Oregon’s most populous county on Thursday sued major oil and gas companies over a deadly 2021 heatwave that killed dozens of people.

The defendants should be held responsible, the lawsuit alleges, for their role in fueling the climate crisis.

From 25 to 28 June 2021, an unprecedented heat dome blanketed the Pacific north-west. The record-shattering temperatures killed 69 in Oregon’s Multnomah county and hundreds more across the region, marking one of the most destructive weather disasters in American history.

“It was this real crisis situation,” said the Multnomah county chair, Jessica Vega Pederson. “It really struck this community and this area in ways that no other event ever, honestly, had.”

The new lawsuit, filed at a state circuit court in Portland, draws on research showing the scorching heat was exacerbated by climate breakdown. It aims to hold 17 fossil fuel companies and interest groups – including Exxon, Shell, Chevron, BP, Koch Industries and the American Petroleum Institute – accountable for their role in the event.

“The heat dome that cost so much life and loss was not a natural weather event. It did not just happen because life can be cruel, nor can it be rationalized as simply a mystery of God’s will,” the litigation says. “Rather, the heat dome was a direct and foreseeable consequence of the Defendants’ decision to sell as many fossil fuel products over the last six decades as they could.”

The suit seeks $50m in damages for the 2021 heat dome’s consequences and $1.5bn for future climate damages. And it demands the defendants spend an additional $50bn on a county plan to upgrade public healthcare services and infrastructure to protect residents from coming extreme heat events and other climate disasters.

“We know that our need to mitigate, to take action, to respond in the future is going to escalate over time as climate change worsens,” said Pederson. “We really want to make sure that we have the resources to do that.”

When 2021’s heatwave struck, Multnomah’s county seat, Portland, broke its own heat records on three consecutive days. The city’s streetcar cables melted. Officials recorded 97 hospital visits for heat illness – nearly the same number of cases they would usually see all summer. Many who perished were seniors and lower-income people who did not have access to air conditioning. A woman and her cat shelter inside a tent at the Oregon convention center cooling station in Oregon, Portland, in June 2021. A woman and her cat shelter inside a tent at the Oregon convention center cooling station in Oregon, Portland, in June 2021. Photograph: Kathryn Elsesser/AFP/Getty Images

At the time, Pederson said she and other officials were “overwhelmed” by the need to distribute supplies, manage cooling centers and otherwise keep communities safe. But later, upon reviewing research showing that the climate crisis made the event at least 150 times more likely, she began to think about accountability.

“Fossil fuel companies and industry organizations really lied about the impacts of using these fossil fuels,” she said. “So it’s about, how do we hold them accountable … since we are dealing with the effects today and we are going to be dealing with these effects for a long time to come.”

The defendants, the challengers allege, committed negligence and fraud and created a public nuisance by covering up their knowledge of the dangers of using fossil fuels. Attorney Jeffrey Simon, a partner at Simon Greenstone Panatier and a law professor of mass tort litigation, said the case was based on well-established laws. skip past newsletter promotion

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“There are no new laws or novel theories being asserted here,” he said.

The suit cites oil companies’ well-documented history of sowing doubt about climate science.

The litigation was filed by the law firms Simon Greenstone Panatier; Worthington & Caron; and Thomas, Coon, Newton & Frost – firms that specialize in large-scale catastrophic harm litigation, including legal actions related to asbestos and lead poisoning. None of the three firms have previously brought climate litigation.

It comes as part of a wave of similar litigation against fossil fuel interests. Since 2017, seven states, 35 municipalities, the District of Columbia, and one industry trade association have sued major oil and gas corporations and lobbying groups, alleging that defendants have for decades known about the dangers of fossil fuels and yet actively hid that information from consumers and investors.

“Multnomah county has joined the growing ranks of local governments that are standing up to big oil and fighting to make these polluters pay for the catastrophic damage they knowingly caused and lied about for decades,” said Richard Wiles, president of the Center for Climate Integrity, which has supported plaintiffs who have filed similar litigation.

The litigation is among the first to demand damages from fossil fuel companies for a specific climate disaster. Last year, Puerto Rico filed a federal lawsuit against oil and coal firms for their role in 2017’s Hurricane Maria.

“Communities should not be forced to pay the price for these catastrophic climate damages while the companies that caused the crisis perpetuate their lies and rake in record profits,” said Wiles. “The people of Multnomah county deserve their day in court to hold big oil accountable.”