(CNN) It's not listed on the ingredient list, but a new analysis published this week found high concentrations of the chemicals known as phthalates in the cheese powder of macaroni and cheese.

The small study evaluated 30 different cheese products which included natural cheese products, including block or string cheese, as well as processed cheese slices and the cheese powder found in boxed macaroni and cheese. The analysis found evidence of the chemical in 29 of the 30 products tested. Natural cheeses had the lowest levels of the chemical, while processed cheese products had the highest levels.

The analysis was done by the the Coalition for Safer Food Processing & Packaging, a consortium of environmental health advocacy groups, and has not been published in a peer reviewed journal.

What are phthalates?

Phthalates are a family of chemicals that are widely used in soaps, plastics, adhesives, rubbers, inks and fragrances. While these chemicals aren't intentionally added into foods, they make their way in through the manufacturing process.

"They are used in the plastic tubing, the plastic gloves, the gaskets all along the food supply chain," said Mike Belliveau , executive director of the Environmental Health Strategy Center, one of the groups participating in the coalition. Diet is considered a major route of exposure to these chemicals.

Banned in children's products

While the US Centers for Disease Control and Prevention acknowledges that some phthalates have a direct impact on the reproductive system of animals, they say that "the impact of low level exposure on humans is unknown" and that more research still needs to be done. However, since 2008, a number of phthalates have been banned in children's products by the US Consumer Product Safety Commission. The European Commission also bans five different phthalates from food packaging materials.

According to Food and Drug Administration spokeswoman Megan McSeveney, for a phthalate to be used in food packaging, "there must be sufficient scientific information to demonstrate the substance is safe under the intended conditions of use." She added that "the FDA continues to examine data on these compounds as it becomes available. "

Just how much is there?

Of the coalition's analysis of 30 cheese products, 10 were boxed macaroni and cheese powders, five were sliced cheese products, and the remaining 15 products were natural cheese products including hard, shredded, string and cottage cheeses. The samples were sent to an independent lab in Belgium, where the fats were extracted and tested for 13 different types of phthalates.

When looking at the fat alone, the powdered cheese mix had a concentration of phthalates more than 4 times that of the natural cheeses, and more than 1.5 times the amount in processed cheeses. To approximate a more realistic serving, the survey calculated levels of phthalates based on the fat content of each product. When doing so, the level of phthalate in a package of powdered cheese was about twice the level in the natural cheeses, and similar to sliced cheese.

Of the 30 products tested, some were labeled organic. Nine were Kraft Heinz products. Kraft Heinz is the largest seller of boxed macaroni and cheese, making up 76% of the market share. When asked about the report, Kraft Heinz told CNN, "We do not add phthalates to our products. 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. Our products are safe for consumers to enjoy."

When trying to estimate how many phthalates we consume and are exposed to overall, Jessie Buckley , assistant professor of environmental health and engineering at Johns Hopkins Bloomberg School of Public Health, said it's not clear.

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"We don't have a lot of information on how much phthalates are in different foods. There's no requirement to release that info," said Buckley. She said that while the chemicals can quickly leave our body -- taking as little as several hours, sometimes -- the concern is the constant exposure we have to them from plastics to food, which can be particularly concerning for pregnant women.

"We don't know what the safe limits are -- but it's prudent to limit exposure if we can," she added. Buckely was not involved in the assessment.

Belliveau of the Environmental Health Strategy Center said, "We're not alleging that any single product is unsafe ... but the risk is already too high, so further research is needed to identify where the phthalates are coming from."

The Coalition for Safer Food Processing & Packaging is petitioning Kraft Heinz to identify the source of chemicals and remove them from the food packaging process.