It all started with a pink sippy cup. 

Michael Green, executive director of the U.S.-based Center for Environmental Health, said he was getting increasingly concerned about the toxic chemicals his kids were being exposed to.

The perfect storm at the Green house happened thanks to an ongoing battle with his daughter, Juliette.

"She had this princesses pink sippy cup that she loved and took with her everywhere, and she always wanted to drink out of that. But I was worried about what the chemicals were that were in there," he said.

Juliette Green

Juliette Green's passion for her pink sippy cup prompted her dad to find out what chemical compounds were in the plastic. (Michael Green)

Green knew the cup was free of bisphenol A, a chemical that had been banned in baby bottles and sippy cups thanks to public outcry. But he didn't know what it had been replaced with.

"My guess is the manufacturer didn't even know what was in the sippy cup because that's the nature of the way we make things today," he said.

So he took Juliette's cup and a few dozen other samples and sent them to two different labs for testing, but the tests were not for specific chemicals like BPA or lead. Green was testing for potential estrogenic effects.

"What we were testing for was the health outcome," he explained. "And that's a much more complicated thing to test for. And what it tells you is not what's inside the sippy cup; it tells you what are the potential health impacts of whatever's inside there."

Green said BPA was originally used as a synthetic estrogen, and the chemical has since been linked to obesity, reproductive problems and cancer.

'Toxic shell game'

It's still used in products like plastic wrap, food can liners and packaging and plastic containers used to store leftovers. And though BPA isn't in bottles and sippy cups anymore, it has been replaced with other, similar chemicals.

"It's a toxic shell game," he said.

"They take out the one that's been found to be toxic and they replace it with a chemical cousin where the health impacts are unknown because it's not well tested yet. If later, that one's found to be toxic, [they] just switch again. That's the plan."

When the lab results came back, nine of 35 products tested positively for estrogenic impacts, including Juliette's pink cup. Seven of those nine products had higher levels than cups made with BPA.

"That can be impacted by, one, just the chemicals leaching from the plastic, but two, other things that have happened to the plastic since," Green said.

"Has it ever been in a microwave? Has it ever been in a dishwasher? Has it ever sat on a window sill in the sun? That would cause the plastic to start to break down."

Green admitted that we don't know how exposure to estrogenic chemicals will affect health in the long run, but he did say minute amounts can have an impact.

Because hormones are chemical messengers that tell your body to act, estrogen-mimicking chemicals like the ones in plastic can send messages too, he said.

"So they might tell your child's body to store fat cells, or stop storing fat cells," he said. "Or it might tell your child's body to grow their reproductive organs in a different way."

Green suggested choosing glass or stainless steel drink containers and wood or ceramic dishes instead of plastic. He added that the best way to minimize preventable risk is to avoid taking that risk in the first place.

"I wouldn't let my child play in the street, even if I'm not certain there's a car coming down the street. If you're talking about your health, you want to err on the side of caution, he said. "We have other options."

But back to Green's daughter, Juliette, whose love of a pink, princess sippy cup got this whole process started. Green said she's just like every other happy, inquisitive five-year-old.

"She doesn't know anything about BPA or what chemicals are in her sippy cup," he said. "It's not fair that you have to have a PhD to figure out what's safe for your kid today. It's just not fair."