for two decades demonstrably are more common than originally believed. Experience, unfortunately, has proved that even our National Capital is not immune, even though it has little heavy industry. Likewise, communities situated in sections commonly regarded as wide-open space, because of the vagaries of wind and weather, combined with traffic volume, residential development, and other aspects of modern civilization, have suffered affliction.

All of these circumstances lend emphasis to the urgency of more determined and intensive efforts, in various fields and different directions, to identify, isolate, and eliminate or control the source of contaminants. To achieve success, a high degree of statesmanship is a basic requirement.

As you well know, I long have felt that additional legislation by Congress is justified and desirable. I also believe that our States, counties, and cities must recognize a greater obligation and, wherever indicated, adopt laws, ordinances, and regulations. To date, I have not been convinced that Federal authority should be exercised in police fashion, but I do fear that unless statesmanship is shown at non-Federal levels there may be no alternative if we are to safeguard the public health,

let alone protect property and animal and plant life, and keep physical discomfort to a tolerable minimum.

To my regret, it was impracticable during the 87th Congress to obtain approval for the bill I introduced which would have given the U.S. Department of Health, Education, and Welfare and the Public Health Service additional authority and responsibilities I feel are essential to maximum progress in this field.

I earnestly hope that during the proceedings of the forthcoming national conference, serious attention will be paid to the desirability of meaningful new legislation on the subject of air pollution. I trust that those participating in these discussions will help provide the degree of statesmanship imperative to drafting and enacting additional measures which will give further impetus to activities already going on and bring into proper focus aspects of the problem to which insufficient attention has been given.

I look forward to reviewing the record of the meetings with real eagerness and with confidence that constructive ideas will be advanced. With best wishes and warm regards.

WOLFGANG E. MEYER Professor of Mechanical Engineering Pennsylvania State University University Park, Pa.

Various aspects of the complex problem of air pollution by motor vehicles will be discussed by the panel members. In order to provide a frame of reference for the experts' discussion of specific aspects of the overall problem we ought to look first at what air pollutants motor vehicles emit.

It is often thought that passenger cars, buses, and trucks produce different types of exhaust emissions. This is only partially true. The real difference lies in the types of engines used; buses and trucks may have either gasoline or diesel engines while passenger cars usually are powered by gasoline engines. We should, therefore, think more in terms of engines than of vehicles when we talk about exhaust emissions. The type of vehicle in which an engine is used does have, however, an influence on the quantity and, to some degree, on the character of the emissions. Engines in passenger cars operate at much lighter load than those in trucks and buses and emissions change with load, speed, temperature, etc.

Both gasoline and diesel engines operate on hydrocarbon fuels that are obtained from petroleum by various refining methods. These fuels are burned within the cylinders of both engine types to convert chemical into mechanical energy. To burn the fuel, air is needed as a source of the oxygen that must be available to combine with the hydrogen and carbon of the fuel. This combination process produces heat and, in the confined space of the engine cylinders, pressure. It is this pressure that propels the pistons and thereby turns the crankshaft and ultimately propels the vehicle.

When the hydrogen and carbon that are the elements that make up petroleum fuels combine with oxygen, water vapor and carbon dioxide are formed. Both of these products of the ideal, com

plete combustion are invisible, cannot be smelled, and are harmless. We see the water on occasion, namely, when the engine and the air are cold. We certainly know it must have been there when we pay good money to replace a rusted-out exhaust system.

Unfortunately, however, combustion in an engine never conforms completely to the ideal and idealized model of the process. The products of imperfect combustion are the prime cause of the motor vehicle air pollution problem. One of these products is the carbon monoxide that gasoline engines emit. Almost everybody knows this and is aware of how dangerous carbon monoxide is. Numerous other substances are produced, but usually in much smaller quantities. Motor fuels also contain certain additives that are necessary to give the performance and life that we have come to expect from engines. These additives undergo chemical changes during combustion before being emitted into the atmosphere. Also a certain amount of lubricating oil burns or partially burns in the cylinders. If an engine is so badly worn that a large amount of oil is pumped by the pistons into the combustion chambers, the vehicle will trail a plume of blue smoke that consists of partially burned or completely unburnt lubricating oil.

It is not only the engine exhaust system, however, that discharges all manner of substances into the atmosphere. Another important emission path is through the engine crankcase. Despite great advances in the technique of scaling pistons, a small amount of the gases in the combustion chamber escapes past the pistons into the crankcase. In the past, this "blowby" was permitted to pass into the atmosphere, but now devices are being used to prevent its discharge.