Krystal Kim, a 53-year-old mother of two from Philadelphia, was 10 when her mother suggested she use Johnson’s Baby Powder to stay “fresh” and “clean smelling.” She continued using it for decades, on her face, between her legs and on her sheets. Many women use baby powder as a feminine hygiene product, applying it to their bodies and breathing in airborne powder.

Five years ago, Ms. Kim learned she had invasive ovarian cancer and was treated with chemotherapy. Parts of her colon and intestines were removed. Ms. Kim, one of the plaintiffs in the Missouri case, wants Johnson’s Baby Powder taken off the shelves and, if not, warnings put on it.

Before the Missouri verdict, Johnson & Johnson had been able to knock back most of the legal challenges that connected talcum powder alone to cancer, by claiming, in part, that the scientific research was flawed and offering studies to the contrary.

Of the six cases that Johnson & Johnson has lost on that issue by itself, three decisions were overturned on appeal, one is still being appealed, and one plaintiff won her case but was awarded no damages. One verdict, for $110 million, has been upheld by a judge; the company is appealing.

But asbestos, unlike talc, is an indisputable carcinogen. Even trace amounts are considered dangerous. Its dagger-like fibers penetrate deep into tissue and can lead decades later to cancer of the lungs, voice box and ovaries, and to mesothelioma.

Several lab tests, some conducted in the past few years by plaintiffs’ lawyers, have found evidence of asbestos in talc. The link between asbestos and ovarian cancer was first reported in 1958, and in 2011, the International Agency for Research on Cancer said it was a cause.