Episode #43: 2024 State of the Air: Record Highs in U.S. Particle Pollution

Dr. Albert Rizzo: Welcome to LungCast, the monthly respiratory health podcast series from the American Lung Association and medical news site HCPLive. I’m your host, Dr. Albert Rizzo, Chief Medical Officer of the American Lung Association.

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Our guest today is Dr. James Balmes, Professor of Medicine Emeritus at the University of California, San Francisco, and Professor of Environmental Health Sciences Emeritus in the School of Public Health at the University of California, Berkeley. He serves as an attending physician in the Division of Occupational, Environmental, and Climate Medicine at UCSF and at the Division of Pulmonary and Critical Care Medicine at San Francisco General Hospital. Dr. Balmes has studied the effects of exposures to occupational agents and air pollution on respiratory, immune, cardiovascular, and metabolic health, and has collaborated on studies of indoor and outdoor air pollution as well as wildfire smoke for many years. He has also served as the physician member of the California Air Resources Board since 2008 and is a valued advisor and national medical spokesperson for the American Lung Association.

Dr. Balmes, thank you for your time and effort over the years, especially today as we discuss our State of the Air Report 2024.

Dr. James Balmes: Thank you, Dr. Rizzo. I’m glad to be here.

Dr. Rizzo: The American Lung Association each year releases our State of the Air report, which is an annual air quality report card that tracks individuals’ exposures in cities nationwide to unhealthy levels of ground-level ozone, or smog, and particle pollution, or soot, over a three-year time frame. The report also publishes a ranking of the most polluted and cleanest U.S. cities for air quality. The ALA just released the 25th annual State of the Air report.

I know you’ve been involved with this report as a reviewer of the health effects section for many years. How long would you say you’ve been working with it?

Dr. Balmes: I think this is at least the fourth edition that I’ve helped with the health effects section.

Dr. Rizzo: You’re a good one to do that based on the background I just read. For more context, the State of the Air report uses recent quality-assured air pollution data from county measuring stations collected by federal, state, local, and tribal governments during 2020, 2021, and 2022. The one-year delay is necessary to collect accurate and validated data.

Now, regrettably, out of the 3,221 counties in the United States, only about 911—less than one-third—actually monitor at least one pollutant. That means more than 71 million people live in counties where their ozone and particle pollution levels are not being monitored. And as we’ll discuss, that can have health consequences.

My review of this year’s report shows that people in the U.S. experienced more days with very unhealthy and hazardous air quality because of particle pollution than in the history of the report dating back 25 years. Dr. Balmes, can you give your views on some of the causes that lead to these spikes in particle pollution, and in particular, comment on the effects of the pandemic and the wildfire outbreaks we’ve seen in recent years?

Dr. Balmes: There are several reasons particle pollution is worse in many of the cities the report covers. I’ll start with wildfires. I live in Northern California, where we’ve had a lot of experience with wildfires. All the progress we’ve made with Clean Air Act enforcement—reducing particle pollution from sources like diesel trucks and coal-fired power plants—has been almost eliminated by the incredible increase in pollution from wildfire smoke.

And it’s not just the Mountain West. Prevailing winds push wildfire smoke across the country. A few years ago, I was interviewed by a New York radio station because air quality there was bad due to California wildfire smoke. This year, Canadian wildfire smoke significantly impacted the East Coast.

Another reason is that the EPA has determined there should be a stricter national air quality standard for PM2.5. That means more cities now fail to meet the “healthy air” standard. Those are the two main reasons more cities are getting poor grades.

Dr. Rizzo: The main particle pollution we measure is PM2.5, and we know it can have numerous health effects when inhaled. Can you describe these health effects and which populations are most at risk?

Dr. Balmes: PM2.5 stands for fine particles smaller than 2.5 microns. For comparison, a human hair is about 60 microns. These tiny particles make it deep into the lungs, and the ultrafine fraction can even cross into the bloodstream.

They cause problems for people with asthma and COPD—leading to exacerbations—but also increase risk for cardiovascular events like heart attacks and strokes. There’s growing evidence of effects on the brain, including higher risks of dementia and impaired cognitive development in children. PM2.5 exposure is also linked to metabolic disorders like diabetes.

The most vulnerable groups are the very old with heart and lung disease, the very young with developing lungs, people with asthma, COPD, or cardiovascular disease, and low-income communities of color. These communities often face greater exposure because of where they live and also have other compounding health and social factors.

Dr. Rizzo: This year’s report reflects the new annual particle pollution standard the EPA finalized this past February. For our listeners: the standard was strengthened from 12 micrograms per cubic meter to 9. Thanks to this stronger standard, the number of people living in places with unhealthy annual particle pollution jumped from 18.8 million in last year’s report to 90.7 million this year.

Can you comment on the implications of these new standards, why the ALA has been advocating for stronger measures, and why there’s a separate measure of short-term versus annual exposure?

Dr. Balmes: The Clean Air Act requires EPA to review the science every five years. Research keeps showing health effects at lower levels. Studies support increased risk of death, mostly from cardiovascular disease, even below 12 micrograms. That justified lowering the standard to 9.

The short-term (24-hour) standard remains at 35 micrograms. Some of us think it should be lowered, but EPA felt the evidence wasn’t strong enough yet. Both standards are important—long-term exposure causes chronic effects, while short-term spikes cause acute effects like asthma attacks or heart events.

Dr. Rizzo: The report also measures ozone. This year’s report shows significant improvements in ozone thanks to the Clean Air Act, but still 131 million people live in places with unhealthy levels. Please remind our listeners of the health effects of ozone and what causes it.

Dr. Balmes: Ozone was the first pollutant to raise big public health concerns, especially in Los Angeles. Ozone is a powerful oxidant that chemically burns the airways, especially worsening asthma. It’s associated with more ER visits, respiratory exacerbations, and even increased risk of respiratory death.

Ozone is not directly emitted; it forms in the atmosphere from tailpipe emissions and power plants. Thanks to regulations, we’ve reduced precursors, but climate change threatens progress because hotter temperatures lead to more ozone formation. Cities like Atlanta and Houston now rival LA in ozone levels.

Dr. Rizzo: What can individuals and organizations like the ALA do to keep moving levels in the right direction?

Dr. Balmes: The most important thing is to reduce reliance on fossil fuels. That means electrifying vehicles and appliances, moving toward clean transportation and power generation. The Lung Association has been a strong advocate for clean air regulations and continues to highlight the link between climate change and air quality. Reducing fossil fuels benefits both climate and public health.

Dr. Rizzo: The ALA is also very concerned about inequities in exposure. Communities of color are disproportionately affected, often due to socioeconomic and historically racist policies like redlining. What does this year’s report tell us?

Dr. Balmes: This year’s report has a stronger focus on inequities, which is important. Low-income communities of color bear a disproportionate burden of exposure, especially from diesel vehicles and power plants.

EPA monitoring focuses on regional averages, often away from freeways or industrial hotspots. But in places like Richmond, California—where freeways, a rail yard, a port, and a refinery converge—residents are clearly exposed to much higher levels. California is moving toward community-level monitoring and emission reduction plans. We need to take that approach nationally.

Dr. Rizzo: To close, can you comment on the role of climate change over the last 25 years and what you might expect for the next 25?

Dr. Balmes: If we double down on reducing fossil fuel use, we can continue making progress. Studies show it’s possible to transition without destroying the economy. But it requires collective action, especially from developed countries. If we succeed, we’ll both mitigate climate change and improve air quality.

Dr. Rizzo: Thank you again, Dr. Balmes, for your time today and for your ongoing volunteer work with the American Lung Association.

Dr. Balmes: And thank you, Dr. Rizzo. I appreciate all that you and the Lung Association do.

Dr. Rizzo: For our listeners, if you want to hear more regarding air quality, health, and climate change, we have a great archive of discussions on our feeds. Be sure to subscribe and rate LungCast on your preferred platform, and visit lung.org and hcplive.com for more news and resources.

Until next time, I’m Dr. Albert Rizzo, reminding you that if you can’t breathe, nothing else matters.