50 US metro areas with the dirtiest air—and why they're at risk during COVID-19

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.5 μg/m^3 (20.8% below EPA standard)
--- Daily average (98th percentile): 23 μg/m^3 (34.3% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 16 μg/m^3
---Second-highest daily average: 36 μg/m^3 (76.0% below EPA standard)

Oklahoma, after years of making improvements in its air quality, saw a dip in 2019. Tulsa, which starts the list of most polluted U.S. cities, saw 10 days of unhealthy air quality that was and one day that was deemed unhealthy for all residents. Some have attributed this change to increased fires. Others, such as Johnson Bridgwater, director of the Oklahoma chapter of the Sierra Club, said that this lower air quality could be a result of President Donald Trump rolling back environmental regulations.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.5 μg/m^3 (20.8% below EPA standard)
--- Daily average (98th percentile): 24 μg/m^3 (31.4% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 14 μg/m^3
---Second-highest daily average: 33 μg/m^3 (78.0% below EPA standard)

Winston-Salem has the lowest air quality of any city in the state of North Carolina. In the state, pollution primarily comes from transportation—mostly automobiles. As in many places, air pollution in the city has decreased due to COVID-19 and social distancing measures.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.6 μg/m^3 (20.0% below EPA standard)
--- Daily average (98th percentile): 24 μg/m^3 (31.4% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 35 μg/m^3
---Second-highest daily average: 129 μg/m^3 (14.0% below EPA standard)

Also known as the Quad Cities, Davenport-Moline-Rock Island are located across Iowa and Illinois. In July 2015, the Quad Cities had the worst air quality in the nation due to smoke from wildfires in Western Canada. Cases of COVID-19 are steadily rising in the Quad Cities, especially in Rock Island County, making the area’s high levels of pollution that much more dangerous.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.6 μg/m^3 (20.0% below EPA standard)
--- Daily average (98th percentile): 30 μg/m^3 (14.3% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 29 μg/m^3
---Second-highest daily average: 80 μg/m^3 (46.7% below EPA standard)

Merced is the first of nine Californian cities on this list. Located in the center of the state in the San Joaquin Valley, the city suffers from pollution coming mostly from cars on nearby highways and from railways. In addition, the area is vulnerable to climate change issues, such as wildfires and rising temperatures, which contribute to ozone pollution. So far, Merced has had relatively few coronavirus cases and deaths—its fourth death came on May 12.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.6 μg/m^3 (20.0% below EPA standard)
--- Daily average (98th percentile): 39 μg/m^3 (11.4% above EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 16 μg/m^3
---Second-highest daily average: 49 μg/m^3 (67.3% below EPA standard)

The Weirton-Steubenville Metropolitan Area has been dealing with the impacts of air pollution for decades. In fact, in the 1970s, the area's reputation for having the most polluted air in the country made it a hub for environmental epidemiology researchers, and city data played an important role in EPA regulations on air pollution. Much of the current air pollution in the area comes from petrochemical plants. As in much of the country, Ohio Valley, where Weirton-Steubenville is located, is seeing its cases of COVID-19 increasing.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.7 μg/m^3 (19.2% below EPA standard)
--- Daily average (98th percentile): 23 μg/m^3 (34.3% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 15 μg/m^3
---Second-highest daily average: 31 μg/m^3 (79.3% below EPA standard)

Although Terre Haute, Indiana is #45 on this list, it has actually made some major improvements in its air quality over the last few years. In 2013, the city did not meet the sulfur dioxide air quality standard. However, in July 2019, after collaborating with the EPA to lower their emissions, Terre Haute now meets ambient air quality standards. Unfortunately, the regulations that helped Terre Haute lower its pollution are now being rolled back, putting it at increased risk.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.7 μg/m^3 (19.2% below EPA standard)
--- Daily average (98th percentile): 25 μg/m^3 (28.6% below EPA standard)

Brownsville-Harlingen is located on the southern tip of Texas, along the Mexican border. The area’s largest city, Brownsville, has one of the highest rates of poverty in the nation. Over 90% of residents are Hispanic or Latinx. Tens of thousands in the region have pre-existing respiratory conditions such as asthma and COPD, making them especially vulnerable to impacts of COVID-19.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.7 μg/m^3 (19.2% below EPA standard)
--- Daily average (98th percentile): 30 μg/m^3 (14.3% below EPA standard)

Grants Pass, Oregon, is located in the Rogue Valley, not far north of the California border. Much of the pollution comes from wildfires in southern Oregon and neighboring California. Wildfire season in Oregon and California is approaching and could create further health problems in combination with the COVID-19 pandemic.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.8 μg/m^3 (18.3% below EPA standard)
--- Daily average (98th percentile): 23 μg/m^3 (34.3% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 19 μg/m^3
---Second-highest daily average: 60 μg/m^3 (60.0% below EPA standard)

Jackson is the most populated city in Mississippi. The city is 81.4% Black or African American, a demographic that has been hit especially hard by the COVID-19 pandemic. Mississippi is one of a number of states reporting disproportionate death rates of African Americans, which is due to a number of factors, including the air quality in the places they live.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.8 μg/m^3 (18.3% below EPA standard)
--- Daily average (98th percentile): 25 μg/m^3 (28.6% below EPA standard)

Home to Pennsylvania State University, State College is #41 on this list in spite of its idyllic surroundings. Its air quality has suffered mostly due to vehicle emissions along with agricultural processes. It has not yet been decided whether the students who attend Penn State will return for classes in the fall, due to the coronavirus.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.8 μg/m^3 (18.3% below EPA standard)
--- Daily average (98th percentile): 37 μg/m^3 (5.7% above EPA standard)

The air quality of Yakima County in Washington has been steadily decreasing over the last few years (2015–17) and is caused in large part by wildfires in Washington, Oregon, and California. This is especially dangerous in Yakima County, which has the highest number of coronavirus cases of any county in Washington State as of May 2.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.9 μg/m^3 (17.5% below EPA standard)
--- Daily average (98th percentile): 21 μg/m^3 (40.0% below EPA standard)

Athens, Georgia, is located roughly 72 miles from Atlanta and shares some of the capital’s air pollution problems. The main cause is emissions from vehicles. In order to keep air pollution levels as low as possible in the state, an open burn ban began on May 1. This helps keep pollution lower during the summer smog season, which will be especially important as the pandemic continues.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 9.9 μg/m^3 (17.5% below EPA standard)
--- Daily average (98th percentile): 25 μg/m^3 (28.6% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 17 μg/m^3
---Second-highest daily average: 39 μg/m^3 (74.0% below EPA standard)

Although Columbus is still 17.5% below the EPA standard, it makes the list as the U.S. city with the 38th-dirtiest air. The city has a population of over 922,000 and has been called a potential coronavirus hotspot after seeing a 61% rise in confirmed cases in the first week of May. The city’s elevated levels of air pollution could prove especially harmful as the city sees more cases.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10 μg/m^3 (16.7% below EPA standard)
--- Daily average (98th percentile): 21 μg/m^3 (40.0% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 17 μg/m^3
---Second-highest daily average: 63 μg/m^3 (58.0% below EPA standard)

In Oklahoma, 27% of adults have one or more chronic health conditions—such as heart disease, diabetes, and asthma—that increase the risk of severe implications from COVID-19. In addition, Oklahoma comes in as the state with the 13th-most vulnerable population to COVID-19, per a WalletHub study. Although Oklahoma City’s air pollution is below the EPA standard, its high levels of pollution could put its population at even higher risk.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10 μg/m^3 (16.7% below EPA standard)
--- Daily average (98th percentile): 31 μg/m^3 (11.4% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 35 μg/m^3
---Second-highest daily average: 111 μg/m^3 (26.0% below EPA standard)

Colorado's Denver-Aurora-Lakewood Metro Area has experienced high air pollution due in large part to wildfires along with vehicle emissions and the oil and gas industry. In the state of Colorado, around 404,012 people have asthma, according to the Centers for Disease Control, which could make them more vulnerable to COVID-19.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.2 μg/m^3 (15.0% below EPA standard)
--- Daily average (98th percentile): 30 μg/m^3 (14.3% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 18 μg/m^3
---Second-highest daily average: 49 μg/m^3 (67.3% below EPA standard)

Air pollution measured by metropolitan area is important but can be misleading. Sometimes different neighborhoods in the same city can have very different levels of pollution. Philadelphia’s metro area, which includes the city itself along with Camden, New Jersey, and Wilmington, Delaware, does not have the same air quality across the entire region. To learn more about this, a team from Villanova are researching pollution in individual neighborhoods throughout Philadelphia. In addition, since the city began to shut down due to the coronavirus, Philadelphia has seen reductions in air pollution.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.3 μg/m^3 (14.2% below EPA standard)
--- Daily average (98th percentile): 19 μg/m^3 (45.7% below EPA standard)

Warner Robins is home to the Robins Air Force Base, which, in spite of the coronavirus is reopening. This city is also home to the 34th dirtiest air in the country, which could be dangerous for the returning members of the military as well as the rest of the city’s 76,500-plus residents. In addition, dozens of personnel on the Air Force Base tested positive for COVID-19 since the first case in late March.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.3 μg/m^3 (14.2% below EPA standard)
--- Daily average (98th percentile): 23 μg/m^3 (34.3% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 19 μg/m^3
---Second-highest daily average: 38 μg/m^3 (74.7% below EPA standard)

Little Rock has a population of over 197,000, of which 41.7% is Black or African American, a high-risk group for COVID-19 complications. Some of this pollution comes from coal and oil-burning power plants. The Trump administration recently rolled back certain regulations to reduce air pollution. However, the operators of some of these plants are actually opposing the rule because they already invested in pollution-control equipment.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.3 μg/m^3 (14.2% below EPA standard)
--- Daily average (98th percentile): 24 μg/m^3 (31.4% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 19 μg/m^3
---Second-highest daily average: 54 μg/m^3 (64.0% below EPA standard)

So far, Montgomery County, where Dayton is located, has been weathering the pandemic relatively well. However, as businesses plan to reopen, a study has identified the county as a potential coronavirus hotspot despite the number of reported cases. This could prove especially risky for Dayton residents, where air pollution—while below the EPA standards—is still the 32nd-highest in the U.S.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.4 μg/m^3 (13.3% below EPA standard)
--- Daily average (98th percentile): 23 μg/m^3 (34.3% below EPA standard)

Springfield is less than 30 miles from Dayton and shares some of its pollution problems. In fact, Charles Patterson, the county's health commissioner, blamed their high ozone levels on downwind emissions from Dayton as well as from nearby highways. "We're not blaming all of it on that, but if Springfield was two counties away from Dayton surrounded by rural areas, our numbers would be much better," Patterson told the Springfield News-Sun's Michael Cooper in 2017.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.5 μg/m^3 (12.5% below EPA standard)
--- Daily average (98th percentile): 30 μg/m^3 (14.3% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 35 μg/m^3
---Second-highest daily average: 99 μg/m^3 (34.0% below EPA standard)

Residents of the St. Louis area have reason to be concerned about its low air quality during the COVID-19 pandemic. According to Eli Chen of St. Louis Public Radio, Mamie Causey, a 79-year-old resident, said, “I live in fear on a daily basis, if you really want to know the truth. [The pollution] impacts your breathing on a daily basis.” In addition, a nearby incinerator was being investigated for possible air poisoning from heavy metals in Nov. 2019.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.5 μg/m^3 (12.5% below EPA standard)
--- Daily average (98th percentile): 34 μg/m^3 (2.9% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 20 μg/m^3
---Second-highest daily average: 58 μg/m^3 (61.3% below EPA standard)

Although Klamath Falls’ fine particulate matter numbers are still below the EPA standard, the region has high levels compared to the rest of the United States, due in large part to fires. One researcher, Addie Clark from Oregon Tech, is spearheading a project to monitor that pollution in order to reduce it. She is also working on a solar-powered monitoring station, so that the monitoring itself is not contributing to further emissions.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.6 μg/m^3 (11.7% below EPA standard)
--- Daily average (98th percentile): 21 μg/m^3 (40.0% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 23 μg/m^3
---Second-highest daily average: 80 μg/m^3 (46.7% below EPA standard)

Of Birmingham’s population of 209,000, 70.5% is African American, a group experiencing disproportionately high death rates from COVID-19. This is likely compounded by the city’s high level of air pollution and is especially dangerous as Montgomery County, where Birmingham is located, is emerging as a coronavirus hotspot.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.6 μg/m^3 (11.7% below EPA standard)
--- Daily average (98th percentile): 23 μg/m^3 (34.3% below EPA standard)

After a coal-fired power plant closed in Louisville in 2015, researchers saw 400 fewer hospital visits and a 55% reduction in lung-irritating pollutants. Although the city still has dirty air, the research made it clear that lowering pollution is beneficial to human health. This could be helpful to the residents of the city during this pandemic. However, the Trump administration is rolling back regulations, so the amount of pollution in the air could get even higher.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.6 μg/m^3 (11.7% below EPA standard)
--- Daily average (98th percentile): 36 μg/m^3 (2.9% above EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 30 μg/m^3
---Second-highest daily average: 104 μg/m^3 (30.7% below EPA standard)

Modesto is one of nine cities on this list located in California, highlighting the fact that the Golden State has problems with air pollution. This increase in air pollution in Modesto and around the country is due to vehicle emissions, increases in wildfires, and relaxation of environmental regulations. Stanislaus County, where Modesto is located, lifted its stay-at-home order May 12, even though it does not meet state guidelines to do so.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.7 μg/m^3 (10.8% below EPA standard)
--- Daily average (98th percentile): 20 μg/m^3 (42.9% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 29 μg/m^3
---Second-highest daily average: 63 μg/m^3 (58.0% below EPA standard)

Like many places with elevated levels of air pollution, residents of the Houston Metropolitan Area suffer from cardiovascular diseases such as asthma. Last year, the Houston Independent School District reported 6,000 children with asthma, saying that it’s the biggest chronic disease they face. While this puts residents at higher risk for COVID-19 complications, the good news is that Houston is currently doing especially well when it comes to keeping their numbers of new cases of the virus low.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.7 μg/m^3 (10.8% below EPA standard)
--- Daily average (98th percentile): 22 μg/m^3 (37.1% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 12 μg/m^3
---Second-highest daily average: 25 μg/m^3 (83.3% below EPA standard)

Augusta-Richmond has a population of nearly 200,000 with an annual average of fine particulate matter in the area only 10.8% below the EPA’s limit. Residents in this city are at increased risk of having serious complications if they contract the COVID-19 disease, which is all the more important now, as Georgia has been one of the first states to reopen, a move many fear could cause another spike in infections, especially in highly populated urban areas like Augusta.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.7 μg/m^3 (10.8% below EPA standard)
--- Daily average (98th percentile): 27 μg/m^3 (22.9% below EPA standard)

Albany, a Georgia city of 73,799, faces many of the same problems as Augusta. Its fine particulate matter pollution was also only 10.8% lower than the EPA standard in 2019, and its residents must also deal with the consequences of the state reopening.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.7 μg/m^3 (10.8% below EPA standard)
--- Daily average (98th percentile): 29 μg/m^3 (17.1% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 25 μg/m^3
---Second-highest daily average: 48 μg/m^3 (68.0% below EPA standard)

The city of Laredo is located along the Texas Gulf Coast and experiences high levels of air pollution due to emissions from nearby oil refineries and chemical plants. Laredo is part of the United States’ petrochemical corridor. Four of the 10 largest oil and gas refineries in the country are located in this region. Unfortunately, even though the country is in the middle of a pandemic that hits people in polluted areas the hardest, the Trump administration has actually rolled back regulations that would lower air pollution.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.7 μg/m^3 (10.8% below EPA standard)
--- Daily average (98th percentile): 30 μg/m^3 (14.3% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 24 μg/m^3
---Second-highest daily average: 50 μg/m^3 (66.7% below EPA standard)

The McAllen-Edinburg-Mission area is located in the Rio Grande Valley. On April 13, AirNow.gov deemed the air quality "unhealthy for sensitive groups." This is especially worrying as Texas is in the midst of the coronavirus pandemic and these sensitive groups were put at even higher risk due to the pollution.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.8 μg/m^3 (10.0% below EPA standard)
--- Daily average (98th percentile): 24 μg/m^3 (31.4% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 17 μg/m^3
---Second-highest daily average: 40 μg/m^3 (73.3% below EPA standard)

Residents of the Atlanta metropolitan area experience both ozone pollution (smog) and particle pollution (soot). The smog comes mostly from cars while the soot comes from diesel emissions, coal-fired power plants, wildfires and wood-burning devices. Unlike in many other cities, Atlanta has so far not seen much of a drop in air pollution during the coronavirus lockdown.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.8 μg/m^3 (10.0% below EPA standard)
--- Daily average (98th percentile): 27 μg/m^3 (22.9% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 44 μg/m^3
---Second-highest daily average: 162 μg/m^3 (8.0% above EPA standard)

The Imperial Valley, where El Centro is located, is known for having dirty air and high levels of associated respiratory diseases such as asthma. This is playing out in a deadly fashion during the coronavirus pandemic. El Centro is the county seat of Imperial County, which has the highest per capita rate of coronavirus hospitalizations in California as of May 13. This is being attributed in part at least to the air quality. Residents in the area have rates of tuberculosis eight times higher than the United States average.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.8 μg/m^3 (10.0% below EPA standard)
--- Daily average (98th percentile): 28 μg/m^3 (20.0% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 19 μg/m^3
---Second-highest daily average: 69 μg/m^3 (54.0% below EPA standard)

The Chicago Metropolitan Area is made up of a number of different neighborhoods with varying income levels and demographics. Chicago’s southside, an area that is nearly 79% African American, also experiences high levels of air pollution. In Southeast Chicago, 75 companies have been investigated for violating the Clean Air Act since 2014. In addition, unlike in other cities, air pollution has not dropped in Chicago since lockdown.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.9 μg/m^3 (9.2% below EPA standard)
--- Daily average (98th percentile): 23 μg/m^3 (34.3% below EPA standard)

Shreveport-Bossier City’s daily average of fine particulate matter in 2019 was only 9.2% below the EPA standard. However, there is some good news coming out of the area, which is that Shreveport ranks among the United States’ best cities for declining trends in COVID-19 deaths per a New York Times analysis.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 10.9 μg/m^3 (9.2% below EPA standard)
--- Daily average (98th percentile): 27 μg/m^3 (22.9% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 31 μg/m^3
---Second-highest daily average: 79 μg/m^3 (47.3% below EPA standard)

As the 16th-worst metropolitan area for air pollution in the United States, residents in the Cleveland area are at higher risk of COVID-19 death. The one bright spot is that, like in many places due to social distancing and quarantine measures, air pollution has gone down in the Cleveland area.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 11 μg/m^3 (8.3% below EPA standard)
--- Daily average (98th percentile): 26 μg/m^3 (25.7% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 15 μg/m^3
---Second-highest daily average: 34 μg/m^3 (77.3% below EPA standard)

The New York City Metro Area has become the United States’ epicenter of the COVID-19 pandemic. New York City alone, excluding Newark and Jersey City, has already seen 193,663 confirmed coronavirus cases and 19,904 confirmed deaths as of May 15. And areas of the city with the highest populations of communities of color—neighborhoods that also tend to have higher levels of pollution—have suffered the most. The one small bright spot is that like many other large cities, pollution levels have dropped in the New York Metropolitan Area since quarantine measures began.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 11 μg/m^3 (8.3% below EPA standard)
--- Daily average (98th percentile): 34 μg/m^3 (2.9% below EPA standard)

A report by the PennEnvironment Research & Policy Center found that in 2016, some communities in the Harrisburg-Carlisle area breathed dirty air for at least half the year. The particulate pollution responsible for the region’s dirty air often comes from burning diesel, coal, and fossil fuels.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 11 μg/m^3 (8.3% below EPA standard)
--- Daily average (98th percentile): 36 μg/m^3 (2.9% above EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 16 μg/m^3
---Second-highest daily average: 51 μg/m^3 (66.0% below EPA standard)

Although Lancaster’s annual average for fine particulate matter in the air was 8.3% below the EPA standard in 2019, its daily average was actually 2.9% above the standard, the first city on this list to reach that milestone. This is especially dangerous for residents of Lancaster if they contract COVID-19, which might be more likely now as Lancaster County plans to begin the next stage of reopening on May 15 even though it has not gotten permission from the governor.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 11.2 μg/m^3 (6.7% below EPA standard)
--- Daily average (98th percentile): 37 μg/m^3 (5.7% above EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 39 μg/m^3
---Second-highest daily average: 234 μg/m^3 (56.0% above EPA standard)

Fresno’s daily average of fine particulate matter in the air was 5.7% above the EPA standard in 2019. In addition, the people who are most impacted by this pollution tend to be poorer, and are now the same people who are suffering financial difficulties due to COVID-19-related job losses. Although air pollution is dipping due to social distancing and quarantine measures, it is still a small reduction and might be temporary.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 11.3 μg/m^3 (5.8% below EPA standard)
--- Daily average (98th percentile): 33 μg/m^3 (5.7% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 59 μg/m^3
---Second-highest daily average: 222 μg/m^3 (48.0% above EPA standard)

The Phoenix Metro Area is currently experiencing its worst air. This is especially problematic now that the novel coronavirus has hit and has worse ramifications in areas with bad pollution. Rollbacks of EPA regulations by the Trump administration won't help the matter and will likely contribute to higher levels of pollution in the region in the coming years.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 11.9 μg/m^3 (0.8% below EPA standard)
--- Daily average (98th percentile): 26 μg/m^3 (25.7% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 20 μg/m^3
---Second-highest daily average: 45 μg/m^3 (70.0% below EPA standard)

Cincinnati’s annual average of soot in the air is 0.8% below EPA standard, just barely making the cut. However, although the city is technically in adherence with the EPA’s recently lowered standards, it still has very dirty air, a problem for its residents. This danger could become more stark as businesses in Cincinnati begin to reopen, even as its coronavirus cases continue to rise.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 12.3 μg/m^3 (2.5% above EPA standard)
--- Daily average (98th percentile): 47 μg/m^3 (34.3% above EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 49 μg/m^3
---Second-highest daily average: 304 μg/m^3 (102.7% above EPA standard)

Hanford is located in California’s San Joaquin Valley and is the first city on this list with an annual average of fine particulate matter above the EPA standard. And its 98th percentile daily average is actually 34.3% above the standard. This is bad news for its residents and the people who work in Hanford, who are at higher risk due to their low air quality. A meat processor in Hanford already had nearly 200 confirmed cases of the virus on May 13.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 12.3 μg/m^3 (2.5% above EPA standard)
--- Daily average (98th percentile): 64 μg/m^3 (82.9% above EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 19 μg/m^3
---Second-highest daily average: 200 μg/m^3 (33.3% above EPA standard)

Fairbanks has some of the worst air in the United States. Its 98th percentile daily average for fine particulate matter is 82.9% above EPA limits. Luckily for the residents there, when it comes to coronavirus, there are so far only 388 cases confirmed across the entire state of Alaska, with 10 deaths as of May 15.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 12.5 μg/m^3 (4.2% above EPA standard)
--- Daily average (98th percentile): 28 μg/m^3 (20.0% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 26 μg/m^3
---Second-highest daily average: 57 μg/m^3 (62.0% below EPA standard)

The Indianapolis Metro Area had an annual average of fine particulate matter pollution that was 4.2% above the EPA standard. However, since the pandemic and associated social distancing measures began, Indianapolis has seen a reduction of air pollution of 38%. Since air pollution is associated with higher levels of COVID-19 death, hopefully this will make residents of the city safer.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 12.6 μg/m^3 (5.0% above EPA standard)
--- Daily average (98th percentile): 31 μg/m^3 (11.4% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 25 μg/m^3
---Second-highest daily average: 65 μg/m^3 (56.7% below EPA standard)

Detroit and its surrounding cities have experienced an especially high number of COVID-19 deaths. Its death rate of 40 people per 100,000 is more than 250% higher than the Michigan average. It's not a coincidence that this region also has the sixth-worst air in the country. On a slightly positive note, pollution levels in Detroit have dropped during the shutdown.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 12.9 μg/m^3 (7.5% above EPA standard)
--- Daily average (98th percentile): 46 μg/m^3 (31.4% above EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 46 μg/m^3
---Second-highest daily average: 284 μg/m^3 (89.3% above EPA standard)

Beginning the top five cities with the dirtiest air is Visalia-Porterville, which in 2019 had an annual average of fine particulate matter that was 7.5% above the EPA standard. Some of this pollution comes from California’s wildfires. Unfortunately for residents in Visalia-Porterville, wildfire season is near, which could make their experience with COVID-19 even worse.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 13 μg/m^3 (8.3% above EPA standard)
--- Daily average (98th percentile): 47 μg/m^3 (34.3% above EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 54 μg/m^3
---Second-highest daily average: 382 μg/m^3 (154.7% above EPA standard)

Bakersfield is located in California’s Central Valley and it is surrounded by oil drilling, contributing to its heavily polluted air. Its location—surrounded by mountains—traps pollutants, which come from a number of sources, such as heavy truck traffic, diesel-burning trains, agriculture, and wood-burning stoves and fireplaces.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 13.4 μg/m^3 (11.7% above EPA standard)
--- Daily average (98th percentile): 30 μg/m^3 (14.3% below EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 28 μg/m^3
---Second-highest daily average: 159 μg/m^3 (6.0% above EPA standard)

The Los Angeles Metropolitan Area is known for its smog, which can be seen from its 2019 EPA data. However, the current pandemic has caused L.A. to have some of the cleanest air of any city in the world. The city is still one of the epicenters of the COVID-19 crisis in the United States, and pre-existing health problems caused by past air pollution could be dangerous for many residents.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 14.2 μg/m^3 (18.3% above EPA standard)
--- Daily average (98th percentile): 65 μg/m^3 (85.7% above EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 23 μg/m^3
---Second-highest daily average: 86 μg/m^3 (42.7% below EPA standard)

Pittsburgh’s daily average of fine particulate matter is 85.7% above the EPA standard. The majority of the industrial air pollution in Allegheny County, where the city is located, comes from 10 industrial facilities, which are responsible for 83% of the pollution. Regulatory rollbacks by the Trump administration are not likely to improve this predicament.

- Fine particulate matter (PM2.5) pollution in 2019:
--- Annual average: 15.4 μg/m^3 (28.3% above EPA standard)
--- Daily average (98th percentile): 36 μg/m^3 (2.9% above EPA standard)
- Coarse particulate matter (PM10) pollution in 2019:
--- Annual average: 46 μg/m^3
---Second-highest daily average: 139 μg/m^3 (7.3% below EPA standard)

Topping the list is the Riverside Metropolitan Area with its annual average of fine particulate matter at 28.3% above the EPA standard in 2019. This is especially unfortunate for its residents, as the county voted to rescind health orders even as coronavirus cases are on the rise.