Mr. Pruitt, according to the employees, who requested anonymity out of fear of losing their jobs, often makes important phone calls from other offices rather than use the phone in his office, and he is accompanied, even at E.P.A. headquarters, by armed guards, the first head of the agency to ever request round-the-clock security…

But as he works to roll back regulations, close offices and eliminate staff at the agency charged with protecting the nation’s environment and public health, Mr. Pruitt is taking extraordinary measures to conceal his actions, according to interviews with more than 20 current and former agency employees…

“There’s a feeling of paranoia in the agency — employees feel like there’s been a hostile takeover and the guy in charge is treating them like enemies,” said Christopher Sellers, an expert in environmental history at Stony Brook University, who this spring conducted an interview survey with about 40 E.P.A. employees.