Whether they are waiting to board a flight at Tokyo’s Haneda airport or taking a break in the lobby of a government ministry in the Kasumigaseki district, smokers nowadays are often herded into areas with prominent air filtering devices.

Smoking zones equipped with large air cleaners have become commonplace in public spaces in Japan as the growing awareness over the ill effects of secondhand smoke has prompted nonsmokers to demand stricter segregation of smokers.

Sales of air purifiers for home use, including those that claim they can filter tobacco smoke, are also on the rise. Some 1.16 million were sold last year, marking a 21.5 percent increase over the previous year, according to the Japan Electrical Manufacturers’ Association, an industry group of electric household appliance makers.

But in contrast to many users’ expectations, medical experts say that such air purifiers, both for homes and public spaces, cannot filter out the majority of hazardous substances in tobacco smoke.

“It is an illusion to think that the devices can purify tobacco smoke, because even the most sophisticated machines can remove only 20 percent of the hazardous chemicals,” said Masaaki Yamaoka, a doctor from Sumoto, Hyogo Prefecture, who has been calling on manufacturers to better explain this aspect of air cleaners to consumers.

“This simply means that such machines are not solutions to the problem of passive smoking, as has long been advertised by manufacturers,” he said.

Although it is not widely publicized, the devices sold as air purifiers have a major limitation — they only reduce particulate matter, not gaseous substances.

This makes such products ideal for reducing pollen and other airborne particles, but not for much of the toxic chemicals in tobacco smoke, most of which are gaseous.

According to the book “Kitsuen no Kagaku” (“The Science of Smoking”), published by the Institute of Industrial Ecological Science of the University of Occupational and Environmental Health in Fukuoka Prefecture, 16 harmful chemicals that account for 89.2 percent of all the hazardous substances in tobacco smoke are gaseous.

Some sophisticated air cleaners are touted as being able to remove some gaseous chemicals, including nitrogen oxides and ammonium, which cause tobacco odor, but those make up only 8.9 percent of all the harmful gaseous chemicals in cigarettes, the book says.

Simply put, although the smoke filtered by the most expensive air purifier may come out clear and odorless, it is still likely to contain 80 percent of the hazardous chemicals it had going in.

“People buy air cleaners that are often touted as if they are the best solution for a family with smokers, expecting that all harmful chemicals will be cut,” Yamaoka said. “But having such machines can often be worse to users’ health, as they make tobacco smoke look and smell clean and lead people to ignore the need for ventilation.”

The World Health Organization said in a report last year that between 147 and 251 out of 1 million people are estimated to die from passive smoking worldwide. Japan’s National Cancer Center meanwhile estimates that between 1,000 and 2,000 people in Japan die each year from lung cancer as a result of passive smoking.

Since August, Yamaoka has sent e-mail to air cleaner manufacturers, demanding they inform consumers that their products do nothing for the majority of the problem chemicals in tobacco smoke.

In response, JEMA in October added to its list of standards for household-use air cleaners the phrase that they “cannot remove some gaseous chemicals in tobacco smoke, including carbon monoxide.”

Since then, member firms have begun explaining that their products cannot remove hazardous chemicals in tobacco smoke.

Midori Anzen Co., the largest manufacturer of air purifiers for buildings and other public spaces, changed the name of its products from “air cleaner” to “particle remover” earlier this year.

“Although their name may give consumers the impression that these devices can fully purify air, an air cleaner’s prime function is to remove dust, large particles, such as pollen, and some odor,” a JEMA official said.

“If we have given the impression that they are the ultimate machine to remove the harmful chemicals in tobacco smoke, we simply have to apologize and make efforts to help consumers learn the products’ limitations,” he added.

Amid mounting public awareness over the dangers of passive smoking, the Health, Labor and Welfare Ministry is expected to release guidelines early this month to assess the validity of efforts to prevent such ills.

The guidelines will say that air purifiers cannot remove gaseous chemicals in tobacco smoke, said Iwao Uchiyama, a professor of environmental engineering at Kyoto University who headed the group of scientists who compiled the guidelines.

“Given the limitation of air cleaners, the only way to purify air that has been dirtied by tobacco smoke is to ventilate,” Uchiyama said. “But the best and cheapest way is to make smokers go outside to smoke.”

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