Results from a new systematic review in Frontiers in Toxicology
For the past six years, since the first lawsuit against Johnson & Johnson that claimed its talcum (baby) powder caused ovarian cancer, women have been caught in a seesaw of opinions over whether or not use of the powder for personal hygiene increases one’s risk of cancer.
Take, for example, the 2018 Healthline article, “Is Baby Powder Safe?” The article addresses the limits and inconsistency of study findings (as of 2018) on whether talc causes cancer, but leaves the reader confused as to what it all means. The article ends by recommending that women use other powders for hygiene, such as cornstarch, but does little to calm the fears of women who have been using it for years, both on themselves and their babies.
The American Cancer Society (ACS) addresses the use of talc by women on its website, focusing on an overall lack of data and study findings that are too inconsistent to draw a conclusion on the safety of its use: “For any individual woman, if there is an increased risk, the overall increase is likely to very be [sic] small. Still, talc is widely used in many products, so it is important to determine if the increased risk is real. Research in this area continues.”
Other media sources are not as nuanced as ACS. They directly claim that talc can cause ovarian and possibly other cancers, and go further to provide information on how to join a class-action lawsuit. The overall lack of clarity and abundance of sensationalism in the media regarding this issue has left many women concerned.
A new systematic review brings clarity to talcum powder and risk of cancer
Fortunately, the findings of a new systematic review might put some women’s minds at ease.
The Center for Truth in Science aims to bring clarity to scientific issues, such as talcum powder, by awarding research grants to top independent researchers from around the world to provide clear answers to difficult questions: What do we really know about the risk of a substance? Are there gaps in the evidence? Is more research needed, and if so, what type?
We are very pleased to announce the publication of an important new systematic review of the studies examining the relationship between talcum powder and women’s reproductive cancers.
Published in Frontiers in Toxicology, it is one of the most comprehensive systematic reviews yet of existing research on genitally applied talcum powder, and possibly the first published review on the topic to apply formal systematic review methods and integrate multiple lines of evidence. The independent review was conducted by Heather Lynch, M.P.H., and a team of researchers at Stantec, a consulting firm that provides scientific support to the government, corporations, law firms, and various scientific and professional organizations.
The new study used a combination of the current most stringent guidelines for systematic reviews from the U.S. Environmental Protection Agency (Toxic Substances Control Act, 2021) and the Institute of Medicine (now National Academies of Sciences, Engineering, and Medicine) framework (2009). The research team at Stantec critically assessed and combined the evidence from human epidemiological studies, toxicology studies in animals, and mechanistic studies in mammalian or bacterial cell lines that attempt to identify how talc could cause cancer.
The search for studies included all published literature on the topic appearing in PubMed as of December 2022. The literature search and selection process identified 40 primary studies, with most information available for ovarian cancers.
The review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, or PRISMA guidelines. This standard is used by very high-quality systematic reviews, which means the work conducted in this review is considered among the highest levels of evidence.
A number of important conclusions were reached by the team at Stantec based on the three lines of evidence that were evaluated:
The four animal studies reviewed did not find any mechanism whereby talc can cause cancer in the female reproductive tract at human-relevant exposure levels. They found no evidence that talc causes ovarian or other reproductive tumors in animals after genital application.
Mechanistic studies were relatively small in number and had limitations based on the methods used. However, current evidence does not support any mode of action whereby talc can cause cancer in the female reproductive tract at human relevant exposure levels.
Most of the human epidemiology studies, 31, focused on ovarian cancer. High-quality studies addressing genital use of talc and ovarian cancer were small in number. However, the better-quality studies had insufficient evidence to conclude a causal link with any confidence.
Five prospective cohort studies (where researchers follow two groups of similar women over time, one group using talc, and the other not) were rated of medium quality and reported no association between genital talc use and ovarian cancer.
Of the 26 case-control studies that compared two groups of women—those with reproductive cancer (the “cases”) and a very similar group who did not have cancer (the “controls”)—many reported inconsistent associations, while some reported no statistically significant associations.
Eleven of the case-control studies were rated medium-quality and 15 were rated low-quality. The low-quality ratings were because the women in the study were asked to self-report their use of talc over a long time period, and this might have made the measurement inaccurate.
It should also be noted that several of the case-control studies were overshadowed by “recall and reporting bias” from the women in the study, who were likely affected by news stories, social media, and advertisements purporting that talcum powder causes cancer.
There were very few studies on endometrial and cervical cancer, but the results mimic those of ovarian cancer reported above. The five published studies evaluated were all rated as medium-quality and did not show an association between genital talc use and these two cancers.
What does this mean for women who have used talcum powder?
The technical conclusion of the systematic review states:
There is suggestive evidence of no association between perineal application of talcum powders and risk of ovarian cancer at human relevant exposure levels.
We also concluded that there is suggestive evidence of no association between genital talc application and endometrial cancer, based on a smaller but largely null [no affects seen] body of literature. Evidence was insufficient to conclude any relationship between talc use and cervical cancer.
What is “suggestive evidence of no association?”
The Institute of Medicine (IOM) developed a strength of evidence ranking for systematic reviews that the authors of this article relied on. As we have explained in earlier blogs, these levels are used by health policymakers and other health professionals to determine what we know about the strength of any causal relationship between an exposure and a health outcome.
The level stated above is the weakest in the hierarchy. This level is chosen when several studies covering the “full range of human exposure” consistently show no association with exposure to a substance at any concentration, and have relatively narrow confidence intervals.
Given the varied quality and low number of studies available for this review, it is important to use the word “suggestive” when stating there is no association between perineal application of talcum powder and ovarian cancer. More high-quality studies could increase the strength of the findings, but there is also the possibility that future findings could go in the other direction and begin to show stronger evidence of an association.
While women who have used talcum powder for personal hygiene cannot be 100% certain they did not increase their ovarian cancer risk, they should perhaps focus on clearer risk factors, like age, family history, and presence of a specific genetic mutation associated with ovarian cancer.
Ovarian cancer is rare, so studies with sufficient numbers of women may be slow in coming. In the meantime, Johnson & Johnson has taken its baby powder off the market, despite a lack of evidence pointing to an association.
It is important to use the best science when evaluating causes of adverse health outcomes. This systematic review represents some of the best science we have to date in this area. We hope it provides a clear and calming starting point for women and health providers regarding their very important concerns on this issue.
Stay tuned for the full research article. In the meantime you can visit the journal to read the abstract here.