The Japanese government has approved a plan to discharge the water used to cool the damaged nuclear reactors. They claim that the treated water is harmless to people and nature.

Japan’s nuclear regulator has approved plans by the operator of the stricken Fukushima nuclear power plant to release treated radioactive wastewater into the sea in 2023. Researchers say the operation is safe and the risks to the environment are minimal.

The plan was submitted by Tokyo Electric Power Company Holdings in December based on last year’s government decision to release the wastewater as a step to clean up and decommission the plant.

A powerful earthquake and tsunami in 2011 destroyed Fukushima’s cooling systems, melting three reactors and releasing large amounts of radiation. Water used to cool the three damaged reactor cores, which remain highly radioactive, has since leaked out, but it has been collected and stored in tanks.

Since then, there have been concerns about the potential threat to human health from the leaking effluent containing tritium, a byproduct of nuclear energy production and a possible carcinogen in high concentrations.

The government says more than 60 isotopes sampled for treatment can be reduced to meet safety standards, with the exception of tritium, but it is safe if diluted. Scientists say the effects of long-term exposure to low doses on the environment and humans are unknown, and that tritium may have greater human exposure when consumed in contaminated fish than in water.