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Widespread pollution was found in fishes across six atolls in the Marshall Islands in a new study from researchers at the University of Hawaii and National Oceanic and Atmospheric Administration.

at the request of the Marshall Islands Marine Resources Authority and tested fish for the presence of metals, certain pesticides, polychlorinated biphenyls and polycyclic aromatic hydrocarbons.

“This is essentially the first study of its kind there,” said Megan Donahue, a research professor at the Hawaii Institute of Marine Biology and co-director of the University of Hawaii’s marine biology graduate program.

Previous studies looking at pollution in the Marshall Islands have often focused on the lingering effects of U.S. nuclear testing. Fish contamination surrounding Kwajalein, the site of a longtime U.S. military base, is already well known. In 2019 the U.S. Army surrounding the atoll posed dangerous cancer risks to Marshallese families.

But the data on contaminants in reef and pelagic fishes across five other atolls — Majuro, Jaluit, Utirik, Rongelap and Wotje — is revelatory.

The results were mixed. Some positive news was that the researchers found very low levels of organochlorine pesticides in fish they tested. But high levels of mercury above both U.S. and European Union thresholds were found in pelagic fish from Jaluit and Rongelap, and lead levels were highest in herbivorous fish such as surgeonfishes.

Polycyclic aromatic hydrocarbons, chemicals that can come from burning fossil fuels, wood and garbage, were found in low concentrations in most study samples.

Donahue said that she sees the study as a sketch map of the fish contamination issue that will be helpful to the Marshall Islands Marine Resources Authority as it determines where to focus its community education and research efforts.

“Locally caught fish are an important source of nutrition, both in the Marshall Islands and globally, and fish and fishing have inherent cultural value. Pollutants, like those measured in this study, put these nutritional and cultural values at risk,” she said. “We hope that this study will help our partners in the Marshall Islands to develop guidance appropriate to their people and place.”

Catherine Pirkle, a public health associate professor at the University of Hawaii who was a collaborator on the paper, said she was particularly concerned by the high level of mercury in dogtooth tuna and the combination of pollutants found in the camouflage grouper.

But she cautioned the results warrant more discussion and research before affecting food choices.

“The good news was yes; we saw the presence of marine pollutants but we didn’t see anything shocking,” she said. What stood out to her was the ubiquity of the contaminants even at low levels. “It really highlights that marine pollution is a global problem.”

Ocean Dumping Grounds

Donahue noted even trace amounts of contaminants can affect coral reproduction. Coral reefs are already under threat from climate change, she said, and limiting land-based pollution can help prevent putting them under further stress.

Pollutants like PCBs were more concentrated in areas with U.S. military activity, Pirkle said, adding that’s something she and her fellow researchers had expected. But the study didn’t specify the causes of the contaminants found in fish. She added they also didn’t collect data on fish consumption locally and aren’t issuing any warnings yet about what people should or shouldn’t eat.

Still, the study is significant not only for its scope but for the challenges researchers had to overcome to complete it. Donahue said she and other researchers at the University of Hawaii were scheduled to fly to the Marshall Islands in mid-March of 2020.

Then the pandemic hit, and the country closed its borders. Plans to work in person with local partners were dashed and community relationships had to be built and strengthened over Zoom.

Fish were shipped to Hawaii, and researchers found themselves scrambling to find an extra freezer in the face of Covid supply chain woes. The fish were dissected in a lab in Kaneohe and eventually sent to a lab on the mainland for specialized analysis.

Robert Richmond, who leads the Kewalo Marine Laboratory at the University of Hawaii, wasn’t involved in the study. Upon reviewing it, he said the analysis underscores how although people think diluting marine pollution is a solution, fish and other creatures that people eat still ingest the contaminants.

“I think it’s a very valuable study to show the importance of understanding of what happens when we use the ocean as a dumping ground for all kinds of pollutants,” he said. “There is this very strong link between environmental health and human health, and especially in the islands where people depend on edible resources culturally, economically and ecologically.”

One strength of the study, he said, was how it showed not just the presence but concentrations of pollutants in various fish. He noted such contaminants can affect the ability of fish to reproduce.

Richmond noted the study is particularly salient in light of the Japanese government’s plan to pour processed nuclear wastewater from the . Richmond is part of a panel of scientists who have raised concerns about the way the pollution could affect the ecosystem.

“The continued use of the oceans as a dumping ground either on purpose or incidentally, is a byproduct of human activities, is certainly taking its toll,” Richmond said. “It’s taking its toll on the health of the oceans and the health of everyone who depends on the oceans. And for that reason, we need to change the way in which we do things.”

Donahue said she and her fellow collaborators plan to publish more findings from their research in the Marshall Islands and to also conduct similar studies in Hawaii.