Hydroxyl radicals
Hydroxyl radicals (⋅ OH) are highly reactive, short-lived oxygen radicals consisting of one hydrogen and one oxygen atom. Often called nature's "detergent," they act as the primary atmospheric cleanser by oxidizing pollutants and greenhouse gases like methane. In biology, they cause severe oxidative stress by damaging cellular macromolecules.
Key Characteristics and Functions
Atmospheric Cleaning Agent: In the troposphere, UV radiation interacts with ozone and water vapor to form hydroxyl radicals. They kick-start the removal of hazardous gases (e.g., carbon monoxide, volatile organic compounds) and break down methane, dictating the lifespan of many pollutants in the air.
High Reactivity and Non-Selectivity: With a half-life of less than a second in the air and even shorter in biological tissues, ⋅ OH reacts non-selectively with almost any molecule it encounters. It destroys organic contaminants by stealing hydrogen atoms, transferring electrons, or through radical addition.
Biological and Health Effects: Because of its extreme reactivity, the hydroxyl radical is dangerous to living organisms. It indiscriminately damages DNA, proteins, and lipids, playing a major role in cellular aging and the pathology of diseases like cancer and atherosclerosis.
Industrial Applications: Due to their destructive power, hydroxyl radicals are utilized in Advanced Oxidation Processes (AOPs) for water purification. They are also generated by specialized indoor air purifiers to disinfect and neutralize pathogens, mold, and volatile organic compounds (VOCs).