Scientists are hitting out at claims some baby formula may contain toxic nanoparticles.
Research commissioned by environmental group Friends of the Earth found calcium phosphate crystals in three out of seven infant products.
The group says regulators should immediately recall the affected brands - Nestle NAN H.A. Gold 1, Nature's Way Kids Smart 1 and Heinz Nurture Original 1 - and test other formula products.
But University of Auckland nanotechnologist Dr Michelle Dickinson says there's nothing to worry about.
"We have nanoparticles in a lot of our food," she told Newshub. "If you ever burn your toast, you put nanoparticles on your toast - we don't all panic about that."
She says Friends of the Earth is using the phrase "nanoparticles" to scare people without a good reason.
"I would say to mothers, keep being amazing parents. Don't be worried some of these scare tactics around nanoparticles in food. If we told you where nanoparticles were, you would realise that you touch them every day in your life, as does your child. It's just a part of being in the modern world."
Dr Dickinson says calcium phosphate crystals can also be found in human bones and some dairy products.
"There are scientists around the world making sure that foods are safe for everybody."
Food Standards Australia New Zealand says there's no evidence the nanoparticles pose a health risk.