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The Relationship Between Stress, Air Pollution and Your Immune System

When we hear about stress we assume it is linked only to life situations at work, in the family, in relationships, etc. Yet stress also happens at micro level, within the body where we are not aware of it. Exposure to polluted air (e.g. fumes from factories, cigarette smoke, farms, cars and household cleaners) leads to the inhalation of microparticles of matter (particulates) less than 2.5micrometers in diameter into the lungs. These particles are real matter that is not expelled through exhalation but tend to become lodged in the lungs causing physical irritation. Some of the particulates are small enough to filter into the blood in the same way as the inhaled oxygen and either cause chemical damage to the body or they cause an immune response. There are many negative effects on health including respiratory problems, risks of cardiovascular disease, inflammation and many others.

Air Pollution Causes Stress

The moment there is bad air in a room, be it smoke from a fire or a stink from chemicals, every person’s response is to quickly open windows and to look for ways to leave the room. What causes that quick reaction is the person’s fight or flight response which helps to save life when there is danger. It is accompanied by the production of stress hormones which help with fast action, either to run or to fight. The same stress response happens in the body when a person breathes in polluted air. Mostly we do not notice that the air is polluted and no one really responds to polluted air by trying to run away. However, the physiological response to stress takes place and it is invisible and unconscious.

We can conclude that one of the negative effects that air pollution has on health is the unconscious fight or flight response. Because they are foreign bodies, the microparticles of matter that remain imbeded in lungs and those that enter the blood cause irritation and sometimes poisoning. Inflammation is the body’s response and that creates stress for the body. It is that stress that makes the body work overtime in the flight or fight mode.

This has been confirmed by scientists. One study that was published in Circulation involved 55 healthy college students in Shanghai where pollution levels are in the middle range compared to other Chinese cities. Researchers put working air purifiers in some of the students‘ rooms and non-working purifiers in the rest. After nine days, the researchers made a number of tests on the students‘ blood and urine to find out the quantity of microparticles present. Then they put non-working purifiers in the first group and working purifiers in the rooms of students who previously had non-working purifiers. Again, after another nine days, they performed blood and urine tests to check the levels of microparticle molecules.

What they found is that the air purifiers reduced exposure to the microparticle levels by half, from 53mg/m3 to 24.3mg/mwhich was still far above the WHO’s air quality guideline of 10mg/m3. They also found that the dirtier the air, the higher the levels of stress hormones norepinephrine, cortisol, cortisone, and epinephrine in the body. Also the dirtier the air, the higher the blood sugar, fatty acids, amino acids, and lipids. Dirtier air was also linked to a lower response to insuline, higher blood pressure, and markers of molecular stress in body tissues (1). All these changes eventually increase the chances of developing heart disease, diabetes and other health problems.

The production of stress hormones is proof that air pollution causes stress response in the body. We may not be consciously stressed but at cellular level the body is stressed.

There is more evidence that higher levels of air pollution increase our stress levels more than normal. In one study conducted by the Harvard School of Public Health and the Boston University School of Medicine, scientists found that increases in air pollution increased stress levels of the participants. This was particularly true of pollution caused by motor vehicle emissions. As if we do not have enough stress from every day life, now we must worry about pollution poisoning us and increasing our stress levels.

What is Stress?

Stress is every person’s non-specific response to any change that requires physical, mental or emotional adjustment or response. The stressor can be air pollution, excessive temperatures (heat or cold), intense emotion (such as fear, anger, or sadness), physical injury, poison, bacterial infection, shock or any real or anticipated threat.

In the case of pollution, the presence of foreign bodies in the lungs and the blood is an invasion that causes a physiological reaction of the body that leads to stress. Stress causes mental and bodily tension. Also, the circulatory system and the endocrine glands are put on red alert in the usual fight or flight response.

How Does Pollution Lead to Oxidative Stress?

Studies have been performed in human exposure chambers involving specific pollutants. The researchers found that short term exposure caused acute inflammatory effects on normal airways. It was diffficult to assess the consequences of long term exposure to air pollution but one can easily conclude that they are generally much worse.

Most of the modern day pollutants, including radiation from our computers and smart phones and wifi routers, generate free radicals that hang around in the atmosphere. Free radicals are nano-particles that have unpaired electrons which makes them chemically unstable. You may be aware that most stable atoms and molecules are the ones with paired electrons. Anyway, when you breathe in the polluted air you also breathe in the free radicals. Because of their instability, the free radicals are always on the hunt for more electrons in order to reach a stable state. So within your body they snatch the electrons from your body atoms in a process known as oxidation which causes inactivation of the target molecules. This can lead to extensive cellular damage. The damage is often called oxidative stress.

The result is organ damage, and then illness which leads to further stress to the body. In fact the illness may be chronic and that leads to chronic stress. There are theories that say oxidative stress is responsible for a number of degenerative diseases including autoimmune and inflammatory disorders such as rheumatoid arthritis and cancer. We can therefore safely conclude that pollution causes oxidative stress which leads to automimmune diseases.

The Stages of Stress and How Diseases Develop

According to Hans Selye, and Austro-Hungarian scientist at McGee University in the 1930s, stressors cause a general adaptation syndrome that occurs in three clear stages, i.e. alarm, resistance (or adaptation) and exhaustion.

The first stage of general adaptation syndrome is alarm in which the body declares war and calls its defensive forces to arms. During alarm, the body’s immune system is challenged, the body‘s resistance is lowered, the sympathetic nervous system fires, brainwaves change, muscles clench in preparation for action, circulation to the muscles increases in case fight or flight occurs, and the adrenal glands secrete stress hormones.

The second stage is known as adaptation or resistance. In adaptation the syptoms of alarm disappear, many of the body’s systems are in increased activity in order to meet current challenges and resistance increases. Adaptation can last for a long or a short time depending on a person’s health level and the intensity of pollution, but it will not go on indefinitely. The body cannot withstand the stressor for too long so it will eventually use up its adaptation energy. How long it can hold on depends on individual inner resources. If pollution continues, sooner or later the third stage is reached.

The third stage is exhaustion. In this stage the body has used up its adaptive properties and its weakest systems begin to break down. Chronic fatigue and illness are the official marks of this stage. If the illnesses cannot be treated, death is the ultimate result.

Stress Affects the Immune System

Depression of the immune system is among the many direct effects of stress. As long as the body is stressed, stress hormones such as epinephrine and corticosteroids tend to depress the activity of the immune system. This makes people to be more susceptible to infections and cancers as the body cannot attack the pathogens and the cancer cells.

The immune system is supposed to adapt to changing environments but the onslaught of more and more new chemicals in the environment in our modern life means that it cannot adapt fast enough. In fact, there are immune system diseases that bother many people these days, possibly contributed by pollution. They range from immunosuppression, immunomodulation and end with autoimmune diseases and allergies.

Stress Exacebates Effects of Air Pollution

Evidence is accumulating that indicates that psychosocial stress, especially chronic stress, worsens the effects of air pollution (2). Whereas a person who has no stress can withstand the effects of air pollution for much longer, a stressed person succumbs faster. Possibly that is because in the fight or flight mode, the body cannot deal effectively with the microparticles in the blood.

Sources of Air Pollution

There are types of pollutions that are created by natural causes such as volcanoes and wildfires. They cause a lot of air pollution such as ashes and volcanic ash. Then human beings create most of the air pollution that is causing problems in both cities and rural areas. They do this through emissions from factories, farm chemicals, construction materials, car emissions, coal burning, wood burning, kerosene lighting, aeroplane fumes, aerosols, and second-hand cigarette smoke.

Air pollution is particularly high in large cities. Sometimes the pollution appears as a cloud that makes the air murky. This is known as smog. In the developed world this is no longer a problem except a few cases such as Los Angeles, California in the US. The problem of smog is more common in the large cities in poor and developing countries such as Beijing, China, Cairo in Egypt and New Delhi in India.

Children are Most Vulnerable

Children tend to be very active, more active than adults through play and sports. So they breathe more rapidly and take in more pollutants than adults do. Also, they tend to breathe through their mouths, bypassing the air filters in the nose, and allowing more pollutants to enter the body. Not forgetting that children spend more time outdoors in summer when smog levels are highest, again breathing in more pollutant than adults.

Unfortunately children‘s lungs and immune systems are still developing and they are affected negatively by polluted air. It is possible for children exposed to high levels of air pollutants to suffer from permanent damage and long term problems like coughing, wheezing, chest congestion, allergies, asthma, shortness of breath, painful breathing and bronchitis.


It is obvious that air pollution, stress and the immune system are closely linked. In order to protect our immune system, especially that of growing children, we must take steps to reduce air pollution in our environment. For example, we can install air purifiers in our homes to reduce the load of particulates that we inhale. We can invoke the health and safety laws of our countries and states and request air purifiers at work as well. I am assuming that in every company there is a health and safety officer who can take up the request and speak to management about it, reminding them that a healthy workforce is a productive workforce.

Another thing that we can do is to reduce how much vehicle emissions we breathe in. For example, when we speak to the drive-through bank teller or fast food clerk, we can switch off the engine to prevent car fumes from getting into the car. Also, we can take time out to exercise away from busy roads and busy intersections in order to stay fit and to reduce stress levels. By reducing stress levels we reduce our susceptibility to the effects of air pollution. Also, by staying fit we improve our immune systems and our ability to withstand the effects of air pollution.

In winter the cold air tends to keep polluted air close to the ground instead of allowing it to move away, so air pollution tends to increase in winter. Check your state’s website daily for the air pollution readings per county. If the pollution level is high outside, then stay indoors as much as possible to avoid breathing in pollutants. Of course, indoors you must have air filters installed.

Whenever air pollution levels are low, and whether it is hot or cold outside, open windows to let out accumulating carbon dioxide which will make you feel lerthagic. If you can, even take a walk whenever air pollution is low in your area and during weekends take a hike in the hills far from polluted areas.


1. Huichu Li & Others. (2017, Aug 15). Circulation, Vol 137 #7. Particulate Matter Exposure and Stress Hormone Levels.

2. Hood E. (2010, Jun). Environmental Health Perspectives. Stress and the City: Measuring Effects of Chronic Stress and Air Pollution.

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