WASHINGTON — The worsening wildfires, floods and hurricanes of climate change threaten at least 60% of U.S. Superfund sites, and efforts to strengthen the hazardous waste sites are stalling in some vulnerable regions as the Trump administration plays down the threat, a congressional watchdog agency says.

The Environmental Protection Agency responded to this week’s report of the Government Accountability Office by rejecting many of its findings. That includes dismissing GAO investigators’ recommendation that the agency and Administrator Andrew Wheeler explicitly state that the EPA’s mission includes dealing with climate change and its increased risk of disasters breaching Superfund sites.

Assistant EPA Administrator Peter Wright largely avoided the words “climate change” in his formal response to the GAO in a statement Monday.

“The EPA strongly believes the Superfund program’s existing processes and resources adequately ensure that risks and any effects of severe weather events, that may increase in intensity, duration, or frequency, are woven into risk response decisions at nonfederal NPL sites,” Wright said.

The GAO report emphasizes the challenges for government agencies under President Donald Trump, who belittles the science of climate change.

Wheeler’s highest-profile public remarks on the matter came in a March CBS interview. The former coal lobbyist called global heating “an important change” but not one of the agency’s most pressing problems.

“Most of the threats from climate change are 50 to 75 years out,” Wheeler said then, rejecting conclusions by scientists that damage to climate from fossil fuel emissions already is making natural disasters fiercer and more frequent.

The GAO review comes after a 2017 review by The Associated Press found that 2 million people in the U.S. live within a mile of 327 Superfund sites in areas prone to flooding or vulnerable to sea-level rise caused by climate change.

The AP analyzed national flood zone maps, census data and EPA records in the wake of Hurricane Harvey, which flooded more than a dozen Superfund sites in the Houston area, with breaches reported at two. At the time, an EPA spokesman derided AP’s reporting as “fear-mongering.”

GAO investigators looked at 1,571 Superfund sites — locations around the country contaminated by hazardous waste being dumped, left out in the open or otherwise improperly managed. That number does not include Superfund sites owned by the Defense Department and other federal agencies.

At least 945 of the sites are in areas identified as at greater risk of floods, storm surge from major hurricanes, wildfires or sea-level rise of 3 feet or more, the GAO says.

Broken down, that includes 783 Superfund sites at greater risk of flooding under climate change, 234 Superfund sites at high or very high risk from wildfires and 187 sites vulnerable to storm surge from any Category 4 or 5 hurricane, the researchers said.

Senate Democrats asked for the GAO review. A dozen senior congressional Democrats on Monday urged the agency to follow the GAO recommendations.

“By refusing to address the worsening impacts of climate change — from flooding to wildfires to more frequent extreme weather events — at our nation’s Superfund sites, this EPA is putting public health at risk,“ said Sen. Tom Carper of Delaware, the ranking Democrat on the Senate’s Environment and Public Works Committee.

GAO investigators cited California’s 150-year-old Iron Mountain mine, where Superfund operators daily prevent tons of toxic sludge from pouring into the Sacramento River system, source of one-fifth of the state’s water.

One major wildfire last year overran the Iron Mountain Superfund site, nearly destroying its water treatment system and risking a massive, poisonous explosion if flames reached the heart of the mine, the GAO said. Firefighters used special gear to stop the flames. Site operators have since swapped out PCB pipes carrying away the toxic waste for flame-resistant steel ones.

And east of Houston along the San Jacinto River, record rains under Hurricane Harvey dissolved part of a temporary cap on a 40-acre Superfund site, exposing contaminated material. EPA testing there afterward found dioxin at more than 2,000 times the maximum recommended level.

Superfund sites in that coastal part of Texas “are incredibly vulnerable,” said Jackie Young, head of the Texas Health and Environment Alliance advocacy group.

The EPA’s current five-year strategic plan does not include goals or strategies for handling growing risks under climate change, the GAO report said. The most recent previous five-year plan, under President Barack Obama, listed addressing climate change as one of four main strategic goals. Obama-era plans specifically addressed climate change’s impact for Superfund sites, the investigators said.

The current EPA said in a statement Monday it recognizes the importance of making the toxic waste sites “resilient” against weather extremes.

A GAO review of climate-change-minded planning for keeping the arsenic, mercury, PCBs and other dangerous waste at Superfund sites away from the public and environment found big differences among the 10 EPA regions nationally.

Officials at four EPA regions were able to point to changes they’d made at Superfund sites to try to adapt to climate change, the report said. At the other EPA regions, however, officials said they had not looked at climate-change projection for flooding or rainfall to gauge risks at Superfund sites, investigators said.

In the EPA region covering Texas and four other south-central states — a region that includes the Gulf of Mexico and Houston and other oil and petrochemical hubs frequently battered by hurricanes — officials “told us that they do not include potential impacts of climate change effects or changes in the frequency of natural disasters into their assessments,” the GAO investigators wrote.

In the Great Lakes states, meanwhile, regional EPA officials “told us that they do not have any formal direction on how to address risks from climate change and are waiting for EPA headquarters to provide information on how to do so,” the report said.