Millions of people across the globe regularly consume arsenic-contaminated water. Exposure to arsenic has previously been associated with the development of various cancers including skin cancer. Research on the underlying molecular mechanisms regulating arsenic-mediated carcinogenesis remains sparse. Using in vitro studies, researchers demonstrate how calcitriol, or activated vitamin D3, inhibits arsenic-mediated carcinogenesis in certain types of skin cells known as ‘keratinocytes.’Millions of people across the globe regularly consume arsenic-contaminated water. Exposure to arsenic has previously been associated with the development of various cancers including skin cancer. Research on the underlying molecular mechanisms regulating arsenic-mediated carcinogenesis remains sparse. Using in vitro studies, researchers demonstrate how calcitriol, or activated vitamin D3, inhibits arsenic-mediated carcinogenesis in certain types of skin cells known as ‘keratinocytes.’