Particulate matter is not ‘junk science.’ Decades of research show it affects human health

Wildfires in Canada drastically affected the air quality in multiple U.S. states in June’s second week, leading residents to reach for face masks to mitigate risks brought about by inhaling particle pollution.

On Fox News, a guest on "The Ingraham Angle" claimed these concerns were unfounded.

Steve Milloy, who served in former President Donald Trump’s Environmental Protection Agency transition team, claimed "there’s no health risk" brought about by the air quality, and wildfire smoke is "natural."

Host Laura Ingraham brought up media coverage that advises people to wear face masks, as they had during the COVID-19 pandemic. Milloy again dismissed health concerns.

"This is all particulate matter, but particulate matter was not a concern until EPA invented it as one in the 1990s," he said. "They have no effect. EPA has all this testing on real live human beings that shows no effect. This is total junk science."

Milloy, a biostatistician and lawyer, founded the website JunkScience.com. We wanted to examine his claim that not even EPA research shows health concerns about particulate matter are legitimate.

We found a breadth of evidence that shows he’s wrong. Here’s why.

Particulate matter, or particle pollution, generally refers to a mixture of solid and liquid droplets suspended in the air. It is a main component of wildfire smoke. These microscopic solids or liquid droplets are so small that they can be inhaled and affect the lungs and heart.

According to the EPA, particles less than 2.5 micrometers in diameter, also known as PM 2.5, pose the greatest risk to health. The CDC said particles called PM 10 can irritate the eyes, nose and throat, and PM 2.5 can get into the deep parts of the lungs, or even into blood.

Particle pollution is associated with serious health effects, including nonfatal heart attacks, an irregular heartbeat, aggravated asthma, decreased lung function and premature death, according to the EPA. It has also been linked to lung cancer and problems with babies at birth.

People with heart or lung diseases, older adults, babies and children are most at risk of experiencing health effects associated with particle pollution.

Shayla Powell, an EPA spokesperson, told PolitiFact that the health risks of inhaling fine particles within smoke are well documented in thousands of peer-reviewed studies.

EPA research bears this out.

The Clean Air Act, first enacted in 1955, required the EPA to establish ambient air quality standards for air pollutants that endanger public health or welfare. Particulate matter is one of six air pollutants with such standards. The EPA established these standards for particulate matter in 1971.

The agency reviews scientific data underpinning these standards every five years.

When PolitiFact reached out to Milloy, he criticized the science behind the EPA’s regulation of particulate matter and cited studies and EPA testimony that supposedly show no causation between particulate matter and health effects or death.

The studies he cited were either epidemiological or controlled human exposure studies. Epidemiology is used to find the causes of health outcomes and diseases in populations. Meanwhile, in controlled human exposure studies, human volunteers are "intentionally exposed to pollutants by inhalation under controlled experimental conditions."

Milloy claimed that EPA’s epidemiological studies don’t show causation between particulate matter exposure and health effects — but that’s an oversimplification. 

The agency’s 2019 evaluation of the scientific data to inform its standards for particulate matter — its latest report — outlined how the agency determined relationships between particulate matter exposure and health effects. 

• A "causal relationship" means there is clear evidence that exposure to particulate matter has been shown to affect health. 

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• A "likely to be causal relationship" means there are studies that are not explained by chance or other biases, but uncertainties remain in the evidence.

What constitutes "clear evidence"? Studies that show particulate matter exposure affected health, with alternative explanations ruled out. This can be demonstrated by controlled human exposure studies, or observational studies that cannot be explained by plausible alternatives or are supported by other evidence, such as animal studies.

The EPA assessed risks in several categories for health effects, including respiratory; cardiovascular; reproduction and fertility; metabolic; and mortality. A "causal relationship" was found between particulate matter exposure and cardiovascular effects, as well as death.