The health risks of eating ocean fish caught near Japan are low because seawater is diluting the radiation from the damaged Fukushima Dai-Ichi plant, said Robert Peter Gale, who coordinated medical relief efforts following the nuclear accident at Chernobyl.
“Eating fish is not something to worry about,” said Gale, a visiting hematology professor at Imperial College London who was in Japan this week to speak to doctors responding to radiation threats. “No one could afford to consume enough sushi to get radiation damage.”
The observations by Gale, who in 1999 was asked by the Japanese government to help treat victims of the nuclear accident in Tokaimura, may help allay concerns that have prompted Taiwan, Singapore, the U.S. and Australia to restrict some imports of Japanese fish.
The Fukushima Dai-Ichi plant may be in danger of emitting sudden bursts of heat and radiation, undermining efforts to cool the reactors and contain fallout. The potential for limited, uncontrolled chain reactions, voiced March 30 by the International Atomic Energy Agency, is among the phenomena that might occur, Chief Cabinet Secretary Yukio Edano told reporters in Tokyo yesterday.
Contamination of seawater found near the 40-year-old plant has increased. Radioactive iodine rose to 4,385 times the regulated safety limit on March 30 from 2,572 times the previous day, Hidehiko Nishiyama, a spokesman for Japan’s Nuclear and Industrial Safety Agency, said yesterday. No fishing is occurring nearby and the sea is dispersing the iodine so there is no health threat, he said.
Too little is known about the potential health risks, said said Gregory Hartl, a spokesman for the World Health Organization in Geneva. The United Nations health agency is advising people to “avoid consumption and harvesting” of aquatic animals and plants including fish, shellfish and algae “in areas considered to be seriously contaminated,” according to its website.
“Public health operates under the precautionary principle,” Hartl said in a telephone interview. “Measuring radioactive contamination in the sea and in fish is not something there is a whole lot of experience in.”
Since last week, the Fisheries Research Agency has tested samples from five types of fish caught off the coast of Choshi city in Chiba prefecture, the fishing area south of the Fukushima nuclear plant. The institute has been monitoring radioactivity in Japanese marine life for the past five decades, after nuclear arms testing by the U.S. and the former Soviet Union raised concerns about contamination.
The institute detected 3 becquerel per kilogram of cesium-137 in anchovy, but nothing in samples from alfonsino, mackerel, spear squid and olive flounder. The level was far below the standard set by Japan’s health ministry of 500 becquerel per kilogram for fish.
Radioactive elements in the ocean are significantly less harmful than if they are airborne or permeate the soil, Gale said.
“From a radiation safety point of view, if it’s got to go somewhere, that’s the best place,” he said. “Radiation is least dangerous to humans when diluted, so the sea is the perfect place.”
The potential for maritime contamination occurs once airborne radioactive particles fall on the water and enter the maritime ecosystem. This happens when elements including iodine-131 and cesium-137 are absorbed by microscopic organisms such as phytoplanktons and zooplanktons, said Qian Pei-yuan, a professor of marine biology at Hong Kong University of Science and Technology.
“Any particle in the water falls into their feeding appendages or apparatus,” Qian said. “If other small fish eat them, then they will go through the food chain.”
Larger fish which live longer and survive by eating smaller fish have a higher chance of being contaminated. Sharks, porpoises and whales are particularly at risk, he said.
“The level of contamination of fish tissues depends on the level of contamination consumed and the exposure time of fish and how much they accumulate or expel contaminants,” Qian said.
While dilution lessens the risks the further marine life is from the source of contamination, Qian said people should avoid any seafood from the immediate vicinity of the Fukushima plant.
“Be alert, but don’t panic,” he said.