Almost 30 percent of Beijing's malls and supermarkets have an excessively high amount of formaldehyde concentration in the air, posing a potential threat to customers, according to a study released yesterday.

Formaldehyde is a type of chemical that smells similar to eggs and is used widely to produce building materials, such as drywall, and household products. Long-term exposure may cause serious health problems since it is listed as a "probable human carcinogen" by the International Agency for Research on Cancer, which is affiliated with the World Health Organization (WHO).

The Beijing municipal health bureau said the formaldehyde concentration failed to meet standards of indoor air quality in its four-month investigation of air toxics in indoor public areas between May to August.

The bureau investigated 157 buildings, including 81 hotels and restaurants, 76 shopping malls and supermarkets. Bureau officials tested for formaldehyde, carbon monoxide, carbon dioxide and sniffable particulate matter.

Approximately 79 percent of the buildings had safe amounts of all the tested toxins combined, and about 78 percent of hotels and restaurants were in line with air quality standards and 80 percent of shopping malls and supermarkets met standards.

Health supervision department took 561 carbon monoxide and carbon dioxide samples from the buildings, 546 sniffable particulate matter samples and 486 formaldehyde samples. All the buildings had safe amounts of carbon monoxide, 87.5 percent had safe amounts of carbon dioxide, 94 percent met standards for sniffable particulate matter and 77 percent met standards for formaldehyde.

But the report stated that only 70 percent of shopping malls and supermarkets had safe levels of formaldehyde.

All the establishments that failed to meet the standards have been asked to improve their air quality. Meanwhile, health department are requiring that all the establishments increase awareness of their air toxin levels and promote better hygiene to provide a better environment for the public.

"Large amount of formaldehyde used in house renovation and furniture are blamed for deterioration in people's health," said Jia Qi, an interior decorator.

"It is far better to use qualified and low-formaldehyde building materials, though the price is a little bit higher."

Each year, about 2.8 million people in the world, and 111,000 in China, die from diseases related to indoor air pollution, according to the WHO.

The WHO also said more than 300 pollutants found in the air can be linked to nearly 60 percent of all human diseases.

"It always happens that when you enter into a newly opened store, there is a strong smell of chemicals," said a 27-year-old woman Gao Yu, " I don't know what kind of finishing materials they used or whether it is safe. It makes me feel so dizzy."

"Owners of such shopping malls should sense this problem. After all, many customers will visit it everyday. That's a serious health concern, especially for children and the elderly," she said. "If I were a mother, I would never go to such unsafe places with my child."

In addition to using environmentally friendly materials when decorating, Jia Qi also suggested shops set up a proper ventilation system.

"Only have a window in the room makes the air hard to circulate, and it may lead to a accumulation of pollutants in the air that is extremely unhealthy," he said.