'State of the Air:' Which cities have the highest pollution levels?

Seven of Texas' 10 largest counties have a failing grade when it comes to ozone pollution levels, according to a new report by the American Lung Association.

AUSTIN (KXAN) — Seven of Texas' 10 largest counties have a failing grade when it comes to ozone pollution levels, according to a new report by the American Lung Association.

The 2022 State of the Air report looks at ozone pollution levels, along with fine particulate matter levels, in cities across the country. In the report, the ALA calls these "two of the most widespread and dangerous pollutants."

ALA has published the report each year since 2000. This year's report analyzes data from 2018 through 2020.

Nationwide, more than 137 million Americans — more than 40% of the country — live in places with failing grades for unhealthy levels of particle pollution or ozone. The report also shows Americans experienced more days of "very unhealthy" or "hazardous" air quality "than ever before in the two-decade history of 'State of the Air.'"

Cities and counties are assigned three grades based on daily and long-term measures of the amount of fine particles in the air and by daily measures of ozone levels. Nearly 19.8 million Americans live in 14 counties that received a failing grade in all three categories.

California cities ranked worst in all three: Fresno had the worst short-term particle pollution, and Bakersfield had the worst year-round particle pollution. Los Angeles had the worst ozone pollution of any city in the country, a distinction it has received 22 times out of 23 State of the Air reports.

Why are fine particles so dangerous?

Fine particles come from various sources and can be incredibly damaging to the lungs. Factories, power plants and gas-powered vehicles directly emit fine particles into the air, or they generate other pollutants, including nitrogen oxides, that can form into fine particles.

They can also come from wildfires, burning wood in fireplaces or wood stoves and burning biomass to make electricity.

Just like their name suggests, individual particles are very small and many can't be seen by the naked eye. On days with high pollution levels, however, the air can appear thick or hazy.

The ALA says our bodies have natural defenses to keep dust, ash, pollen and smoke out of the deepest part of our lungs. Smaller particles can get trapped in air sacs. Some are so small that they can pass from the air sacs into our bloodstream and disperse to other organs.

Exposure to these kinds of particles can trigger illnesses and even death. Researchers estimate this type of pollution is responsible for almost 48,000 premature deaths nationwide each year.

Short-term exposure is linked to increases in respiratory and cardiovascular issues, including heart attacks, strokes, asthma and COPD. Exposure on a year-round basis is "associated with elevated risks of early death," in addition to higher likelihoods of diabetes, lung cancer and impaired cognitive function, such as Parkinson's, Alzheimer's and other dementias later in life.

Long-term exposure can also be harmful to pregnant women, fetuses and infants, including an increased risk of preterm birth or low birth weight, as well as increased fetal and infant mortality. Children exposed at a young age also have an increased likelihood of developing asthma, according to the ALA.

Which cities have the most particle pollution?

Short-term spikes of unhealthy particulate matter levels are becoming increasingly common. More than 63 million Americans live in counties that got an F grade in this category, an increase of almost 9 million from last year's report.

The 25 most polluted cities in the short-term are concentrated in the West, with the exception of Pittsburgh. Eleven of the cities are in California, and nine are in the Pacific Northwest. The ALA cites the increasing number and size of wildfires resulting from climate change-induced heat and drought as a primary reason for this geographic cluster.

80 cities across the nation recorded zero high short-term particle days, including several in the Midwest, and along the East Coast. The Midland-Odessa metropolitan area is the only in Texas to feature on the cleanest cities list.

When it comes to year-round unhealthy levels of particulates, the worst offenders are more geographically diverse. While the intensity and scale of wildfires impacts some of the top 25 cities on this list, others are impacted by high power plant emissions, as well as local industrial sources of pollution.

More than 20.3 million Americans live in counties that received a failing grade for long-term pollution levels, a slight decrease from last year's report.

Two Texas cities appear in the top 25 most polluted nationwide. McAllen-Edinburg ranks 18th worst, and Houston ranks 22nd worst.

Bakersfield, California, is the most polluted city year round, for the third year in a row. According to the report, the city averages more than 16 micrograms of particulate matter per cubic meter. Cheyenne, Wyoming, has the cleanest air in the country, with 3.4 micrograms per cubic meter.

Ozone pollution — more of an issue in Texas cities

Ozone air pollution, also sometimes known as smog, forms in the lower atmosphere when a combination of other pollutants "cook together in sunlight through a series of chemical reactions." The other pollutants are usually nitrogen oxides and volatile organic compounds that are produced by the burning of fossil fuels or when solvents evaporate. These pollutants are emitted from power plants, gas-powered vehicles, gas stations and even from paint.

You may have heard of Ozone Action Days, which are declared when ozone pollution is forecast to be dangerously high. The ALA calls ozone a "powerful lung irritant" that can cause inflammation and impact multiple body systems.

Short-term risks include worsening of existing breathing problems such as asthma and COPD. Longer-term exposure can leads to increased allergies and development of asthma or COPD. The ALA says exposure can also damage tissues, DNA and proteins in the body, increasing the risk of metabolic disorders, diabetes, cognitive decline, reproductive or developmental problems and reduced fertility, among other effects.

As such, people — especially those with existing conditions — are advised to stay indoors as much as possible on days when ozone pollution levels are high.

Perhaps unsurprisingly, California's largest city ranks the worst in the nation for ozone levels. Think of Los Angeles, and images of thousands of cars on sprawling highways likely come to mind.

In Texas, ozone pollution is more of an issue than particulate matter. Indeed, four cities in Texas appear on the top 25 most polluted cities nationwide when it comes to ozone levels: Houston ranks 8th worst, El Paso ranks 12th, Dallas/Fort Worth ranks 16th, and San Antonio ranks 25th.

Meanwhile, 64 cities across the country had zero high ozone days, including five in Texas: Brownsville, Corpus Christi, Laredo, McAllen-Edinburg and Waco.

Which Texas counties are the most polluted?

The State of the Air report also looks at pollution data in 932 counties across the country, including several in Texas.

When it comes to ozone pollution, 13 of the 34 counties included in the report received a failing grade. In fact, seven of the state's 10 largest counties received an F grade: Harris, Dallas, Tarrant, Bexar, Collin, Denton and El Paso. Travis County received a D grade, and Hidalgo County was the only county among the 10 largest to receive an A grade. Fort Bend County, the state's 10th largest, was not included in the report.

Meanwhile, eight counties received an A grade, including Cameron, Hidalgo, McLennan and Nueces Counties.

In Texas, 22 counties received a grade for short-term particle pollution levels. Of those, only three received a failing grade: Cameron, Hidalgo and Kleberg. Dallas and Harris Counties received a D grade, while Travis County received a C grade. Three West Texas counties received an A grade: Brewster, Ector and El Paso.

When it comes to year-round particle pollution, the State of the Air report gives each county either a "pass" or "fail" rather than a letter grade. Of the 15 counties in Texas with complete data, all 15 received a passing grade.

"New threats" causing rising pollution levels

The ALA's report identifies three "emerging threats" that are causing increases in air pollution levels.

Climate change is the first threat identified. "Rising global temperatures and disruption of short- and long-term weather patterns caused by climate change are putting the health of Americans at risk," the report states. The ALA highlights an increase in extreme weather events, the deterioration of air quality from increase ozone formation and wildfire smoke, the range expansion of disease-carrying pests and the increased stresses that can affect mental health as particularly prominent issues.

"These health impacts are no longer a concern for the future. They're happening now."

American Lung Association State of the Air 2022

Wildfires pose a "growing threat to public health" in many parts of the country, according to the report. Citing data from the Lancet, the ALA says in 2016-19, Americans experienced a 19% increase in the number of days they were exposed to high wildfire risk compared to 2001-04. In addition to the particles that contribute to pollution, wildfire smoke also contains a number of gases and toxins that poses a direct threat to health.

The third, and perhaps more unusual, threat identified is the increase in online shopping, particularly during the COVID-19 pandemic. With more people making purchases online, there is a rising number of delivery trucks on roads. According to the report, the Environmental Protection Agency estimates 72 million Americans live along major freight routes.

The report also highlights the backlog of cargo ships at ports in Los Angeles and Long Beach, California. According to the California Air Resources Board, as of October 2021, the backlog had caused container ship emissions increases of 20 tons per day of nitrogen oxides, and 0.5 tons per day of particulate matter.

That increase in nitrogen oxide emissions from container ships is "roughly equivalent to the total emissions from 5.8 million passenger cars," and the increase in particulate matter is "comparable to the exhaust particulate matter emissions from almost 100,000 Class 8 diesel trucks."

What can be done to protect our health?

The ALA's report lists several recommendations ranging from personal action to governmental policy change to address pollution.

Everyone is encouraged to reduce your own contributions to air pollution. Specific examples include using public transit or prioritizing walking or biking over the use of gas vehicles. You can also check daily air pollution forecasts online and adjust your plans if levels are high. If you live in a fire-prone area, you're also encouraged to protect yourself from possible wildfire smoke by learning about masks and creating a "clean room" inside your home.

On the governmental level, the ALA encourages cities and counties to switch to zero-emission vehicles for buses, garbage and recycling trucks and other vehicles, as well as using clean energy sources such as wind, solar, geothermal or tidal power.

The report also called on Congress and the White House to "act now to dramatically reduce air and climate pollution" and drive an "urgent" nationwide transition to zero-emission transportation and electricity.