According to a new study published on Tuesday, small amounts of industrial chemicals known as phthalates, which are used to soften plastics, have been found in food samples from popular restaurants such as McDonald’s, Pizza Hut, and Chipotle far too frequently.

Lariah Edwards, professor Ami Zota, and their colleagues from George Washington University purchased 64 fast-food items from national burger chains McDonald’s and Burger King, pizza chains Pizza Hut and Domino’s, and Tex-Mex chains Taco Bell and Chipotle in and around San Antonio, Texas. The majority of the samples collected were found to contain harmful chemicals, according to the study. Phthalates have been linked to a variety of health issues, including endocrine system disruption, fertility and reproductive issues, and an increased risk of learning, attention, and behavioral disorders in children.

Currently, there are no legal thresholds limiting phthalate concentrations in food set by the Food and Drug Administration, which regulates food safety. The levels of phthalates found in the fast food tested by the researchers were below the Environmental Protection Agency’s health-protective thresholds, according to Edwards. The levels of phthalates discovered by the researchers would not have raised an alarm at federal agencies.

The FDA stated in a statement that the George Washington study will be reviewed and considered as part of the body of scientific evidence.

Although some phthalates have been banned from toys and other products, they are frequently used to make rubber gloves, industrial tubing, or food conveyor belts pliable, and can migrate from those materials into the foods we consume.

According to the study, all of the foods tested by the GWU researchers contained one or more phthalates or other plasticizer chemicals. The study was funded by foundations that promote liberal or left-leaning policies. Fast-food items are heavily processed, packaged, and handled, increasing the chances of coming into contact with these phthalates and plasticizers. Many of the restaurants tested positive for these chemicals, so the researchers collected food-handling gloves from them.

While identifying the sources of the chemicals was not part of the study, the researchers hypothesized that the concentration of these chemicals was due to phthalates and replacement plasticizers being present throughout the food supply chain, with food coming into contact with packaging and food-handling gloves, as well as processing equipment such as industrial tubing and conveyors, according to Edwards, the lead author.

The researchers discovered that more than 80% of the food samples contained DnBP, a phthalate linked to an increased risk of asthma, and 70% contained DEHP, a phthalate linked to an increased risk of reproductive problems.

According to Edwards, the team also discovered that 86 percent of the foods contained a plasticizer called DEHT, which was developed to replace phthalates. The potential effects of these non-phthalate plasticizers on human health and the environment have not yet been thoroughly investigated.

Foods containing meat had higher levels of phthalates in the George Washington University study, with chicken burritos and cheeseburgers testing the highest for DEHT (gloves collected from the same restaurants also contained this chemical). The lowest levels of most chemicals were found in cheese pizzas and fries.

Previous research by Zota, a professor of environmental and occupational health at GWU’s Milken School of Public Health, found that people who frequently cook their own food at home have lower levels of these chemicals in their bodies, most likely because they do not use food handling gloves or as much plastic packaging.

The new study, published in the Journal of Exposure Science and Environmental Epidemiology, is one of the first to look at the relationship between fast food and non-phthalate plasticizers like DEHT, which are increasingly being used in food packaging and processing equipment in place of banned or restricted phthalates.

According to Edwards, the team chose restaurants based on market share data that were the most popular in each category, testing multiple outposts for each chain and sampling their best-selling food items, ordering each item with standard toppings or fillings. Items were transported to the lab in their original packaging in a cooler, and then each menu item was blended into a slurry, which was then tested for these chemicals using a technique known as gas chromatography-mass spectrometry.

Three liberal California-based foundations contributed to the research: the Passport Foundation, which supports environmental and left-leaning economic and social policy causes; the Forsythia Foundation, which supports research aimed at reducing harmful chemicals in the environment; and the Marisla Foundation, which supports health-service organizations and environmental causes.