Potential Dilemma: The Methods of Meeting Automotive Exhaust Emission Standards of the Clean Air Act of 1970

This review attempts to provide an overview of the interconnected industrial changes associated with compliance with the exhaust emission standards of the Clean Air Act of 1970. To understand the complex nature of air pollution problems, Federal legislation, and compliance with this legislation requires an understanding of automotive technology, petroleum refining, atmospheric chemistry and physics, economics, and public health. The endeavors of all of these different areas impinge to a greater or lesser extent on the final response to the Clean Air Act which is designed to safeguard public health. This overview begins by examining gasoline refinery practice and gasoline composition. Included in this discussion are average values for trace contaminants in gasoline, and an explanation of the function of the many gasoline additives. Next, exhaust emissions are characterized, average values of exhaust components given, and a summary of important atmospheric air pollution reactions presented. Emission control devices and sulfate emissions from these devices are described. This is followed by a complete discussion of methyl cyclopentadienyl manganese tricarbonyl, a substitute antiknock for tetraethyllead. In the event TEL is legally banned from gasoline, or removed because it poisons the catalytic muffler surface, this manganese antiknock is the most efficaous replacement. In this discussion, the adverse health effects caused by exposure to manganese oxide particulates, the possible exhaust emission products from this additive, are examined in detail. The review concludes with comments on automotive engine and gasoline composition redesign as an approach to automotive air pollution.