The article discusses federal legislation pushing Indiana to regulate more stringently, state legislation pushing localities to do the same, private rights of action, interstate air pollution control compacts, and the issue of enforcement.
For those who think that environmental law before 1970 was nonexistent or ineffective, here's what the article has to say about water pollution law in Indiana:
The Water Pollution Control Board has been quite successful in coping with Indiana's water pollution problem. A state legislator, Senator Mankin, in a recent comment on the Water Control Board's work has stated: "Since the enactment of the Indiana Law, 170 orders have been issued to municipalities and 85 to industries. As a result of this aggressive enforcement program, 97% of the municipal sewage in Indiana is treated, and 85% to 90% of the industrial waste."For more on the history of pollution law in Indiana, see here.