12/20 Article: Wildfires, Health Concerns

Wildfire smoke the mixture of gases and fine particles resulting from burning trees, plants, buildings, and other materials. Wildfires can be caused by a plethora of things, however the most common causes are an accumulation of dead matter such as twigs, leaves and dead trees that create enough heat to spontaneously combust which ignites the surrounding area. Another, more uncommon, cause of wildfires includes lightning strikes. Human caused wildfires can be accidental, intentional or from an act of negligence. Wildfire smoke inhalation is particularly deleterious to the body because the fine particles in smoke are microscopic and capable of penetrating into the lungs, causing burning eyes, runny nose and even aggravated chronic heart and lung diseases(1). Individuals at the greatest risk for wildfire smoke inhalation are people with heart or lung diseases, older adults, and you children are more likely to be affected by the health threats from smoke inhalation(2).

Wildfire smoke contains many different air pollutants that are of great concern to public health organizations and the general population. Among which include water vapor, carbon monoxide, carbon dioxide, nitrogen oxides, VOCs, air toxics, and particulate matter (0.2–0.7 um), which poses the largest threat to the lung health of individuals due to its small size and ability to travel deep into the lungs. According to the EPA’s National Ambient Air Quality Standards for criteria pollutants, the level of carbon monoxide (CO) deemed safe for public health and the environment is 9 ppm over an 8 hour averaging time, and 35 ppm over 1 hour. For nitrogen dioxide (NO2) it is 100 ppb over 1 hour and 53 ppb over 1 year. For particulate matter (2.5 um) it is 12.0–15.0 ug per cubic meter over 1 year and 35 ug per cubic meter over 24 hours. Lastly, for particulate matter (10 um) it is 150 ug per cubic meter over 24 hours(3). Wildfire smoke is a danger to public health because it is present in the atmosphere for prolonged periods of time after a wildfire has occurred, increasing the levels of air pollutants such as these well above the EPA’s standards. For example, a wildfire in Southern California in 2003 resulted in a several fold increase in these air pollutants(4). PM2.5 specifically increased by “approximately 30 to 100 micrograms per cubic meter.”

Carbon monoxide (CO) can also pose a threat to people’s health. Many people know carbon monoxide as a silent killer. But why is this? How does carbon monoxide impact health? Well, to start we should look at how oxygen, which is essential for human life, gets around the body. Hemoglobin ( is a molecule found in red blood cells that can bind to oxygen to transport it around the body. Each molecule has four spots where an oxygen atom can bind. However, oxygen isn’t the only thing that can bind in these spots. If CO is present, it will compete with oxygen for these spots. And it turns out, hemoglobin and CO actually fit together better and bind more tightly. This results in CO taking up all the spots on hemoglobin where oxygen could bind and because it fits better and binds more tightly it isn’t released from hemoglobin as easily as oxygen is either. Not only does CO take up spots on a hemoglobin that oxygen could be using, it also alters the hemoglobin to bind more tightly to oxygen, which means that less oxygen is released. This results in a greatly diminished ability of your hemoglobin to disperse the necessary oxygen around your body. If your cells can’t get enough oxygen, this will eventually result in tissue death. Continued oxygen deprivation of the heart and brain specifically can result in death. Once a person stops inhaling CO, oxygen will slowly start to replace the CO bound to hemoglobin. This can be sped up by increasing the amount of oxygen, which is why carbon monoxide poisoning is often treated by supplying 100% oxygen or in a hyperbaric chamber(5).

Air pollution produced in wildfires is a complex mixture of invisible gases with solids and liquids. Particulate matter (PM) is the proper term for this mixture, and it has the potential to make those exposed very ill. These particles are between 2.5 to 10 micrometers, which is extremely small and able to be inhaled into the lungs bringing hundreds of different chemicals into your body. The size of the particle is directly linked to the severity of short and long-term effects, according to the EPA, with finer particles being more harmful because they can go deeper into your lungs(6). Research has linked PM with the following health issues:

Increased risk of asthma

Irregular heart beat

Decreased lung function

Coughing, or difficulty breathing

Acute heart attacks

Long-term exposure to any of these factors causes greater risk of adverse neurological and metabolic symptoms.

But exactly how does PM damage our respiratory system and even our brain and metabolism? The various chemicals in PM have created what is called oxidative stress on the cells of our airways. Oxidative stress is damage to multiple components that make up cells including membranes, RNA, and DNA(7). The body can neutralize these reactive oxygen and nitrogen molecules, or repair the damage they cause, but inhaling PM hurts the body’s ability to do so. Reactive molecules (oxidizing agents) are harmful because when they react with the molecules in our bodies, they transfer electrons in an oxidation reaction and affect the cell’s function. When cells can’t function properly and die, the consequential health issues can be detrimental. Thankfully, balance can be achieved through antioxidants in foods or in our respiratory tract lining fluid which maintain redox homeostasis. In areas like California or Oregon, residents are exposed to PM at such a high volume from the fires, the body can’t keep up with balancing the harmful oxidants.

The term “nitrogen oxides” (NOx) refers to any of the multiple potential compounds elemental nitrogen can form with oxygen. The majority of nitrogen in the air on Earth is found in its diatomic molecular state which is essentially inert(8). In contrast, elemental nitrogen is quite reactive and under the right conditions will readily react with oxygen to create NOx. NOx’s are released in excess by wildfires as well as more well known culprits such as vehicles, construction sites, and factories(8).

Before delving into the direct chemical effects of NOx on the body, it is important to discuss one of the most harmful pollutants related to the way NOx reacts with other compounds found in air. NOx can mix with sulfur dioxide to create the tiny particles mentioned above (PM) which contribute to the visual thickness and color of smog, fog, and haze(8). These particles are all incredibly harmful to breathe in, damaging the lungs and even making it into the bloodstream if small enough. When it comes to direct effects of NOx’s on the human body, short-term exposure can cause cough, shortness of breath, tiredness, and nausea with symptoms becoming more severe as concentrations and exposure times increase. Nitrogen dioxide is one of the most harmful NOX’s released in the combustion of organic matter. NO2 causes inflamed airways and reduced lung function. Chronic exposure to this compound leads to allosteric inhibition of glutathione peroxidase and glutathione S-transferase, enzymes which are important to our lung’s mucous membrane(9). Inhibiting these enzymes generates harmful free radicals which results in damage to the tissues of the lung.

After living through 2020, nothing seems to come as a surprise anymore. The globe as a whole has been subjected to a dizzying variety of biological, political, social, and economic threats. Amongst all these catastrophes, wildfires stand out as an immediate danger to local communities and ecosystems as well as — on a larger scale — a force which makes the air unsafe to breathe and destroys the Earth’s atmosphere. Unfortunately, wildfires can’t be abated by a vaccine or a change in political office; wildfires are a natural disaster just like any other and, while measures can be taken to prevent them, they will persist. The only way to avoid the negative effects of wildfire smoke (and other negative effects of wildfires) is to understand the effects on a biochemical level and, with that knowledge, take precautions to protect communities in high-risk areas.

References:

US EPA, O. (2018, November 12).How Smoke from Fires Can Affect Your Health [Reports and Assessments]. US EPA.https://www.epa.gov/pm-pollution/how-smoke-fires-can-affect-your-health

CDC. (2020, August 3).Wildfire Smoke. Centers for Disease Control and Prevention.https://www.cdc.gov/nceh/features/wildfires/index.html

US EPA, O. (2008).NAAQS Table.US EPA.https://www.epa.gov/criteria-air-pollutants/naaqs-table

Indoor Air Quality Scientific Findings Resource Bank. (2020).Wildfires. Berkeley Lab.https://iaqscience.lbl.gov/cc-wildfires#:~:text=Wildfires%20can%20cause%20temporary%20large,acetaldehyde%20%5B40%2D43%5D.

Blumenthal I. (2001). Carbon monoxide poisoning. Journal of the Royal Society of Medicine,94(6), 270–272.https://doi.org/10.1177/014107680109400604

“Nitrogen.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine,https://bit.ly/33DnQt5

“Health and Environmental Effects of Particulate Matter (PM).”EPA, Environmental Protection Agency, 13 Apr. 2020,https://bit.ly/3ohC2zY

Clean Air Technology Center. “Nitrogen Oxides (NOx).”U.S. Environmental Protection Agency,https://bit.ly/33FhadQ

Elisa Couto Gomes and Geraint Florida-James. (May 14th 2014). Lung Inflammation, Oxidative Stress and Air Pollution. IntechOpen. https://www.intechopen.com/books/lung-inflammation/lung-inflammation-oxidative-stress-and-air-pollution