Toxic air emissions are dropping rapidly, down nationally 8% in 2011 and 13.8% in the Mid-Atlantic States, including Pennsylvania. The sharp drops are the result of more natural gas and renewable energy to make electricity, more scrubbers installed on coal-fired power plants, and more efficiency in electricity use.
Even bigger declines in toxic air emissions almost certainly took place in 2012, given the surging use of gas and renewables to make electricity and the installation of pollution controls on still more coal plants. Burning gas emits no mercury, lead, arsenic, and only tiny amounts of soot.
Soot is a particularly serious public health threat, as it nationally causes 34,000 premature deaths per year and hundreds of thousands of illnesses.