More than half a century after the United States ignited 67 nuclear weapons in the central Pacific, a former naval base in the Bay Area continues to bear its nuclear legacy.
Residents were informed last week by the San Francisco Department of Health that tests conducted at the former Hunters Point Naval Shipyard site in November 2024 showed that airborne plutonium-239 radiation levels exceeded the Navy’s “action levels,” requiring the military to investigate further.
The city and residents were not informed until 11 months after the initial report.
Hunter’s Point, a 500-acre peninsula jutting into San Francisco Bay, served as a military research laboratory studying the effects of nuclear weapons from 1946 to 1969 after World War II. The research primarily focused on how to decontaminate U.S. warships and equipment targeted by the atomic bomb, but the experiment left much of the shipyard full of radioactive contaminants and toxic chemicals.
For the past 30 years, the Navy has been trying to clean up the area, now a U.S. Superfund site, with the long-term goal of redeveloping it into new housing and parks.
But some Bay Area community leaders argue that haphazard restoration efforts and lackluster public engagement are putting the health and safety of residents in the Bayview-Hunters Point neighborhood, which is next door to the former shipyard, at risk. And they point to the Navy’s nearly one-year delay in notifying it of elevated plutonium-239 measurements taken in November 2024, as the very latest example.
Plutonium-239 is a radioactive isotope and a byproduct of a nuclear bomb explosion. The elevated readings for November 2024 are from a 78-acre parcel of land in the northeast portion of the shipyard known as Parcel C.
“The City and County of San Francisco is deeply concerned by both the scale of this exceedance and the lack of timely notification. Such delays compromise our ability to protect public health and maintain transparency. Immediate notification is a regulatory requirement and is critical to ensuring community confidence and safety,” San Francisco Health Officer Susan Phillip wrote.
Navy officials and some health experts maintain that although radiation levels detected at the scene were above the Navy’s action levels, they did not pose an immediate or significant threat to public health. A Navy spokesperson said daily exposure to this level of plutonium-239 for a year would be less than one-tenth the radiation dose from a chest X-ray.
“The San Francisco Department of Public Health’s letter refers to a single anomalous air sample that detected plutonium-239 above regulatory action levels,” a Navy spokesperson said in a statement to the Times. “Regulatory action levels have been intentionally and conservatively set below the level of health concern, and a single detection of Pu-239 at this level does not pose a risk to human health or public safety.”
The Navy said it has collected more than 200 air monitoring samples from Parcel C since beginning the field survey in 2023. The November 2024 sample was the only reading with elevated plutonium-239, a Navy spokesperson told the Times.
Plutonium isotopes cannot pass through solid objects, so they emit relatively harmless alpha radiation outside the body. But inhaling these radioactive particles can damage your lungs and increase your long-term risk of developing certain cancers, according to the Centers for Disease Control and Prevention.
“Our general concern about alpha emitters is that they get into the body whether it’s through inhalation, ingestion, or accidental injection,” said Kathryn Higley, a professor of nuclear science at Oregon State University.
But a lack of transparency and an 11-month delay in reporting measurements has heightened community distrust and raised questions about the military’s ability to safely clean up the contaminated shipyard. In 2000, for failing to notify residents of a fire at a dangerous landfill in Hunters Point. In 2017, two employees of the consulting firm Tetra Tech were hired by the Navy to assess radiation levels at Hunters Point to avoid additional cleaning efforts in some areas of the shipyard.
The presence of all levels of radioactive air pollutants further exacerbates the health risks in the Bayview-Hunters Point neighborhood, which already faces high exposure to toxic diesel particles from big rigs plying nearby highways and cargo ships visiting the Port of San Francisco.
The Hunters Point Biomonitoring Foundation, a local nonprofit, found concerning levels of toxic substances in urine screenings it provided to several nearby residents, particularly the elderly and those living near the former Naval Shipyard.
“Now you’re talking about adding one of the most destructive radionuclides known to the human cardiopulmonary system to the chemical load,” said Dr. Armitha Porter-Sumchai, the foundation’s medical director and principal investigator.
“The particulate matter is enough to kill a person,” Samchai added. “But when you add a little plutonium-239 to it, it’s a recipe for death.”
Philippe, the San Francisco health officer, said in a statement that he met with Navy officials on Oct. 31 and received assurances that air and dust monitoring is “ongoing” and that military officials are “reviewing duct management practices to ensure full public health protection.”
As a result, “there is no need to take immediate action from a public health safety perspective,” she said, adding that her office will continue to closely monitor the situation.
Other experts argued that the situation was exaggerated. Phil Rutherford, a radiation risk expert and corporate consultant, called the delay in notification “unacceptable,” but said the San Francisco Health Department’s letter was “given the low levels of radioactive material.”
Higley, a professor at Oregon State University, said the site had a long history of delays and scandals, likely adding to the backlash from local residents. “I understand (residents’) frustration in wanting this area to be cleaned up so it can be used safely,” Higley said. “And there are many reasons why this process takes so long. But from a radiological perspective, the actual residual radioactivity at the site is fairly modest.”
In November 2024, a Navy contractor was grinding asphalt on the property. The construction project, although unrelated to the site’s historic contamination, prompted the Navy to monitor air quality issues. One of the air samplers on Parcel C collected 8.16 times more plutonium-239 at 10 to 15 picocuries per milliliter, a Navy spokesperson said. This is twice the level of measures set.
Navy officials sent the samples to a laboratory for analysis, and the first results came back in March 2025, showing high radiation levels. In April they ordered the lab to reanalyze the samples. In follow-up analysis, plutonium-239 radiation levels were below action levels.
Between May and September, the Navy “further investigated the test results and systematically reviewed the laboratory’s procedures and practices to ensure compliance with standards,” a Navy spokesperson said. “A third party also conducted an analysis of the institute’s performance.”
In late September of that year, the Navy briefed the U.S. Environmental Protection Agency and several government agencies in California about elevated airborne radiation levels from plutonium-239 in preparation for an upcoming regional conference. This information was later brought to the San Francisco Department of Health.
At one point, the Navy released some of Parcel C’s air quality data collected between October and December 2024, where it administers several environmental monitoring reports. It only showed that the low plutonium-239 radiation levels from the reanalysis were below action levels.
A Navy spokesperson told the Times it was “uploaded in error.”
While the Navy worked to verify the results, “the Navy became aware that an incomplete report had been uploaded and immediately removed it from its website,” the spokesperson said.
All of this has caused confusion and concern among local residents and supporters alike. Navy officials are scheduled to attend the Hunters Point Shipyard Citizen Advisory Committee meeting on Nov. 17.
During field surveys at the shipyard, the Navy is monitoring plutonium-239 and several other radioactive elements that may have resulted from historic fallout from nuclear weapons tests.
Acquired by the Navy in 1940, Hunter’s Point was originally a base for ship construction, repair, and maintenance during World War II. After the war, it became the home of the Naval Radiation Protection Laboratory, a military research facility dedicated to studying the effects of nuclear weapons and radiation safety.
The Navy bombarded a U.S. military convoy with nuclear weapons as part of the The irradiated ship was towed to Hunter’s Point, where scientists used materials and hardware to test decontamination methods.
In 1974 the shipyard closed. The U.S. Environmental Protection Agency placed the site on the Superfund list in 1989 because of hazardous chemicals and low-level radioactive contamination.
The Navy has led cleanup efforts, including excavating contaminated soil and demolishing buildings. Parcel A, the base’s largely residential area, was turned over to San Francisco and redeveloped with new townhouses and condominiums. 300 artists live and work in the former naval building.
However, dangers continue to arise during the ongoing restoration work.
In recent years, the Navy has recovered radioactive materials such as dials and deck markers that were coated with paint containing radium isotopes, which gives a glow-in-the-dark effect. Sumchai, medical director of the Biomonitoring Foundation, said they observed large amounts of contaminated soil being stockpiled in areas without protective fences to prevent contaminants from spreading outside the site.
“I consider this a local public health emergency,” Sumchai said. “I think we should do everything we can to contain the infection and, if necessary, safely remove people from areas of documented exposure.”
But to the casual observer, this place seems unremarkable.
Hunter’s Point juts out into San Francisco Bay, just north of Candlestick Park, the former home of the San Francisco 49ers. Beyond the abandoned barracks and dry dock, much of the site is now an empty space of grass and reeds, with unobstructed views of the bay.
The cleanup site, including Parcel C, remains fenced off and only authorized personnel are allowed access to the site.
On a recent weekday afternoon, crows flew and cawed over the long-vacant shipyard building. Meanwhile, construction workers and trucks were moving up and down Hill Drive, a steep road leading to brand new homes that stand guard over the former shipyard.
And there was no way to find out what was going on other than to wait for a new Navy report.
