Scientists have revealed the profound impact of air pollution on the human body, demonstrating how breathing in pollutants like ozone and PM2.5 harms nearly every major organ system. The comprehensive analysis comes as environmental experts express concern about potential regulatory changes that could weaken air quality protections.
The Personal Experience of Pollution
Jenni Shearston, an environmental epidemiologist at the University of Colorado Boulder, recalls her first visit to Denver in the early 2000s. "I grew up in rural Colorado, deep in the mountains, and I can still remember driving out of the mountains toward Denver," she explains. "The entire plain was covered in a brown, hazy cloud that obscured the city skyline."
That brown haze was primarily composed of ozone, a lung-irritating gas that causes decreased lung function, inflammation, respiratory symptoms like coughing, and can trigger asthma attacks. While Denver's air quality has improved since then, the city still faces pollution challenges due to its geographical position, which creates temperature inversions that trap pollutants near ground level.
Regulatory Success Under Threat
Air quality across the United States has shown significant improvement over recent decades. Since 1990, ozone levels have decreased by 18% nationwide, while concentrations of PM2.5 - tiny dustlike particles of air pollution - have fallen by 37% since 2000. These improvements are largely attributed to the Clean Air Act, first passed in 1970, which regulates air pollution emissions and authorises the Environmental Protection Agency to set national air quality standards.
However, environmental scientists are now concerned about proposed changes to how regulatory impacts are calculated. The Trump administration plans to drop the monetary health benefits of reducing both ozone and PM2.5 from economic impact assessments when regulating pollution sources. This represents a significant departure from historical practice, where the EPA weighed both health costs for Americans and compliance costs for businesses.
What Pollution Does to Your Body
Breathing air pollution containing ozone and PM2.5 particles has devastating effects on multiple bodily systems:
- Cardiovascular System: PM2.5 exposure is associated with increased death from cardiovascular diseases like coronary heart disease. Even short-term exposure can increase hospitalisations for heart attacks and strokes.
- Respiratory System: PM2.5 exposure is linked to a 10% increased risk for respiratory diseases and symptoms such as wheezing and bronchitis in children.
- Neurological System: Emerging evidence suggests PM2.5 exposure can increase the risk of Alzheimer's disease and other cognitive disorders.
- Cancer Risk: The International Agency for Research on Cancer has designated PM2.5 as a carcinogen, recognising its cancer-causing properties.
Quantifying the Health Benefits
Reducing air pollution has been proven to save lives, reduce healthcare costs and improve quality of life. A study led by EPA scientists estimated that a 39% nationwide decrease in airborne PM2.5 from 1990 to 2010 corresponded to a 54% drop in deaths from ischemic heart disease, chronic obstructive pulmonary disease, lung cancer and stroke.
During the same period, a 9% decline in ozone corresponded to a 13% drop in deaths from chronic respiratory disease. These illnesses represent significant costs for both patients and the public healthcare system, through treatment expenses that raise insurance prices and economic losses when people are too ill to work.
Another study found that nationally, an increase of 1 microgram per square meter in weekly PM2.5 exposure was associated with a 0.82% increase in asthma inhaler use. Researchers calculated that decreasing PM2.5 by that amount would mean approximately $350 million in annual economic benefits.
The Uncertainty Argument
The EPA has stated that uncertainty in calculating precise monetary savings from pollution reduction policies led to their decision to exclude health costs from cost-benefit analyses. In a notice dated January 9, 2026, the agency wrote that its historical practice of providing estimates "leads the public to believe that the EPA has a clearer understanding of these monetary benefits than it actually does."
Shearston counters this argument by comparing it to weather forecasting: "This is like ignoring weather forecasts because they might not be perfect. Even though there is uncertainty, the estimate is still useful." She emphasises that estimates of monetary costs and benefits help determine whether regulations are worth their implementation costs.
Evidence from Power Plant Studies
Several studies demonstrate the direct impact of pollution sources on public health. Research examining the retirement of coal and oil power plants found a reduction in preterm births among mothers living near these facilities. Scientists studied 57,000 births in California and discovered that the percentage of babies born preterm to mothers living within 3.1 miles of a coal- or oil-fueled power plant fell from 7% to 5.1% after the plant was retired.
Another study in the Louisville, Kentucky area found that when four coal-fired power plants either retired or installed pollution-reduction technologies, there was a corresponding drop in hospitalisations and emergency department visits for asthma, along with reduced asthma medication use.
Reducing preterm births, hospitalisations, emergency department visits and medication use generates substantial economic savings by preventing expensive healthcare treatments, hospital stays and medications. Researchers estimated that for children born in 2016, the lifetime cost of preterm birth - including medical and delivery care, special education interventions and lost productivity due to disability in adulthood - exceeded $25.2 billion.
Returning to Denver's Challenge
The Denver region is experiencing rapid growth as a data centre hub, with utilities expecting power demand to skyrocket over the next 15 years. This expansion will require additional power generation capacity, and with the EPA's proposed changes to pollution standard calculations, new facilities may be held to lower pollution standards.
Shearston concludes: "Without considering the health costs and benefits, it may be easier for infrastructure that emits high levels of air pollution to be built and operated. The evidence clearly shows that reducing air pollution saves lives and reduces healthcare costs - we should be strengthening protections, not weakening them."
