“Green” may be beautiful to a company’s marketing department, but according to the Federal Trade Commission’s new Green Guides, it’s not a word to be used lightly.

Earlier this week, the agency that monitors unfair and deceptive advertising practices released updated guidance on marketers’ use of environmental claims. First issued in 1992, and most recently updated in 1998, the revised guides incorporate three new categories—renewable materials, renewable energy, and carbon offsets—while also providing clarification on existing categories, such as ozone-safe, recyclable, non-toxic, and general environmental benefits.