Newly released, Japan's Fukushima's nuclear-contaminated water began to be discharged into the sea, and it may continue to be discharged for another 30 years.
The relevant person in charge of the Ministry of Ecology and Environment (National Nuclear Safety Administration) of the mainland said that it will continue to strengthen relevant monitoring work, timely track and judge the possible impact of Fukushima's nuclear contaminated water discharge into the sea on China's marine radiation environment, and effectively safeguard the interests of mainland countries and people's health.
This "man-made disaster" has begun, what impact will it have on the marine ecological environment and human health? What are the possible dangers of eating Japanese seafood in the future? Southern + journalists spoke with experts.
Experts interviewed:
Jiang Ningyi, Leader, Director, Professor and Doctoral Supervisor of the Department of Nuclear Medicine Science, Seventh Affiliated Hospital of Sun Yat-sen University
Zhang Li, researcher and doctoral supervisor of the South China Sea Institute of Oceanology, Chinese Academy of Sciences
Xie Wei, professor and doctoral supervisor of the School of Marine Sciences, Sun Yat-sen University
Yao Fengchao, Associate Professor, School of Marine Sciences, Sun Yat-sen University
The picture shows the storage area of nuclear-contaminated water Source: CCTV
"It's like constantly irradiating X-rays in the body"
South+: What's in the contaminated water?
Jiang Ningyi: According to research, Japan's nuclear-contaminated water may contain 64 radionuclides such as tritium, strontium-90, cesium-137, cobalt-60, and carbon-14. Radionuclides have carcinogenic, teratogenic and mutagenic properties on organisms, which can damage the DNA of people and organisms, cause genetic mutations and offspring malformations, and induce a variety of cancers.
For example, tritium can be ingested by the human body through the respiratory tract and skin, and it is easy to accumulate in the human body and cause radiation damage; Cesium-137 can cause soft tissue tumors and cancers, such as ovarian cancer and bladder cancer; Iodine-129 is prone to thyroid cancer.
South+: How should Japan understand Japan's claim that the contaminated water has already been treated?
Xie Wei: According to the data released by the Japanese side, the removal efficiency of nuclear wastewater treatment systems for a variety of nuclides is very unstable, and the concentration of some nuclides in the treated nuclear contaminated water varies by up to 100,000 times, and the removal effect of tritium, carbon-14 and iodine-129 is poor.
Zhang Li: Japan claims to have processed most of the nuclides other than tritium and carbon-14, but there are two issues worth noting. First, can the contaminated water reach the level of safety they claim? Are other more hazardous radionuclides really completely removed?
Second, there is no historical precedent for such a large-scale discharge of nuclear-polluted water into marine waters, and the actual degree of harm may not be judged by the cognition of closed environment and small-scale water bodies.
South+: How do radionuclides harm the human body?
Jiang Ningyi: For example, strontium-90 and cesium-137, they will remain in bone and muscle tissue after entering the human body, just like installing an X-ray machine in the body, irradiating 24 hours a day, although the amount of radiation is smaller than X-ray, but the long-term impact cannot be underestimated.
South+: Do radionuclide effects have to be long-term?
Jiang Ningyi: It is necessary to discuss by category. The first thing to understand is the half-life of radioactive material, which to put it simply, refers to the time it takes for radioactive material to decay into half of its original level. After a half-life, only half of the radioactive material remains, after another half-life, a quarter remains, and so on.
We go to the hospital for X-rays, and the radiation can be a few seconds at a time, and the radioactivity hardly resides in the body.
The Department of Nuclear Medicine will use a very small amount of radionuclides for examination or treatment, but the use of them is very short, such as technetium-99 for examination, the half-life is about 6 hours, and the half-life of iodine-131 for the treatment of hyperthyroidism is about 8 days. With the advancement of technology, the amount of radionuclides used for examination is getting lower and lower, and the impact is becoming less and less; Therapeutic nuclides remain in specific areas of the body and are safe for the rest of the body.
But radionuclides in nuclear-contaminated water are completely different. The half-life of strontium-90 and cesium-137 just given is about 30 years, even after two half-lives, it will have a 1/4 effect after 60 years. They affect more than just one person, one generation, and may alter the genetic material of the human body, causing indelible effects for generations.
South+: What other impact will it have on children, pregnant women, etc.?
Jiang Ningyi: Children and adolescents are more sensitive to radioactivity than adults, and long-term consumption of a large amount of radioactive contaminated seafood, or exposure to nuclear-contaminated water, may lead to developmental deformities. In pregnant women, fetal malformations can occur.
Numerical simulation of ocean circulation in the western Pacific Ocean, Sun Yat-sen University. In the picture, yellow is an ocean current, and a small-scale vortex will move westward; The black arrows indicate the main direction of the current.
Small-scale vortices carry nuclear-contaminated water to mainland coasts
South+: Will nuclear-contaminated water affect mainland coasts?
Yao Fengchao: Yes. While not the main impact, it does have an impact.
The main structure of the North Pacific Circulation is a clockwise circulation, and the Kuroshio (famous ocean current, named for the dark blue color of the water) near Fukushima is dominant, and the Kuroshio flows mainly eastward after leaving Japan, so the main direction of diffusion of nuclear contaminated water is to the east.
But at the same time, small-scale vortices can carry nuclear-treated water westward into the coastal areas of the mainland. Previous studies by the Tsinghua University team and the German team have pointed out that the impact of nuclear contaminated water will reach the mainland coast after a period of time.
South+: Japan plans to continue to discharge nuclear-contaminated water for 30 years or more. Will the currents change direction and turn to the continent during this period?
Yao Fengchao: The direction of the North Pacific circulation is fixed on a large scale and is unlikely to change. However, studies have shown that if Japan continues to emit, nuclear pollutants will gradually spread over time, with implications for the world's seas.
South+: What are the threats that nuclear leakage will bring to marine ecology?
Zhang Li: Strictly speaking, we don't know the threat posed by this nuclear contaminated water, because we haven't started to discharge it yet, so we can only speculate based on theory.
However, the Fukushima nuclear accident occurred in March 2011, and there has been a lot of research on the accident. For example, polonium-210 from the Fukushima nuclear reactor was detected in bluefin tuna caught off the coast of California in August 2011.
Even 10 years after the incident, in 2021, new research showed that becquerel (a unit of radioactivity, higher activity indicates greater radioactivity) can still be detected in freshwater fish 22 kilometers away from the nuclear power plant, which exceeds the standard of caesium-137, which shows that the impact of the nuclear leak is far-reaching.
South+: What are the possible effects of discharging nuclear-contaminated water only theoretically?
Zhang Li: Radionuclides entering the ocean pollute the marine ecological environment through seawater diffusion and ocean current transport, and enter organisms through biological absorption and food chain transport.
The first to be affected may be microbial communities near the discharge area, which exchange and iterate quickly with environmental substances, and radionuclides such as tritium and carbon-14 may act more pronouncedly on them. Changes in their community structure can have unpredictable impacts on other parts of the ecosystem.
Xie Wei: There are many links in the marine ecosystem, and they maintain a balance with each other. If the contaminated water has a drastic impact on some of these links, such as a large decrease or increase in the number of a key species, it can disrupt the balance of the entire system. Such damage may not be reversed in a short period of time.
The famous water pollution incident occurred in Japan
South+: How are contaminants in marine organisms generally detected?
Zhang Li: Generally, marine organisms that need to be tested, such as fish, shellfish, etc., are collected through fishing and other methods, brought back to the laboratory for dissection and sample pretreatment, and then selected corresponding professional equipment for detection and analysis according to different pollutant types.
In the case of fish, for example, it is mainly to detect contaminants in muscles. The muscles of fish account for about ninety percent of body weight, and most of the fish we eat also eat muscles, so detecting muscles is more representative.
South+: Do radionuclides accumulate step by step in the food chain?
Xie Wei: In the food chain, organisms with high trophic levels (such as fish) feed on organisms with low trophic levels (such as algae, zooplankton, etc.), so pollutants such as radionuclides may be transmitted from low to high and accumulate in the bodies of fish with high trophic levels.
For example, strontium-90 will accumulate in foods such as fish and shellfish, and after human ingestion, strontium-90 can replace calcium ions into human bones, continuously releasing radiation energy, aggravating the risk of bone cancer, leukemia and so on.
South+: Will these accumulated radioactive elements eventually affect humans?
Zhang Li: I do marine ecotoxicology, and in this field, one of the most serious pollution incidents in human history occurred in Japan.
In 1956, the strange disease incident in Minamata Bay, Japan, caused a sensation in the world, the patient's brain central nervous system and peripheral nerves were damaged, the hands and feet were deformed, and severe cases of nervous disorders and even death, this disease was named Minamata disease. Local factories discharge mercury-containing wastewater into the sea, and after mercury is ingested by aquatic organisms, it is enriched through the food chain, and then eaten by humans to cause harm, which becomes Minamata disease.
The enrichment of cesium-137 in the contaminated water is similar to that of mercury in marine organisms, and the higher up the food chain, the higher the concentration of cesium-137. Moreover, cesium-137 is radioactive and has a half-life of about 30 years, and once it enters the organism or human body, it will have long-term radiation effects, which may be more harmful than mercury.
South+: Will this be another Minamata disease incident?
Zhang Li: The current data is not enough to speculate. But I believe that a responsible country or institution should do a full, open and transparent study.
The effects of Minamata disease continue to this day, and Japan suffers from it; And the impact of nuclear-contaminated water can be global, and it is not known who will ultimately "pay".
South+ trainee reporter Wu Yanan Reporter Zhong Zhe
【Author】 Wu Yanan; Zhong Zhe
【Source】 Southern Press Media Group South + client