Japan has started to release nuclear wastewater, should we be worried?

[New Sancai Compilation and First Release] Japan's decision to release water from the Fukushima nuclear power plant has caused panic in the local fishery, as well as in China and several Pacific island countries. China and Hong Kong, which import more than $1.1 billion a year in seafood from Japan, currently ban all seafood imports from Japan, citing health concerns.

Tokyo demanded that the ban be lifted immediately. "We strongly encourage experts to discuss based on scientific evidence," Japanese Prime Minister Fumio Kishida told reporters on Thursday. Japan has previously criticized China for spreading "claims that have no scientific basis."

Japan remains steadfast in its pledge that the water is safe. The discharge process takes 30 years and was approved by the International Atomic Energy Agency, the intergovernmental organization that sets safety standards for radioactive waste management. Seawater samples taken after the water was released showed radioactivity levels more than seven times lower than the limit set by the World Health Organization for drinking water.

Now that the world's top radioactive waste authority supports Japan's plans, should we also dismiss concerns raised by Pacific nations and local fishermen as mere irrational fears of radioactivity?

polluted water

In 2011, a magnitude 9.0 earthquake hit the northeast coast of Japan's main island of Honshu, triggering a tsunami that devastated much of the country's coast. The tsunami knocked out backup power supplies at the Fukushima plant and caused three reactors to melt down. The event is considered one of the worst nuclear accidents in history.

Since the accident, water has been used to cool the damaged reactor. But the cooling water has been contaminated because the reactor core contains large amounts of radioactive elements, including ruthenium, uranium, plutonium, strontium, cesium and tritium.

Contaminated water is stored in more than 1,000 steel tanks at the power plant. It has been treated to remove most of the radioactive contamination, but traces of the radioactive isotope tritium still remain.

Removing tritium from water is a challenge. Tritium is a radioactive form of hydrogen that forms water molecules with properties similar to ordinary water.

It does decay over time to form helium (which is less harmful). But tritium has a half-life of slightly longer than 12 years.

This is relatively fast compared to other radioactive pollutants. But it will still take about 100 years for the radioactivity of tritium in the Fukushima tanks to drop below 1%.

To safely store water that will continue to be polluted during this period (approximately 100 tons of water per day), plant operators will need to build an additional 2,700 storage tanks. This may not be practical - Fukushima will run out of storage space very quickly.

Should we be worried?

Past studies have examined the health effects of tritium exposure. However, much of this research has focused on organisms such as zebrafish and mussels. For example, research in France found that titrating tritium in the form of water caused DNA damage, altered muscle tissue and altered movement patterns in zebrafish larvae.

Interestingly, the zebrafish were exposed to tritium concentrations similar to those estimated in the Fukushima tanks. But the tritium from the Fukushima nuclear power plant is significantly diluted before it is released, and its levels are nearly a million times lower than the levels that cause health problems in zebrafish larvae.

Marine life in the discharge zone will continue to be exposed to this low concentration for the next 30 years. We cannot definitively rule out this potential impact on marine life. And, importantly, the results of these studies cannot be generalized to all animals.

Notably, however, organisms can eliminate half of the tritium in their bodies through biological processes (known as the biological half-life) in less than two weeks.

but that's not all

In theory, potential health problems associated with tritium could also be exacerbated by the presence of other chemical pollutants. In China, researchers found that exposing zebrafish larvae to tritium and genistein, a natural compound produced by certain plants and commonly found in water, resulted in reduced survival and hatch rates.

The amount of tritium used in this study was more than 3,000 times less than that used in the French study. But it's still nearly 250 times higher than the level emitted from Fukushima into the Pacific Ocean.

However, other chemical pollutants present in the ocean near Japan or in storage tanks could interact with tritium in a similar way, potentially negating the benefits of dilution.

Given our lack of accurate knowledge of the exact chemical contaminants present in Fukushima's tanks and their potential combined effects with tritium, it may be unwise to casually ignore the very real concerns raised by Pacific nations and fishermen.

(Author: Edmond Sanganyado is Assistant Professor of Environmental Forensic Medicine, Northumbria University, Newcastle)

(compiled by: Wang Jimin)

(Editor in charge: Jiang Qiming)

(Source of the article: New Sancai first release)