The United Steelworkers say that workers at an Exxon refinery in Texas may strike in June if the company does not agree to new safety language in their contract. The union has raised safety issues after worker injuries, but says that Exxon refused to accept it in their negotiations. The company says that they have made an effort to work with the union, and that they would continue operating in the event of a strike. Similar language is in place at other Exxon refineries.
See "Workers Threaten Strike at Exxon Refinery", Ben Lefebvre, The Wall Street Journal, April 29, 2013