Plastic baby bottles might have to go the way of asbestos and lead, an expert says, after the discovery bottle-fed babies could be drinking millions of fragments of microplastic every day.
Scientists in Australia tested bottles made of polypropylene-based plastics, which are generally considered safe to use in food packaging. They're heat-resistant - a necessity when it comes to preparing milk for a baby - and often used for items meant to be microwaved.
Polypropylene's also become widely used because it doesn't contain BPA, a chemical that was phased out about 10 to 15 years ago by most manufacturers after it was discovered to cause chromosomal abnormalities.
The testing found the bottles leeched microplastics, particularly after being heated to the kinds of temperatures needed for sterilisation. Each day, bottle-fed babies are likely consuming 2-3 million particles a day, the researchers found - about 16 million per litre of milk.
"Infant exposure to microplastics is higher than was previously recognised," the study, published in journal Nature Food, says, highlighting "an urgent need to assess whether exposure to microplastics at these levels poses a risk to infant health".
"It's probably not a surprise," University of Canterbury scientist Sally Gaw told The AM Show on Tuesday.
"There's been a lot of focus on the wider environment - what's in the marine environment, what's in our rivers - now some of us are starting to come back a little bit closer and look at what people are exposed to in their everyday lives."
The good news - if it can be called that - is that it's not clear if microplastics alone are bad for us.
"The honest answer is, we don't know," said Dr Gaw. "That's part of the problem - as we get better and better at finding microplastics in the environment, we're going to find them everywhere and there's going to be more research needed to try and understand what the impacts are."
Last year, researchers in Canada found tea drinkers were also consuming polypropylene particles - potentially billions in every cup, leaching from the bags.
"Plastics are found in people," said Dr Gaw. "There have been some horrendous studies I'm glad someone else has done, where they've looked at human waste - basically taken poo samples - and seen that yes, people are being exposed to plastics and they're passing through people.
"There is concern about whether plastics will then be able to move around in the body... and do some damage."
Prior studies have found microplastics can have adverse effects on marine life, and microplastics eventually degrade into even tinier nanoplastics, which are small enough to perhaps directly interfere with cells or cross the blood-brain barrier.
Dr Gaw said with little still known about the effects of microplastics on the human body, parents shouldn't panic.
"Follow the manufacturers' instructions and midwives' instructions about how to sterilise them, don't use ones that are broken or damaged - that's probably the best course of action."
As the science improves, Dr Gaw says it's likely we'll change how we use plastics.
"Plastic is a very, very useful material that we use in our everyday lives - but... we're going to have to decide which uses are sensible, which uses are not sensible, when we want to use them, how we want to use them and particularly which types of plastic we want to use... We've done this before with other materials - think of asbestos - widely used, now not widely used."