A team of munitions disposal experts from Japan is in Palau to remove unexploded bombs lying dormant since World War Two.
The team intends to remove many hundreds of tonnes of depth charges, underwater in a shipwreck for seven decades.
Matsuko Ikeda from the Japan Mine Action Service says they will begin the clearance work by May at the latest.
"They are getting deteriorated," Ms Ikeda said.
"Some of them are leaking toxic acids right now, so it's very urgent to take off those bombs."
After seven decades underwater the weapons are corroding, posing a risk to the environment and the local population.
Ikeda told Radio Australia's program the picric acid found leaking from the bombs has caused headaches and dizziness in humans.
The clean-up team itself includes skilled ex-members of the Japan Maritime Self-Defense Force, who will be wearing special diving suits to prevent them from being affected by any toxic substances.
The Helmet Wreck site operation is expected to take a year and a half, but Ms Ikeda says they are surveying other sites that also need attention.