The mysterious packet of powder that turns boxed pasta into mac and cheese may contain potentially harmful chemicals, according to new research.

The chemicals, known as phthalates, are used in hundreds of products, foods, and drinks and have been linked to serious health complications. However, it’s still unknown how low levels of the chemicals can affect someone.

Read: The Problem With Phthalates: Fast Food May Expose You To Harmful Industrial Chemicals

The study, conducted by The Coalition for Safer Food Processing & Packaging, analyzed 30 different types of cheese products, including natural items like block or string cheese, as well as processed products such as the cheese powder that comes in boxed macaroni and cheese. The analysis revealed that nearly all of the samples (except for one) contained phthalates.

“The phthalate concentrations in powder from mac and cheese mixes were more than four times higher than in block cheese and other natural cheeses like shredded cheese, string cheese and cottage cheese,” Mike Belliveau, executive director of the Environmental Health Strategy Center, which was one of the funders of the report, told The New York Times.

Researchers choose to specifically look at cheese products because a recent scientific review revealed that dairy products were the greatest source of dietary exposure to DEPH (the most widely restricted type of phthalate) consumed by infants and women of reproductive age.

Read: Phthalates Exposure During Pregnancy May Disrupt Male Genitals Development​

Nine of the products analyzed were created by Kraft, which is the leading provider of mac and cheese products across the country. In response to the findings, the coalition created a petition aimed at Kraft titled “#KleanUpKraft.” The petition was launched in hopes that America’s biggest cheese brand removes all sources of the chemical from their products.

However, despite small amounts being detected in the products, a spokesperson for the Kraft Heinz Company assures the products are safe and no phthalates are added.

“The trace amounts that were reported in this limited study are more than 1,000 times lower than levels that scientific authorities have identified as acceptable,” the company told TIME. “Our products are safe for consumers to enjoy.”

The chemicals, commonly referred to as plasticizers, are used in raincoats, personal care products, and other items to make them more flexible and harder to break. They’re also often used in children’s toys, but six types of phthalates are banned in the United States for use among kids’ toys because of their potential health effects. Past research has indicated some types have been shown to affect the reproductive system of laboratory animals, but “more research is needed to assess the human health effects of exposure to phthalates,” according to the Centers for Disease Control and Prevention.

See also: Diabetes And Obesity Epidemic May Be Caused By Environmental Chemicals, Like BPA And Phthalates

Phthalates Fail To Serve As Safe Replacements: 2 Chemicals That May Be Rising Risk For Metabolic Syndrome Among Kids And Teens