BANGKOK - Asean has "become seized" with the issue of plastic waste pollution in the oceans, and it is good that the regional bloc has taken a stand on this, Prime Minister Lee Hsien Loong said on Sunday (June 23).

He was referring to a first-of-its-kind agreement aimed at tackling marine debris that the 10 member nations adopted on Saturday.

Among other things, Asean nations have committed to adopting a more holistic land-to-sea approach, strengthening research capabilities, enhancing regional and international cooperation, and increasing public awareness.

But PM Lee on Sunday noted that it is still a long way to solving the problem because four of the biggest sources of plastic waste in oceans are in South-east Asia.

A 2017 Ocean Conservancy report found that five Asian countries - China, Indonesia, the Philippines, Vietnam and Thailand - dump more than half of the eight million tonnes of plastic waste that end up in the oceans every year.

Asean leaders came together at the 34th Asean Summit in Bangkok over the weekend, and environmental issues were at the top of the agenda. Thailand, who is Asean chair and played host, had chosen sustainability as its theme for the event.

In his interview with Singapore media, PM Lee said transboundary haze continues to be on the agenda.

But leaders were also increasingly concerned with waste exports, he said, citing recent reports in which the Philippines found that containers meant to be filled with recyclables turned out to be full of waste garbage instead.

Manila managed to send the trash back to Ottawa, Canada, but PM Lee noted that the issue of waste exports is a problem for many countries, "both practically handling this stuff, and certainly politically".

"To be seen as a place where rich countries dump their garbage I think it's not politically wearable. And so we are talking about it, trying to concert some kind of a common approach to it," he said.

In Singapore, waste is not exported but incinerated, and the little that cannot be burned is put in the landfill island, Pulau Semakau.

"But even Pulau Semakau is finite," PM Lee said. "The more we can recycle the better, so that's the message which the young people have understood, and it's good that they are focused on it."