How NIEHS Research is Unraveling the Complex Link Between Asthma and Air Pollution
The simple act of breathing is under attack, and science is racing to understand why.
Imagine a world where every breath could trigger a health crisis. For the 25 million Americans living with asthma, this is not a hypothetical scenario but a daily reality 1 . Asthma, once viewed primarily as a genetic condition, is now recognized as a complex disease where environmental exposures play a crucial role in both its development and severity. As asthma rates continue to climb, particularly in vulnerable populations, researchers are digging deeper into the invisible toxins in our air that contribute to this silent epidemic.
Americans living with asthma
Americans breathing unhealthy air
Higher risk for people of color
The National Institute of Environmental Health Sciences (NIEHS) stands at the forefront of this investigation, supporting a diverse portfolio of extramural research that spans from laboratory benches to community health centers. These studies are revealing that asthma is not a single disease but a syndrome—a collection of symptoms that can arise through different pathways when environmental triggers activate various immune responses 1 . This article explores the groundbreaking work being done to understand how the air we breathe rewires our respiratory health, and how this knowledge is empowering both patients and physicians to fight back.
For decades, the conversation around asthma focused heavily on family history and genetic predisposition. While these factors certainly matter, NIEHS research has dramatically expanded our understanding of how environmental exposures interact with our biology. Stavros Garantziotis, M.D., a lung specialist and researcher at NIEHS, explains this paradigm shift: "We need to see the patient in the context of their environment, which is where they live, work, and play. Looking only for asthma symptoms and ignoring the exposures that may have caused these symptoms provides an incomplete picture" 1 .
This holistic approach has revealed several critical aspects of asthma's environmental origins:
Our immune systems can overreact to environmental exposures. NIEHS research has identified specific proteins that play a central role in regulating these immune responses 1 .
A 2025 hospital-based study revealed that individuals with high polygenic risk scores faced significantly increased asthma risk when combined with air pollution exposure 9 .
While we've long known that air pollution worsens asthma, not all pollutants are created equal. A groundbreaking Harvard T.H. Chan School of Public Health study, supported by NIEHS funding, set out to identify which specific components of fine particulate matter (PM2.5) contribute most significantly to asthma hospitalizations 4 .
| Pollutant | Primary Sources | Impact on Asthma |
|---|---|---|
| Nickel | Burning heavier fuel oils used in larger buildings | Among the strongest contributors to asthma hospitalizations |
| Vanadium | Fuel oil combustion | Among the strongest contributors to asthma hospitalizations |
| Sulfate | Coal burning power plants | Significant contributor to asthma hospitalizations |
| Nitrate | Vehicle emissions, power plants | Notable contributor to asthma hospitalizations |
| Bromine | Multiple sources including vehicle exhaust | Notable contributor to asthma hospitalizations |
| Ammonium | Agricultural and industrial processes | Notable contributor to asthma hospitalizations |
Source: Harvard T.H. Chan School of Public Health study 4
"We know that PM2.5 increases the risk of asthma attacks and hospitalizations, but those particles are made of many compounds, and we haven't known which are most harmful. Our study teases out which specific compounds in the PM2.5 mixture necessitate the strongest control efforts in order to improve asthma outcomes."
The findings, published in the American Journal of Respiratory and Critical Care Medicine, revealed that for each decile increase in the pollutant mixture, asthma hospitalizations increased by 10.6% among children and 8% among adults ages 19 to 64 4 .
Understanding the connection between air pollution and asthma requires sophisticated tools and methods. NIEHS extramural researchers employ a diverse array of approaches to decode this complex relationship.
| Research Method | Application | Example |
|---|---|---|
| Land-use regression (LUR) models | Estimating individual exposure to air pollutants based on residential location | Used in large population studies to assign pollution levels to participants' homes 6 |
| Weighted quantile sum (WQS) regression | Identifying most harmful components in pollutant mixtures | Helped pinpoint nickel and vanadium as key drivers of asthma hospitalizations 4 |
| Environmental epigenetics | Studying how environmental exposures alter gene expression without changing DNA sequence | Exploring how air pollution might "reprogram" immune responses in asthma development |
| Exposomics | Comprehensive analysis of all environmental exposures throughout life | Investigating cumulative impact of multiple pollutants on asthma risk over time |
| Wearable sensors | Tracking personal exposure to pollutants in real-time | Providing granular data on how and when exposures happen throughout daily routines |
The turn toward personalized monitoring represents a particularly promising development in the field. As noted in a 2025 analysis of air pollution knowledge practices, "The recent monitoring of asthmatic bodies (rather than environments) with wearable sensors are informing knowledge about how and when exposure happens and is particularly harmful" .
Another critical tool in the research arsenal is the use of large-scale cohort studies. The UK Biobank project, which recruited over 500,000 participants, has provided invaluable data for understanding air pollution's health impacts 6 .
As research advances, the field is moving toward a more personalized approach to both prevention and treatment. Personalized environmental medicine—evaluating each person's specific exposures and susceptibility factors and tailoring treatment accordingly—holds promise for more effective interventions 1 .
"Personally, I have been able to improve symptoms and even reduce the amount of medication my asthma patients need by thoroughly evaluating their exposure profiles and taking steps to address them. These are low-cost, low-tech, but high-impact solutions that can help patients tremendously."
This approach empowers patients to become detectives in their own asthma cases, identifying patterns between exposures and symptoms 1 .
The future of asthma research will also focus on prevention rather than just management, creating targeted strategies to prevent the disease before it starts 5 .
Research on the protective effects of certain environments offers intriguing clues about how we might build resilience against asthma 5 .
| Rank | Metropolitan Area | Impact on Residents |
|---|---|---|
| 1 | Los Angeles-Long Beach, CA | Repeated exposure to unhealthy ozone levels |
| 2 | Visalia, CA | High asthma risk from ground-level ozone |
| 3 | Bakersfield-Delano, CA | Multiple pollution challenges (ozone and particles) |
| 4 | Phoenix-Mesa, AZ | Growing ozone problems in warming climate |
| 5 | Fresno-Hanford-Corcoran, CA | Agricultural area with ozone formation |
Source: American Lung Association 2025 Report 2
The work supported by NIEHS extramural research is transforming our understanding of asthma—from a fixed genetic destiny to a modifiable environmental disease. By uncovering the specific mechanisms that connect air pollutants to asthma development and exacerbation, scientists are developing more effective strategies to protect respiratory health.
This research carries a powerful message of hope and agency. While we cannot change our genes, we can change our environments—through policy decisions that target the most harmful pollution sources, through clinical practices that address environmental triggers, and through personal actions that reduce exposure. As Dr. Garantziotis reminds his patients, "They visit my clinic only once every six months, but they are experiencing asthma 24/7" 1 . Equipping people with knowledge about their environmental health is perhaps the most important outcome of this research.
The air may be invisible, but its impact on our health doesn't have to be a mystery. Thanks to the innovative work of NIEHS-supported researchers, we're learning how to decode the complex relationship between our environment and our health—and taking steps toward a future where everyone can breathe easier.