A growing number of home-cleaning products that call their ingredients “natural” are hitting store shelves. Now, an industry group is trying to clarify what the term means and whether manufacturers are using it appropriately.

The Natural Products Association, a Washington-based group representing manufacturers and retailers including Clorox Co. and Whole Foods Market, plans to release new standards Thursday for natural home care products. The group is issuing the guidelines out of concern that products like household cleaners and detergents say on labels that they are natural when they are made mostly of synthetic ingredients, says Daniel Fabricant, the association’s vice president for scientific and regulatory affairs. Products that meet those standards will be able to display the association’s seal.

Natural generally means that the product’s ingredients are derived from renewable resources like plants and minerals. (It is not to be confused with organic, which refers to a method of agriculture that avoids the use of pesticides and antibiotics.) But there is currently no uniform standard among manufacturers for use of the word in home-care products.

To display the seal, products will have to meet criteria including the following: 95% of the ingredients in the product, excluding water, must be derived from natural sources. Non-natural ingredients should be used only when alternative natural ingredients are unavailable. The product should contain no ingredients with suspected human health risks. NPA says it is reviewing full ingredient lists from manufacturers who have applied for certification to determine whether their products qualify. The seal will be seen on products in the next several months.

The association released similar standards for personal-care products such as lip balms and skin creams in 2008. So far about 350 products have its seal.

Some manufacturers say guidelines for home products are needed. “It’s time for there to be a standard so that when consumers see the word ‘natural’ they can see that it meets a meaningful standard, ” says Martin Wolf, director of product sustainability and authenticity at Seventh Generation Inc., one of the companies advising NPA on the initiative.