In the not-so distant past, you may not have thought twice about your exposure to radiation. While Roentgen discovered the X-ray in 1895, it would not be until the early-mid 1900s that the general public—let alone the scientific community—would accept the malignant potential of an invisible, devastating force, powerful enough to pierce bone, burst cells, and warp DNA. It would take years of tragedy before we finally recognized radiation for what it was—a threat to human health. That begs the question, why aren’t we doing the same for air pollution?

The word “air-pollution” can more aptly be described as a broad “category” for a raft of airborne pollutants with well-characterized effects on the human body. Typically, air pollution comes in two varieties (1) particulate matter (e.g. fine dusts) and (2) gaseous, organic compounds (VOCs).

Scientists often distinguish particulate matter based on size, giving rise to commonly used measures such as PM2.5, PM5, PM10. The latter number represents the size, in microns, of the particulate matter.

Measuring particle size, impact

Size matters insofar as the dimensions of a particle determine its ability to travel within the airways and ultimately wreak havoc on our biological systems. For this reason, larger particles such as those greater than or equal to PM10, are not commonly associated with adverse events. The airways act like a potent sieve, filtering-out and sequestering the otherwise noxious particles from the respiratory tract. However, the smallest of the trio, PM2.5, is nearly to the physical defenses of our upper respiratory tract, floating gleefully down to our alveoli where it then enters systemic circulation.

Research into the health effects born of exposure to PM2.5 and its ilk is voluminous, clear, and deeply unsettling. Chronic exposure to PM2.5 has been with cardiovascular disease (ischemic heart disease, atherosclerosis, etc), dementia, respiratory conditions (including asthma and COPD), early mortality, and a laundry list of equally pernicious diseases. To be clear, these associations are unlikely to be purely correlational, either. They are dose-dependent, linear, and have been replicated by many previous authors. In other words, the more PM2.5 you are exposed to, the greater your risk. Moreover, the risk is not limited to the frail or infirmed. Those exercising in PM2.5 laden areas, for instance, may suffer immediate alterations in autonomic balance, possibly including significant alterations in measures of respiratory functions such as forced expiratory volume (FEV) or total lung capacity (TLC). Over time, these exposures culminate in what the WHO has noted is now the single most dangerous pollutant world-wide. Again, causality is difficult to prove with nearly anything, but it is likely, to a degree of measured certainty, that exposure to PM2.5 is a threat to public health. So, why aren’t we acting like it?

Regulation of air quality is an evolving science globally. In the U.S., air quality has been the subject of regulation since 1971. Domestically, the EPA is the chief regulator and enforcement agency responsible for upholding air quality standards nationwide. Beginning in 1971, the EPA established limits on “air pollution,” creating an air quality index (AQI) for the purposes of informing the public about the outdoor, or ambient risk, associated with a particular zip code’s air quality throughout the U.S.. The AQI ranges from 0-500 and comes fitted with labels such as “Good (0-50), Moderate (50-100), Unhealthy for Sensitive Groups (101-150), Unhealthy (151-200), Very Unhealthy (201-300), or Hazardous (302-500)” which correspond to 24-hour periods of PM deposition measured in microgram/m3. Location specific data is easily visible and can be accessed officially at airnow.gov, in addition to a multitude of other third-party and public databases. Most recently, the EPA has proposed to revise its annual PM2.5 standards, or primary health-based standards, from 12 to 9-10 microgram/m3, reflecting the scientific community's burgeoning understanding of the risks posed by PM pollutants.

A call for action

Despite recent strides in public awareness and central legislation, there is vastly more action to be desired. While measures of air quality have improved in the last two decades, they have been nearly stagnant since 2016. Moreover, areas impacted by adverse AQIs tend to concentrate in low-middle income areas, afflicting marginalized populations disproportionately. The right to clean air should not be a privilege and, yet, there are few clearer, modern examples of a segregated public good. And, accounting for AQI’s impact on individual’s health span, the picture becomes all the more disturbing.

In the District of Columbia, while air-quality related disease has halved in the last decade, broad segregation exists with more impoverished wards such as 5, 7 and 8 facing the brunt of PM2.5 pollution and associated morbidity. These same wards also experience outsized incidence of lung cancer, cardiovascular mortality, and obstructive pulmonary diseases including asthma and chronic obstructive pulmonary disease (COPD). The trend is simple: Neighborhoods with less wealth suffer greater air pollution.

The D.C. Department of Energy and Environment (DoEE) has indeed made efforts to remediate air pollution. Still, disparities exist and tend to afflict the city's most vulnerable populations. Asthmatic children are notably sensitive to the effects of PM—indeed, there is evidence that greater exposure to PM2.5 is itself a risk factor for the development of asthma and asthma-associated conditions.

The problem with introducing meaningful change is multifactorial. Both the risk of exposure to PM2.5, and the risks associated with dose-dependent exposure, have yet to be precisely quantified. Furthermore, the technology required to monitor and ameliorate PM related pollutants is difficult to access, especially for less affluent communities. And, to make matters more complex, the “problem” of air pollution may also involve household and community exposure to volatile organic compounds including benzene, toluene and formaldehyde. Such gaseous agents, like their PM counterpart, are robustly linked to dose-dependent effects and have more thoroughly outlined impacts on carcinogenesis, DNA damage, and respiratory disease. Sadly, such compounds are even more difficult to measure and more complicated to remediate. Gas stoves, for instance, may be repositories for these compounds. Natural gas is derived from deep underground, where volatile compounds mix with the natural gas, and are subsequently released into the home environment.

Educate the community and empower public health departments

So, what are the solutions? Awareness and legislative efforts are critical. The importance of education is perhaps cliche, but in this case, underutilized. Public health officials and healthcare providers, may not be aware of the dangers associated with PM and volatile compounds due to the literature being relatively nascent. The key, then, is to educate the community and empower public health departments to not only recognize, but define the threat of PM associated pollution.

The second arm of this approach is instituting legislative consequences. It’s not enough to set limits on pollution or to encourage “clean air.” It’s time for action. Air quality is routinely measured. That data, and its implications, should not be the provenance of a federal agency or a disembodied arm of the county. The city, the state, and the community should take ownership of public spaces, identify sources of pollution, cite polluters and take immediate steps to improve air quality. A failure to act accordingly isn’t simply a risk to the environment, it’s a matter of public health and, indirectly, economic well-being. Let’s start to act like it.

About the authors

	Jacob M. Hands is a first-year medical student at the George Washington University School of Medicine and Health Sciences. His research interests include evolutionary biology, air pollution, CVD, glucose metabolism, and omega-3 supplementation. Twitter: @jacobmhands
	William M. Rienas is a first-year medical student at the George Washington University School of Medicine and Health Sciences. He graduated with a bachelor's in Neuroscience and secondary in Economics from Harvard College in 2020. His professional interests include clinical research and healthcare innovation.
	Brij Kathuria is a first-year medical student at the George Washington University School of Medicine and Health Sciences, with a scholarly concentration in Clinical and Translational Research. He graduated with a bachelor's in Molecular and Cellular Biology and a bachelor's in Health Sciences (BSHS) in Physiology from the University of Arizona. Brij serves as the director of Fundraising and Development for GW's Healing Clinic, which is one of Washington D.C.'s largest free health care programs.
	SeungEun (Blaire) Lee is a first-year medical student at George Washington University School of Medicine and Health Sciences. She graduated with a bachelor's in Neuroscience from University of Michigan-Ann Arbor. Her professional interests include health equity, clinical and translational research, and surgical innovations.
	Renxi Li is a first-year medical student in the MD-Clinical Research Practice Graduate Certificate Program at The George Washington University School of Medicine and Health Sciences. He graduated with a bachelor's in mathematics, physics, Chemistry, Astronomy-Physics, Biochemistry, Molecular and Cell Biology, Neurobiology, Zoology, and Psychology from the University of Wisconsin-Madison. His professional interests include vascular surgery, clinical research, and healthcare equity.

**Feature photo obtained with a standard license on Shutterstock.

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