As published on Medium

The latest cover story of the Cardiology Magazine by the American College of Cardiology explores the complex and evolving understanding of how wildfire smoke and extreme temperatures affect cardiovascular health. Long-term, cumulative exposure to smoke has been linked to increased mortality rates and chronic diseases. Similarly, short-term exposure — such as during a wildfire event — has been associated with spikes in emergency room visits for cardiovascular conditions and increased mortality risks. However, these short-term outcomes were not consistently observed across wildfire events in the cited study. Even the long-term associations between particulate matter from smoke and mortality are not always clear-cut. Taken together, these mixed findings raise important questions about how reliably we can assess the health risks of smoke exposure.

This discussion reminded me of a paper led by Dr. Yaguang Wei at the Harvard T.H. Chan School of Public Health, which caught my attention when it was published in 2023. The researchers found that exposure to PM2.5 and NO2 was associated with increased risks for certain types of cancers. Of real interest to me was that the study also pointed to a negative relationship between PM2.5 levels and at least one type of cancer. Even more puzzling, the researchers noted that “at exposure levels below the newly updated World Health Organization Air Quality Guideline, we observed substantially larger associations between most exposures and the risks of all cancers.”

These are merely two examples.

Why the Unexpected Results?

The smoke study authors suggest that increased public awareness and protective behaviors — such as mask usage and staying indoors — may have helped reduce exposure and therefore risks during one fire event. They hypothesize that these behaviors, along with contextual factors like public health advisories and school closures, could help explain the differing health outcomes between the fire events studied. Another proposed explanation is the “depletion of the susceptibles” effect: individuals most at risk may have already experienced outcomes during the earlier fire, reducing the likelihood of similar outcomes during a subsequent exposure. These factors could certainly help explain some of the variations observed — though school closures, for example, seem unlikely to directly reduce cardiovascular risk.

Still, could there be other explanations? Here’s a theory worth pondering:

1. Commercial particulate matter (PM) sensors, frequently employed in epidemiological research, generally fail to detect particles smaller than 0.3 microns (PM0.3). Meanwhile, these particles are abundant in wildfire smoke and other critical pollutants.
2. Although prevalent, these tiny particles typically contribute minimally to standard PM2.5 mass measurements (μg/m³).

These measurement gaps may be distorting the data — potentially contributing to the inconsistent results observed across studies. In my recent article for International Filtration News, “The 0.3-Micron Blind Spot in IAQ: Far-Reaching Implications for Airborne Pathogen Transmission and Climate Adaptation,” I raised concerns about the health significance of PM0.3. These super-fine particles often go undetected by standard sensors, yet they can penetrate deeply into the respiratory system, posing risks that may be underestimated or entirely missed due to current measurement limitations.

Facing the Unknown with Better Awareness

The immediate solution doesn’t rest on technological advancement — although developing improved sensor technology remains essential. More urgently, widespread education on current sensor limitations can make a significant difference. Increasing awareness of these gaps empowers public health officials, researchers, and communities to better interpret air quality data and effectively address the implications for public health, especially in wildfire-prone regions.

Key Takeaways

• Wildfire smoke can significantly impact cardiovascular health, though some findings have been inconsistent.
• Limitations in PM sensor technology may be contributing to these conflicting findings.
• Education about these limitations is essential for informed public health action.

Recognizing the limitations of how we currently measure air pollution is essential — not just for refining future research, but for improving the public’s ability to interpret and act on air quality information today. This isn’t about claiming to have the answers — but rather about acknowledging a critical gap that deserves closer scrutiny. I hope researchers and academics will take this challenge seriously, and explore whether the limitations in our sensing methods might be contributing to the conflicting health data we continue to see. With better awareness and communication, we can bridge the gap between data and action to better protect public health.