Stay up to date on all the latest news from Boston.com
What’s in that fast-food burger? Sometimes, harmful plastics.
A new study out Tuesday reports that far too often, small amounts of industrial chemicals called phthalates (pronounced THA-lates), which are used to make plastics soft, have been found in samples of food from popular outlets including McDonald’s, Pizza Hut and Chipotle.
George Washington University researcher Lariah Edwards, professor Ami Zota and their colleagues 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, all around San Antonio, Texas.
The study found harmful chemicals in a majority of samples collected. Phthalates are linked to health problems, including disruption to the endocrine system, and fertility and reproductive problems, as well as increased risk for learning, attention and behavioral disorders in children.
All six restaurant chains did not respond to requests for comment.
Currently, the Food and Drug Administration, which regulates the safety of food, has no legal thresholds limiting phthalate concentrations in food. The levels of phthalates found in the fast food that researchers tested were below the Environmental Protection Agency’s health protective thresholds, Edwards said. Under current guidelines, the levels of phthalates researchers found would not have raised alarms at federal agencies.
The FDA said in a statement that it will review the George Washington study and consider it as part of the body of scientific evidence.
“Although the FDA has high safety standards, as new scientific information becomes available, we reevaluate our safety assessments,” said an FDA spokesperson. “Where new information raises safety questions, the FDA may revoke food additive approvals, if the FDA is no longer able to conclude that there is a reasonable certainty of no harm from the authorized use.”
Although some phthalates have been banned from toys and other products, they are frequently used to make such things as rubber gloves, industrial tubing or food conveyor belts pliable, and can migrate from those things into the foods we ingest.
All of the foods the GWU researchers tested contained one or more phthalates or other plasticizer chemicals, according to the study, which received funding from foundations that promote liberal or left-leaning policies.
Food items sold by fast-food chains are heavily processed, packaged and handled, providing more opportunities to come into contact with these phthalates and plasticizers. The researchers collected food-handling gloves from many of the restaurants, which also tested positive for these chemicals.
While identifying sources of the chemicals was not part of the study, the researchers hypothesized that the concentration of these chemicals was because phthalates and replacement plasticizers exist 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, said Edwards, the lead author.
The researchers found more than 80 percent of the food samples contained a phthalate called DnBP, which has been linked to heightened risk for asthma, and 70 percent contained DEHP, which has been found to be linked to increased risk of reproductive problems.
Additionally, the team also found 86 percent of the foods contained a plasticizer called DEHT, which was developed to replace phthalates, according to Edwards. These alternative non-phthalate plasticizers’ potential effects on human health and the environment are not yet well-studied.
The Chronic Hazard Advisory Panel of the U.S. Consumer Product Safety Commission has strongly recommended that appropriate federal agencies study exposure to the phthalate alternatives and assess potential health risks, according to Patty Davis, the CPSC’s press secretary. The FDA is charged with regulating food packaging and food processing equipment as “indirect food additives.”
In the George Washington University study, foods containing meats had higher levels of phthalates, with chicken burritos and cheeseburgers testing highest for DEHT (gloves collected from the same restaurants also contained this chemical). Cheese pizzas and fries had the lowest levels of most chemicals tested.
Previous research by Zota, a professor of environmental and occupational health at GWU’s Milken School of Public Health, showed that people who often cook their own food at home have lower levels of these chemicals in their bodies, probably because home cooks do not use food handling gloves or as much plastic packaging.
She also previously tracked fast-food consumption in a national survey and found people who reported eating more fast foods had higher levels of phthalates.
The new report, published in the Journal of Exposure Science and Environmental Epidemiology, is among the first to examine the link between fast food and non-phthalate plasticizers such as DEHT that are increasingly being used in place of banned or restricted phthalates in food packaging and processing equipment.
The study results also raise concerns that people of color and low-income Americans may be disproportionately affected by these chemicals, according to Zota.
“Disadvantaged neighborhoods often have plenty of fast-food outlets but limited access to healthier foods like fruits and vegetables,” Zota said. “Additional research needs to be done to find out whether people living in such food deserts are at higher risk of exposure to these harmful chemicals.”
Edwards said the team selected restaurants that were ranked most popular in each category by market share data, 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 a cooler in their original packaging, and then each menu item was blended into a slurry, the liquid tested for these chemicals via a technique called gas chromatography-mass spectrometry.
Among the funders for the research were three liberal California-based foundations: the Passport Foundation, which funds environmental and left-leaning economic and social policy causes; the Forsythia Foundation, which funds research that aims to reduce harmful chemicals in the environment; and the Marisla Foundation, which supports health-service organizations and environmental causes.
Stay up to date on all the latest news from Boston.com