35 Pa. Stat. § 4101
It is the policy of this State to cooperate with other states sharing airsheds with this State. It is recognized that the quality of regional air masses is affected by sources of air contamination anywhere within an airshed, and that interstate concentrations of population, industry, motor vehicles, and other factors make coordination of air pollution control activities on a regional basis highly desirable. In order to promote this coordination, it is the policy of this State to administer its air pollution control programs with due regard for the quality of air masses moving between or among this State and one or more other states. It is further the policy of this State to provide for the development of recommendations concerning standards of air quality and their implementation applicable in interstate airsheds or regions through activities carried on under interstate administrative agreements, and for this State to give full consideration to these recommendations.
35 P.S. § 4101