Greenhouse gases have kept the Earth’s climate habitable for humans and millions of other species by trapping heat from the sun. These gases — carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), water vapor and fluorinated gases — act like a blanket absorbing the sun’s energy and not allowing it to escape into space.
Greenhouse gases were essentially positive until the Industrial Revolution, when, as humans began burning fossil fuels, the release of gases into the air accelerated beyond the Earth’s ability to absorb them. Greenhouse gases vary in their abilities to absorb energy and the time that they stay in the atmosphere: the IPCC’s Global Warming Potential (GWP) of each greenhouse gas allows comparisons of their differing effects. Read more on the Greenhouse Gases page.
This release of gases into the atmosphere has decreased the quality of the air we breathe, creating many health risks. Polluted air is shown to damage mental health in children and adults. And, as heat accelerates, so do respiratory and lung illnesses due to climate change related wildfires and smog. As the concentrations of heat grow ever greater, the Earth will change which living things can survive on this planet — and where. Almost 102 million Americans live in areas with poor air quality, and air pollution is the world’s leading environmental cause of illness and premature death.
The Clean Air Act identifies six common air pollutants found in the United States. These are particulate matter, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide and lead.
Particulate Matter (PM) can come from construction sites, wildfires, agricultural activities, roads, power plants, vehicles and buildings. Particulate Matter from wildfires and droughts will increase with climate change.
Ground-level ozone, which can harm human health, vegetation and ecosystems, and contribute to climate change, is expected to increase with a warming climate.
Carbon Monoxide (CO) is produced by cars, trucks, and other fossil-fuel-burning machinery.
Sulfur Dioxide (SO2) is mostly produced by the burning of fossil fuels.
Sources of Nitrogen Dioxide (NO2) include the burning of fuel, and emissions from cars and power plants.
Lead (Pb) gets in the air primarily from aviation fuel, waste incinerators, and lead-acid battery manufacturers.
Air pollutants from outdoor sources can also contribute to indoor air pollution.
The wildfire crisis is increasing hazardous air pollution and worsening respiratory illnesses.
The Clean Air Act of 1970 (amended in 1977 and 1990) was designed to protect human health and the environment from the effects of air pollution.
President Joe Biden delivered a slew of clean air and carbon issues as top environmental priorities for his administration in a new executive order signed on his inauguration. In it, agencies were directed to examine dozens of Trump-era rules, including carbon emission, clear air rollbacks, and Clean Air Act rules.
The U.S Court of Appeals for the District of Columbia Circuit handed Biden a huge win on Jan. 19, 2021 when it struck down President Donald Trump’s carbon rule for coal-fired power plants. This gave Biden’s White House a fresh start to craft greenhouse gas standards for existing sources.
The Biden Administration went on to finalize stronger clean air standards for chemical plants, the strongest-ever pollution standards for cars (encouraging EVs), $150 million in grants to help reduce truck air pollution, up to $1.5 billion in grants to reduce legacy pollution, and cracked down on fine particulate matter (like soot) in air pollution.
Additionally, the Biden Administration’s 2023 Executive Order on Environmental Justice includes regulatory protections for clean air and reducing air pollution.
In July 2024, the administration announced a new plan to detect and reduce Climate Super Pollutants.
Air pollution is an environmental justice issue. Low-income communities and communities of color are disproportionately impacted by air pollution. In the United States, researchers have found that “Black Americans are exposed to more pollution from every type of source, including industry, agriculture, all manner of vehicles, construction, residential sources, and even emissions from restaurants. People of color more broadly, including Black and Hispanic people and Asian-Americans, are exposed to more pollution from nearly every source.” Long histories of environmental racism persist in the United States, as sources of air pollution are disproportionately clustered near communities of color, especially Black communities.
A clear example of this happened recently when, on September 29, 2024, a chemical fire at a Georgia plant led to evacuations and school closures in the majority-Black county. Residents have filed lawsuits against the company, BioLab, which has a history of chemical fires and releases.
For the first time in the almost 55-year history of the Clean Air Act, the Trump administration’s Republican-led U.S. Congress passed legislation, on strict party lines, to abolish core protections against cancer-causing hazardous air pollutants. President Trump immediately signed it into law on June 20,2025.
Not to be outdone by Congress, the EPA proposed a repeal of power plant pollution standards.
CREDIT: NCA
