SciLine fact sheets are evidence-based, factual summaries of newsworthy scientific issues, reviewed by experts. They are designed to be quickly and easily scanned by journalists and others seeking scientifically derived information on topics in the news. Individual points of information can be included in stories with confidence that they reliably reflect the findings of scientific studies. Journalists can also simply refer to these documents to fact check their stories before publication. Our fact sheets are written by SciLine editors and reviewed by at least three scientists with deep expertise in relevant disciplines to ensure accuracy as of the date of publication. SciLine fact sheets do not aim to support or oppose specific policy positions or proposals; the goal is to enrich public conversation and science journalism by providing trustworthy information for consideration.