Talc is a soft white mineral made of hydrated magnesium silicate.
Talc can be found in eyeshadows, powder, pigments, baby products, etc.
Talc has become problematic as a cosmetic ingredient over recent years because it naturally forms next to (and entangled with) asbestos in the earth. Cross-contamination is very difficult to avoid during mining. This has led to concerns over contaminated talc getting into products because of asbestos’ known links to cancer.
In addition to the connection to asbestos, talc in and of itself has been found to travel into the ovarian tract and possibly accumulate over long term exposure.
Talc is not banned, but Europe and the United States have taken steps to get products tested for asbestos contamination more seriously. The FDA specifically has warned against buying products that contain talc that test high for asbestos.
 FDA. Constituent Update regarding products testing positive for asbestos. (2020). https://www.fda.gov/cosmetics/cosmetic-ingredients/talc
 NIH. NCBI. The relationship between perineal cosmetic talc usage and ovarian talc particle burden. (1996). https://www.ncbi.nlm.nih.gov/pubmed/9065120
 ECHA (The European Chemical Agency). Annex III of the REACH Act. https://echa.europa.eu/substance-information/-/substanceinfo/100.035.328
 NIH. NCBI. Cytotoxicity and apoptosis induction by nanoscale talc particles from two different geographical regions in human lung epithelial cells. (2014). https://www.ncbi.nlm.nih.gov/pubmed/22331707
 NIH.NCBI. Asbestos in commercial cosmetic talcum powder as a cause of mesothelioma in women. (2014). https://www.ncbi.nlm.nih.gov/pubmed/25185462