Q: You mentioned that air pollution can produce ‘oxidative stress’ in the skin. What is oxidative stress and why is it a problem?
A: Oxidative stress is implicated in the cause of many common diseases, such as heart disease from atheroscleosis and high blood pressure, diabetes, cancer, and even Alzheimer’s disease. It is also linked to skin aging, skin cancer and common skin diseases like atopic dermatitis (or eczema). Oxidative stress occurs when the body’s own defenses against oxidative injuries are overwhelmed.
Oxygen is both good and bad at the same time.
Oxygen, of course, provides the key to animal life. We breathe in oxygen from the atmosphere and use it to access the energy stored within the foods we eat. But oxygen has its dark side. As our cells use oxygen to capture energy in glucose and other fuels, they also generate on the side a number of highly reactive compounds, called ‘reactive oxygen species’ or ROS for short. These include: superoxide, hydrogen peroxide, hydroxyl radicals and singlet oxygen. These undesired ROS can cause damage to membranes of the cell, as well as its proteins and DNA. This damage can lead to inflammation, cell death or cell proliferation – processes that underlie many of these chronic diseases associated with aging.
This type of oxidative stress, produced as a byproduct of normal metabolism, represents the vulnerable, underbelly of life.
Oxygen is essential for our very existence, but, in using its magic, we also risk its unwanted other effects. To prevent or minimize these undesirable and even lethal injuries to our cells, we have evolved an abundant array of defenses. These include a host of antioxidant molecules and detoxifying enzymes. When this system is in balance – when the generation of ROS is counteracted by these antioxidant defenses – the injury from our dependence on oxygen is minimized.
But when out of balance – when our antioxidant defenses are weakened or overwhelmed – ‘oxidative stress’ ensues, and cellular injury and disease can result.
In addition to the internal oxidative stress that can result from our own body’s metabolism, oxidative stress can also be engendered from the outside. Ultraviolet rays from the sun act directly on components of the skin to generate ROS. Sunlight also interacts with certain air pollutants, to produce ozone, nitrous oxide and other free radicals – all ROS that can damage the skin.
Skin, not surprisingly, has a robust antioxidant defense system, because it is continually exposed to outside. But even the most robust defenses can become overwhelmed when there is a sustained ROS attack, leading to oxidative stress, and with sufficient stress, leading to injury and disease.
The best way to protect yourself from the oxidative stress generated by ultraviolet light is to practice good sun-protection. On days with a high air-pollution index, you should protect your lungs and your skin by staying indoors. If you must be out and about, you could protect your skin by wearing long-sleeves and long pants, and laundering them when you return home.