More than 44m Americans are living in areas with toxic levels of pollution linked to asthma attacks and strokes

Toxic air pollution levels in the US are at the worst levels in the last 25 years, raising health concerns for more than one-third of Americans.

The American Lung Association (ALA) revealed in a new report that 39 percent of Americans are living in regions with unhealthy air pollution levels.

To discern the heightened pollution levels, the ALA looked at the daily and annual averages of particle and ozone pollution, released from plants and refineries.

California was found to have six of the top 10 cities ranked as having the worst air quality - and more than 33.2 million people live in those location.

The report cited climate change as a culprit, sparking wildfires and droughts, but also pointed to combustion sources like cars and manufacturing facilities.

The American Lung Association ranked the top cities that suffer from the worst air quality in the US - affecting roughly 131 million Americans

Last year, the US saw the highest levels of air pollution in 25 years. The report said the cause is likely due to climate change, making temperatures rise and wildfires spread. Pictured: Smog covered the Golden Gate Bridge in San Francisco in 2020 due to ongoing wildfires

The Clean Air Act allows the EPA to impose restrictions on how much emissions can be produced in the US. Pictured: Climate change activists protested outside of the Supreme Court in Washington, D.C. in 2022

Air pollution causes tens of thousands of deaths every year and short-term exposure can cause respiratory issues like asthma, but long-term exposure could lead to an increased risk of heart attack, stroke or lung cancer. 

'When we started doing 'State of the Air' in 2000, I never imagined that in the 25th edition we would be reporting that more than 100 million people are still breathing unhealthy air. It's unacceptable,' said Paul Billings, ALA's senior vice president of public policy. 

The ALA's report showed the issue is becoming more severe despite efforts to ramp up efforts to clean air pollution, with more than 131 million people living in hot spots with unhealthy particle pollution in 2023 - 11.7 million more people than the previous year.

Particulate pollution is made up of tiny particles that individually are too small to be visible, but when pollution levels are higher, the air can appear to be thick and hazy - also known as smog.

People living in low-income areas are most at risk from particle pollution because of their close proximity to pollution sources, like industrial sites or mines.

The ALA used a grading system to define particle pollution and ranked 112 counties across 19 US states with an 'F' for their daily particle pollution, impacting 65 million people.

'There is no safe level to particle pollution,' Dr. Kari Nadeau, the John Rock professor of climate and population studies at the Harvard T.H. Chan School of Public Health, told USA TODAY. 

'We were not meant to breathe this in as humans.'

The amount of air pollution people are exposed to has skyrocketed over the last decade as wildfires region the West Coast

Bakersfield, California was reported as the worst metro area for air pollution, followed by the Visalia and Fresno, California areas.

Roughly 2.6 million Californians currently suffer from adult asthma, a major jump from East Coast states like Massachusetts where 660,000 people are diagnosed with the respiratory illness.

In 2021, the Centers for Disease Control and Prevention (CDC) reported that more than 18,000 Californians died from a stroke compared to 2,200 in Massachusetts.

Other areas affected include Fairbanks, Alaska, Phoenix, and Springfield, Oregon which are home to more than five million people.

The report marks the fifth consecutive year that air pollution levels have increased even though the six National Ambient Air Quality Standards have dropped by 78 percent since 1970, with the EPA attributing it to the amount of smog and wildfire smoke in the air.

Pollution in the US dropped about 40 percent between 1990 and 2020, but the improvements were primarily in East Coast states.

Meanwhile, the West Coast is being hammered by having the most dangerous and very dangerous air quality days in recorded history.

'The severity of the pollution is unprecedented,' Katherine Pruitt, national policy director at the ALA told NPR.

'We've pretty much addressed the easiest ways of reducing pollution,' she said. 'So we have catalytic converters on our vehicles, we have diesel particulate filters on our trucks, we have scrubbers on our power plants.' 

Wildfires are causing rising air pollution levels as the smoke spreads, causing people to have major respiratory problems and can cause heart attack, stroke and lung cancer. Pictured: The 2020 Bobcat Fire spread in the Angeles National Forest in California

Smoke from wildfires can spread to neighboring states and cities, covering the area in smog. Pictured: New York City in June 2023 after wildfires broke out in Canada, sending smoke south

'We've pretty much addressed the easiest ways of reducing pollution,' she said. 'So we have catalytic converters on our vehicles, we have diesel particulate filters on our trucks, we have scrubbers on our power plants.'

She confirmed that climate change has become the major issue, adding that it shows we need to tackle both problems at once.

'It just really underscores that we need to do both things at the same time,' Anenberg told the outlet.

'We need to reduce carbon emissions that are causing anthropogenic climate change, and we need to continue to pursue stringent regulations on air pollution emissions.'

Lawmakers' back-and-forth response to addressing air pollution is making it difficult for the EPA to impose regulations and seems poised to block a policy that would reduce the amount of air pollution that crosses from one state to another - called the 'Good Neighbor' rule.

READ MORE: Health groups slam US's new air pollution cap as 'not strong enough'

Health groups have warned that the government's new air pollution cap are not strong enough and will lead to more cancers and lung diseases. 

If implemented, the rule would set a limit for the amount of smokestack emissions power plants and other industrial sources could produce in downwind areas that could carry it over to other states. 

Yet the Supreme Court's conservative majority was skeptical of approving the rule in February, calling it costly and ineffective. 

Proposed legislative efforts to curb air pollution come after a decades-long fight to protect people from harmful smog.

In 1948, the 'Donora Smog' disaster fueled the movement to take action against air pollution.

The Donora Smog killed 20 people when a temperature inversion - which traps cold air at low altitudes with warmer air above - blew into Donora and Webster, Pennsylvania, causing major respiratory problems for 6,000 of the 14,000 residents.

A storefront sign in Donora reads: 'Clean Air Started Here,' because it kicked off a revolution and ongoing fight to make the air safer to breathe.

Despite the number of people affected, attempts to instate air regulations in the 1950s failed, and it wasn't until the mid-1960s that then-President John F Kennedy called for action.

'In the light of the known damage caused by polluted air, both to our health and to our economy, it is imperative that greater emphasis be given to the control of air pollution by communities, States, and the Federal Government,' Kennedy said at the time.

However, 60 years later, Americans are still suffering from the highest air pollution levels in 25 years.

'A lot of people feel at this point that there's not much that they can do to address it or change it,' Sarah Sharpe, a Fresno resident and the collaborative's deputy executive director told USA TODAY. 

'It's just kind of a state of where we either have to live, or we choose to live.'