“I think that the health implication is a big question mark,” says Trinity College Dublin materials engineer John Boland, coauthor of the new paper. “But I think the results of our study show the proximity of microplastics to food. It really suggests that now is the time to begin looking at these studies much more carefully.”To count the release of microplastic particles from polypropylene bottles, Boland and his colleagues followed the World Health Organization’s protocol for the safe preparation of baby formula. That includes sterilizing an empty bottle in boiling water, drying it, letting it cool, then filling it with water at 70 degrees Celsius, or 158 degrees Fahrenheit. Then you add the powder, shake the bottle, and let cool, at which point it’s ready for consumption. Or in the scientists’ case, they passed the liquid through a filter and counted the microplastic particles left behind.
They actually did this for three preparations—baby formula, tap water, and deionized water—and found that each resulted in a similar number of shed microplastic particles. But because it’s easier to filter plain water for the particles than goopy formula (and because they tested 10 different baby bottle products repeatedly over three weeks) they experimented with deionized water as a stand-in for fully prepared baby formula. Their filter could catch microplastics down to .8 microns (a million of a meter) but what slipped through were the even smaller bits: nanoplastics.
“Every baby bottle released on the order of a million microplastic particles following exposure to the 70 degrees centigrade water,” says Boland. “When we look at what came beneath the filter, we found that you typically have trillions of nanoparticles, so many that it's hard to count. They tend to stick together.” So Boland and his colleagues would dilute this solution to get the nanoparticles to separate, count them, and “still find numbers that correspond to trillions per liter of the original solution,” he adds. But because there was still some nanoparticle clumping, the team wasn’t able to provide an exact quantification, like they could with the larger particles caught in the filter.
Long before climate change became recognized as one of the world’s major problems, water scarcity was widely recognized as a challenge for humanity.Unfortunately, the rise of awareness about the challenges of climate change had a perverse result when it came to the world working collectively to reduce global water scarcity.
The researchers took the extra step of having an independent laboratory verify their counting technique. And sure enough, the lab, too, returned an astonishing quantification of microplastic particles—a mean value of 4.3 million particles per liter versus Boland’s 4 million. “This is a serious topic,” says Boland. “And the last thing we want to do is to unduly alarm parents about the potential exposure of microplastics. So we wanted to be absolutely certain about this.”