Theresa Opalinski was warming up her border collies for their agility training one day in 2011 when she couldn’t catch her breath. Her husband, Michael, suggested they go to urgent care, and a few days later, a specialist drained more than a liter of fluid from her left lung. After ping-ponging between local hospitals, she underwent an exploratory surgery, which confirmed she had mesothelioma.

The diagnosis puzzled them. Asbestos exposure is the only known cause of the vicious cancer, which kills most people who get it within a few years. Because cases often involve occupational exposure in industries like shipbuilding and construction — and because it can take decades for the cancer to develop — mesothelioma is sometimes thought of as an old man’s disease. Theresa was just 53 and held a master’s in public administration. She had been a congressional aide, she’d managed a nonprofit, she’d worked in marketing. Never with asbestos.

Far from her mind was the fact that she and Michael had grown up a mile away from a plant in North Tonawanda, New York, that used a type of asbestos that is blue in color to make industrial plastics. The plant’s owner, OxyChem, closed and demolished the facility in the 1990s. But the company has since faced at least 10 lawsuits alleging that the plant released so much asbestos into the environment that residents of the surrounding neighborhood developed mesothelioma and other ailments associated with the toxic substance.

The blue dust settled onto windowsills and on a Little League field and atop fresh snow, lawsuits allege and residents recall. It got stuck in workers’ hair and on their clothes and wound up on the seats of their cars and inside their homes. One woman, married to a plant employee, died after years of washing her husband’s asbestos-soiled uniform, her family said.

OxyChem declined to comment on the lawsuits involving its plastics plant. Most of the cases have been settled out of court, records show. Two are pending. In some of the cases, OxyChem said it was not responsible for the plaintiff’s injuries. In at least one, the company said the lawsuit had not been filed by the legally required deadline.

The latest suits, filed earlier this year, come as the company is forced to reckon with its other uses of asbestos — and contemplate a future without it. Unlike some 60 other countries, the United States hasn’t banned asbestos. OxyChem is one of two chemical companies that import and use the potent carcinogen to make chlorine. For decades, it has maintained that the workers in its chlorine plants face no threat of exposure; in recent months, it has used that argument to fight a proposed federal ban on the substance.

But last week, ProPublica reported that asbestos accumulated in a number of areas inside and around OxyChem’s chlorine plant in Niagara Falls, New York, and that employees worked amid the dust until the plant closed late last year. They often went without protective suits or masks in the building where asbestos was removed from equipment, they said. “We were constantly swimming in this stuff,” one former employee said.

Though the two OxyChem plants that have come under scrutiny used different types of asbestos for different industrial processes, there are striking similarities between the facilities, which are 10 miles apart. Experts say both situations speak to OxyChem’s poor track record of containing asbestos in its plants, and they both illustrate the carcinogen’s long tail and broad impact.