You almost certainly have BPA in your bloodstream -- nine out of ten Americans do, according to government tests. It’s also in some of the places most likely to affect the most vulnerable among us: studies have found BPA in breast milk and amniotic fluid in the umbilical cord.

BPA, or bisphenol-A, is a compound used to make the plastic that lines the inside of food and beverage cans. Unfortunately, it doesn’t stay bound to the containers. Most of the BPA flowing in our veins and arteries enters through packaged food we ingest. It’s not the sort of chemical you want flowing through your body. BPA mimics the effects of the female hormone estrogen, causing reproductive problems along with cancer, obesity, and abnormal brain development.

“Thousands of studies have shown that BPA is harmful, even at low levels,” said Dr. Sarah Janssen, a physician and senior scientist at the Natural Resources Defense Council (which publishes OnEarth).

By the end of this month, the United States Food and Drug Administration is required to decide whether or not to continue to allow BPA in food containers.

It’s not a decision the FDA is making willingly. In 2008, NRDC filed a legally binding petition asking FDA officials to ban BPA in all food containers. By law, the agency had 180 days to either say yes or no to the request. Following its preferred course of inaction, the FDA did nothing. It didn’t even open the question to public comment. Two years passed, and the mountain of evidence against BPA grew taller. Last August, NRDC filed a lawsuit to force the FDA to respond. In December, a court ruled that the FDA had to give NRDC an answer by March 31.

The FDA first approved BPA in the 1960s, before scientists were aware of its dangers, said Nick Morales, an NRDC legal fellow who is working on the case. One reason for the agency’s foot-dragging is that industry groups like the North American Metal Packaging Alliance have lobbied hard to keep using BPA. They claim that it is safe and protects against food poisoning by preventing air and bacteria from entering through perforations in the cans, even though several companies successfully use cans that are not coated with BPA.

Under the law, said Morales, the onus is on the FDA to prove that BPA -- or any other food additive -- is safe, not the other way around. “And scientific evidence shows that it is not safe,” said Morales. Hard science leaves the industry-friendly FDA in a tight space.

Eleven U.S. states, the European Union, Canada, and China have banned the use of BPA in children’s feeding products. Even the American Chemistry Council, long an advocate of all things BPA, petitioned the FDA in October to ban the use of the chemical in baby bottles and sippy cups (but not cans of infant formula). Interestingly, the FDA moved promptly to open that industry request to public comment. Perhaps the agency’s alacrity can be attributed to the fact that a ban would be meaningless. Under pressure from worried consumers, baby bottle manufacturers stopped using BPA several years ago.

In spite of the evidence, there is a real chance the FDA will deny NRDC’s petition and continue to allow BPA in food packaging, Morales said. Or that it will take half-measures: banning it in baby products but allowing it elsewhere. “The agency has a long history of finding ways to get around its obligation to protect public safety,” he said. “We’ll all have to be on the lookout.”

In the meantime, on her blog, NRDC’s  Janssen offers the following advice for consumers who want to protect themselves and their children:

• Limit your consumption of canned or processed food by eating fresh or frozen produce and buying processed food in "brick" cartons, pouches or glass.
• Limit your consumption of canned soda and beer: whenever possible, choose glass as an alternative.
• If you have a newborn, avoid feeding him/her any prepared liquid formula in a can. Breast is best, but if you are using formula, powdered formulations are known to be BPA free.
• Use a BPA-free reusable water bottle, such as an unlined stainless steel bottle.

The good news, according to Janssen, is that research shows that as soon as you stop ingesting BPA, its level in your blood begins to drop. Which means that if the FDA does its job and implements a BPA ban, all Americans will be safer.

Image: Steven Depolo/Flickr