The water had been used to cool the reactors in the defunct nuclear plant that was damaged in the 2011 tsunami

In spite of Beijing and some local residents’ fierce opposition, Japan’s plan to discharge treated radioactive water into the ocean from the tsunami-wrecked Fukushima plant was approved by the U.N.’s nuclear watchdog on Tuesday.

After a two-year review, the International Atomic Energy Agency concluded that Japan’s plans had a “negligible radiological effect on people and the environment”.

The plan would see enough water to fill 500 Olympic swimming pools into the Pacific Ocean.

The Japanese government maintains that the process is safe since the water used to cool the fuel rods of the Fukushima plant was treated after the earthquake and tsunami damaged it in 2011.

Japanese fishing unions oppose the plan, saying it would further tarnish their reputation which had already taken a hit following the 2011 disaster, after which some countries banned their products.

Beijing has emerged as the most vocal critic of the plan, leading calls to scrap the proposal from several neighbouring countries on the grounds of threats to marine and public health.

A petition from the regions around the plant has garnered more than 250,000 signatures since the proposal was first made.

Japan says most radioactive elements have been removed from the water except tritium, which is difficult to separate from water, but the released water will be diluted well below internationally approved levels of tritium.