A recent article in The Wall Street Journal, entitled Air Purifiers Draw Scrutiny, discusses the mounting concern over ozone-releasing air purifiers that actually pollute the air while claiming to clean it.

Although as a component of the upper atmosphere, ozone filters UV rays,it is considered a toxic gas by the Environmental Protection Agency (EPA). When breathed, it can cause lung damage, trigger asthma attacks, and even lead to an increased risk of death.

Ozone air purifiers and ionic air purifiers both release ozone. Ozone air purifiers purposely release high amounts of ozone into the air in order to break down contaminants. Ionic air purifiers, also known as ‘ionizers’ or ‘electrostatic precipitators,’ charge airborne contaminants in order to gather them more easily. Ozone is released as a byproduct.

Manufacturers contend that such machines are safe when used as directed (including running the machines when the area is unoccupied) and that further research is needed before ozone and ionic air purifiers are condemned. Meanwhile, acceptable levels of ozone go unregulated because the U.S. Consumer Product Safety Commission (CPSC), has yet to set ozone limits for air purifiers.

Currently, the CPSC is evaluating whether a limit of 50 parts per billion (ppb) of ozone, the limit set by the Food and Drug Administration for Medical Devices, is safe for human health.

For now, even this limit is voluntary. Many ionic air purifier manufacturers voluntarily comply with the 50 ppb limit; ozone machine companies, though, are unable to comply, and generally produce levels of ozone in the neighborhood of 250 to 500 ppb.

Richard Shaughnessy, director of the University of Tulsa's Indoor Air Program, says that the machines ‘are still being sold on a regular basis and the public is still buying them.’ A study performed by the University of California, Berkeley found that an estimated 500,000 California residents were ‘routinely exposed’ to unhealthy ozone levels due to their air purifiers.

The ozone gas itself is not the only cause for concern. Ozone also reacts with other household chemicals and surfaces to produce additional harmful chemicals. For instance, a 2006 study in Environmental Science and Technology discovered that after just three hours of exposure to ozone, carpets and cooking oil residue reacted with ozone gas to produce formaldehyde.

Ozone gas also produces ultrafine particles, which can penetrate deeply into the lungs. Ion-generating air purifiers, even though they may conform to the 50 ppb standard, are still of concern in this area. Air fresheners and pine-oil cleaners were tested in a study at the University of Texas, and both turned into ultrafine particles in the presence of ionic air purifiers.

Dr. Jeffrey Siegel, a reasearcher in the study, stated, ‘Every single one of the ion generators we tested was a net producer of particles, so they ended up generating more particles than they could remove.’

Concern for ozone-generating air purifiers has led to a class-action suit against Sharper Image Corp., a leading marketer of electrostatic air purifiers.

For more information about the harmful effects of ozone, see Ozone: A Powerful Lung Irritant.