Perineal talc use and ovarian cancer risk: a case study of scientific standards in environmental epidemiology

A number of observational studies (largely case-control) conducted over the last two decades suggest an association between use of talc powders on the female perineum and increased risk of ovarian cancer. A subset of these reports shows a roughly 30-60% increased risk of ovarian cancer associated with perineal talc exposure. A number of researchers partly base their conclusions of an association on the '…chemical relationship between talc and asbestos', the latter substance being a known human carcinogen. Although separating causal from noncausal explanations for an observed statistical association is a difficult process, there currently exist commonly accepted guidelines by which such inferences can be made. These scientific approaches include consideration of the strength of the association, the consistency of the finding across studies, and existence of a biological explanation of the observed phenomenon, among others. When applied to the context of a proposed talc/ovarian cancer association, we conclude that the weak statistical associations observed in a number of epidemiological studies do not support a causal association.