Growing numbers of people with allergies and asthma are coughing up hefty sums for heavily marketed indoor air cleaners they hope will provide purer air to breathe.
But a study in the May issue of Consumer Reports describes some of these devices as not just ineffective but capable of exposing people to ozone -- a gas that, in large enough quantities, can damage the lungs, irritate the respiratory system and aggravate asthma, according to the Environmental Protection Agency.
Sharper Image, whose Ionic Breeze cleaner ($400) drew particular criticism in the report, disputed the findings, saying its product is "safe" and produces only "trace levels of ozone as a byproduct," according to a printed statement to which the company referred news media. Other manufacturers whose products did poorly in the report also found fault with the study methods and the findings.
The devices, known as ionizing air cleaners or electrostatic precipitators, work by electrically charging airborne particles and trapping them on oppositely charged metal plates, according to the American Lung Assn. Ozone, a super-charged oxygen molecule, is a byproduct of this process.
In contrast, says the association, the most common type of air purifier includes a high-efficiency particulate air (HEPA) filter, which traps most particles and removes odors while producing much lower amounts of ozone.
The findings are particularly worrisome because about 80 percent of people who buy air cleaners have asthma or allergies, according to the magazine. Air ionizers make up about 25 percent of the $410 million-a-year air cleaner market, according to the report, which was issued by the nonprofit Consumers Union, publisher of Consumer Reports books and magazines.
The report marks the Consumer Union's second criticism in two years of the Ionic Breeze, which leads the ionizer market; once again, the product earned "poor" ratings for cleaning dust and smoke from the air. The new report also found the device poor at removing pollen.
Sharper Image sued Consumer Union for libel after an October 2003 report said that the Ionic Breeze performed poorly at removing dust and smoke particles from the air; a federal court dismissed the suit.
The more than 1 million Ionic Breeze units sold testify to the machine's effectiveness, said E. Robert "Bob" Wallach, legal counsel for Sharper Image.
Ionizers -- advertised in TV commercials, infomercials and magazines -- are typically sleek and slender and have quieter motors than other types of portable air cleaners. And there are many potential buyers: 18.2 million adults had hay fever in 2002, according to the National Center for Health Statistics, and about 21.9 million had asthma.
Jeff Asher, vice president and technical director at Consumer Union, said air ionizers gave off a deceptively "fresh air" smell, similar to the scent just after a thunderstorm.
Buyers, he said, "think that this is a good smell ... that in fact, without that smell, that the ionizer isn't cleaning the air."
What they smell, Asher said, actually is ozone.
Richard Thalheimer, founder, chairman and CEO of Sharper Image, issued a sharply worded statement disputing the findings.
"This Consumer Reports piece is, in my view, irresponsible in the way it casually and unscientifically speculates about public health and safety," the statement read.
Calling the report "an unfair assault by Consumers Union," it stated that the Ionic Breeze was no different than many common household electronic devices, such as TVs and hair dryers, in producing "trace levels of ozone as a byproduct."
In a separate statement, Wallach objected to the classification of the Ionic Breeze as an ionizer rather than an electrostatic precipitator; the EPA views the terms as synonymous.
Thalheimer distinguished the Ionic Breeze from a category of air cleaner known as ozone generators, which intentionally produce ozone to combine with other substances.
"Ionic Breeze is emphatically not an ozone generator," Thalheimer wrote.
Thalheimer also stated the Ionic Breeze "meet(s) the strictest standard" in ozone emissions -- 50-parts-per-billion -- referring to a limit set by the Food and Drug Administration for indoor medical devices. The agency doesn't consider air cleaners medical devices.
Allowing large quantities of ozone -- the same gas found in high amounts on hot, sunny, smoggy summer days, when those with respiratory ailments are often warned to stay inside -- to be produced indoors can be harmful to asthma patients, said David M. Lang, head of the allergy and immunology division at the Cleveland Clinic Foundation.
Lang cited studies that show that exposure to ozone at high concentrations is harmful to the health of people without asthma; those with the respiratory ailment face greater risk, he said.
"I think it's reasonable to discourage the purchase of the air cleaners that emit substantial amounts of ozone ... based on the fact that this may be injurious to your health, particularly if you have asthma," Lang said. "I think it's a situation where ... caveat emptor -- buyer beware -- is appropriate."
Last year two large studies, one in the Journal of the American Medical Assn. and the other in the American Journal of Respiratory and Critical Care Medicine, linked high ozone exposure in cities to a rise in premature deaths from cardiovascular and respiratory causes. The EPA neither certifies nor recommends air cleaners.
While all air ionizers create ozone, some give off more than others. The report recommended only one ionizing air cleaner -- the Friedrich C-90A ($450) -- calling it a "fine" performer "with negligible ozone." All five other ionizers were given failing grades because of "poor performance, some with relatively high ozone."
A HEPA device, the Whirlpool 45030 ($250), also won high marks from Consumer Union's testers.
Consumer Union evaluated the cleaners in a sealed room, where testers measured ozone amounts two inches from the machines, and in an "open, well-ventilated lab," where testers took measurements two inches and three feet from the machines, according to the report.
The Whirlpool and Friedrich models earned a mix of "excellent" and "very good" ratings for ridding the air of particles containing dust, cigarette smoke and pollen; both got only fair ratings for noise. The Ionic Breeze earned an "excellent" noise rating.
Any air cleaner that produced ozone amounts exceeding the FDA's 50 ppb ozone limit failed Consumer Union's tests. Only the Whirlpool and the Friedrich models passed the sealed-room test.
In the two-inch test in the open lab, the Surround Air XJ-2000 ($80) produced the most ozone, 319 ppb, followed by the IonizAir P4620 ($70) at 168 ppb, the Ionic Breeze at 48 ppb, the Ionic Pro CL-369 ($150) at 33 ppb and the Brookstone Pure-Ion ($300) at 26 ppb. In the three-feet open lab test, the Brookstone emitted the least ozone of the ionizers at 2 ppb, and the IonizAir producing the most at 28 ppb.
The makers of the Brookstone, Ionic Pro and SurroundAir disputed the Consumer Union's findings and said their products were safe and effective; they said that independent tests showed that their devices met ozone emission standards. The maker of the IonizAir did not return several calls seeking comment.
The two recommended cleaners, in contrast, emitted far less ozone than the others. In the open lab, the Whirlpool produced 2 ppb of ozone at two inches away; the Friedrich emitted 5 ppb. At three feet away, the Whirlpool produced 1 ppb, and the Friedrich emitted 4 ppb.
Some allergists said that they had long recommended HEPA cleaners over ionizers because of fears about ozone output. They advise consumers to eliminate allergens such as tobacco smoke, mold and pet dander from the home instead of relying on an air cleaner to do the job.