OnAir: Three Scientists Define One Elusive Phrase: “Oxidative Stress”

It has been long known that air pollution causes harmful health effects in people. But scientists have only recently begun to uncover some of the mechanisms behind this causal relationship, a necessary step in understanding how to best regulate air pollution and protect human health.

One key mechanism that EPA-funded research helped identify is oxidative stress. Though it is the subject of scores of scientific papers, finding a single, comprehensible definition of the term is a surprisingly arduous task.

During an October visit to the Southern California Particle Center, I asked three scientists to define oxidative stress in the context of air pollution. Here’s what they had to say:

Arthur Cho, PhD, Organic Chemist
“As the name implies, it stresses the cell and promotes the cell to secrete chemicals that stimulate an immune response, such as symptoms of asthma. The idea is that you’re exposed to air pollutants, the pollutants enter your lungs, components of the pollutants react with components in your lungs and these potentially harmful chemical reactions are initiated.”

Ralph Delfino, MD, PhD, Epidemiologist:
“It can be thought of as a biochemical imbalance in which large molecules are oxidized to the point where they become either toxic or, in the case of important biochemicals, dysfunctional. It induces a cascade of events that leads to inflammation and, at its worst, cell death. Inflammation, as seen in immune responses to bacteria or virus, can be a good thing. But there are types of inflammation, like arthritis for example, that are not good. Oxidative stress can lead to inflammation in lungs that worsens asthma, or inflammation in blood vessels that leads to atherosclerosis.”

Andre Nel, MD, PhD, Immunologist:
“The easiest way to describe oxidative stress is to give an analogy: If you bite an apple and you hold it up in the air it will go brown after a few minutes, same with a banana. What you observe there is decay in the fruits’ tissues because oxygen radicals in the air are attacking their cell membranes. The same principle applies in humans, where oxidative stress is damage to organs and cells by oxygen radicals we are exposed to.”

Next I’ll share some surprising research I encountered at the Southern California Particle Center and report from the second leg of my tour- Harvard.

Editor’s Note: Look for more of Becky’s “On Air” posts this Science Wednesday about other EPA-funded scientists she has recently met on her travels.

About the Author: Becky Fried is a student contractor with EPA’s National Center for Environmental Research, part of the Office of Research and Development.

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