There's been a longstanding debate -- and a slew of lawsuits -- over whether baby powder containing talc plays any role in the development of some cancers.
A large new study isn't likely to settle the controversy any time soon.
The latest research included more than 250,000 women and failed to find a statistically significant connection between talc-based powders and ovarian cancer.
But study author Katie O'Brien, an epidemiologist with the U.S. National Institute of Environmental Health Sciences, said the findings are "not definitive."
"We found a small, but nonstatistically significant, risk. We cannot establish causality. If there is a true association [between talc powder use and ovarian cancer], the increase would likely be very small," she explained.
Talc is a mineral that is sometimes found naturally in areas that also contain asbestos. Asbestos is a known cancer-causing substance. But U.S. manufacturers of cosmetic talc products agreed to ban asbestos in 1976, according to the study. Since that time, the International Agency for Research on Cancer has said there is only "possible" evidence that genital use of talc-based body powder may be linked to cancer.
The use of talc powder has been linked to other types of cancer, such as mesothelioma. Mesothelioma affects the tissue that lines the lungs and other organs. A jury recently awarded a California couple nearly $30 million from Johnson & Johnson for the wife's mesothelioma, according to a CNN report.
And just last week, the state of New Mexico filed a lawsuit against the company, accusing it of misleading consumers, especially children and black and Hispanic women, about the safety of its talc products.
The New Mexico lawsuit, the first to be filed by a state, is the latest in an avalanche of legal claims against the consumer products giant. More than 16,800 other talc-related lawsuits have been filed on behalf of individuals, according to The New York Times.
How might talc powder cause ovarian cancer? The study authors explained that when women use talc-based powders in their genital area, the powder may enter the body and irritate tissue in the fallopian tubes or ovaries. This irritation might then cause inflammation, and start a cascade of responses in the body that could contribute to the development of cancer.
But it's not easy to prove that talc powders might lead to cancer with any certainty. One reason why is that ovarian cancer is an uncommon cancer. In this large group of more than a quarter million women, ovarian cancers were found in just under 2,200 women -- that's less than 1%. Plus, only 38% of women said they used powder in their genital area. Of those, just 10% reported long-term use, and 22% reported frequent use.
Past studies that have found a link were "case-control" studies. Dr. Dana Gossett, author of an editorial accompanying the study, explained that these type of studies compared people who have a disease with people who don't.
"If you've just given someone a devastating diagnosis, they are far more likely to report using all sorts of things. That's because they're looking for reasons why they have the condition they have. It's called recall bias," Gossett explained, adding it's a known concern with that type of study.
This latest research, published Jan. 7 in the Journal of the American Medical Association, combined four different prospective studies. Those are studies that follow people over time, gathering information as they go.
"This is the best study of this topic done to date," Gossett said. "They found no clear association to ovarian cancer with genital powder use at all."
She added that this study may provide some reassurance to women who regularly used powder in the past. "This study is large enough and designed well enough that if there was a substantial risk, we would see it," Gossett said.
In a statement, Johnson & Johnson said, "Another study has found there is no statistically significant association between use of talc for feminine hygiene and ovarian cancer. This study drew from data already gathered on tens of thousands of women followed over many years and reaches a conclusion that is consistent with the more than 40 years of independent research and clinical evidence that supports the safety of talc."
Study author O'Brien said the new research "doesn't give firm evidence one way or the other" when it comes to the association between ovarian cancer and genital-area talc powder use. She also noted that this study only looked at ovarian cancer, so it can't address any possible links between talc powder and any other type of cancer.
Read more about the debate over the talcum powder and cancer association from the American Cancer Society.