Is there a link between talcum powder and ovarian cancer? 

• SLUG SIGNORINO

This is about the use of talcum powder and the risk for ovarian cancer. If there is in fact a link between the two, since it's regularly used on babies, wouldn't there be an increased number of females contracting cancer at a younger age?—H. Gearhart

You've found a rare bird indeed, H.: A question about the whole talcum-powder-and-cancer debate for which there's an actual answer. If talc is related to ovarian cancer at all, which is still a big if, the disease doesn't result from use in infancy, for the simple reason that when babies are exposed to it, it's for only a short time—the diaper years. The alleged cancer association, on the other hand, pertains to long-term use, over decades and decades, by adult women looking to keep things clean and dry.

That was the setup in one recent high-profile lawsuit against the company that's taken most of the anti-talc heat, Johnson & Johnson. The plaintiff, a medical receptionist from Los Angeles named Eva Echeverria, started using J&J baby powder on her genital area daily once she began menstruating, around 1965, and kept at it until 2016, some nine years after she was diagnosed with ovarian cancer. Thousands of women have filed similar lawsuits, and a number have won in court; what made Echeverria's suit special was that last summer a jury awarded her a massive $417 million judgment. The justice system has spoken, right? Well, the story keeps going.

But let's pause and freshen up everyone's memory. Talcum powder comes from talc, a mineral comprising mostly magnesium, silicon and oxygen. In its natural state, talc can contain a little asbestos, too, though commercial talc products have been free of that carcinogen since the 1970s. Still, the asbestos angle means there are actually two routes by which it's been suspected that talc causes cancer. The first involves talc miners, who according to a 1995 study were more likely than the general population to suffer both lung cancer and non-cancer lung diseases, leading the National Institute for Occupational Safety and Health to claim tentatively that talc exposure might be "linked" to illness. This isn't completely settled, either—other researchers implicate the miners' smoking habits, and working underground increases your exposure to radon, itself a source of lung cancer.

But the major controversy is about ovarian cancer, where inhaling talc (or asbestos) isn't the issue. Here the theory is that when sprinkled on the perineal area, talc particles move up the genitourinary tract and lodge themselves in the ovaries, where subsequent inflammation leads over time to cancer. Concerns along these lines have been around for nearly 50 years; I fielded a question on the topic back in 1990. Some doctors continue to insist there must be a connection, but information gathered in a few big studies since 2000 has tended to point the the other way. The most substantial recent data comes from a 2014 paper in the Journal of the National Cancer Institute, which followed more than 60,000 postmenopausal women for about 12 years. A little more than half the subjects reported using talcum powder; researchers weren't able to establish that it made a difference one way or another vis-a-vis incidence of ovarian cancer.

Still, the American Cancer Society continues to hedge its bets, acknowledging there's always a chance; the International Agency for Research on Cancer says the genital application of talc is "possibly carcinogenic to humans." More work is needed, but of course it's not like you can run a controlled trial where you expose various cohorts to a substance you think might cause cancer and see who gets it.

So what we're looking at is disturbing anecdotal information piled up over decades, but no preponderance of evidence to back it up. That's a messy status quo, and helps explain what's happened in the Echeverria case. The jurors heard enough to assess record damages for a talc-cancer suit, but the judge, Maren Nelson, concluded they didn't get it. In October she overturned their verdict, ruling that (among other problems) Echeverria had failed to establish "specific causation" between her baby powder use and her cancer. To argue that talc "more probably than not" causes ovarian cancer, Nelson wrote, Echeverria's key expert (her doctor) had to demonstrate that women who used it had a 50 percent greater incidence risk than women who didn't, and the risk numbers in the studies submitted as evidence couldn't meet that standard. (Grimly enough, Echeverria lived to hear the jury's verdict, but not Nelson's subsequent ruling.)

The proceedings also saw some Big Tobacco-esque intrigue over internal Johnson & Johnson memos alleged to reveal the company's knowledge that their product was harmful—but their language, the judge found, didn't say what Echeverria said it did. The initial read on Nelson's ruling is that it's great news for J&J, given that she's also presiding over some 800 other talc lawsuits against the company in California. Anyone following the talc-cancer issue should keep their powder dry, though; we won't see the end of this one anytime soon.

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