A knock on the door forced Cathy Flint to her feet. It had been five years since her diagnosis of multiple myeloma, a cancer that has left her with bones protruding from her neck and down her spine, bone damage and hunched shoulders.

On that day in spring 2023, her neighbor stood in her doorway with a letter.

It was a questionnaire from environmental lawyers asking residents in her Charleston, W.Va., neighborhood if they had experienced any injuries or ailments, including cancer, because of exposure to ethylene oxide — a gas, released by nearby chemical manufacturing plants, that federal agencies have said is linked to numerous cancers.

Flint looked toward the plants, one of which stood less than 750 feet away. It was the first time she had questioned how safe they were or wondered whether her cancer could be linked to exposure to potentially unsafe chemicals.

“It was just part of life in this valley. There’s plants everywhere,” said Flint, 64, a resident there for nearly 30 years. “I didn’t really think much about it. I thought it was safe. Evidently, it wasn’t.” This month, Flint filed a lawsuit in Kanawha County Circuit Court against Dow Chemical’s Union Carbide subsidiary and numerous other companies that manufacture the gas, often used to sterilize medical equipment. A growing number of lawsuits are taking on companies that release what plaintiffs claim are dangerous levels of an odorless, colorless gas associated with numerous types of cancer.

The lawsuit filed by Flint — who believes the gas caused her incurable multiple myeloma — alleges that the companies’ “dangerous, negligent, harmful and reckless emission of ethylene oxide gas” during production, storage and transportation of the substance caused high concentrations throughout the area.

Meanwhile, a slew of environmental groups have sued the Environmental Protection Agency in federal court, arguing that a March update of national emissions standards doesn’t do enough to protect residents from cancer-causing pollutants, including ethylene oxide.

“Over the years, there’s been no education of the public, by government agencies or anybody else, to advise people on what the risks are living in an area where there are countless toxic molecules belching out of these plants daily,” said Stuart Calwell, an environmental attorney representing Flint. “If you choose to keep those molecules, those dangerous instruments on your property, then you are responsible if any of them get out.”

In a statement, Union Carbide Corp. said the facilities in the area continue to operate in compliance with all their permits and have taken actions to reduce ethylene oxide emissions “below their already safe levels.” “UCC has successfully litigated these issues already in West Virginia” and is “ready to defend this misguided complaint,” the company said.

Calwell said Flint’s lawsuit is the first of more than two dozen to be filed by area residents who have claims related to cancer or other health issues, including Parkinson’s disease. At least 200 other people have made inquiries that his attorney group is still investigating.

Kelly McCown grew up on Flint’s block and lived in the area for over two decades. By the time she was 16, McCown learned that severe symptoms during her periods were a result of polycystic ovary syndrome — cysts on her ovaries — and that she also had cysts in her breast.

“I would say that I’m a rock,” the 44-year-old said with a wry laugh about her cysts and routine kidney stones. Doctors recently found cysts on her liver.

Doctors told her it would be nearly impossible to get pregnant. Concerned that the nearby chemical plants could be affecting her health, she said, doctors even suggested she consider moving. Now, McCown, working with Calwell, says she is in the process of filing a lawsuit against the same group of companies.

Current EPA standards for all air toxins limit the acceptable lifetime cancer risk to 1 in 1 million people. A mapping tool from the EPA shows that cancer risk for residents in Flint’s neighborhood was 300 in 1 million in 2020. The risk was 200 in 1 million in 2018, the year Flint received her diagnosis.

The Biden administration said the updated standards were expected to curb ethylene oxide emissions by more than 90 percent, also reducing the cancer risks. The administration estimated that the standards would put the cancer risk from ethylene oxide at or above 1 in 1 million — a reduction from about 7.2 million people to about 6.3 million — but advocates say that doesn’t go nearly far enough.

“That doesn’t really comport with EPA’s obligation to minimize the number of people who are exposed to cancer risk like that,” said Abel Russ, a senior attorney at the Environmental Integrity Project, a watchdog group. Lawyers are likely to challenge the EPA by alleging that the agency failed to reduce ethylene oxide emissions and to protect people from cancer.

“You could reduce emissions further, and it’s important that you do so, because this rule is going to leave nearly 6 million people in harm’s way,” said Russ, who is also director of the group’s Center for Applied Environmental Science.

Dealing with ethylene oxide is a top EPA priority, said agency spokesman Remmington Belford. Although the agency can’t comment on pending litigation, he said, it is “coordinating with air agencies to share information with communities about the risks from long-term exposure to [ethylene oxide] in the outdoor air and has provided technical support to air agencies as part of this work.”

Long-term exposure to ethylene oxide can increase the risk of various cancers, including breast cancer, leukemia and lymphoma, according to the EPA. It also has been linked to developmental complications, miscarriage and other reproductive impacts.

The gas is harmful to humans even at low concentrations.

The North Charleston community was “known as ‘Cancer Bottom’ for a while,” McCown said. Both of her paternal grandparents, who lived in the area, died of cancer.

“We didn’t realize that it was so dangerous,” McCown said. “You wouldn’t think that anyone would put something out that would hurt people, or that anyone would be allowed to put anything out to hurt anyone.” Flint was heartbroken when she was diagnosed with multiple myeloma, a cancer of the plasma cells. She has received stem-cell treatment and will have to undergo chemotherapy for the rest of her life. Multiple myeloma “eats holes in your bones,” she said, explaining why she gets monthly shots to strengthen them.

She said she worries about developing other cancers and noted that two of her neighbors have died of cancer in recent years. “I just hate it that I have to live this life. It’s not fun,” she said. A 2023 analysis by the Union of Concerned Scientists found that more than 14 million people live within five miles of facilities that emit ethylene oxide. Almost 60 percent of those people identified as people of color, and 31 percent are low-income.

In June, researchers at Johns Hopkins University found that ethylene oxide measurements across parts of Louisiana were routinely underestimated by the EPA’s screening tools, leaving communities at much greater risk for cancer than previously thought. The Hopkins researchers found that average concentrations at some locations were 10 times the EPA’s acceptable cancer risk for a lifetime of exposure.

The EPA risk model is based on estimates reported by the facilities, said senior author Peter DeCarlo, an associate professor in the university’s Department of Environmental Health and Engineering. “I think they’re very frequently, and most of the time, very big underestimates.”

Calwell hopes lawsuit’s like Flint’s will force regulators to consider the cumulative emissions in an area, instead of allowing emissions up to the maximum acceptable cancer risk.

Flint said she hopes her suit will also help the community understand more about emissions and the potential health risks.

“These plants need to be held accountable,” she said.