SNIP The eldest Kardashian daughter, Kourtney, 41, is catching flak for peddling eyebrow-raising claims about the supposed health risks of surgical masks to her 102 million Instagram followers. On Halloween, the “Keeping Up With the Kardashians” star reposted an unattributed blurb that read in part, “Those Blue Masks Mandated at grocery stores & airplanes are made of PTFE, a carcinogen made of synthetic fluoride.” The medical warning about PTFE, or polytetrafluoroethylene — a man-made chemical found in nonstick cooking coatings like Teflon — included a picture of a ubiquitous three-ply, single-use blue surgical mask. The post went on: “According to...