If you eat out, especially in places that serve food in plastic containers, you are getting something more than extra salt and fat in your food — you are picking up phthalates.

Teens who ate a lot of food purchased outside the home had 55 percent higher levels of phthalates than those who only ate their food at home, a study by public health researchers at George Washington University and the University of California, Berkeley, has found. And it wasn't just teens. People who ate sandwiches at fast food outlets, restaurants or cafeterias had phthalate levels that were 35 percent higher than those who hadn't.

Phthalates are chemicals found in a wide variety of plastics, where they are used to make plastic more flexible. The also are endocrine disrupting compounds (EDCs). Likely sources of phthalates in food include storage in plastic containers and handling by food workers wearing plastic gloves.

People who ate sandwiches at fast food outlets, restaurants or cafeterias had phthalate levels that were 35 percent higher than those who hadn't.

Elevated levels of phthalates have been linked to a greater likelihood of miscarriage, and the Environmental Protection Agency classes bis(2-ethelhexyl) phthalate or DEHP, as a probable human carcinogen. While it is not yet known exactly how harmful phthalates are, for these and other reasons, many people would like to avoid them, or at least minimize their exposure.

In this study, people were asked if they had dined out in the last 24 hours and to list all foods they had eaten in that time period. Those who reported eating out had higher amounts of phthalate breakdown products in their urine. This held for all age groups, but was strongest for teenagers.

Cheeseburgers and other sandwiches were only associated with more phthalate in the body if they were purchased outside of the home.

“Preparing food at home may represent a win-win for consumers,” said author, Amy Zota, in a statement. “Home cooked meals can be a good way to reduce sugar, unhealthy fats and salt. And this study suggests [they] may not have as many harmful phthalates as a restaurant meal.”

The study builds on earlier work that found higher amounts of phthalates in people who reported eating a lot of fast food. The current study looked at food from restaurants and cafeterias, as well as fast food outlets.

The study appears in Environment International.