It was back in 1993 when Stanford endocrinologist David Feldman accidentally backed into his startling discovery: potentially dangerous molecules known as bisphenol A, or BPA, were leaching from the plastic flasks he and his colleagues were using for experiments.

“We were growing yeast in the flask to see if we could find estrogenic molecules,” said Feldman, who was doing experiments on steroid hormones like estrogen. They found them, but not where they expected. After sterilizing the empty flask with very high heat and pressure, Feldman said he “discovered the molecules must be leeching from the plastic, because they weren’t coming from the yeast.”

No one paid much attention. But 15 years – and billions of plastic bottles – later, Feldman’s discovery seems downright ominous.

Wal-Mart recently announced it will stop selling baby bottles containing BPA early next year, and Nalgene announced it will phase out production of its hard-plastic sports bottles that contain BPA. Governments are also taking notice – Canada placed exposure limits on the chemical, calling it “toxic” to human health. And federal toxicology investigators in the United States recently concluded there is “some concern” that fetuses, infants and children may be harmed by BPA, commonly found in juice bottles, campers’ water containers and even that icon of the modern cubicle world – the office water cooler. The FDA, meanwhile, says it has found no links between BPA and health problems.

The problem, Feldman said, is polycarbonate, the clear, sturdy plastic found in thousands of items on grocery-store shelves, including food cans lined with polycarbonate-laced epoxy resin. And it all first surfaced when Feldman heated that plastic flask in his lab.

“That set off an alarm in my head,” he said. “Because when BPA was first synthesized, it was known to be structurally connected to DES, or diethylstilbestrol. And 20 years after mothers had been treated with DES to prevent miscarriages, some of their grown children were developing vaginal cancers from that therapy.”

The repercussions of what Feldman and research associates Aruna Krishnan and Lazlo Tokes had stumbled upon by accident were alarming. Since BPA leaches from the plastic when it’s sterilized and perhaps when washed with certain detergents, the potential for health risks could be immense, even though industry groups say there are no serious health risks associated with plastic bottles containing BPA.

“I’m not an alarmist, and I’m not saying that drinking from plastic bottles will cause breast cancer,” said Feldman, who advises his own children not to put plastic containers in the microwave or dishwasher and to limit the amount of canned foods they consume. “But I am worried about the effects of BPA on babies, expectant mothers and fetuses. To me, it’s better to be safe than sorry, and we should at least know when people are exposed to this.”

So why did it take 15 years for the world to notice?

“Our discovery was a big deal at first, even in Japan,” said Feldman, who at a 1994 symposium in Washington, D.C., presented a paper titled “Estrogens in Unexpected Places: Possible Implications for Researchers and Consumers.” Feldman said that while many other scientists built upon his research and continue to this day to explore the effects of BPA, initial attempts to push the industry to do more studies and implement safeguards came slowly.

“Why didn’t it move faster? Politics, I think. There’s a lot of money involved. Billions of pounds of this stuff is being made,” he said. “So there’s not much incentive by industry to do anything. And scientists can only say so much.”

Feldman, who at 69 is still at Stanford but no longer researching BPA, said he’s encouraged by the growing precautions taken by industry and government, even if a clear link between health risks and BPA in polycarbonate and perhaps other kinds of plastic has not been conclusively established.

“Maybe the BPA doesn’t hurt us or kill us,” he said. “But there have been studies where mice and rats are exposed to it, and they’re finding changes in their prostate and breast tissue. The question is, how does that translate into human use? And we don’t yet know the answer.”