In previous articles here, here and here, I wrote about the dangers of an environmental toxin called bisphenol-A (BPA). BPA is a chemical that is found in several plastics and plastic additives. It’s in the water bottles some folks carry to gyms, the canned tomatoes and coconut milk they cook with, and in the baby bottles moms use to feed their infants.

We’ve known for decades that BPA has estrogenic activity. In vivo animal studies and in vitro cell-culture research has linked low-level estrogenic activity associated with BPA exposure to all kinds of fun stuff, like diabetes, ADHD, heart disease, infertility and cancer.

There is now significant evidence suggesting that even low levels of BPA-exposure can cause harm, and this is particularly true in vulnerable populations like pregnant women, infants and the chronically ill. (1)

Because of this research, and the growing public awareness that BPA should be avoided, a new crop of “BPA-free” plastic food containers and baby bottles has been introduced. However, a recent study published in the journal Environmental Health Perspectives in July has shown that even BPA-free plastics have chemicals with estrogenic activity (EA), and can cause serious health problems as a result. (2)

What is “estrogenic activity” (EA)?

Chemicals with estrogenic activity (EA) are those that mimic or antagonize the actions of naturally occurring estrogens. These chemicals are capable of binding with one or more of the nuclear estrogen receptors in the body.

The best way to think of chemicals with EA is as a counterfeit key fitting into a loose lock.

When these chemicals activate the estrogen receptor, they produce an increase in circulating estrogen, which in turn can cause problems such as early puberty in females, reduced sperm counts, altered function of the reproductive organs, obesity, increased rates of certain cancers and problems with infant and childhood development. ( 3

As I mentioned above, vulnerable populations such as pregnant women, developing fetuses, infants and children are especially sensitive to even very low doses of chemicals with EA. (4)

BPA-free is not EA-free

In the Environmental Health Perspectives study, Yaniger et al. set out to determine the estrogenic activity of commonly used plastic consumer products.

They bought more than 500 plastic products at places like Wal-Mart, Whole Foods, Trader Joe’s, Target, and other major retailers. They selected from all categories of plastic, including tupperware containers, bags and wraps.

Then they cut the containers into pieces, put them into liquids that contain similar chemicals found in food and drinks, and subjected them to stresses that mimic normal use, like UV light (sunlight), microwaving, or moist heat (like boiling or dishwashing).

Their results showed that over 90 percent of the products leached estrogenic chemicals before they were even stressed, and after being stressed essentially all of the products showed estrogenic activity.

According to Stuart Yaniger, one of the lead authors of the study:

Baby bottles, plastic bags, plastic wrap, clamshell food containers, stand-up pouches: Just about anything you can think of that’s made of plastic that food or beverages are wrapped up in, we found this activity. It was shocking to us.

What plastics do and don’t have EA? It’s impossible to tell.

Perhaps the most troubling outcome of this study is that it’s currently impossible to determine which consumer plastic products are likely to have chemicals with EA, and which are not.

The exact chemical composition of most plastic products is proprietary and thus not known, and a single plastic item containing many parts (e.g. a baby bottle) may consist of >100 chemicals, all of which can leach from the product.

In light of the researchers’ finding that nearly all of the 500 plastic products they tested leached when stressed, and 90 percent of them leached even without stress, I think it’s pretty safe to assume that most plastic products you can buy in the store have chemicals with EA.

It’s important to reiterate that this is true even with BPA-free plastics. In fact, the Environmental Health Perspectives study found that some BPA-free products had even more EA than BPA-containing products!

Should you be concerned about chemicals with EA?

There are still a lot of unknowns in the discussion of the EA of various chemicals in plastic products, such as the number of chemicals having EA, their relative EA, their release rate under different conditions, and their half-lives in human beings of different ages.

However, there are 3 strong arguments for being “better safe than sorry” when it comes to plastics and EA (5):

in vitro data overwhelmingly show that exposures to chemicals with EA (even in very low doses) change the structure and function of human cell types;

many studies present clear cellular, molecular and systemic mechanisms by which chemicals having EA produce changes in cells, organs and behaviors; and,

recent epidemiological studies strongly suggest that chemicals with EA produce measurable changes in the health of various human populations.

Perhaps the study authors summed it up best in their conclusion:

Many scientists believe that it is not appropriate to bet our health and that of future generations on an assumption that known cellular effects of chemicals having EA released from most plastics will have no severe adverse health effects.

I couldn’t agree more.

What you can do to reduce your exposure to chemicals with EA

Here’s a list of things you can do to reduce your exposure – and especially your baby’s and children’s exposure – to chemicals with EA.

Use glass containers and canning jars at home for food storage. Be aware that the lids of Mason and Kerr brand canning jars contain BPA and chemicals with EA. There are BPA-free lids, but they still may contain chemicals with EA, and I’ve been told they’re made with formaldehyde. Weck makes 100% glass jars that are a good alternative. Crate and Barrel sells them here.

Use stainless steel containers in the freezer instead of freezer bags.

Use a stainless steel water bottle (like the Klean Kanteen) instead of plastic bottles.

Don’t drink bottled water from plastic bottles, especially when they’ve been exposed to sunlight.

Parents: use glass baby bottles instead of plastic. Evenflo is a commonly available brand you can buy at Target, Wal-Mart, Walgreens, Rite-Aid, etc. and online at Amazon and other retailers.

Special note for Sous Vide users: After reading this study, I’m feeling very uncomfortable about the idea of eating anything that comes out of a plastic bag that has been sitting in a hot water bath for several hours. This is a crushing blow, as I love cooking with the Sous Vide. But in light of the evidence that even BPA-free plastics bags leach chemicals with EA even without added stress like a hot water bath, I think erring on the side of caution is probably wise.

UPDATE 10-28-11: make sure to read the comments section for some good recommendations.

UPDATE 11-7-11: check out this article on Nom Nom Paleo, one of my favorite Paleo food blogs. She did some homework and found some information claiming that re-usable silicon bags don’t have EA chemicals. However, Stuart Yaniger, one of the authors of the paper I referenced in this article, commented on her post (and below) that most silicon products do, in fact, leach EA chemicals. I’m also wary of the claim that FoodSaver bags don’t have any EA without 3rd party, independent testing. As Yaniger’s article demonstrated, we should assume all plastics have EA until proven otherwise.