ,2

When discussing key programs to protect public health against harmful transportation pollution, the impact of California’s landmark motor vehicle pollution policies cannot be overstated. These policies have benefitted Californians—and all Americans—with cleaner air, reduced oil consumption and less greenhouse gas pollution that drives climate change. These advances are critically important to public health, and there is still much work to do to clean up pollution from cars and trucks.

California’s programs to control harmful motor vehicle emissions span back decades—from identifying tailpipes as a key source of smog in Los Angeles in the 1950s to requiring the first catalytic converters in the 1970s to the nation’s first greenhouse gas emission standards for cars in 2004—with cleaner air following each step. 

California’s Advanced Clean Cars Standards target reductions in smog-forming NOx, particle pollution and greenhouse gases, while also requiring increasing numbers of zero-emission vehicles to be sold in the state. Adopted in 2012, these programs were designed to reduce NOx by 75 percent, dramatically control particle pollution and reduce climate pollution from passenger vehicles by over one-third between 2017 and 2025.

Under the federal Clean Air Act, California can request a waiver from EPA to enact stronger-than-federal standards to help achieve health-protective pollution reductions that are especially important for Californians. Other states can decide to follow California’s more stringent standards, which now cover roughly one-third of the U.S. vehicle market (Colorado adopted the standards in 2018). Through this process, California’s more health-protective standards have become a model for other states and the single national program we now rely on to reduce harmful pollutants.

Despite the national contribution of California’s cleaner cars standards, the Trump Administration is considering a proposal to weaken the national cleaner cars standards for greenhouse gases and revoke California’s authority to enact stronger standards. This attack on clean air and public health provoked widespread condemnation among America’s leading health and medical organizations. A letter of opposition endorsed by over 90 national health organizations, declared the Trump Administration’s proposed replacement program to be “directly at odds with the interests of protecting and improving public health and the air we breathe.”

The letter summed up the proposal as follows:

No rational basis exists for curtailing advancement of vehicle technologies that reduce harmful levels of emissions, fuel consumption and consumer costs. The proposed standards will lead to the consumption of an additional half million barrels of oil a day, raising direct health impacts associated with criteria air pollutants and carcinogenic toxic emissions for communities already most impacted by the “upstream” pollution associated with the extraction, transportation and refining of petroleum products, and creating an overall increase in particle pollution as compared to the existing standards in 2025 and beyond.

We must view this attack on the cleaner car standards, and on states’ Clean Air Act authority to protect their citizens, within the context of the dozens of clean air rules now being targeted for reversal or repeal under the Trump Administration. There is no rational basis for undercutting proven programs protecting all Americans’ health.    

The American Lung Association and our health and medical partner organizations call on the Trump Administration to prioritize the health of Americans, implement current cleaner car standards, and work with states to create future cleaner car standards with the urgency required to protect the air we breathe and promote a stable climate.

You can help by sharing your story. Tell us why you care about cleaner cars so that we can share your perspective with decision-makers. Please help us put a human face on the health impacts of air pollution from vehicles.


  • California Air Resources Board. Mobile Source Strategy.
  • U.S. Environmental Protection Agency. Inventory of U.S. Greenhouse Gas Emissions and Sinks
Asthma Basics Workshop - National
, | May 07, 2024
Asthma Basics Workshop - National
, | May 15, 2024