The publication this week of the UN nuclear watchdog’s positive assessment of Japanese plans to pump more than 1m tonnes of water from the wrecked Fukushima Daiichi nuclear power plant into the ocean has failed to placate opponents. China is fiercely opposed to the plans, despite a report by the International Atomic Energy Agency (IAEA) backing the scheme, while the support of the government of South Korea has failed to quell widespread public opposition to the idea in the country. The government in Seoul said on Friday that it “respected the IAEA’s review of plans by Japan and the plant’s operator, Tokyo Electric Power (Tepco), to pump water from the plant into the Pacific over the next 30 to 40 years”. The discharge would have “negligible consequences” for South Korea, it said in an attempt to win over a deeply sceptical public. The country’s ban on food and seafood products from the Fukushima region will remain in place, however. But South Korea, whose conservative president, Yoon Suk Yeol, is attempting to mend diplomatic fences with Japan over the countries’ wartime legacy, is a lone voice of support in the region. On the same day, China announced a ban on food imports from 10 of Japan’s prefectures over “safety concerns”, and said it would conduct stringent radiation tests on food from the rest of the country. “The Japanese side still has many problems in the legitimacy of sea discharge, the reliability of purification equipment and the perfection of monitoring programmes,” Chinese customs said. The IAEA review brought Japan closer to the start of the long operation to pump the water – a mixture of groundwater, rain that seeps into the area, and water used for cooling damaged nuclear fuel – into the ocean, with reports suggesting it will begin in August. About 1.3m tonnes of water stored in huge tanks on the site has been filtered through Tepco’s advanced liquid processing system (Alps) to remove most radioactive elements except for tritium, an isotope of hydrogen that is difficult to separate from water. The treated water will be diluted with seawater so that the concentration of tritium is well below internationally approved levels before being released into the ocean 1km from the shoreline via an undersea tunnel. The water is contaminated after being used to cool fuel rods that melted after the plant was hit by a powerful earthquake and tsunami in March 2011, triggering a triple meltdown at the Fukushima plant. Japan’s top government spokesperson, Hirokazu Matsuno, responded to criticism of the plan by saying that Fukushima Daiichi would pump far less tritium into the ocean than Chinese and South Korean nuclear facilities. Japan’s standard for the release of tritium, at below 22tn becquerels a year, is far stricter than that of its neighbours, Matsuno said. According to Japan’s trade and industry ministry, the Yangjiang nuclear plant in China discharged about 112tn becquerels of tritium in 2021, while the Kori power station in South Korea released about 49tn becquerels. That is unlikely to placate opponents in Fukushima, where fishing communities have warned the water discharge will undo more than a decade of work to repair the damage the meltdown inflicted on the reputation of the region’s seafood, which is subject to one of the world’s strictest radiation testing regimes. “We here in Fukushima have done absolutely nothing wrong, so why do they have to mess up our ocean?” said Haruo Ono, a fisher in Shinchimachi, 34 miles north of Fukushima Daiichi. “The ocean doesn’t belong to only us humans – and it isn’t a rubbish tip. “It’s been 12 years [since the meltdown] and fish prices are rising, so we were finally hoping to really get down to business. Now they’re talking about releasing the water and we’re going to have to go back to square one again. It’s unbearable.” Fisheries cooperatives in three prefectures were due to submit a petition with 33,000 signatures on Friday expressing their opposition to the water discharge. While their government has given Japan breathing room, many South Koreans remain sceptical of Tokyo’s safety assurances. Some are panic-buying salt amid contamination fears, while a Gallup poll conducted in June found 78% of South Koreans were either “very worried” or “somewhat worried” about potential harm to the marine environment. “It’s much more difficult to make sales now, as customers are asking more questions as they worry a lot,” said Jin Wol-sun, a stallholder at Seoul’s Noryangjin market, where market officials carried out random radiation tests on seafood in an attempt to reassure shoppers. Rafael Grossi, the head of the IAEA, conceded there had been a lack of unanimity among the IAEA scientists, who come from 11 countries, including China, involved in the safety review. One or two “may have expressed concerns” over the plan, he said in an interview with Reuters. “I heard that being said … but again, what we have published is scientifically impeccable.” China’s state-run Global Times newspaper on Thursday said Liu Senlin, a Chinese expert in the IAEA’s technical working group, was disappointed with the “hasty” report and had said the input from experts was limited and only used for reference. Other experts openly voiced concerns about the impact the discharge could have on marine and human life, and accused Tepco and the IAEA of cutting corners. “We have repeatedly pointed out to Tepco and IAEA substantive concerns we have with Japan’s approach and flaws in their methodology,” said Ferenc Dalnoki-Veress, an adjunct professor at Middlebury Institute of International Studies at Monterey in the US. Dalnoki-Veress, a member of a panel of scientists that advised the Pacific Islands Forum, cited Tepco’s controlled tritium-exposure experiments on fish, which he said included only three species that were being fed on commercial fish pellets rather than exposed smaller fish, which would normally be their food source. “We have repeatedly offered to help advise on how to conduct these experiments, but each time Tepco rejected them,” he said. “We take as proof that they are not truly interested in collecting relevant data that may demonstrate and confirm concerns regarding their present plans.” The “dumping” of treated water into the ocean, he said, would cause potentially irreversible damage to the local fishing industry. “When we think about the effect of radiation we can’t just think about the effect on the environment, we have to consider the effect on cultures, societies and peoples who suffer psychological effects, a sense of fear, and reputational damage. Trust has been broken, and it will be difficult to repair.” Shaun Burnie, a senior nuclear specialist with Greenpeace who regularly visits Fukushima, said claims that tritium posed no risk to human health were “scientifically bankrupt”. “The concern is not over external exposure,” Burnie said. “It is internal exposure to organically bound tritium that is the problem – when it gets inside fish, seafood, and then humans. When tritium gets inside cells, it can do damage. “Tepco and the Japanese government are making a conscious decision to increase marine pollution with radioactivity, and they have no idea where that will lead.” This article was amended on 7 July 2023. An earlier version misnamed Rafael Grossi as “Emanuel Grossi”.