What’s in the water?
It’s a question that may forever haunt current and former residents living in or around Andersen Air Force Base in Yigo, Guam.
A joint investigation conducted by independent media outlets, The Margin and The War Horse, found cancer-linked pesticide contamination was present for many years in building foundations, nearby soil, and the area’s water supply.
Federal officials knew about it. But multiple residents, past and present, told the investigative outlets that they were never privy.
“We spoke to community members who described their reaction as moving from disbelief to anger and to guilt,” Hugo Hodge, the reporter for The War Horse who authored the joint investigation, told Military.com. “Many were wondering if they exposed their children to toxic pesticides by simply cooking them dinner each night.”
Military.com reached out to Andersen Air Force Base for comment.
Hodge’s investigative piece, published Sept. 22, raises serious questions of who knew what, and when, about pesticide contamination at Andersen Air Force Base that apparently spread into Guam’s drinking water.
Records Show Regulators Knew For Decades
The banned pesticide Dieldrin has been detected in the water serving Yigo, a village near the base, for at least 17 years, according to the report, citing public records that show regulators knew about the contamination as early as 2008.
“Dieldrin is a pesticide that was widely applied to building foundations to prevent termites, beginning in the 1940s,” Hodge said. “It was banned in 1987 over concerns that it was harmful to humans and the environment.
“Military documents that we reviewed from the Guam EPA under the Freedom of Information Act show that Dieldrin was widely applied to housing foundations on Andersen AFB in the 1950s.”
But Hodge’s investigation found the pesticide didn’t stay on the foundations. It remains present in the soil, as well as in the area’s water supply.
“Andersen Air Force Base sits directly above an aquifer that supplies 80% of Guam’s drinking water,” Hodge said. “The Dieldrin that was discovered in the soil is essentially in the basin above the well that is supplying the Yigo community with water.
“What makes it worse is that the Guam Water Works Authority and the Guam EPA later admitted that they’d been working on a solution to the Dieldrin in the drinking well since 2023. That’s nearly two years before residents were told anything.”
Hodge said he reviewed thousands of pages of previously unreleased military and regulatory records that documented a years-long Department of Defense effort to excavate and relocate pesticide-contaminated soil at Andersen AFB.
He also documented the apparent spread of the contamination beyond building foundations, including a 2004 pesticide management report produced by a military contractor called GHD, which found that the pesticide residues that were applied decades ago are still in the ground today.
“Pesticides are very persistent in the environment,” he said. “They stick to the soil, and they can also attach themselves to dust particles and travel long distances in the wind.
“The issue in a place like Guam is that it is a tropical island with very high rainfall, frequent typhoons and storms, which is all happening above an aquifer with a very thin veneer of soil.”
Who Knew What, When Raised Concern
For Hodge, the contamination was just the start of his troubling discoveries.
Questions over who knew about it, and who was kept in the dark, raised even more concern.
“Internal military emails show the Guam EPA had really little to no idea about pesticides in the soil on Andersen, and the years-long work to excavate it,” Hodge said. “So, after the public found out about the Dieldrin contamination in the drinking water, our research found that the Air Force did not inform environmental regulators about what it knew about its soil management activities.”
Hodge said his findings went even further.
Early on, Joint Region Marianas (JRM), which is the command responsible for Guam and the Marianas Islands, distanced themselves from the Dieldrin contamination when it was first made public in September 2025.
Reporters obtained emails from JRM stating: “At this time there was no data that identified a specific origin of Dieldrin, and any decisions regarding response actions would be guided by verified findings and applicable environmental regulations.”
Meanwhile, area residents had apparently been suffering unexplained health effects, including a cluster of cancer and reproductive issues diagnosed in the 2000s.
Residents on Base Did Their Own Digging
One individual interviewed was a former military spouse and resident named Tessa Robinson, who lived on Andersen Air Force Base for a three-year period and saw friends of hers on base suffering miscarriages, reproductive issues and stillbirths.
“Some of her friends who were living at Andersen were dying from aggressive cancers,” Hodge said. “These were women, otherwise healthy women, in their 30s.”
Hodge said Robinson did some investigating of her own and found an online survey, created by another former Andersen resident, asking people who had lived there in the 2000s about serious or unexplained health problems.
She circulated it on social media and military community networks, and it drew more than 150 responses reporting aggressive cancers, reproductive issues, stillbirths, birth defects and other illnesses.
“However, it must be noted that this was a survey of self-selected respondents who were recruited online. Their diagnoses have not been independently verified, and the responses don’t establish that anything on Andersen actually caused these health problems,” Hodge added.
“But what it did do was identify a previously unrecognized group of former residents who believe they have experienced serious health problems during and after living there.”
EPA Versus US Air Force at Supreme Court
The pesticide investigation comes as the Air Force is locked in a related battle at the Supreme Court over EPA oversight on Guam and at other U.S. military bases regarding so-called “forever chemicals” known as PFAS.
The core dispute involves the military’s open detonation of unexploded World War II-era ordnance and munitions on Tarague Beach.
“So, while these two cases involve different contaminants, they both sort of document an environmental regulator at odds and often struggling to get the Air Force to comply with its requests, and being kept in the dark,” Hodge said.
As for the pesticide contamination, JRM, the command responsible for Guam and the Marianas Islands, told Hodge that they are coordinating with the Guam EPA to address the potential origin and movement of Dieldrin.
Also, the Guam EPA and the federal EPA made a joint request in December last year, according to Hodge, essentially saying that a probable source of the Dieldrin contamination is the base housing.
“They are now working with environmental regulators,” Hodge said. “But it should be noted that the documents and the emails that we reviewed show environmental regulators were kept in the dark about what the Air Force knew and when.”
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