Fish radioactive Fukushima, few health risks - The Sciences

Into The risk to human health due to the consumption of fish contaminated by radioactive material spilled at sea during the accident at the Fukushima nuclear power plant can be quantified in the United States in two cases of fatal cancer of more than ten million inhabitants. This is the conclusion of a new study on the dose absorbed by the flora and fauna of the Pacific Ocean following the accident, which is two orders of magnitude lower than the lowest reference value proposed for radiation protection of ecosystems (red)

The environmental contamination by radioactive material always arouse a lot of attention in the media and in public opinion and no exception in the case of a recent research that revealed the presence of radionuclides released in the nuclear accident at Fukushima Daiichi in the flora and fauna of the Pacific Ocean.

A study appeared in the “Proceedings of the National Academy of Sciences” written by Nicholas S. Fisher of the Faculty of Marine Sciences and weather at Stony Brook University in New York State, has now calculated the dose to which it was exposed biota (the set of flora and fauna) in the Pacific, and the possible health consequences for the human being, in particular quantifying the risk to the level of exposure of the U.S. population, which is negligible because far below the level of natural radioactivity and other sources of radioactivity such as medical devices or air travel.

Into More than two years after the accident in Fukushima, the strongest concerns about the loss of radioactive material are related to secondary sources of contamination, ie to radionuclides absorbed by the body of animals and plants that enter the food chain, typically fish and seafood.

A lot of frozen tuna from Japan confiscated by Thai authorities a few days after the accident at Fukushima Daiichi (© Narong Sangnak / epa / Corbis) A case in point of how news is disseminated about it was the communication of the presence of cesium-134 and cesium-137 in some specimens of tuna Pacific bluefin (Thunnus orientalis ) migrated from the waters of Japan to those in California. It was in that case of an official news spread by government authorities, who had also pointed out that the concentration levels of the two

radionuclides were well below all the safety limits established at the national level all over the world. Nevertheless, the news of tuna contaminated with cesium isotopes released from the accide nt at the Fukushima power plant has prompted a state of red alert in the media and in public opinion.

This gap between public perception and actual risk, according to Fisher and colleagues, is due in part to the fact that the studies report the activity of radionuclide concentrations in the tissues of marine biota but not the estimates of doses and risks to human consumers of contaminated fish.

Wholesale tuna at the fish market in Tokyo (© Eyal Warshavsky / Corbis) In this study, the authors have calculated the radiation doses absorbed by various marine organisms and humans due to a possible consumption of contaminated tuna. The analyzes show that in all cases the doses are mainly due from polonium-210, an alpha emitter natural: the doses arising from radionuclides of Fukushima were from three to four orders of magnitude lower. The doses of marine biota are also two orders of magnitude lower than the lowest reference value of radioprotection proposed for ecosystems, equal to ten MicroGray hour (the gray is the unit of measurement of radiation absorbed dose).

The additional dose due to the consumption of tuna contaminated with radionuclides from Fukushima in the United States was estimated between 0.9 and 4.7 microsieverts (the sievert is the unit of equivalent dose, and quantifies the biological damage from radiation). These doses are significantly lower than those due to other contamination already present in foods, natural radioactivity, which for example in Italy is on average about three millisieverts, or to diagnostic apparatus: in the case of a chest X-ray, it is 0, 02 millisieverts, or 20 microsieverts.

In conclusion, according to the study, despite the uncertainties remain in the assessment of the risks from exposure to ionizing radiation at low doses, the damage due to human consumption of contaminated tuna Fukyshima of the accident, the worst case scenario, namely that of an equivalent dose of 4.7 microsieverts, can be estimated in two cases of fatal cancer in more than 10 million people, always considering a population exposed to natural radioactivity, other sources of food contamination and radioactive sources used in diagnostic equipment.