91% of the world’s population are currently living and breathing in air where air quality levels exceed World Health Organization (WHO) limits. What this means is a significant amount of people are at risk of serious health issues, including coronary and respiratory diseases, higher chances of cancer and preliminary death. Though low-income countries, a majority of which are located in the global south, are hit hardest by the effects of air pollution, the US suffers its fair share of health issues as well. But which are the most polluted cities in the US? Earth.Org has gathered data to find out. 

In April 2021, the American Lung Association published their annual State of the Air report on the most polluted cities in America, which analyses data from 2017-2019, found that 4 in 10 people – amounting to about 135 million people – in the US currently live in places with unhealthy and polluted air. 

Caused by the burning of fossil fuels in power plants and motor vehicles, high ozone and smog, and climate change-induced weather events such as wildfires, air pollution has only exacerbated by global warming changes with increased heat waves and prolonged pollen seasons. 

The report has also found that people of colour are 60%  more likely to live in a country or city with air pollution than Causasians, and are three times more likely to live in a place that has failed all three air quality thresholds established by the American Lung Association. 

15 Most Polluted Cities in the United States in 2021

  1. Bakersfield, California
  2.  Fresno-Madera-Hanford, California
  3. Visalia, California, 
  4. Los Angeles-Long Beach, California
  5.  Medford-Grants Pass, Oregon
  6. Fairbanks, Arkansas
  7.  San Jose-San Francisco-Oakland, California
  8.  Phoenix-Mesa, Arizona
  9.  Pittsburgh-New Castle-Weirton, Pennsylvania-Ohio-Wyoming 
  10.  El Centro, California 
  11.  Cincinnati-Wilmington-Maysville, Ohio-Kentucky-Indiana
  12.  Detroit-Warren-Ann Arbor, Michigan
  13.  Indianapolis-Carmel-Muncie, Indiana
  14. Cleveland-Akron-Canton, Ohio
  15.  Chicago-Naperville, Illinois-Indiana-Wisconsin 
most polluted cities in the us

Figure 1: Cities with the highest year-round levels of particle pollution in the U.S. (2017-2019). Credit: Statista/Forbes

Air Pollution in California 

A stunning number of cities from the state of California have topped the rankings when it comes to air pollution, whether it be by year round particle pollution, by short term particle pollution, or by levels of ozone. 

For example, Los Angeles California, which has a population of 10,039,107, received a Grade F in the State of the Air report with its weighted average of 106.5 in air pollution. Outdoor air pollutants largely come from fossil fuel sources – California particularly has a massive car culture where a majority of Californians drive rather than take public transportation or walk. 

Wildfires in California are a big contributor to air pollution in the state. Areas like El Dorado and the Bay Area have suffered a number of deadly and devastating wildfires over the years. Smoke and carbon emissions from these forest fires released into the atmosphere, prolongs wildfire seasons in the region and worsen quality of air in the long run. 

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How to Stem the Effects of Air Pollution

The Clean Air Act (CAA) is a comprehensive US federal law that regulates all sources of air emissions. It was first legalised in 1970, later establishing the National Ambient Air Quality Standards, which protects the public health and welfare by specifically regulating emissions of hazardous air pollutants. The landmark law has been able to stem air pollution levels from exponential increases, and it’s been projected that the CAA managed to prevent over 230,000 deaths and save nearly $2 trillion in 2020 alone.

However, this alone does not solve the problem, especially as climate change and global temperature increase continues to grow. At the 2021 Climate Leaders’ Summit, President Joe Biden has pledged to cut US emission by half by 2030 from 2005 levels, as well as setting the target of reaching zero carbon emissions by 2050. Biden is taking a number of climate actions, including an executive order to make half of all new US cars and trucks to go electric by the end of 2030, to make those goals a reality.  This in turn, would significantly improve air quality and decrease the health risks for the general population. 

How Does Air Pollution Contribute to the Spread of COVID-19 in Societies

There’s been new research on the role of air pollution gases plays in the transportation of virus molecules. Preliminary studies have identified a positive correlation between COVID-19-related mortalities and air pollution, and the possibility of airborne particles assisting the viral spread. Similarly, long-term exposure to high levels of air pollution can be linked to more severe symptoms and worse health outcomes from COVID-19,  as well as a higher rate of mortality.