Air Pollution
Most of what we consider as air pollution comes from burning fossil fuels.
What is air pollution?
Air pollution is a combination of particulate matter and a soup of toxins, many of which are not monitored regularly. The exact mix of pollutants depends on what is being discharged into the air locally, but also events that can be on another continent depending on the wind patters (e.g., large wildfires,).
Many chemical pollutants we just lump as “volatile organic compounds” (VOC). There are hundreds, perhaps, thousands of those. Some, like benzene, are known carcinogens. Benzene is also found in cigarette smoke, contributing to indoor pollution!
Smog was first described in Los Angeles. It was unknown before World War ll. The name is a combination of smoke and fog. Smog is fog and photochemical reactions of nitrogen oxides and VOC from burning fossil fuels, primarily cars. These photochemical reactions are driven by sunlight, and lead to the formation of ozone and chemicals like peroxyacetylbutyrate, which is so destructive that it can degrade rubber!
The pollutants that the government is mandated to monitor are the “criteria” air pollutants:
Ground level ozone
Particulate matter
Carbon monoxide
Lead
Sulfur dioxide
Nitrogen dioxide.
Air pollution is made worse by climate change
Higher temperatures create more ozone (although also more breakdown of ozone, a complex interaction, but in balance more is usually created).
We are used to thinking of ozone as a good thing, because in the upper atmosphere where we can’t breathe it, ozone blocks some of the Sun’s harmful radiation, so we don’t get as many skin cancers and the like. But the ozone we live with on the ground is very irritating, a strong oxidant, and worsens asthma and other lung diseases.
There are indirect ways climate change increases air pollution: particulate matter and noxious substances from burning structures from wildfires that are increasing due to climate change can be a severe health hazard.
Climate change also has complex influences on wind patterns, clouds and humidity, all of which can alter how air pollution is dispersed. The details are still being sorted out in climate models as it is so complex.
Climate change is clearly made worse by pollution since carbon dioxide (CO2), nitrous oxide (NOx, the x means it can be different oxides), sulfur dioxide (SO2), ozone, and chlorofluorocarbons are all pollutants that are greenhouse gases (GHG).
CO2 is now classified as a pollutant
CO2 is now classified on a federal level as a pollutant, thanks to the Inflation Reduction Act that was signed into law in August 2022. It isn’t clear how much it will change things, but there is a chance it will make lawsuits to counter EPA regulations less likely to prevail, in part countering the effects of the recent Supreme Court ruling limiting the EPA’s role in dealing with climate change.
The good news
We have made some strides with regulations, inventions and interventions like catalytic converters.
We also have alternatives to fossil fuels: less fossil fuels, we get less pollution and less GHG, so less heat and less ozone in our lungs. The pressure point for pollution is decreasing fossil fuel use and decreasing global warming. Two for one in a positive feedback loop.
The bad news
The Lancet Commission on Pollution and Health in 2018 concluded that globally 9 million deaths were caused by pollution, which was 16% of all premature deaths. Indoor air pollution may result in 3.8 million additional deaths each year. Your gas stove may be as polluting as secondhand smoke!
One estimate is that fine particle air pollution is the fifth leading risk for death in the world and more than 103 million disability-adjusted life-years lost.
From the UN/WHO:
Yikes!
Particulate Matter (PM)
Particulate matter (PM) is a pollutant, but not a GHG, though it is associated with burning material, including fossil fuels, in coal plants, combustion engines, other industrial processes and wildfires, which do produce GHG emissions.
In fact, particulates block sunlight and are potentially cooling (we see this after large volcanic eruptions), but at the very steep price of being terrible for our health and associated with processes that produce GHG.
Particulate matter (PM) is divided into 3 size groups. The largest, PM10 (less than 10 microns across) gets deposited in the upper airways. PM2.5 (less than 2.5 microns) is mostly deposited in the lungs, though some may be absorbed. PM1 (less than 1 micron) can be absorbed into the bloodstream and transported throughout the body. In most clinical studies it is not measured directly or reported separately.
Health effects of pollution
Heart:
Long-term exposure to PM2.5, NO2, and ozone have been associated with advanced atherosclerosis. Particulate matter and other air pollutants have been associated with high blood pressure. PM2.5 is associated with a small (2.5%) increased risk of having a heart attack, with some additional risk from PM10, SO2, and NO2. PM2.5 and ozone were associated with a higher death rate 5 years after a heart attack.
The effect on human health from closing a polluting coke plant can be seen over just a few years. Closing the Shenango Coke Works near Pittsburgh resulted in “a 90 percent drop in sulfur pollution near the plant and an immediate 42 percent decrease in emergency room visits for cardiovascular disease among nearby residents. And over three years, those ER visits dropped even further – 61 percent compared with past years.” Note that “The Shenango plant was closed by DTE Energy after years of protest from neighboring communities.
Lungs:
Air pollution clearly makes asthma worse. Also, greater exposure to PM10 and NO2 at birth was associated with a higher prevalence of asthma 20 years later. Ozone and PM2.5 were associated with more chronic obstructive lung disease in asthmatics. PM2.5, NOx, and ozone were associated with emphysema progression and worse lung function. They may also adversely impact acute respiratory distress syndrome and pulmonary fibrosis. PM2.5 and NO2 were associated with more respiratory infections overall, as well as higher incidence of mortality with Covid-19 infections, although there were many confounding factors in the study. In fact, millions of pediatric asthma attacks could be prevented by switching to clean energy and electric vehicles.
Diabetes:
Diabetes is more likely with higher exposures to PM 2.5, PM10 and NO2, most likely in those already predisposed (overweight, prediabetic).
Urinary:
Particulates in the blood may be filtered in the kidneys, and there has been an increase in chronic kidney disease and end-stage disease associated with pollutants.
Gastrointestinal:
Associations with inflammatory bowel disease, fatty liver (the liver also filters PM) and maybe GI cancers.
Immune:
Particulate matter can stimulate some aspects of the immune system. That may sound good, but it is a response that is not geared to fighting infections or cancers! Systemic immune diseases, such as rheumatoid arthritis and maybe juvenile lupus, may be associated with increased air pollution.
Cancer:
Air pollution exposure was associated with increased mortality, particularly in digestive, lung, breast and female genital cancer. As noted above, some organic compounds in air pollution are carcinogenic. We don’t even know just how many!
Neurologic:
Increased risk of stroke, dementia and Parkinson’s disease. PM10 may increase anxiety, depression and even suicide risk.
The eye:
It will come of no surprise that walking around in a soup of volatile hydrocarbons and particulate matter, higher temperatures and at times ash from wildfires, is hard on the ocular surface. There is evidence that these pollutants and climate change, directly and indirectly, may play a role in:
worsening ocular allergies
dry eye
ocular infections
glaucoma
uveitis
retinal vascular abnormalities
diabetic eye disease
macular degeneration
myopia
Yikes is right!
The point is: air pollution is bad for our health, and controlling fossil fuel burning will control climate change, and controlling climate change will decrease many forms of pollution. Love co-benefits!
The costs of pollution from fossil fuel use have been estimated by the International Monetary Fund. They believe that besides saving money from avoiding pollution caused (or exacerbated) illnesses, measures to decrease fossil fuel subsidies would save millions of lives: “Full fuel price reform also reduces global air pollution deaths from fossil fuel combustion by 50 percent below baseline levels in 2030, or 1.6 million a year.”
Now other bad news: air pollution impacts everyone, but some more so: those who commute, live near heavy traffic, factories or power plants, and workers who are exposed, often the people who profit the least from causing the pollution. This is the concern of climate justice or climate equity.
Know your air
As a health professional you might need to counsel about activities to curtail when air pollution is bad. Here is a set of guidelines from the United States government site: www.airnow.gov
If you want to know the local air quality for yourself or your patients, you can check local air quality by zip code on the same site: https://www.airnow.gov
https://www.airnow.gov/publications/activity-guides-publications/ These are short (two page) illustrated practical guides for ozone, particulate pollution and a guide for schools.
See also the Clinician’s Corner on this website.
Indoor (including household) air pollution
Indoor pollution has been estimated to cause about 1.6 million deaths a year (some estimates are higher) and lead to an increase in chronic lung disease, respiratory infections, lung cancer, heart disease and strokes.
There are many sources of indoor pollution. It is a combination of outdoor pollution that enters the building and pollutants generated within the building. For example, PM2.5 levels indoors can be half that of outdoor levels, or even more when people decide to open windows to let in some “fresh” air!
In many parts of the world, particularly sub-Saharan Africa, Latin America and south Asia, low-income households use stoves that burn solid biofuels (e.g., charcoal, wood, coal, dung) that release smoke without adequate ventilation.
About one third of the world population relies primarily on these solid biofuels. It is a huge problem.
The use of wood and charcoal can lead to deforestation.
The pollutants generated include particulate matter (PM2.5 and larger), volatile organic compounds (VOC) and polycyclic hydrocarbons (including known carcinogens), carbon monoxide and carbon dioxide, and NO2.
In addition, the pollutants generated from burning these solid biomass fuels add to outdoor pollution and atmospheric GHG.
Smoking and the resulting secondhand smoke and leaks of natural gas (methane) from gas stoves cause indoor pollution that is not limited to low-income households. Cooking with natural gas produces pollutants (CO, CO2, organic compounds) that are GHG from incomplete combustion or leaks of methane. Cooking with natural gas has been associated with respiratory illness in children in some, but not all, studies.
Poorly maintained or ventilated furnaces and other sources can result in indoor pollution, particularly carbon monoxide, which can be fatal.
Household chemicals, particularly cleaning products, are another source of indoor air pollution. You know it when there are clearly irritating fumes, but even more pleasant smells can hide potent VOCs. Some fragrances combine with other pollutants, including VOCs and ozone, to make a toxic brew. Building materials are a source of pollutants. Historically asbestos was an important carcinogen that was used freely. Compounds from mold and other organisms can also contribute.
There are environmental justice concerns: these problems disproportionally affect low-income groups, children, the elderly, people of color and indigenous populations.
There are steps you can take:
Be careful and sparing with cleaning materials and similar chemicals. Ventilate well when cleaning, painting, varnishing.
Carbon monoxide detectors for the home are available.
Maintaining gas furnaces, stoves and gas hot water heaters is important. Testing for leaks in natural gas pipes can be considered. Furnace filters should be changed regularly.
Air purifiers, including portable models meant to filter a single room, can remove many, but not all pollutants. HEPA filters can be considered for removing particulate matter. They are effective for allergens and even particulates way smaller than PM2.5 (as small as 0.3 microns)
Additional Resources
Much of this material is from:
Health and Clinical Impacts of Air Pollution and Linkages with Climate Change.
Anjeni Keswani, M.D., M.S.C.I.,1 Hana Akselrod, M.D., M.P.H.,2 and Susan C. Anenberg, Ph.D.3 NEJM Evidence June 15 2022 DOI: 10.1056/EVIDra2200068
The Lancet Commission on Pollution and Health. Landrigan PJ et al The Lancet 20i8;391:462 . A recent update.
Air Pollution and Noncommunicable disease, Part 1: the damaging effects of air pollution. Schraufnagel DE et al, Chest 2019; 155(2):409
Global Climate Change and Human Health from science to practice. eds. Jay Lemery, Kim Knowlton, Cecilia Sorensen. Jossey-Bass (Wiley), 2021.
Air Pollution and Climate Change, the basics. John K Pearson and Richard Derwent. Earthscan from Routledge, 2022. A great little book on the subject.
There is material on air pollution and other toxic exposures in:
Planetary Health, protecting nature to protect ourselves. Ed. Samuel Myers and Howard Frumkin. Island Press, 2020.
Planetary Health, safeguarding human health and the environment in the Anthropocene. Andy Haines, Howard Frumkin. Cambridge University Press, 2021.
Keswani A et al. Health and Clinical Impacts of Air Pollution and Linkages with Climate Change. NEJM 6/15/22. Part of the 9/15/22 New England Journal of Medicine issue with a group of articles on climate change, pollution and health.
The connections between climate change and pollution:
There is a good lecture, session 4 “Air Quality Change” in the Dartmouth Echo Climate and Health course on YouTube https://video.dartmouth-hitchcock.org/media/Project+ECHO+Climate+and+Health+ECHO+Session+4/1_cpqdywjs
Disparities of air pollution in cities:
Rise of urban air pollution and what that means, United Nations blog: https://www.un.org/sustainabledevelopment/blog/2016/05/un-health-agency-warns-of-rise-in-urban-air-pollution-with-poorest-cities-most-at-risk/
Air pollution and climate justice in Los Angeles: https://www.psr-la.org/our-issues/air-climate-justice/
American Lung Association: https://www.lung.org/clean-air/outdoors/who-is-at-risk/disparities
Indoor/household air pollution:
The EPA Introduction to Indoor Air Quality, a good summary with internal EPA links to related topics.
The WHO also has in-depth information on household air pollution around the world