In recent years, ozone devices have attracted a great deal of negative attention. But what exactly are ozone air purifiers, and do they even work? Isn’t ozone a part of nature? If it’s already in the air we breathe, how could it possibly cause any harm? As we’ll see, the harmful aspects of ozone are verified by numerous reputable studies, and the risks of ozone air cleaners vastly outweigh any possible benefits.
The Power of Three
Ozone is oxygen with, shall we say, a little something extra. Because of the empty spaces in the outer electron shells of oxygen atoms, they tend to bond well with each other in molecular pas de deux. (Okay, we were showing off a little there. “Pas de deux” is just French for “dances for two,” or “duets.”) A duet of two oxygen atoms bonded by their outer edges is called an O2, pronounced “oh two,” molecule. The air we breathe is composed of 78% nitrogen, 21% oxygen, and 1% of various other gases including carbon dioxide and water vapor. Most of the oxygen floats around in the stable O2 form, but another form of oxygen can result when air becomes charged with electricity, as in the vicinity of a bolt of lightning. In such an environment, stable O2 atoms can split apart and recombine in less stable O3 configurations. An ozone molecule is just such a trio of oxygen atoms.
The weakness of the bond in an ozone molecule is what makes it both helpful and dangerous to humans, because the third oxygen atom is easily pulled away by other molecules, especially organic (hydrocarbon) molecules. In fancy chemical terms, we say O3 is highly reactive, and that’s the general idea behind ozone air purifiers. Gas gets charged with electricity in a quartz tube, thus generating a blast of ultraviolet light. UV light is similar to the high-frequency aspects of sunlight that can cause sunburn, and the energy of these UV waves acts to split airborne O2 molecules near the quartz tube into their component atoms. The atoms are then more likely to bond into loose ozone triads. Not long thereafter, a drifting speck of air pollution drifts close to an ozone molecule, which releases its third oxygen atom. Thanks to a negative electrical field generated by the purifier, the third atom then bonds with the contaminant, changing its molecular structure into something less harmful. The process is called oxidation, and it’s the same chemical process that creates rust on metallic surfaces. The rust is just areas in which iron molecules have oxidized.
Ozone occurs naturally in the upper atmosphere, where it shields us from harmful UV sunlight by scattering and absorbing it. Closer to Earth, ozone molecules are capable of oxidizing a wide variety of harmful or just plain smelly contaminants. The list includes animal dander, body odors, carbon monoxide, chemical fumes, cooking odors, diesel exhaust, fuel oil, home permanents, household cleansers, ketones (a group of carbonyl, or carbon-oxygen, molecules) from insulation or furnishings, mildew, mold, paint, pesticides, sewer gas, and smog. The problem is ozone can oxidize and demolish organic molecules inside human beings. That’s why the U.S. government has set a standard safe limit of only eighty parts of O3 per billion over the course of an hour.
Millions of ozone air devices have been sold in the U.S. alone, and in three different forms. The first is an in-duct unit for central air heating and cooling. The second is a portable indoor unit. The third is a personal unit actually worn on the body. All are promoted as air “purifiers” and marketed primarily to people with allergies or other respiratory ailments. Ozone is touted as a “natural” substance—which it certainly is, especially in the stratosphere and near lightning blasts and waterfalls. None of these natural conditions are particularly safe for human beings, however. Is artificially-created ozone any better?
Think of Ozone as Oxygen with a Vengeance
In January of 1998, the California Department of Health Services did an extensive test of the health benefits and dangers of ozone air cleaning devices. The evaluation points out the harmful effects of ozone in the lower atmosphere, i.e., human airspace. Prior to the late 1990s, California set a minimum safe standard of ninety parts per billion over eight hours, but that was phased out in favor of the new federal standard. Now ground-level ozone is regulated by both federal and state clean air legislation informed by a series of government reports, including the Environmental Protection Agency’s “Air quality criteria for ozone and related photochemical oxidants” in 1996. These reports reveal the hazards of O3 exposure.
According to a report by M. Lippmann in the Journal of Air Pollution Control (1989), for example, even low-level ozone can cause “significant temporary decreases in lung capacity in healthy, exercising adults.” Moderate levels irritate the eyes, nose, throat, and lungs. Ozone toxicity is especially dangerous for children and people with asthma, who could suffer serious airway constriction. Ozone causes increased sensitivity to airborne allergens and can damage the immune system. It’s even believed that “summertime ozone episodes in the northeastern U.S.” led to increases in hospital admissions of up to twenty percent.
According to a study by R.J. Shaughnessy and L. Oatman for the Workers’ Compensation Board of British Columbia (1992), home ozone air purifiers produce room concentrations far in excess of FDA standards. Some models used so-called “ozone sensors” to limit the amount of ozone released into the air, but no independent analysis was found to verify the effectiveness of these sensors. The purifiers were found to be so dangerous that even use in unoccupied spaces was questioned; ozone gas is capable of oxidizing rubber, upholstery, and paint, thus causing damage to building materials and electronic devices.
Okay, so they’re not extremely safe. But do they work? In 1997, K. Foard found (in Applied Occupational Environmental Hygiene) that while ozone can kill infectious microbes in water, it’s ineffective as a biocide in air; which is to say, it will not kill airborne bacteria and fungi, at least not at safe concentrations. Furthermore, EPA studies in the mid-1990s concluded that “safe levels of ozone do not effectively oxidize air pollutants or improve air quality (California DHS Indoor Air Quality Info Sheet).” This led to a statewide warning against the use of ozone devices in California, dated April of 1997. In the years that followed, Minnesota, North Carolina, and Florida issued similar warnings, culminating in legal action put forward by the Federal Trade Commission.
In December of 1997, the FTC filed suit against Alpine Industries, Inc., the leading manufacturer of ozone air purifiers at the time, for violating a 1995 FTC consent order. That suit was successful, and in January of 2000, a federal court ordered Alpine Industries to stop making positive health claims for its ozone purifiers. Fifteen months later, the judge assessed a civil penalty of almost one and a half million dollars (plus costs and interest) against Alpine Industries and its president, William J. Converse.
The California Department of Health Services says the best way to clean indoor air “is to remove the pollutant sources or prevent emissions in the first place.” Barring that, DHS studies show HEPA air filters are safer and more effective than ozone purifiers, as are activated carbon and ionic cleaners. (These can generate ozone, but at much lower concentrations than solely ozone cleaners.) As early as October of 1992, Consumer Reports anticipated U.S. government findings and actions by saying, “We wouldn’t recommend an ozone generator even as a last resort.”
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