Steel manufacturers are coming under scrutiny from the Environmental Protection Agency.
The EPA is looking at new emissions limits for iron ferroalloys, which are used to produce steel.
The EPA originally proposed the ferroalloys emissions requirements in 2011, but announced Friday in the Federal Register it is revising the proposal to reflect the latest advancements in science.
The proposal includes tougher compliance requirements for manufacturers intended to protect the environment, according to the agency. They would apply to the only two facilities around the country that produce a specific type of ferroalloys known as ferromanganese and silicomanganese.
"This action would result in significant environmental improvements through the reduction of fugitive manganese emissions and through more stringent emission limits for several processes," the EPA wrote.
The public has 45 days to comment on the proposed rule.