Tokyo Electric Power Company (TEPCO) has announced that they plan dump 777,000 tons of tritium-contaminated water into the Pacific Ocean, as part of their multi-billion dollar recovery efforts at the Fukushima Daiichi nuclear power plant. The total amount of radioactive material involved would be approximately 115 times the annual safety limit for this type of discharge. The move has yet to be approved by the Japanese government, although TEPCO says that they still plan to go ahead with the decision.

The waste water in question was used as coolant in an attempt to control heat levels in the site’s nuclear reactors, following the series of meltdowns triggered after a tsunami struck Japan’s east coast in 2011. Most of the radioactive contaminants can be easily separated from water; tritium, however, is a super-heavy isotope of hydrogen (carrying two neutrons that ordinary hydrogen doesn’t have) that is difficult to extract from water. It has a half-life of 12.32 years, and thankfully only gives off a low-energy beta particle when it decays — a form of radiation that can’t penetrate the outer layer of our skin.

Tritium is relatively harmless to humans if ingested in small doses: it has a short biological half-life of only 7 to 14 days, helping mitigate health risks if the otherwise extremely rare isotope is ingested. This also means that it does not accumulate in the body, as is the case with other radioactive byproducts like iodine-131 and caesium-137. Also, the total amount of tritium that is slated for disposal should only amount to less than 5 grams (0.18oz); TEPCO claims that the material will dissipate to safe levels when it disperses in the ocean.

Despite the low health risks involved, there are still protests against these disposal plans: fishermen in the area argue that public fears of their catches being contaminated may devastate their businesses, as many countries have already banned imports on specific Japanese fish in the wake of the original meltdowns. Additionally, environmentalists fear that this one-time event might be used as an example by other players in the nuclear industry to improperly dispose of difficult to process waste.

"They say that it will be safe because the ocean is large so it will be diluted, but that sets a precedent that can be copied, essentially permitting anyone to dump nuclear waste into our seas," explains Green Action Japan anti-nuclear activist Aileen Mioko-Smith.