We just celebrated International Day of Clean Air for Blue Skies. Here’s what the U.S. has done well and what it must do next.

September 7 was International Day of Clean Air for Blue Skies, which was adopted by a UN resolution stressing “the importance of, and urgent need to, raise public awareness at all levels and to promote and facilitate actions to improve air quality.” The day is observed annually, and this year’s theme is “Invest in #CleanAirNow,” an area in which the United States, particularly in the last couple of years, has shown strong leadership. In celebrating the day, it’s worth reflecting on the progress and ongoing work on clean air policy in the U.S.  

Since the enactment of the Clean Air Act Amendments in 1970, the U.S. has been a leader in improving air quality, reducing combined emissions of six common air pollutants by 78%, including fine particulate matter (which is linked to cardiovascular problems, cancer, and even death) and ozone precursors (ground-level ozone, or smog, is linked to serious respiratory issues, including asthma attacks). The Environmental Protection Agency (EPA) also regulates emissions of hazardous air pollutants from sources like coal-fired power plants, which emit mercury (a potent neurotoxin) and carcinogenic metals like arsenic, lead, and chromium.  

Federal legislation and regulation for cleaner air 

Recent legislation, including the Infrastructure Investment and Jobs Act (colloquially referred to as the Bipartisan Infrastructure Law) and the Inflation Reduction Act have provided substantial funding for air quality monitoring (critical for identifying and addressing pollution problems), the Environmental and Climate Justice Program, and cleaner transportation through clean school buses, vehicle charging stations, and funding to clean up emissions at ports. This is in addition to important tax credits supporting cleaner electricity and transportation. 

In recent years, EPA has also taken critical steps to advance public health protections on a variety of fronts. These include: 

1. The recent finalization of a revision to the National Ambient Air Quality Standards (NAAQS) for fine particulate matter (one of the most harmful air pollutants), strengthening the annual health standard to 9 µg/m³—which is a significant win for public health. 

Current status: This rule must be successfully defended to allow the extensive implementation process in the Clean Air Act to occur, and the rule is currently being litigated in the D.C. Circuit, where CATF represents Citizens for Pennsylvania’s Future and Conservation Law Foundation, and with other environmental groups intervened to defend the rule. 

2. The recent finalization of a revision to the National Ambient Air Quality Standards (NAAQS) for fine particulate matter (one of the most harmful air pollutants), strengthening the annual health standard to 9 µg/m³—which is a significant win for public health.  

• Current status: This rule must be successfully defended to allow the extensive implementation process in the Clean Air Act to occur, and the rule is currently being litigated in the D.C. Circuit, where CATF represents Citizens for Pennsylvania’s Future and Conservation Law Foundation, and with other environmental groups intervened to defend the rule.  

3. The Mercury and Air Toxics Standards Technology Review strengthened emissions standards for mercury and other metal hazardous air pollutants for coal-fired power plants and required continuous emissions monitoring to ensure compliance and improve transparency. Hazardous air pollutants can be particularly harmful, and even relatively small amounts can bioaccumulate in the environment to levels that pose a threat to human health. 

• Current status: CATF is representing Alliance of Nurses for Healthy Environments, Citizens for Pennsylvania’s Future, Clean Wisconsin, Natural Resources Council of Maine, and the Ohio Environmental Council in litigation to defend the rule at the D.C. Circuit and on the Supreme Court’s emergency docket.  

4. The Good Neighbor Plan is a rule to address emissions of nitrogen oxides (an ozone precursor) from sources (including fossil fuel-fired power plants and other large industrial polluters) in upwind states that cause attainment problems in downwind states.  

• Current status: While this rule has been temporarily blocked during litigation by the Supreme Court, we continue to work toward a solution that will allow this critically important rule to protect downwind communities as required by the Clean Air Act.  

5. Multi-pollutant standards for light-duty and medium-duty vehicles, which reflect investments already being made, as well as ongoing market shifts and increasing consumer interest in clean vehicles. This rule will help to reduce emissions of particulate matter, nitrogen oxides, hydrocarbons, and greenhouse gases from new vehicles by encouraging industry investments in cleaner vehicles starting with 2027 models.  

• Current status: CATF is participating in litigation in the D.C. Circuit to defend this important rule on behalf of the Alliance of Nurses for Healthy Environments, American Lung Association, American Public Health Association, Appalachian Mountain Club, Clean Air Council, and National Parks Conservation Association. 

What comes next?  

We anticipate additional EPA actions in the near future, including implementation steps for the particulate matter NAAQS, a supplemental good neighbor rule to address upwind emissions from additional states, and a review of the ozone NAAQS. It is important that EPA continues to move forward and have the resources necessary to complete these actions, and in the process pursue its mission of protecting human health and the environment. EPA’s efforts can also encourage private investment in clean air, as strong regulatory policy can push industry to invest in cleaning up existing sources or pursue cleaner alternatives. 

Of course, climate change and clean air are connected, with climate change exacerbating the severity of wildfires that directly contribute to more air pollution, and more hot sunny days causing high ozone levels.  CATF continues to work on both of these issues while looking for and leveraging opportunities for collaboration in tackling climate change and air pollution.