A survey of 200 sites in 20 countries around the world has found that bisphenol A, a synthetic compound that mimics estrogen and is linked to developmental disorders, is ubiquitous in Earth's oceans.

Bisphenol A, or BPA, is found mostly in shatter-proof plastics and epoxy resins. Most people have trace amounts in their bodies, likely absorbed from food containers. Its hormone-mimicking properties make it a potent endocrine system disruptor.

In recent years, scientists have moved from studying BPA's damaging effects in laboratory animals to linking it to heart disease, sterility and altered childhood development in humans. Many questions still remain about dosage effects and the full nature of those links, but in January the U.S. Food and Drug Administration announced that "recent studies provide reason for some concern about the potential effects of BPA on the brain, behavior, and prostate gland of fetuses, infants and children.”

The oceanic BPA survey, presented March 23 at an American Chemical Society meeting in San Francisco, was conducted by Nihon University chemists Katsuhiko Saido and Hideto Sato. At an ACS meeting last year, they described how soft plastic in seawater doesn't just float or sink intact, but can break down rapidly, releasing toxins. In their new findings, they showed that BPA-containing hard plastics can break down too, and found BPA in ocean water and sand at concentrations ranging from .01 to .50 parts per million.

As for what those numbers mean for public and environmental health, it's hard to say. BPA can cause reproductive disorders in shellfish and crustaceans, and doses below a single part per trillion can have cell-level effects, but the path from water and sand to ocean animals needs to be studied.

One disturbing possibility is that BPA could bioaccumulate, with animals eating BPA-tainted animals that have eaten BPA-tainted animals, finally reaching high concentrations in top-level ocean predators and the humans who eat them. For that to happen, BPA would have to be stored in fatty tissue, rather than passing quickly through the body.

"That's a really difficult, unsettled question," said Shanna Swan, a University of Rochester environmental medicine specialist who wasn't involved in the survey.

In a 2009 Environmental Health Perspectives study of BPA concentrations in people who had recently fasted, Swan found that BPA levels remained high longer than expected. It's possible that BPA indeed accumulated in their fat, said Swan. They could also have picked up BPA from as-yet-unappreciated non-dietary sources, such as household dust or leaching from PVC water pipes. Or both scenarios may be true.

The BPA contamination found by Saido and Sato likely comes from a mix of boat paint and plastic. About three million tons of BPA-containing plastics are produced each year. The United Nations estimates that the average square mile of ocean contains 46,000 pieces of plastic trash.

"Marine debris plastic in the ocean will certainly constitute a new global ocean contamination for long into the future," wrote Saido and Sato in their presentation.

Image: Polihale/Wikipedia

See Also:

Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecological tipping points.