Devon Hill, a lawyer in Washington who has experience with companies that make phthalates, said many phthalates have been phased out of food processing and packaging, and that those still in use result in very low exposures. The cheese tests looked for the presence of 13 different phthalates and detected all but two, with some food items containing up to six different phthalates in a single product.

Environmental and food safety groups petitioned the F.D.A. last year to remove all phthalates from food, food packaging and food processing and manufacturing equipment, though the petition has been delayed temporarily for technical reasons, said Tom Neltner, chemicals policy director for the Environmental Defense Fund, which is coordinating the petition process for 11 advocacy groups, including the Center for Science in the Public Interest, Natural Resources Defense Council, the Environmental Working Group and others.

“A chemical is not allowed in food unless there is a reasonable certainty it will cause no harm,” Mr. Neltner said, adding that because of all the evidence regarding the potential harms of phthalates, “We don’t think the F.D.A. can say there is a reasonable certainty of no harm.”

An F.D.A. spokeswoman said the agency regulates all substances in food contact materials that can be expected to migrate into food, including phthalates, and said there must be “sufficient scientific information to demonstrate that the use of a substance in food contact materials is safe under the intended conditions of use before it is authorized for those uses.” The spokeswoman said: “The F.D.A. continues to monitor literature and research on these compounds as it becomes available.”

Phthalates are not deliberately added to food. They are industrial chemicals used to soften plastics and are used as solvents, in adhesives and in ink on packaging.

The chemicals migrate into food from food processing equipment like plastic tubing, conveyor belts and gaskets and other plastic materials used in the manufacturing process, and can also seep in from printed labels or plastic materials in the packaging.

Since they bind with fats, they tend to build up in fatty foods, including not just cheese but baked goods, infant formula, meats, oils and fats, and fast food, studies show.