Carrying out those and other steps in the region, with its $2.8 trillion annual economy, could lead industries to adopt them nationwide, said Ellen Hanak, an economist and senior fellow at the nonpartisan Public Policy Institute of California.
But Judge Williams said the appeals court was constrained by its own precedent, a 1980 decision known as the Lead Industries case that specifically barred the agency from considering any factor other than public health.
Although it declined to review Lead Industries when the decision was issued, the Supreme Court is familiar with the cost-benefit issue from a series of regulatory battles in the early 1980's involving the Occupational Safety and Health Act.
Complicating this already complicated case is the fact that the District of Columbia Circuit, in a 1980 decision known as Lead Industries, interpreted the Clean Air Act to bar the kind of cost-benefit analysis for which Mr. Warren was arguing.
The amendment evokes the history of notorious anti-science efforts by the tobacco and lead industries to avoid accountability for the damage caused by their products, focusing similar ire on the fossil fuel industry's decades-long climate cover-up.
The oil and lead industries used various strategies to forestall regulation of lead in gasoline.
