The US Centers for Disease Control and Prevention now says people exposed to certain types of Lumber Liquidators's laminate flooring are three times more likely to get cancer than the agency previously predicted.
The CDC said that in its original report it had used an incorrect value for ceiling height. It said that resulted in health risks calculated using airborne concentration elements about three times lower than they should have been.
It now estimates the risk of cancer at six to 30 cases per 100,000 people. It previously estimated two to nine cases per 100,000 people.
The agency said that its recommendations will likely stay the same - that people take steps to reduce exposure to formaldehyde emitted from the Chinese-made flooring.
Formaldehyde was added to the government's list of known carcinogens in 2011. It is a colourless gas with a pungent smell, used among other things to manufacture building materials and household products. It's a common indoor air pollutant. Researchers say the amount of formaldehyde given off by new products ebbs over time.
Lumber Liquidators said in a statement on Monday that it has strengthened its "quality assurance procedures", such as testing sample products.
The company stopped selling the Chinese-made laminate floors in May, a few months after CBS news show 60 Minutes reported that those floors contain high levels of formaldehyde. Lumber Liquidators also began providing customers with free air quality tests.
The CDC says homeowners can reduce the amount of formaldehyde in their homes by letting in fresh air for a few minutes every few days and choosing products with low or no formaldehyde.
The health agency said it's not necessary to test homes unless there's a strong chemical smell or someone is having symptoms - burning of the eyes, nose and throat - and only experiencing them in the home.
Earlier this month, it was announced in a separate case that Lumber Liquidators would pay more than $US13 million ($A17.97 million) for illegally importing hardwood flooring, after the company pleaded guilty to environmental crimes last year. The company pleaded guilty to environmental crimes in October.
Shares of Lumber Liquidators Holdings slid $US2.81, or 19.8 per cent, to close at $US11.40 on Monday. Its shares have fallen more than 83 per cent over the past year.
