HOME OZONE GENERATORS: HAZARDOUS OR HELPFUL?

By Charles W. Moore

Health Canada recently issued a public warning against using ozone generators as air purifiers in homes or other inhabited areas, and expressed concern about alleged potential adverse health effects that may result from deliberate exposure to ozone. "Ozone," says the warning, "is an irritant that can cause coughs, chest discomfort, and irritation of the nose and throat."

Apparently at the urging of Health Canada the Canadian Standards Association (CSA) has rescinded its certification of these products for household use.

Based on five years of using ozone generators in my home, Health Canada's warning seems extreme and the health risks alleged sound greatly exaggerated.

Use of ozone for indoor air purification is nothing if not controversial. Proponents claim that ozone kills household odours, breaks down chemical and microbial air contaminants, and reproduces outdoor air freshness indoors, creating a healthier environment. Skeptics assert that ozone is itself a dangerous air pollutant, and that introducing it into domestic airspace can cause health problems.

I am a journalist, not a scientist or physician, but I have researched the issue of domestic ozone generators extensively. I have no axe to grind and am open to new information. However, as I presently understand it, the highest naturally- occurring ozone levels, up to 0.065 parts per million (ppm), are by the sea, in forests, in mountainous areas, and near waterfalls. The slightly pungent odour in the air after a lightning storm is ozone, as is the fresh smell of air-dried laundry. Ozone is created by the action of nitrogen oxides and ultraviolet light from the sun, and outgassing of hydrocarbon compounds from trees. Anywhere in nature that hydrocarbons coexist with strong sunlight and moisture, ozone will be produced.

Ozone is also created by industrial processes, engine combustion, and by electric arcs. Therefore, substantial amounts of ozone will exist in polluted areas. However there is widespread confusion about cause and effect that gives rise to the notion, even among relatively well-informed individuals, that ozone itself is the problem in smog. Ozone actually reacts with hydrocarbon pollutants to help eliminate them.

Is ozone safe? Like virtually everything -- even oxygen -- ozone can be harmful if you're exposed to too much for too long. Average outdoor ozone levels in unpolluted land areas range between 0.03 and 0.055 ppm. Average indoor ozone levels are 0 to 0.1 ppm. Domestic ozone machines are engineered to restore outdoor ozone levels indoors -- approximately 0.045 ppm. The U.S. Occupational Health and Safety Agency (OHSA) cites 0.05 PPM as the maximum safe level for 24 hour a day exposure, and the U.S. FDA sets a limit of 0.05 parts per million of ozone for medical devices. This is an extremely conservative evaluation -- unless we accept that fresh sea breezes are unhealthy -- since they can contain natural levels of ozone up to 0.065 ppm -- 25% higher than the "safety" limit.

The U.S. governmentÕs National Institute of Science and Health (NIOSH) considers 0.1 ppm the possible hazard threshold (24 hour exposure), and 5.0 ppm a toxic level of ozone. ThatÕs more than 110 times the level ozone generators produce when used as directed.

In any case, ozone exposure tends to be self-limiting, because concentrations likely cause significant harm to the average person are unpleasant to breath. The threshold is probably lower for persons with respiratory illness, and some people may be allergic to ozone, but over the past three years, at least one and often two ozone generators have been running 24 hours a day in our home, and none of the five people living there have developed any of the respiratory distress symptoms Health Canada describes. Ozone really does kill odours, and coincidentally or not, we have had only about 20 percent as many colds as usual. I am personally sensitive to many common chemicals, but ozone doesn't bother me, and indeed its presence helps eliminate odours that do.

In 1992, Consumer Reports published a negative article on ozone generators, making assertions similar to those cited by Health Canada. Ozone generator manufacturer Bill Converse of Alpine Industries

says that: "suddenly we were confronted with a barrage of negative publicity."

"Full revalidation took three years," says Converse, "at which time we proved in court that Alpine purifiers work as claimed and are safe. Based on decades of documentation on ozone and ionization, there was never any doubt, but IÕm proud that we stood our ground."

Health Canada's speculations are nebulous, and their claim that ozone is ineffective as an air purifier at recommended levels produced by domestic machines is plain wrong. I have no idea whether Health Canada's blanket condemnation of home ozone generators is based in poor science and sloppy research, or whether there is some other unstated agenda, but my own experience convinces me that ozone generators, used as directed, can be beneficial and pose no significant heallth hazard.

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