The researchers at the Political Economy Research Institute at the University of Massachusetts listed about 100 top corporate companies that are responsible for air pollution. This list is officially called the Toxic 100. The corporate companies are listed as an important source of air pollution. This is based on air releases of hundreds of chemicals from industrial facilities across the United States.
The various factors that are considered are the quality of air release, relative toxicity of chemicals, the populations that is being exposed, prevailing winds and height of smokestacks. The corporate companies are among those being listed in the Fortune 500, Forbes 500, and Standard & Poor's 500 lists of the country's largest firms. In the top five in the list of Toxic 100 are E.I. Du Pont de Nemours & Co., US Steel, ConocoPhillips, GE, and Eastman Kodak.