Providing a reminder about the importance of complying with the Federal Trade Commission’s Green Guides, the agency recently sent 15 warning letters to marketers of plastic bags touted as “oxodegradable,” cautioning that the claims may be deceptive.

Oxodegradable plastic is made with an additive that causes the bag to degrade in the presence of oxygen, the FTC explained. But most waste bags are intended for landfills where not enough oxygen is present to completely degrade the bag in the time expected by consumers.

“If marketers don’t have reliable scientific evidence for their claims, they shouldn’t make them,” said Jessica Rich, director of the FTC’s Bureau of Consumer Protection, in a press release about the letters. “Claims that products are environmentally friendly influence buyers, so it’s important they be accurate.”

The agency’s updated Guides For the Use of Environmental Marketing Claims frown upon unqualified “degradable” or “biodegradable” claims for items that are typically disposed of in landfills, incinerators, and recycling facilities. The conditions in such locations do not allow for complete decomposition within one year.

As consumers understand the terms “oxodegradable” or “oxo biodegradable” are interchangeable with “biodegradable,” consumers expect they will completely degrade in one year. “Contrary to the marketing, therefore, these bags may be no more biodegradable than ordinary plastic waste bags when used as intended,” the agency said.

The FTC did not disclose the text of the letters or the names of recipients, but provided a deadline for recipients to respond with competent and reliable scientific evidence or remove the oxodegradable claims.

To read the FTC’s press release about the letters, click here.

Why it matters: Marketers that did not receive a letter should not assume their claims pass muster, the FTC noted in its press release, and staff members regularly conduct reviews of green claims in the marketplace. Since the 2012 updates to the Green Guides, the agency has kept a close eye on environmental marketing claims and has brought actions against mattress manufacturers and the makers of plastic lumber products, and has sent other advertisers a not so subtle message to ensure compliance.