(CNN) A new study finds that those fast food drive-thru hamburgers and take-out pizzas could increase your exposure to hormone-disrupting chemicals called phthalates.
Researchers looked at the relationship between how much fast food people consume and the level of phthalates in their urine. The data were collected by the Centers for Disease Control and Prevention between 2003 and 2010 as part of nationwide surveys on health and nutrition that included more than 8,877 children and adults.
About one-third of the participants in the study said they had eaten fast food in the last 24 hours. Those who consumed a lot of fast food during that time, meaning that at least 35% of their calories came from fast food, had 23.8% and 39% higher levels of two phthalates called DEHP and DiNP, respectively, compared with participants who did not report having any fast food in the last day. More modest fast food consumers -- those who ate fast food but it made up fewer than 35% of their calories -- had 15.5% and 24.8% increases in DEHP and DiNP in their urine.
The researchers did not find a link between fast food consumption and another endocrine disruptor called bisphenol-A, or BPA, which has infamously been linked with early puberty and problems in brain development.
"There are increasing recommendations from scientific and clinical bodies suggesting the general population and vulnerable populations like pregnant women reduce their exposure to phthalates, but up to now there have been very few sources that people can have control of," said Ami R. Zota, assistant professor of environmental and occupational health at the George Washington University Milken Institute School of Public Health. Zota is the lead author of the study, which was published Wednesday in the journal Environmental Health Perspectives.
The American College of Obstetricians and Gynecologists released a report in 2013 stating that high levels of exposure to phthalates could lead to adverse reproductive outcomes in women. Research has linked these chemicals with increased risk of fibroids and endometriosis, which can cause infertility, and reduced IQ and behavioral problems in children exposed in the womb. High phthalate levels have also been linked with diabetes risk in women and adolescents.
There are countless ways that people can be exposed to phthalates. They are found in soaps, perfumes, nail polish, medications, and we can ingest, inhale and absorb them through the skin. Out of all these routes of exposure, however, diet is emerging as a major one.
Food can be a major source of phthalates because packaging materials and equipment used in food processing such as conveyor belts and tubing contain phthalates, and these chemicals can leach into food.
"This study shows that fast food may be an especially important source of phthalate exposure," said Linda Birnbaum, director of the National Institute of Environmental Health Sciences and the National Toxicology Program. "In fast food, it's even more handling and more packaging" than food you might buy at the grocery store, she added. For example, just about everyone handling ingredients at a fast food joint is supposed to wear gloves, which contain phthalates that can be transferred to food.
More studies will need to be done to see which menu items specifically lead to spikes in phthalates, Birnbaum said. The current study found that grain-based items and fast foods containing meat were linked with greater increases in phthalate levels. This could be because of the way these foods are processed and packaged or because the fats in these foods bind phthalates better.
Although the current study did not find a link between fast food consumption and BPA exposure, it is too soon to say for sure, Birnbaum said. One of the biggest sources of BPA is thought to be canned foods, and fast food restaurants that serve canned soda could also be serving up BPA, she said. Birnbaum was not involved in the current study, although she has recently done research with Zota looking at the relationship between pesticides and other environmental pollutants and cancer markers in the body.
The study looked at two phthalates, but the CDC survey included measurements for about 10 phthalates in total, and some of them could also have been higher in people who eat a lot of fast food, Zota said. She and her colleagues focused on DEHP and DiNP because they are the main phthalates used in food processing and packaging to keep plastics soft.
So far there is the most evidence incriminating DEHP and its effect on health, including brain development, behavior and respiratory health, but studies are starting to suggest that DiNP could have similar effects, Zota said. As a result, efforts to replace DEPH with DiNP in consumer products, which her earlier research suggested could be taking place, could be futile, she said.
DEHP has been banned from all children's toys in the United States and Europe, and DiNP has also been banned from toys that children put in their mouth.
The National Restaurant Association and the American Chemistry Council, which are working together to review the study, said the levels of phthalates in the CDC surveys are "well below" the levels the U.S. Environmental Protection Agency deemed likely to increase health risk. A spokesperson for the National Restaurant Association said that consumer safety is paramount in the restaurant industry.
However the levels the Environmental Protection Agency set for DEHP have not been revised since 1988, and in the meantime, "there has been a wealth of additional scientific evidence suggesting adverse health effects of [DEHP and DiNP] at low levels," Zota said. Many of the studies that have found a link between phthalate exposure and reproductive and developmental problems involved populations that had similar low levels of exposure as in the CDC sample, she added.