Misti Leon avoids checking weather forecasts or listening to news when temperatures rise. “This period of the year is incredibly challenging for me,” Leon says. This summer, temperatures in many parts of the U.S. have reached triple digits, shattering long-standing heat records; both June and July were recorded as the third warmest months since 1850.
She steers clear of any mention of the term “heat dome,” which describes a meteorological event where the atmosphere traps hot air, leading to elevated temperatures. It was during a record-breaking heat dome in Washington in 2021, when temperatures climbed to 108°F, that Misti lost her mother, Juliana Leon.
Julie, as she was affectionately known, was driving home from a doctor’s appointment on June 28, 2021, with her windows lowered when she began to feel the intense heat. She pulled off the highway onto a residential street before losing consciousness and was discovered two hours later. The official cause of Julie’s death was hyperthermia; her internal temperature was 110°F at the time of her passing.
Misti’s mother died at 65, on the hottest day ever recorded in Washington state, during a heat wave that scientists determined was not natural. An international team of scientists concluded in 2022 that the heat experienced that day would have been impossible without human-induced climate change. The heat dome, which persisted from mid-June to early July, was linked to more than 250 deaths in the United States and 400 in Canada.
Now Misti is suing seven major oil companies—including Shell, Chevron, and ExxonMobil—for wrongful death. She alleges that their knowledge that fossil fuel use was causing catastrophic environmental harm, coupled with their failure to adequately warn the public, created the conditions that led to her mother’s death.
“These companies possessed this information, they were aware of it, and they had an opportunity to share it and potentially mitigate the effects. Because of their choices not to be open and honest about it, there have been deaths, and that includes my mom,” Leon states.
A 2024 study found that 80% of the world’s global fossil CO2 emissions since 2016, following the signing of the Paris climate agreement, can be attributed to just 57 oil, gas, coal, and cement producers. Consequently, oil companies have faced numerous climate lawsuits over the years.
“Over the past decade, oil and gas companies have encountered dozens of lawsuits in the U.S. filed by cities, states, and counties, alleging that the oil and gas industry concealed its knowledge about climate change for decades and misled the public about the problem,” says Ben Franta, associate professor of climate litigation at the Oxford sustainable law program, who is not involved with this lawsuit. California, Minnesota, and Delaware are among the states that have initiated cases against Big Oil regarding climate deception, though no case has yet proceeded to trial.
However, the lawsuit filed May 29 on behalf of Julie Leon is the first legal action against oil companies based on an individual dying from an event exacerbated by climate change. “They knew, decades ago, with great accuracy what our climate would be like today, and then they deliberately deceived the public, not just in Washington state, not just in the United States, but worldwide, about their knowledge of their role in climate alteration. Therefore, we are alleging that they are responsible for that change,” says Misti’s attorney, Timothy Bechtold. “That alteration is what they are responsible for. And that alteration is ultimately, what we allege, is the cause of death of Misti’s mom.”
“The stakes are enormous,” says Franta, who draws a comparison between this case and precedent-setting lawsuits filed against tobacco and opioid companies.
The lawsuit, which was submitted to the Superior Court of Washington for Kings County, is the first personal tort suit brought against major oil companies for individual loss—with Misti’s legal team seeking direct financial compensation for wrongful death. The suit also asserts that companies are liable for failure to warn under Washington’s product liability act and public nuisance laws.
BP, which manages the Olympic Pipeline Company, ConocoPhillips, and Phillips 66 stated they do not comment on pending litigation. Shell declined to comment. Exxon Mobil did not respond to TIME’s request for comment.
In a statement to TIME, Chevron Corporation’s counsel, Theodore J. Boutrous, Jr. of Gibson, Dunn and Crutcher LLP, wrote: “Exploiting a personal tragedy to promote politicized climate tort litigation is contrary to law, science, and common sense. The court should add this far-fetched claim to the growing list of meritless climate lawsuits that state and federal courts have already dismissed.”
Leon’s lawsuit alleges that as early as the 1960s, the decade Julie Leon was born, oil companies were aware of how burning fossil fuels would impact the environment—but they downplayed and withheld that information from the public. By the 1980s, the American Petroleum Institute and major fossil fuel companies, like Exxon, had conducted extensive research on climate change.
“They were monitoring climate science and predicting when the world would notice climate change was occurring, and forecasting many of the impacts that we observe today,” says Franta.
By the 1990s, companies initiated a disinformation campaign that continued into the early 2000s, publishing advertisements disguised as editorials in major newspapers. Internal memos show Exxon’s strategy was to “emphasize the uncertainty in scientific conclusions” about climate change.
Today, major oil companies acknowledge the climate crisis, but they have also faced accusations of greenwashing. A 2022 study published in a journal examined the records of ExxonMobil, Chevron, Shell, and BP and found that the companies’ actions on climate change very rarely aligned with their stated pledges.
For Misti, the legal action is about holding oil companies accountable for what they knew about climate change—and the profound impact of concealing that knowledge.
“I cannot bring my mom back. No matter what happens, that loss will forever be present. However, hopefully, with sufficient awareness, knowledge, and accountability, we can prevent this from happening to other people and spare others from experiencing this kind of loss,” she says. “Unfortunately, I was affected in a very deep way. But I am not the only one, and that is what keeps my focus on accountability.”