In 2014, W.L. Gore & Associates stopped using a harmful chemical called PFOA in the technology it makes for waterproofing raincoats, hiking boots and other gear. The Newark, Delaware-based company’s shift came amid federal government pressure for the industry to phase out by 2015 the use of the cancer-causing compound, which is part of a broad group called per- and polyfluoroalkyl substances, or PFAS.