Researchers have discovered about 70 percent of apartments in Guangdong's provincial capital contained formaldehyde levels exceeding national standards, the Guangzhou Daily reported.

On average, levels were 64.3 percent higher than the standard, it said.

Experts have urged local residents to avoid undertaking extensive home improvements, the newspaper reported.

They also urged home-buyers to wait until their new residences pass environmental inspections before moving in. If toxicity levels exceed the standard, remedial measures should be undertaken before owners take up residence in the homes.

In addition to installing ventilators and air filters, residents can grow Spider Plants, aloes and kumquats, which absorb toxins in the air.

Researchers made the remarks in Guangzhou during the 4th Seminar of Sustainable Development of Guangdong Province, Hong Kong and Macao Special Administrative Regions on Monday.

Guangzhou municipal environmental monitoring center official Li Yingwen said most dwellings with indoor air pollution were constructed with substandard artificial panels and fiber boards, and poisonous paints. Some leather furniture also emitted formaldehyde.

The chemical can irritate the eyes and lungs, and even trigger asthma attacks. Long-term exposure has also been linked to leukemia.

"The more luxurious the apartments are, the more likely they are to be seriously contaminated," Li said.

The formaldehyde levels in some recently completed luxury apartments are as high as 0.6 mg per sq m - 5 times the national standard.

Li urged local residents to use high-quality materials for home improvements.

In addition to formaldehyde, researchers found levels of many other toxins in Guangzhou apartments often exceeded national standards.

Local white-collar worker Liang Xiangqiong said she waited for months to move in after her apartment was completed last year to allow the airborne toxins to disperse.

"But I have no idea what else to do, because it is hard to find quality interior decorating materials," she said.