The Federal Trade Commission sent warning letters to five providers of environmental certifications and seals and 32 businesses that used them expressing concern that they may be deceptive. Their names were not released.

Released in October 2012, the Guides for the Use of Environmental Marketing Claims—better known as the FTC's Green Guides—provide guidance for advertisers making environmental marketing claims on issues ranging from "compostable" claims to advertising products made with renewable energy.

The Guides specifically require that marketers using third-party certifications and seals be able to substantiate all claims that are reasonably communicated, noting that if the seal or certification does not communicate the basis for the certification or seal, a misleading general environmental benefit claim could be conveyed.

The warning letters quoted the Guides: "Because it is highly unlikely that marketers can substantiate all reasonable interpretations of these claims, marketers should not make unqualified general environmental benefit claims."

To illustrate the problem, the agency provided two examples of environmental certifications. In the "bad" example, the seal states "Green Approved." Such a general claim is likely deceptive because "it does not convey the basis for certification" and it "is highly unlikely that marketers can substantiate all the attributes implied by general environmental benefit claims," the FTC explained.

Alternatively, a "good" example of a certification may state "Green Approved" but includes additional terminology such as "Biodegradable, Recyclable, Compostable." If the claims are accurate, the seal "is not deceptive because it lists the specific attributes that form the basis for the product's certification," the agency said.

In some cases, consumers may click on the seal or certification logo for more information. However, "the logo itself is not likely an effective hyperlink label leading to the necessary disclosures," the FTC wrote, per the Dot Com Disclosures guidance document. The symbol or icon might not provide sufficient clues about why the claim is qualified or the nature of the disclosure, and consumers may view the symbol "as just another graphic on the page."

While the FTC declined to take any legal action at the current time, the letters requested a response with an explanation of "the steps you are taking to ensure" compliance with the Green Guides.

To see the FTC's examples of "Good" and "Bad" seals, click here.

To read the letters to the certification or seal providers, click here.

To read the letters to the businesses using the certifications or seals, click here.

Why it matters: "Environmental seals and certifications matter to people who want to shop green," Jessica Rich, director of the FTC's Bureau of Consumer Protection, said in a statement about the letters. "But if the seals' claims are broader than the products' benefits, they can deceive people. We are holding companies accountable for their green claims." Green advertisers should take care to reduce the risk of deceptive claims by using "clear and prominent qualifying language that clearly conveys that the certification or seal refers only to specific and limited benefits," as suggested by the Green Guides.