A hydroxyl radical is a reactive molecule formed by one oxygen and one hydrogen. It’s a neutral form of the hydroxide ion (OH-).
Hydroxyl radicals are oxidizing agents, which are one of nature’s main ways of removing contaminants from the air.
An oxidizing agent has the ability to remove electrons from other chemicals, like those found in the air. Most reactions, but not all, involve transferring oxygen. Rust is technically an oxidation reaction, and so is fire.
Hydroxyl radicals are extremely reactive - they react almost as soon as they encounter compounds in the air. Actually, the only compounds in the air they don’t react with are carbon dioxide, chlorofluorocarbons (say that ten times fast) and nitrous oxide.
They also react more slowly with methane, which is why methane concentrations in the air can get higher than other chemicals.
Hydroxyl radicals are formed naturally in our atmosphere - but only during the day. Radiation from the sun breaks down ozone (O3) into oxygen atoms, which react with water to form hydroxyl radicals (OH).
This is why ozone is such an important part of our atmosphere, even though it isn’t healthy for humans to breathe. They’re an important component of creating hydroxyl radicals, which are natural air scrubbers (that are completely safe to breathe).
It’s an extremely important process. Humans are very susceptible to poor quality air, both indoors and out. Poor air quality can cause both long- and short-term health effects, including what’s known as “sick building syndrome” indoors.
Low building ventilation, high concentrations of VOCs, and indoor mold can cause sick building syndrome. Headaches, nausea, respiratory infections, and stress-like symptoms (often mistaken for work stress in office buildings) are common symptoms.
Pollution, poor ventilation, or industrial processes can lead to contaminated air inside and out - and so hydroxyls are one of the best ways to support healthy air.
On a global scale, the most common reaction for hydroxyl radicals is forming carbon dioxide from carbon monoxide - about 40% of all naturally-generated OH molecules end up reacting with carbon monoxide.
About 15% goes to methane reaction, while 30% reacts with other organic compounds. 15% reacts with ozone or hydrogen gas.
The result is usually water, carbon dioxide, and peroxides, which are an important part of the ozone formation and repair process.
Still, nobody said the atmosphere was efficient: more than 97% of O atoms react back with ozone. Less than 3% end up contributing to creating hydroxyl radicals.
Sometimes, the earth needs a little help. Hydroxyls are the most important natural air purifiers - they’re vital to the earth and human survival.
Not convinced? Read more here!