Ozone is a highly reactive form of oxygen with three atoms instead of the usual two, and it serves a surprisingly wide range of purposes. In the upper atmosphere, it shields life on Earth from harmful radiation. On the ground, its powerful oxidizing ability makes it useful for purifying water, preserving food, treating medical conditions, and cleaning everything from laundry to wastewater. That same reactivity also makes it dangerous when inhaled, so understanding both its benefits and risks matters.
Protecting Earth From UV Radiation
The ozone layer, sitting roughly 15 to 35 kilometers above the surface, is the planet’s primary sunscreen. It blocks 100% of the most dangerous ultraviolet radiation (UVC) from reaching the ground and filters out about 90% of UVB radiation, the type responsible for sunburns and skin cancer. Longer-wavelength UVA rays pass through essentially unimpeded, which is why sunscreen is still necessary even with an intact ozone layer. The thinning of this layer, particularly over Antarctica, has been a major environmental concern since the 1980s and drove the global ban on ozone-depleting chemicals.
Water and Wastewater Treatment
Ozone is one of the strongest disinfectants available for treating drinking water. Its oxidation potential of 2.076 volts makes it far more reactive than chlorine, allowing it to destroy bacteria, viruses, and parasites by breaking apart their cell walls. Unlike chlorine, ozone leaves no lasting chemical taste or smell in the water because it rapidly breaks back down into ordinary oxygen.
Municipal wastewater plants increasingly use ozone to tackle a newer problem: pharmaceutical residues. Drugs like anti-inflammatories, antidepressants, and antibiotics pass through conventional treatment largely intact and end up in rivers and lakes. Ozone treatment removes a median of about 60% of these compounds by concentration, with some drugs like diclofenac, carbamazepine, and sulfamethoxazole seeing removal rates above 90%. There’s a catch, though. The process can create transformation byproducts that carry their own toxicity risks, which is why ozone treatment is often paired with activated carbon filtration as a second step.
Food Preservation
Ozone extends the shelf life of fresh produce by killing the mold and bacteria that cause spoilage. It can be applied as a gas in storage rooms or dissolved in wash water. In one study on tomatoes, gaseous ozone treatment reduced spoilage to just 14% of the fruit, compared to 54% in untreated batches. Carrots washed with ozonated water lasted about 1.8 times longer than those washed with plain tap water, and tomato shelf life was extended by roughly 10 days. Because ozone breaks down into oxygen quickly, it doesn’t leave chemical residues on food, which makes it attractive to producers looking to reduce their use of synthetic preservatives.
Commercial and Industrial Cleaning
Large-scale laundry operations, particularly in hotels and hospitals, have adopted ozone systems to cut costs and energy use. Ozone dissolved in cold water can do much of the work that hot water and detergent normally handle. One study from the Electric Power Research Institute found that ozone laundry systems reduced hot water use by 78%, detergent use by 57%, chemical costs by 65%, and natural gas consumption by 32%. The cold-water washing also causes less wear on fabrics, which extends the life of linens and uniforms.
Medical and Therapeutic Uses
Ozone therapy has been studied for a range of conditions, particularly chronic pain. For musculoskeletal problems like low back pain, knee osteoarthritis, and tendon injuries, ozone is typically injected near the affected area or administered through a process where a patient’s blood is drawn, mixed with ozone, and reinfused. In a study of 25 patients with fibromyalgia, pain scores dropped by roughly 43% after treatment, and those improvements partially held at six months. Anxiety and depression scores fell by more than 65%, and fatigue improved significantly. A separate study found that over 70% of fibromyalgia patients achieved at least a 50% improvement in symptoms.
These results are promising but come with important context. Most studies so far have been small, and ozone therapy is not approved by major regulatory agencies like the FDA as a standalone treatment for any condition. It’s used more widely in parts of Europe and Latin America than in the United States.
Dental Applications
Dentists in some countries use ozone to treat early cavities and improve root canal outcomes. The gas destroys the bacteria responsible for tooth decay by oxidizing their cell walls, and early evidence suggests it can help remineralize weakened enamel, potentially halting cavity progression without drilling. In root canal procedures, ozone has been used as an additional disinfection step, with patients experiencing less post-treatment pain when ozone was activated with ultrasonic energy during the procedure. One lab study found that ozone reduced bacterial counts in infected tissue from one million colony-forming units down to just ten. However, the same study noted that ozone exposure can weaken the bond between tooth structure and filling materials, so its use before restorations requires caution.
Health Risks of Ozone Exposure
The same chemical reactivity that makes ozone useful for killing bacteria also makes it harmful to human lungs. Even at relatively low concentrations, inhaled ozone causes chest pain, coughing, shortness of breath, and throat irritation. It aggravates asthma, inflames lung tissue, and increases vulnerability to respiratory infections. The Occupational Safety and Health Administration sets the workplace exposure limit at 0.10 parts per million (ppm) averaged over eight hours, while the FDA caps indoor medical device ozone output at 0.05 ppm.
These limits matter because consumer ozone generators marketed as “air purifiers” can easily exceed them. In one test, a generator rated for spaces up to 3,000 square feet was placed in a 350-square-foot room and quickly produced concentrations of 0.50 to 0.80 ppm, five to ten times above public health limits. Even with doors open to adjacent rooms, some powerful units produced levels of 0.12 to 0.20 ppm, still above safe thresholds. The EPA has stated clearly that ozone generators should not be used as air cleaners in occupied spaces, because the concentrations needed to effectively remove indoor pollutants far exceed what’s safe to breathe.
Ozone’s usefulness, in short, depends entirely on where it is and how it’s controlled. Contained in a water treatment system or applied in a sealed food storage facility, it’s a remarkably effective tool. Released into a room where people are breathing, it becomes a health hazard.