Fukushima discharge row: Hong Kong experts warn over radioactive contamination risk for Japanese seafood if waste water released
- Shellfish, oysters and large fish may still be at risk of contamination despite treatment of waste water from Fukushima Daiichi power plant, according to specialists
- Japanese Consul General Kenichi Okada says city’s reputation will ‘surely be damaged’ if import ban goes ahead in response to plan to discharge waste water into the sea
Experts weighed in on contamination risks as Japan planned to discharge waste water from the Fukushima Daiichi power plant into the sea as early as this month.
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Some specialists told the Post that the risks could not be eliminated for marine creatures caught in Japanese waters outside the 10 prefectures covered by Hong Kong’s proposed ban.
Professor Rudolf Wu Shiu-sun, a marine ecology professor from the Education University of Hong Kong, said oysters, clams and other bivalve mollusks with two-part hinged shells were at higher risk of accumulating radioactive substances from the water and the food they fed on.
“Some of the big fish, which are feeding on small fish, rely on this trophic chain and these are [also] more susceptible. Smaller fish and seaweed have lower accumulation,” he said, adding his assessment was based on research on general toxins found in the ocean.
Wu expressed his reservations about releasing tritium, a radioactive isotope of hydrogen found in the treated water, into the sea and warned it would be difficult to track its mutations.
“If tritium enters the marine environment, it will change into organic tritium, which can accumulate along the food chain … it’s irreversible, it’s high-risk, so I would take a more cautionary approach,” he said.
Professor Kenneth Leung Mei-yee, who chairs the Advisory Council on Food and Environmental Hygiene, also said predatory species higher up in the food web would have a greater chance of bioaccumulation and biomagnification of radioactive substances.
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Bioaccumulation refers to the accumulation of substances within an organism over time, while biomagnification refers to the increase in the concentration of a substance as it moves up the food chain.
“Benthic species are frequently in contact with contaminated sediment and may be exposed to elevated levels of [radioactive substances],” Leung said.
Examples include clams, oysters, crabs, lobsters, sea stars, sea urchins and species of fish, such as flounder and halibut.
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Studies have shown that some species of clams and snails are more sensitive to radiation than others such as crustaceans and polychaete worms.
“Filter-feeding organisms such as oysters, mussels and scallops could acquire [radioactive substances] via their foods,” he said.
The Hong Kong government earlier said it would immediately ban food imports from Tokyo, Fukushima, Chiba, Gunma, Tochigi, Ibaraki, Miyagi, Niigata, Nagano and Saitama prefectures if Japan released the treated nuclear waste water.
Tokyo is expected to begin the process in August but has yet to set a specific start date. The whole process could take 30 years.
The waste water will be treated using the Advanced Liquid Processing System, which removes most of the radioactive elements, including the stronger contaminants caesium and strontium. The primary remaining contaminant is tritium.
According to Luk Bing-lum, chairman of the Hong Kong Nuclear Society, tritium is a relatively weaker radioactive substance that only has a biological half-life of one to two weeks.
“Like all organisms, we drink water and expel water through urination and perspiration. So the impact of tritium on us is minimal as it has a low level of bioaccumulation and will not stay in our bodies,” he said.
Secretary for Environment and Ecology Tse Chin-wan had estimated that about HK$300 million (US$38.4 million), or HK$10 million a year, could be spent by the Hong Kong government on testing Japanese food imports every year if there was no ban.
While the government stopped short of explaining how they chose the 10 “high-risk” prefectures, some of which were landlocked, Leung of the advisory body said the risk of exposure to radioactive substances would be lower on the coasts north of Fukushima.
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He referred to a study done in 2011 shortly after the nuclear meltdown, which showed that water currents from Fukushima flowed southeast.
Hongkongers are the fourth-biggest group of foreign tourists in Japan, with more than 186,300 visitors from the city heading there in June alone. Concerned travellers could consider bringing along a dosimeter to test radiation levels in their food for peace of mind, said Luk of the nuclear society.
He visited the site of the nuclear meltdown in March and consumed food and drink from the prefecture during his trip. Life in Fukushima was largely “back to normal” and the local government was very active in sampling aquatic produce, Luk said.
“You can use a dosimeter or gamma spectrometer to test for radioactivity in your food for peace of mind, but usually levels are so low that it will not show up on the [testing devices],” he said.
