"The Trump administration might be weakening the case for future climate change policy by removing an important metric that lowers the cost of reducing carbon: simultaneous cuts to conventional air pollution.
EPA is considering whether it will count the co-benefits that come along with cutting greenhouse gases, like the health gains from reducing particulate matter. Narrowing the scope of health benefits achieved in climate-focused regulations would sharply curb the public health estimates used to justify their existence, according to experts.
It may also complicate future efforts to craft climate policy.
"It is just a way to make these rules look less cost-effective," said Janet McCabe, acting EPA air chief under former President Obama."