Nearly three years ago, President Barack Obama responded to long-standing concerns that workers exposed to toxic chemicals at the country’s nuclear weapons labs were not receiving proper compensation. Obama created an advisory board to be composed of scientists, doctors and worker advocates. Their recommendations have led to significant changes, including the repeal of a rule that made it more difficult for workers who’d been injured in the last two decades to get compensation. President Donald Trump and his administration have taken a different approach: His Labor Department has let nearly all of the board member’s terms expire — and so far hasn’t nominated new ones. “For two years our board put a lot of brain power and cutting-edge expertise into developing recommendations,” said Ken Silver, an occupational health professor at Eastern Tennessee State University, who until last month was a board member.