The highway billboard at the entrance to town still displays a giant campaign photograph of President Trump, who handily won the election across industrial Ohio. But a revolt is brewing here in East Liverpool over Mr. Trump’s move to slow down the federal government’s policing of air and water pollution.The City Council moved unanimously last month to send a protest letter to the Environmental Protection Agency about a hazardous waste incinerator near downtown. Since Mr. Trump took office, the E.P.A. has not moved to punish the plant’s owner, even after extensive evidence was assembled during the Obama administration that the plant had repeatedly, and illegally, released harmful pollutants into the air.“I don’t know where we go,” Councilman William Hogue, a retired social studies teacher, said in frustration to his fellow council members. “They haven’t resolved anything.”Scott Pruitt, the E.P.A. administrator, has said the Trump administration’s high-profile regulatory rollback does not mean a free pass for violators of environmental laws. But as the Trump administration moves from one attention-grabbing headline to the next, it has taken a significant but less-noticed turn in the enforcement of federal pollution laws.