Justin Smarsh and his family used to kayak a few times a year on the rivers and creeks near their home in Cherry Tree, Pennsylvania. High on the Appalachian Plateau, northeast of Pittsburgh, he spent hours in the woods and taught his two sons to hunt. Today, Smarsh said, he gets “suffocated just walking.” He has a constant dry cough, and he loses his breath if he bends down to tie his shoes. A few years after he graduated from high school and g…