Ozone Pollution and Its Effect on Immune System

Ozone pollution or what is known as Ground-Level Ozone pollution, is not a pollution that directly emitted to the air. It is created by serious of chemical reactions occur between oxides of nitrogen (NOx) and volatile organic compounds (VOC). This event is fused by pollutants which are frequently emitted by cars, power plants and refineries. They react in the presence of sunlight.

Unhealthy levels of ozone is usually reached during summer months when the sunlight is powerful and consistent enough to constantly drive these reactions however, there is a possibility of having high ozone levels in colder months as well. Ozone also can travel long distances which leads to the fact that although rural areas might not have high pollutant levels, they can be exposed to ozone that travels from urban areas.

Figure 1. Ground-Level Ozone

There are a lot of health issues related to ozone exposure such as:

• coughing and sore or scratchy throat.
• more difficult to breathe deeply and vigorously and cause pain when taking a deep breath.
• Inflame and damage in the airways.
• Make the lungs more susceptible to infection.
• Aggravate lung diseases such as asthma, emphysema, and chronic bronchitis.
• Increase the frequency of asthma attacks.

Some of these effects have been found even in totally healthy people, but impacts can be more severe in people with lung diseases such as asthma. They may lead to increased school absences, medication use, visits to doctors and emergency rooms, and hospital admissions. 

Alongside of these effects, there are also micro-scale impacts which we might overlook until it becomes severe to the extent that it cannot be overlooked.

According to a study conducted by Duke University Medical Center in 2007, ozone causes the innate immune system to overreact, it kills immune system cells which makes lungs more susceptible to other invaders such as bacteria.

Innate system is one of the most significant keystones of our immune systems since first of all, they are the first step when there is a threat, and they don’t discriminate invaders as adaptive immune system does. This quality makes innate immune system a primitive one.

In this experiment, the mice were exposed to normal quality air and pre-ozone exposed air to observe the after effects on mice. Regarding results, one of the important cell kind of innate immune system which is called macrophage (the big-eater) number were distinctively lowered in the count results of ozone exposed mice. This exposure caused macrophages to go under a process which is called programmed cell death, or apoptosis.

Figure 2.Macrophage

Figure 3.Apoptosis of A Cell

The reason why this can lead to a lethal outcome is because these cells represent a primary defense of the lung and create a link between non-immunologic and immunologic defense mechanisms. As immune cells, their major functions are to ingest and process antigens for naive T-lymphocytes to acknowledge dangerous beings, to nonspecifically kill microorganisms and tumor cells, to kill antibody- and complement tagged cells, and to secrete mediators.

The worst part is that inhaled ozone was not observed only in the lungs but it actually moved to lower parts of immune system which are immune system cells circulating in the bloodstream.

The chemical and toxicological property of ozone as a strong oxidant, which results in being able to cause oxidative damages to cells and immune-inflammatory responses within and beyond the lung as mentioned before. These findings add substantially to the already existing challenges in controlling ozone pollution and management of it. For instance, in the United States in 2016, 90% of non-compliance to the national ambient air quality standards was due to ozone whereas only 10% was due to particulate matter and other regulated pollutants. Climate change, through creating atmospheric conditions that favors ozone formation, unfortunately has been and will continue to induce ozone concentrations in many parts of world.

Ozone is responsible for several hundreds of thousands of premature deaths and tetens of millions of asthma-related emergency room visits annually. To combat ozone pollution globally, more strict mitigation acts in fossil fuel consumption are needed to cut NOx and VOCs as well as greenhouse gas emissions. Meanwhile, preventive and therapeutic strategies are needed to alleviate the detrimental effects of ozone especially in more susceptible individuals such as elderly and children.

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