Can Too Much Oxygen Be Toxic?

Health Professional, Medical Reviewer

On my last blog, I discussed the important role of oxygen in the generation of energy, and how when the oxygen supply runs out, there is an accumulation of lactic acid which stops all activity, causing muscles cramps and sometimes muscles becoming flaccid. This instigates the question: Is there a benefit in having large amounts of oxygen in reserve for use when needed in the future, just like money sitting in the bank  for a rainy day?

Understanding how oxygen works

The truth is that oxygen can be toxic if it is present in too large amounts. In order to make this discussion clear, I would have to torture you with basic high school chemistry and remind you of the principles of oxidation and reduction.    Basically, all elements of nature are not static particles. They have a dynamic change in their magnetic charges, by releasing or gaining electrons, which gives them a charge that is either positive or negative. This allows these elements to bind to others (just like magnets bind metal) and form the complex particles that create the vast universe of our inner body.

Oxygen is one of the most potent oxidizing elements which donates electrons giving particles a negative charge.  That can be a useful thing when you think about the many reactions that take place in the body, but it also has some consequences by the production of byproducts that have charge. They are called "free radicals" that can cause many negative effects on the body, from scarring to cancer.

Imagine proteins which are large molecules composed of chains of small chemical products called amino acids. All of them have the capacity to become charged and also form free radicals (compounds that can negatively impact health). That process occurs in a random fashion, responding to different situations that are commonly referred to by health professionals as "oxidative stress".   The most common stressors are sun exposure and cigarette smoke, which you know cumulatively raise the risk of skin cancer and lung disease respectively.

Potential harmful effects of too much oxygen

Normally, oxygen comprises 21% of the air we breathe in. The human body adapts to this level and functions to access all the energy necessary for both rest and exercise. In certain disease states, however, the oxygen gain is impaired and it's necessary to use supplemental oxygen.   Your health provider would write a prescription and you would use a device that delivers the extra oxygen. This increases the concentration of oxygen to anywhere from 32% to as much as 100% of the inspired air. The problem is that this carries the risk of "reactive oxygen species," highly oxidant particles.   The most well-known of these are superoxide anion, hydroxyl radical and hydrogen peroxide. They produce tissue damage and cause an inflammatory response, and in some cases they cause cells to self-destruct.   This process is called apoptosis.

In adults, during situations where a high concentration of oxygen is needed, for example a hospitalized patient requiring critical care, there is what is known as Adult Respiratory Distress Syndrome (ARDS), a dreadful condition that causes alveolar damage in the lungs.

In newborns, a high level of oxygen causes deformities of the lungs known as bronchial dysplasia. When pregnant women are exposed to a high level of oxygen, it can cause a condition in the baby known as retrolental hyperplasia, which results in blindness. The most famous case of retrolental hyperplasia is that of musician Stevie Wonder.

Having excess oxygen levels also causes another negative outcome. Normally, air is mostly comprised of nitrogen, which carries no charge of electrons, and is typically not absorbed. When nitrogen is replaced by oxygen, the oxygen is readily absorbed by the tissues, causing the lungs to collapse due to the loss of air that would normally keep it inflated.

There is an antioxidant system in the body that protects against the oxidizing effects, known as the antioxidant system, but when that system is overwhelmed, the free radicals accumulate, resulting in disease.   The practice of taking antioxidants like vitamin C and other vitamins is to enhance that antioxidant defense system.

To illustrate how the body naturally protects itself against extra oxygen consider this: most of the oxygen is bound to hemoglobin in the blood cells, about 834 milliliters of oxygen at any one time circulating in the blood stream.

Given that the average consumption of oxygen is 250 milliliters per minute at rest, this is only enough time - about three to four minutes - before all the oxygen stores in the body are depleted. This coincides with the period of time it takes for the brain and other tissue and organs in the body to experience damage, when someone stops breathing.   That's why it is so critical to start CPR (cardiorespiratory resuscitation) quickly and effectively.

This is the way the human body is delicately set to manage oxygen.   The way to sustain life is not by just having oxygen present (and stored), but rather by constantly retrieving it from the environment, utilizing it and metabolizing it into carbon dioxide and water.  Nothing is static in this process.   And it's important to reiterate that the benefits of exercise are to make this process more efficient.