The government is considering a ban on cosmetic products containing plastic microbeads, two decades after scientists first sounded the alarm about them polluting waterways.
The United States and Canada are banning microbeads, and the Australian government is pushing for a voluntary phase-out of affected products, including face scrubs and body wash.
Some products contain more than 330,000 of these tiny plastic fragments in a single tube.
Auckland University ecologist Mary Sewell said some were small enough to be eaten by tiny plankton, called copepods, the base of the food chain.
"We're all aware of what happens when turtles or seabirds eat large pieces of plastic.
"It's not hard to imagine that a copepod has the same problem in that its gut gets filled with something that has no nutritional value and they die from that."
Associate Professor Sewell said to make matters worse, most beads were made of polyethylene, which attracted "nasty chemicals" like PCBs.
Canterbury University environmental chemist Sally Gaw said microbeads, which have been around since the 1990s, probably "seemed like a good idea at the time" because they do not trigger allergies, are easy to sterilise and relatively stable.
"Many of these products have been tested in terms of safety for the consumer - not necessarily safety for when they end up in the environment."
It was not only microbeads but chemicals from every-day consumer products such as sunscreen which ended up in waterways, she said, and a "regulatory focus shift" was needed.
Several brands popular with New Zealanders - including The Body Shop, Unilever, L'Oreal, Clarins, and Clearasil - have pledged their support to an Australian campaign to stop using polyethylene microbeads in their products.
A spokeswoman for The Body Shop said the company had already stopped making products with microbeads, but it could be the end of the year before old lines are off New Zealand shelves.
One of the New Zealand's major supermarket chains, Progressive - which runs Countdown, Foodtown and Woolworths - is following its Australian parent company (Woolworths) in banning the use of microbeads in its own skincare brands.
A company spokeswoman said the Home Brand and the Signature and Select brands had all reformulated, except for one product, which would be done in the next couple of months.
The other major supermarket chain, Foodstuffs, which operates New World, Four Square, Write Price and Pak 'n Save said it was unable to comment.
Coles Australia said all its "home brands" were now microbead-free.
Johnson & Johnson earlier went public with plans to reformulate their products by this year, but their website now said they aimed to be microbead-free by the end of 2017.
Green Ideas magazine editor Greg Roughan said the government was often reluctant to impose extra costs on business.
But the risk was the country could become "a dumping ground" for products banned elsewhere, he warned.
"It's impossible to be the perfect consumer and have your head around all these issues all of the time. And there will always be some people who just don't care, or haven't heard of it.
"So I think it should be legislated against."
Environment Nick Smith said he was expecting a report from his ministry next month on options for ridding the waterways of microbeads, and the Cawthron Institute is also carrying out research into their long-term effects.
"The government is quite open-minded about a regulatory ban. It's just we want to do the background work before we get into the detail."
Dr Smith was also watching developments across the Tasman.
"It would make good sense for us to have a consistent regulatory approach across Australia."
As for other potential pollutants, Dr Smith said the Environmental Protection Agency had the "discretionary power" to investigate existing products if there was new evidence they could be harmful.