Auckland Mayor Phil Goff is calling on Aucklanders to dispose of single-use masks correctly, following reports council staff are finding hundreds littered throughout the city.
At Covid-19 level 2 the masks are compulsory on public transport and Aucklanders are being encouraged to wear them whenever they leave their house.
The council said its rubbish collectors have noticed more masks discarded in parks, reserves and on the streets.
Goff said the masks in streets and parks posed a health risk and they needed to be disposed of properly.
"It is great that so many Aucklanders are following health advice by wearing a mask, but we also need to remember to throw disposable masks in the bin.
"We all know the importance of being a tidy Kiwi and this is no different. Used masks being thrown on the street is not only a health risk but is also terrible for our environment.
"Most masks are made from materials that do not easily degrade and this means they can harm wildlife. They can also leach microplastics and other chemicals into our waterways.
RNZ reporter Katie Doyle and cameraman Dan Cook asked Aucklanders how they were getting on with "masking-up":
Goff said if someone with Covid-19 sneezed into a mask and didn't dispose of it safely, that could further the spread.
"It's really important to dispose of it safely so you don't get kids coming along and picking them up and playing with them. There is a potential risk there. It's not a huge risk, but it is a real risk."
Aucklanders could be fined up to $400 for chucking their single use masks on the streets.
Auckland councillor Richard Hills said fines were a last resort but Aucklanders needed to lift their game.
He said contractors were seeing a couple hundred masks a day littered around the city.
"So we're not seeing monumental numbers of masks around, but if it grows it's pretty bad for our environment and of course when it rains those masks head down the waterways and into our beaches and oceans. So we're just really keen for people to take those masks home."
Hills said the single-use masks were made from plastics and synthetics and did not break down.
"They will just sit in the drains and end up making their way out to our beaches."
He said it wasn't a "massive issue", but something to be aware of. Compliance officers could hand out $400 fines, but it seldom happened, he said.
"I'm sure people aren't meaning to drop it out of their pocket or whatever, so we don't want to go heavy-handed on people. There is that stick approach, but the carrot approach is just having a good clean environment, parks and streets."