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updated 3/30/2011 3:46:54 AM ET 2011-03-30T07:46:54

Plastic wrappers, food cans and storage tubs deposit at least two potentially harmful chemicals into our food, confirmed a new study. By cutting out containers, people can dramatically reduce their exposures to these toxins.

The chemicals -- bisphenol A, or BPA, and a phthalate called DEHP -- are known to disrupt hormonal systems in the bodies of both animals and people, leading to developmental and reproductive problems, as well as cancers, heart disease and brain disorders. And both appear in a wide variety of food packaging materials.

But when people in the new study avoided plastic and ate mostly fresh foods for just three days, the levels of these chemicals in their bodies dropped by more than 50 percent, and sometimes much more.

"What this says is that food packaging is really the major source of exposure to BPA and DEHP," said Ruthann Rudel, a toxicologist at the Silent Spring Institute, a research and advocacy group in Newton, Mass. "The good news is that we provide some evidence that people can make everyday decisions about their kitchens and their diets if they want to reduce exposure to these compounds."

These chemicals appear in a huge range of consumer products. DVDs, eyeglasses and cash-register receipts may contain BPA. PVC toys, medical tubing and pipes can hold DEHP. Previous studies have also found them in foods and food-packaging materials, including plastic wraps, plastic containers and the epoxy linings of metal cans.

To solidify the link from food packaging to human exposure, Rudel and colleagues altered the diets of 20 Bay-Area families, each with two adults and two kids. All of the households reported that they either drank from polycarbonate water bottles, dined out at restaurants, microwaved food in plastic containers, ate canned foods or frozen dinners, or used plastic storage materials -- all of which would suggest exposure to at least some chemicals of concern.

During an eight-day study, the researchers took urine samples from participants on a nightly basis to look for evidence of both BPA and four types of phthalates.

For a couple days at both the beginning and end of the week, families stuck with their normal diet. But for three days in the middle of the study, they ate only food that was prepared for them by a caterer who conformed to specific guidelines.

The majority of food was fresh. Cans were not allowed. Food preparers avoided using plastic utensils or nonstick cookware. Food and drinks were stored in glass or stainless steel containers at levels low enough that the contents did not touch BPA-free lids. Even coffee had to be made in a French press or ceramic drip so that no plastic was involved.

During the three-day intervention, average levels of BPA in people's urine dropped by 66 percent, the researchers report today in the journal Environmental Health Perspectives. The highest measured levels dropped by 75 percent. For DEHP, average levels of certain breakdown products dropped by more than 50 percent, and maximum measured levels dropped by 95 percent.

When the researchers looked at phthalates that show up in places like fragrances, glue and nail polish, but not in food packaging, they didn't detect any change at all during the study -- suggesting that food packaging was indeed the major source of exposure to BPA and DEHP.

The findings align with recent work showing higher levels of BPA in canned foods than in fresh versions, said Arnold Schecter, a public health physician at the University of Texas School of Public Health in Dallas, who has pioneered a series of studies on chemicals in our food supply.

Scientists are concerned about the unknown and accumulative health effects of exposure to multiple toxic substances from many sources, Schecter added. Finding ways to lower levels of any chemical by any amount is encouraging.

"Their study and ours are more or less pointing in the same direction with the conclusion being that we'll probably poison ourselves a little bit less if we use food not stored in BPA-lined cans or phthalate-containing materials," Schecter said. "It seems to me this is good news. From a public health standpoint, if we can reduce our levels of these chemicals, that's a good thing."

As much as food-related choices can help limit the chemical burdens on our bodies, however, it is virtually impossible to eliminate exposures altogether. Many food-processing procedures, including cow milking, use plastic vats and PVC tubing.

That's where policy comes in, Rudel said. Some countries have already banned BPA in cans and DEHP in food packaging. This kind of legislation may ultimately be the only way to keep these chemicals out of our food and our bodies.

"Because we can't really shop our way out of the problem," she said, "I think it's most important to support efforts to replace these kinds of chemicals in food packaging with safer alternatives."

© 2012 Discovery Channel

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