The next time you add fries to your burger order, you may also be adding extra chemicals. A new study found that people who ate more fast food had higher levels of phthalates than non-consumers, suggesting the quick eats may expose diners to the potentially harmful chemicals.

The study, published Wednesday in Environmental Health Perspectives, used data from the 8,877 participants of the Centers for Disease Control and Prevention’s (CDC) National Health and Nutrition Examination Survey. The group, all age 6 or older, is a sample size large enough to reasonably reflect the U.S. population, researchers noted, and about one-third of the study group reported eating some fast food in the prior 24 hours. Fast food included processed or packaged food, carryout or delivery food, and food obtained from restaurants without waiter service.

Participants reported on their diet in the past 24 hours and provided urine samples, which were tested for breakdown products of two specific phthalates, DEHP and DiNP.

“We focused on diet in one day because the half-life of these chemicals, in the body, is very short,” lead author Ami Zota, ScD, MS, an assistant professor of environmental and occupational health at George Washington University Milken Institute School of Public Health, told FoxNews.com. “The chemicals in urine basically reflect the prior 24 hours.”

People with the highest consumption of fast food had 23.8 percent higher levels of the breakdown product for DEHP and nearly 40 percent higher levels of DiNP metabolites, compared to those who didn’t eat fast food in the reported time period.

“Not only are our results highly statistically significant, you also want to look at whether the effects are meaningful,” Zota said. “In our case, we saw a 20 to 40 percent difference between those who didn’t eat fast food and the high consumers, which we also found was striking. This is after accounting for differences in age, sex, ethnicity, household income and BMI.”

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Previous research has suggested that phthalates, which belong to a class of industrial chemicals used to make fast food packaging materials and other items used in the production of fast food, can leach out of plastic food packaging and contaminate highly processed foods.

Researchers assessed the data for total caloric intake and dining in restaurants with waiters and their findings suggested that the increased chemical levels were specifically related to fast food, not to high caloric intake or other types of food.

"Just eating more food alone is not a predictor of phthalates," Zota said. “Our fast food effects were relatively unchanged even after accounting for consumption of restaurant food. There’s always the possibility that there may be other factors we haven’t accounted for, but our effect seemed fairly stable and the analyses we have done do suggest something specific to fast food.”

Meat and grain were the biggest culprits of increased phthalate exposure. The grain category includes bread, cake, pizza, burritos, rice dishes and noodles.

“We found the most consistent association with grain items, which was a little surprising to us,” Zota said. “Prior research has shown animal products, especially animal products that are higher in fat, often have higher phthalates because some phthalates are fat-loving.”

Phthalates are found in a wide spectrum of commonly used consumer products, including shampoos and adhesives, and have been associated with a range of health problems. The chemicals are endocrine disruptors, which have been shown to affect the reproductive system of laboratory animals. According to the CDC, more research is needed to assess the human health effects of exposure to phthalates, but the chemicals have been linked to infertility problems in men with high levels and altered genital development in boys exposed in utero.

At the grocery store and in the food packaging process, food may be exposed to phthalates through the processing and handling. For example, the tubing used to process and transfer dairy has been shown to leach phthalates into food. Gloves employees wear while handling and serving food may also leach.

“Things like grease and heat can often accelerate the transfer of phthalates from packing or the gloves to the food itself,” Zota said. “If someone with gloves is handling food that’s hot, the heat is going to act as a catalyst for the phthalates to come out of the gloves and into the food.”

Chronic exposure to phthalates can increase risk to a range of adverse health effects, especially during pregnancy, when developing babies are particularly vulnerable to increased risk of male reproductive problems in male offspring and learning and behavior problems in children, Zota noted. Another emerging area of concern is the role chemicals play in chronic disease risk, such as obesity.

“These chemicals are suspected to play a role in a range of diseases and health problems, particularly reproductive and developmental problems and potentially chronic disease risk,” Zota said. “What that means for any one individual is hard to say.”

Researchers also looked at exposure to BPA, a chemical found in plastic food packaging. The study did not find association between total fast food intake and BPA, but they observed that those who ate fast food meat products had higher levels of BPA than people who reported no fast food consumption.

Issues BPA has been connected to  include obesity, cancer and childhood anxiety, though Europe’s food safety watchdog agency said in 2015 that the chemical posed no health risk to consumers of any age, including unborn children.

The study’s findings suggest consumers eat less fast food to limit their exposure to phthalates, which is well-aligned with other public health goals that suggest limiting fast food consumption for other health reasons including obesity, diabetes and heart health, Zota said.

“From a public health perspective, it points to the problem of chemicals getting into our bodies from our food supply and from the food industry and raises attention to this bigger problem that will involve a variety of stakeholders and decision makers to address,” Zota said. “This is important: An individual can do something [even though] these chemicals, such as phthalates, are so widespread that they alone cannot eliminate exposure.”