New Zealand is lagging behind the rest of the world in its lack of action to phase out single-use plastic bags, according to a senior university lecturer.
Massey University's Dr Trisia Farrelly says the problems plastic bags create in the environment are "many and vast".
But the majority of the issues they cause are invisible, and it's when they break down into microparticles that they start causing major damage, she says.
Dr Farrelly says while strangulating or blocking the intestinal tracts of animals are the obvious problem, the issue many people don't realise is the toxic one.
"While plastic bags don't have a lot of toxins in them, relatively speaking in terms of other plastics that are produced, they do attract a lot of toxins."
These include persistent organic pollutants such as flame retardants and pesticides, she says.
"So fish eat them, they get in the food chain and we eat them."
These pollutants contain carcinogens and endocrine disruptors, which mimic the estrogen hormone and can impact reproductive and sexual health.
She says by 2050 there will be as much plastic in the sea as there are fish.
"It's not at all good for the sustainable and healthy volume of our fish in the future for feeding our populations."
The Green Party today launched its single-use plastic bag levy bill, which would see consumers charged 15 cents for each one.
The levy would apply not just to supermarkets, but to any store that uses single-use plastic bags.
Dr Farrelly says it's time for New Zealand to act on plastic bags because "the oceans connect us all".
"We all draw our food source from the same seas.
"Everybody's really responsible for these global issues, we can't simply say we're a small country and our contribution is relatively small. We can't afford to do that anymore."
She says our contribution is slow.
"We talk about this clean, green image until it becomes meaningless.
"If we are going to continue to rely on tourism to support our economy, if we are going to encourage more people to come here and visit, we've got to start catching up to the rest of the world."