Half of the mattresses sold in Beijing are substandard, the city's consumer watchdog said on Sunday.

Of the 50 products tested at the National Center for Quality Supervision and Inspection of Furniture and Indoor Environment, 25 failed for such things as color fading, fabric use, toxic substances and durability.

Samples were taken from 50 manufacturers in Beijing and Tianjin, as well as Hebei, Shandong, Guangdong, Guizhou and Zhejiang provinces. Thirteen were palm fiber mattresses and the others were spring mattresses.

Seven products faded too easily, three used thin fabric, eight had excessive formaldehyde content and 17 were beneath national durability standards of durability, according to the Beijing Consumer Association, which organized the study.

Straw was also used in some products instead of palm fiber.

The color of the exterior fabric will run onto sheets or clothes if the mattress's fading resistance does not meet national standards and the fabric will easily fray if it's durability is substandard, Sun Shudong, a division chief overseeing furniture inspection at the National Center for Quality Supervision and Inspection of Furniture and Indoor Environment, was quoted as saying by China Central Television.

The formaldehyde content in some products was 30 times acceptable levels, according to Liu Hailing, a division chief overseeing indoor environmental inspection at the center.

Under the national standard, formaldehyde emissions from a mattress may not exceed 0.05 milligrams per square meter per hour.

"Inhaling formaldehyde could cause constriction in the chest and coughing, and other respiratory diseases. It could also lead to cancers and leukemia in children if the exposure to the formaldehyde is lengthy," said Zhao Ping, vice-president of the Cancer Foundation of China.

The consumer association said it informed the manufacturers of the substandard mattresses and commerce authorities are investigating.

Qu Shengping, general manager of Beijing Hongdameidi, whose products showed excessive formaldehyde and weak durability in testing, admitted they used cheap glue and fabric to produce mattresses.

Qu said the sample the Beijing Consumer Association tested was from the inventory.

"We received the test results from the association in February, and, actually, we did not put that batch of products on the market," he said.

The test results showed that a product of Beijing Yasili, another furniture producer, was substandard in color fading resistance, fabric used, formaldehyde content and durability.

Chen, general manager of Yasili, said the association had the product tested early this year but it took the sample from the company in June last year.

"In fact, some customers had called us and complained that the mattresses gave off bad odors and we refunded their purchases," he said.

Chen said they recalled those mattresses from dealers at the end of November.

"The mattress makers involved should compensate customers, and commerce authorities should fine them," said Ge Youshan, a lawyer who specializes in consumer rights. "More serious penalties, such as suspending or revoking their business licenses, could be used if producers continue to make substandard goods."