Smog’S Effect On Your Respiratory System – The Molecular Pathway

Depending on its location in the earth’s atmosphere, ozone plays two contrasting roles. When it is in the stratosphere (upper atmosphere), it acts as a protective layer that prevents the entry of UV rays into the troposphere (lower atmosphere). And when it is present in the troposphere, it is a product of photo chemical smog, which acts as an air pollutant which has harmful health effects on the human respiratory system.

Upon getting exposed to high levels of ozone for long durations, people are at an increased risk of death from respiratory diseases. This risk is more than three times higher in metropolitan areas where tropospheric ozone concentrations are high. The biochemical and physiological outcomes of ozone inhalation have been studied extensively, but the molecular level mechanism has not yet been.

A new research for the first time provides us the glimpse of the underlying chemical mechanism. Professor Richard O’Hair from the University of Melbourne and Professor Stephen Blanksby from the Queensland University of Technology have co-authored this study.

The researchers examined how ozone reacts with models of lung proteins using a mass spectrometer. They introduced a component of lung proteins called cysteine, an amino acid, and ozone molecules inside the mass spectrometer’s near – vacuum, highly controlled environment.

They observed an instant effect where cysteine got radicalized in the presence of ozone. The free radicals thus generated can rage numerous chemical transformations. The free radicals formed inside the body, like on the lining of the lungs, cause damage, resulting in inflammation and breathing problems. If these get out of control, they can harm and destroy the entire system, leading to cancers and cardiovascular diseases.

At near the collision limit, many reactions took place, giving rise to a cascade of products. The sequential oxygen atom abstraction reactions generated cysteine sulfinate, sulfonate and sulfenate anions. And then, the ejection of a hydroperoxy radical caused the formation of sulfenate radical anions. It was observed that these reactions occurred only in the presence of carboxylate and thiol components. This indicated that electron-transfer is an important step of this free-radical pathway. The same reaction was also observed in cases of small cysteine – containing peptides, implicating a likely role for this chemistry in protein ozonolysis.

This study provides an insight into the molecular level happenings in the body upon ozone inhalation. However, the limitation of the study which is the performance of the tests in an artificial environment, further work needs to be carried out to validate the production of protein free radicals in lungs and the association of their impacts on human lung physiology.

The scientists involved in this study expect that fellow researchers will build on their findings. Such studies will be beneficial to those who are very much susceptible to smog, such as patients suffering from respiratory illnesses like wheezing and asthma.

Professor O’Hair added that free radical damage to lung proteins is irreversible, and so drugs cannot be invented to undo the harm. So, his message is that we need to reduce pollution to avoid ozone inhalation.

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