When Dora Williams started wearing a mask last spring to stop the spread of the coronavirus, she noticed a side effect: She could breathe more easily. The 73-year-old retiree has spent most of her life in a 5-mile stretch of Delaware known as the Route 9 corridor. Home to several historic African American communities, the area is circled by interstate highways, a chemical manufacturing plant and other industrial facilities, which residents like Williams say have contributed to persistent health problems. “My granddaughter said to me, ‘When Covid is gone, we’ll still be wearing masks.’ I said, ‘Yeah, we will,’” said Williams, a soft-spoken community activist with Delaware Concerned Residents for Environmental Justice. Last year, President Biden’s home state became the first in the country to set up a committee to carry out the Justice40 Initiative, the president’s signature environmental justice policy calling for 40 percent of federal benefits from climate and energy programs to reach disadvantaged communities. How Delaware implements the plan may set a national precedent, considering that the fate of Justice40 — which was announced through an executive order — and its effects on the energy sector hinge in part on states.