It's an issue dating back to 1944 to 1963, when the U.S. Coast Guard operated a long-range navigation or Loran station on Cocos Island.

Coast Guard Engineer Mark Marini from Honolulu spoke with KUAM News about that decision that's making waves over the years.

"That we have found that most of the Loran station, prior to any environmental laws came into play, disposed of stuff via landfill, dumping, and it was very standard protocol back then unfortunately," he said.

A fish consumption advisory has been in effect at Cocos Lagoon since 2006 when high levels of PCBs, or polychlorinated biphenyls were discovered in the fish.

It's a toxic chemical banned in the U.S. for its harmful health effects.

"Fast forward to 2016-2017, NOAA was asked to come out and do some human health risks on the fish in the lagoon," Marini said. "So they did bio sampling. For not only PCB but DDT, which we weren’t aware was an issue."

The banned pesticide DDT was also found in the sediment and fish prompting the coast guard to take action.

"We had a project and the intent was to check the islands, specifically the Loran station specifically, for DDT, along with any further PCB source that may be on the island. And to verify that the diesel plume isn’t moving."

The recent remedial investigation found higher levels of PCBs concentrated at Dano’s Pier.

We asked Marini if that meant the fish could be too toxic to consume.

"It's not like you’re consuming straight-up PCB oil or anything like that," he said. "It’s just that the level that the EPA has said ‘Hey we feel comfortable’ and they’re very conservative on that number. So we want to do the same. But it’s in the vicinity of that Dano Pier. If you go out into the lagoon, we are getting the same numbers as NOAA which is good."

Marini added that they didn’t find any source of PCB or DDT on the island.

"We basically combed it and combed it over the years for stuff," he said. "We did take things out. We did find things. But at this stage, whatever is happening in the water is in the water, not on the island."