Johnston Atoll is a remote, unincorporated U.S. territory situated approximately 750 nautical miles southwest of the Hawaiian Islands in the North Pacific Ocean. Beginning in the 1930s, the atoll was transformed into a sprawling, multi-purpose military installation under U.S. control. It served as a naval refueling depot, an airbase, and a site for testing and storage of various military materials, including chemical weapons. Military activities conducted there, particularly during the Cold War era, introduced a lasting environmental hazard, raising the question of whether the atoll remains radioactive today.
Historical Sources of Radioactive Material
The primary source of radioactive contamination on Johnston Atoll stems not from successful nuclear detonations but from a series of high-altitude missile launch failures during the 1962 Operation Fishbowl tests. These tests involved launching Thor missiles equipped with nuclear warheads. The failures caused the dispersal of unexploded weapons material onto the atoll itself.
The most significant incident was the “Bluegill Prime” test on July 25, 1962, where a missile malfunctioned on the launch pad and was intentionally destroyed before liftoff. This catastrophic failure scattered weapons-grade plutonium across the launch site on Johnston Island and into the adjacent lagoon. Another failed launch, the initial “Starfish” test, also resulted in radioactive debris falling back onto the island. The contamination from these accidents consisted of dispersed materials from the nuclear device’s casing and payload, rather than the fallout associated with an actual nuclear yield.
Current State of Residual Contamination
Johnston Atoll is still contaminated with residual radioactivity today. The specific radionuclides that remain are Plutonium-239 and its decay product, Americium-241. Plutonium-239 is an alpha-emitting radionuclide with a half-life of over 24,000 years, meaning the contamination is a permanent fixture of the environment.
The contamination is concentrated in specific areas of the atoll. The highest levels are found at the former missile launch complex and in the lagoon sediments near the launch site. Americium-241, a decay product, also contributes to the hazard and is used to monitor the contamination. The presence of these long-lived radionuclides makes the soil and sediment in these localized areas unsafe for unrestricted human access.
Remediation Efforts and Cleanup Projects
Following the 1962 accidents, immediate cleanup actions were taken to mitigate the most severe contamination. This involved scraping the top layer of contaminated soil and debris from the launch area, which was then used as a ramp to load other contaminated scrap onto barges for ocean disposal. This initial process inadvertently incorporated some of the plutonium-laden fill into the lagoon environment.
More comprehensive remediation efforts were conducted in the following decades, including projects to process contaminated soil for volume reduction using specialized technology. Authorities surveyed the island and collected approximately 45,000 tonnes of soil contaminated with radioactive isotopes. This soil was ultimately stockpiled in a designated, fenced area on the north side of Johnston Island. The closure of the Johnston Atoll Chemical Agent Disposal System (JACADS), which incinerated chemical weapons, also included a separate cleanup and demolition process, certifying that the facility met closure requirements for hazardous waste.
Environmental Management and Restricted Access
Today, Johnston Atoll is managed as a National Wildlife Refuge by the U.S. Fish and Wildlife Service (USFWS) and is part of the Pacific Remote Islands Marine National Monument. This designation protects the atoll’s significant marine biodiversity and thriving seabird populations.
Due to the persistent presence of radioactive contamination, the atoll is entirely closed to the general public. Entry is strictly controlled and requires a special use permit from the USFWS, granted only for activities consistent with conservation purposes. Ongoing environmental surveillance monitors the levels of residual radionuclides in the soil, the marine ecosystem, and local wildlife.