President Richard Nixon set a clear mission for the EPA when he created the agency in 1970: Establish and enforce standards for air and water quality, monitor the condition of the environment, and help states control pollution.

That began to change last week, from a mission safeguarding the environment and human health to one also promoting business and fossil fuels. From an agency that—through five fellow Republican presidents after Nixon, and four Democrats—remained grounded in science, to one now responsive to economic indicators.

The Environmental Protection Agency will “unleash” energy, “revitalize” the auto industry, and lower costs for Americans during …