A Japanese researcher says ocean currents can carry Japan's plastic waste as far as North America.
Shinsuke Iwasaki of the Civil Engineering Research Institute for Cold Region conducted a simulation to track about 6,300 tons of plastic garbage flowing into the sea from major Japanese cities.
The simulation shows that the waste can reach the US west coast, Canada and Alaska.
Iwasaki says scrap plastic also drifts to Southeast Asian countries such as the Philippines, and some is also washed ashore in Japan.
Plastic bags and bottles are polluting the oceans and posing a serious threat to ecosystems.
The Group of 20 environment ministers will discuss the issue when they meet this weekend in the resort town of Karuizawa in Nagano Prefecture, central Japan.
Iwasaki says people should be aware that scrap plastic produced in Japan can affect countries in other parts of the world. He says action is needed on a global scale to reduce plastic waste.