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The problems of photochemical smog and associated phytotoxicants are receive ing considerable attention throughout the country. Most of the projects within the Agricultural Section, DAP, are at present concerned with this general problem.

There is still much effort being devoted by all workers to defining the wide variety of symptoms induced by photochemical air pollution on vegetation, and relating patterns of injury to measurable materials in the air. There is also considerable work being done vith specific known products photochemical smog to define the nature of the injury to vegetation which they cause. The group in California has been able to define the gross effect of PAN and has made some significant steps in studies of the effects of ozone on the biochemical systems of the plant. The Agricultural Section of DAP has made considerable progress in defining the symptoms developed by plants exposed to the complex of phytotoxicants produced by irradiated auto exhaust. It is also making some significant progress in studies of the effect of other environmental factors upon the sensitivity of plants to irradiated auto exhaust and to ozone. The Crops Division of the U.S. Department of Agriculture has been working with ozone and with natural photochemical smog. This work has demonstrated the possibility of breeding new plant varieties—of tobacco, for example-with increased re. sistance to markings caused by ozone.

In recent years we have become deeply concerned about some seemingly air pollution-induced diseases of forests, in addition to the older and still present problems from sulfur dioxide and from fluoride. One of the common blights of white pine has been demonstrated as probably due to ozone, while another one can only be associated with stack gas. The U.S. Forest Service is continuing work in this field and is finding other disease conditions of forest trees which may be due to air pollution.

While we have a long history of work on sulfur dioxide, we still do not know the exact mechanism by which the plant detoxifies sulfite or exactly what systems sulfate accumulation affects to produce the so-called chronic type of injury. We need much more detailed knowledge of these matters in order to better select and breed varieties more resistant to sulfur dioxide and better describe the variations in atmospheric concentrations which would permit normal or optimum growth.

A similar situation applies to the fluoride problem. We know the general symptoms of fluoride injury to plants and of clinical fluorosis in animals. Our knowledge of the mechanism of action of fluoride in the living tissue is fragmentary. In the case of dairy and breeder cattle, we know enough about fluorides to set reasonably certain safe dietary limits. We need to learn more about the action of fluoride on the growth and development of the animal in order to better define safe diet for feeder stock and fattening beef. We suspert such stock can safely ingest higher levels without developing serious fluorosis before marketing. We do not have adequate information on the effects of fluoride on feed utilization or on quality of meat to make really definitive recommendations. This knowledge might permit better utilization of areas with elevated fluorides.

In the case of injury to plants, we still need far more complete knowledge of what fluoride does at low levels if we are to adequately answer the questions that arise regarding fruit set, reduced growth, decreased quality, and a host of other rather vague symptoms that are attributed to fluoride. Because of the extremely low levels of fluoride in the air which are associated with some of these problems, we must have considerably more information to improve our ability to recommend levels for control purposes. Along with these problems we need much better knowledge as to forms of fluoride in the air, better analytical data on air levels, and better information on rates of uptake by various species from known air levels.

The problems associated with the effects of photochemical smog on vegetation are only partially recognized ; we know about ozone and PAN and have good reason to suspect that there are other phytotoxicants in the complex. Soine of the symptoms we see may be the result of interaction among specific phytotoxicants. Before we can hope to unravel this complex we need more information on symptoms resulting from single toxicants from the smog complex, a better understanding of the effect these have on the plant, similar information from mixtures of the toxicants, and a better understanding of the interaction of other environmental factors. Along with this we must have a better understanding of the complex chemical reactions and absorption phenomena which are occurring in the atmosphere, as well as better and more detailed analytical data.

There are aspects of air pollution other than those associated with sulfur dioxide, fluorides, and photochemical smog which require consideration from an agricultural standpoint. The problem of the white pine blight associated with stack gases is one pressing example. We are reasonably certain this is not due to fluoride or sulfur dioxide. While it may prove to be a photochemical pollution problem, we should not prejudice our thinking on such an important disease. We must also keep up with knowledge of the effects of some of the other possible pollutants. Some of these which are now of only local concern mas tomorrow become widespread. The fluoride problem is a good example of what can happen. While the problem of particulate material has been of some local concern, we do not have a good understanding of its effects on vegetation. The direct action of materials settled out on the leaves as well as the shifts in light intensity by suspended matter deserve more attention.

Program effort concerning the economic aspects of air pollution is at a minimal level and largely limited to the Public Health Service. In total approximately $55,000 is available for this activity within the Public Health Service, of which about $10,000 is budgeted in support of a study conducted under contract with a university, to identify and assess possible methodologies for quantifying the economic costs of air pollution. In addition, a short-term study, also carried out under a contract, is directed toward assessing the extent to which the effects of heavy fluoride emissions are reflected in land-value changes in a citrus and cattle grazing region of Florida.

A project to assess the deteriorating effects of air pollution on property is presently in progress. The immediate objective is to determine, by means of various laboratory and field study investigations, the degree of damage to various materials directly and indirctly attributable to air pollution. The ultimate objective is to use this information to prepare a comprehensive economic analysis.

Five individual field studies are in various active stages. These deal with the atmospheric corrosion behavior of some metals, with the deterioration of cotton fabrics, and with the fading of a number of dye-fabric combinations. The atmospheric corrosion studies are being conducted in St. Louis, Chicago, and Birmingham, and at each of the original Continuous Air Monitoring Program (CAMP) network sites. The cotton fabric deterioration study was launched in the St. Louis area, and the dye-fabric fading investigations are being made in Washington, D.C.; Sarasota, Florida ; Phoenix, Arizona; Los Angeles: Tacoma. Washington; and Chicago. For each study, the relationship between the measured amount of air pollution and the degree of damage over and above that which naturally occurs will be evaluated.

In various stages of planning are cotton fabric regradation studies in Chicago and Charleston, W. Va.; and atmospheric corrosion programs in Charleston, W. la.; in metropolitan St. Louis; and at about 60 selected National Air Sampling Network sites.

Current efforts toward determining the economic costs of air pollution, both on a national basis and in specific urban areas, should be substantially expanded and accelerated. Particular attention needs to be given to the integration of this line of inquiry into a total cost-benefit analysis of the air pollution problem as a basis for public policy formulation with regard to the types and magnitudes of control efforts which are warranted. This line of economic research should include a study of the externalities, or third-party effects, of air pollution so as to provide a guide to the appropriate minimum size for planning and administrative units for air pollution control. Methods for application of cost-benefit analysis to air pollution control in specific metropolitan areas also need to be dereloped. 6. Expanded research efforts by American industry

There are encouraging signs that important segments of U.S. industry are voluntarily undertaking to abate their own harmful effluents. Some specific research projects have already been mentioned. This section will provide a rough estimate of industry's overall contribution.

Estimates by the National Association of Manufacturers indicate that industry is currently spending at the rate of $500 million a year for air pollution control. The same NAM estimates put expenditures for this purpose since World War II by the electric light and power industry at $350 million. A single company. Consolidated Edison of New York, has testifier that it has spent since 1937 over $100 million for control equipment and its installation. The Manufacturing Chemists' Association has stated that 125 of its member companies have invested altogether about $250 million in air pollution control facilities and are spending $34 million a year to operate them.

Members of the Western Oil and Gas Association are asserted to have spent since 1948, in Los Angeles County alone, $144,456,000 on the operation and maintenance of controls, and on research. Also in Los Angeles County, all industry is said to have spent about one-fourth of its total equipment cost for air pollution control devices. In these instances, of course, the expenditures were probably dictated largely by the stringent control regulations in that area rather than “undertaken voluntarily."

The steel industry in many areas has cooperated with control authorities by agreeing to invest substantial sums in equipment to curb its own emissions, notably those caused by the comparatively new, and exceptionally "dirty," oxygenlance process. In Chicago, for example, four companies, responsible for some 90 percent of Chicago's steel production, have undertaken virtually to eliminate from their operations, within an eight-year period, all particulate emissions, which had totalled some 60,000 tons a year. The cost to these companies is said to be in excess of $50 million. In a single Kaiser steel plant at Fontana, California, control measures which cost $17 million are reported to be 99 percent effective in reducing objectionable effluents.

In order to accomplish the historic cleanup of Pittsburgh emissions of visible smoke and soot, industry in that area was required to expend more than $250 million for anti-pollution equipment. On a smaller scale, but no less impressive, is the experience of Union County, New Jersey, where 27 industries spent for air pollution control, in the ten years prior to 1963, $9,149,000.

A further clue to industry's expenditures is provided in a report by the U.S. Department of Commerce dated June 14, 1965 on the Industrial Gas Cleaning Equipment Industry; the total value of 1963 shipments by 65 manufacturers of electrostatic precipitators, fabric filters, mechanical collectors, and scrubbers amounted to $50 million.

Industrial associations, including those representing the chemical, steel, oil, and automotive industries, have made substantial contributions to air pollution research.

III. THREE RESEARCH AREAS OF SPECIAL INTEREST As mentioned in the Introduction to this report, three areas have been selected for more extended treatment, because they have high priority in the United States and are of special interest in all Member countries. These are motor vehicle emissions, sulfur-containing fuels, and adverse effects as related to air quality criteria. 1. Motor vehicle emissions

The population of motor vehicles in the United States is increasing at the rate of almost 5 percent a year. Concurrently, the quantity of harmful emissions from vehicle exhaust tailpipes, carburetors, and fuel tanks grows with the increasing use, as well as the increasing number, of these vehicles.

Studies have already revealed to some degree the extent and detrimental effects of motor vehicle pollution. But much more data on the effects of air pollution on people, animals, plants, materials, and atmospheric visibility are needed to provide sound technical foundations for the promulgation of criteria which can be used as guides in setting legal standards for air quality. These data are equally needed in every Member country.

There are four sources of emissions in conventional automobiles: tailpipe exhaust, crankcase ventilation, carburetor evaporation, and fuel tank ventilation. Evaporative losses from the carburetor and fuel tank reflect the character of the fuel. Thus, the kinds of hydrocarbons evaporated depend upon the kinds that are present in the fuel, and their volatility. The gases that "blow by" the piston rings are vented from the crankcase. These crankcase vent gases consist of about 80 percent unburned fuel-air mixture and 20 percent cylinder combustion products. The large proportion of unburned fuel in the blow-by is explained by the fact that the fuel-air mixture in the annular space between the cylinder and piston does not burn, because of the quenching effect of the closely adjacent cool walls, and is forced past the piston rings as raw gasoline.

Blow-by can be burned by returning it to the engine intake system. This practice is not new to European car makers and has been used for years in America on certain special-purpose vehicles. No new engineering concepts were required for direct application; therefore the crankcase emission problem was the first to be solved. Different manufacturers used different designs, however ; some returned the blow-by to the dirty side of the air cleaner, others to the clean side, and still others to the intake manifold through a variable-orifice metering valve. A further variation, common in California, consists of dual return paths of blow-by gases to both the intake manifold and the air cleaner.

Exhaust emission is the most important vehicular source of hydrocarbons and the only significant vehicular source of carbon monoxide, oxides of nitrogen, and lead. The three general approaches for reduction of exhaust emissions are fuel modification, afterburners, and engine modification.

The potentital of better engine maintenance for reducing air pollution was recently tested, but no significant improvement was attained through conventional maintenance practices alone. Emissions were substantially reduced only when cars were serviced in shops equipped with elaborate engine diagnostic and tuneup equipment and with special instruments for measuring vehicular pollutant emissions. The equipment and procedures are presently too costly and too delicate for routine use in today's conventional U.S. service garages. Nevertheless, proper maintenance is an important part of any program, in order to keep a car running more nearly within its designed emission rate.

Fuel modification is one method being studied as a means of lowering hydrocarbon emissions. The only regulation of fuel composition in the United States intended to abate automotive emission is Los Angeles Air Pollution Control District Rule No. 63, which provides that no gasoline may be used which has a degree of unsaturation greater than Bromine Number of 20. Its purpose is to limit the olefin content of gasolines; certain olefins, when emitted to the air, are more active than other components in producing photochemical smog. However, it should be noted that olefins are still produced in the exhaust even though none are present in the gasoline. The Public Health Service is investigating the possibility of reducing gasoline evaporation by the use of a surfactant additive. This would lower evaporative losses at the fuel tank. Special fuel tank filler caps, with one-way valves, to allow air to breathe into the tank but prevent vapor outflow except when the fuel tank becomes overpressured, have been examined experimentally.

Any change in fuel composition which would provide the required octane ratings without alkyl lead additives would make possible lead-free exhaust. There is no national regulation in the United States limiting the quantity of alkyl lead additives in gasoline. However, there is a voluntary agreement between manufacturers of lead additives and the Public Health Service as to the maximum lead content of gasoline; this is at present 4.0 milliliters per gallon (TEL).

Manifold air injection and other engine modifications are the first methods being utilized to control hydrocarbon emission in exhausts. California standards of exhaust emission are now:

Hydrocarbons : 275 ppm by volume, as hexane (measured by nondisper. sive infrared spectrophotometers).

Carbon Monoxide: 1.5 percent by volume. The 1966-model cars having engine displacements greater than 140 cubic inches which are produced for sale in California will be equipped, with few exceptions, with exhaust control systems that will meet California standards.

In October of 1964, the California State Department of Public Health reduced the limits on hydrocarbons to 180 ppm and on carbon monoxide to 1.0 percent, effective January, 1970. In the Federal Government, Public Law 89–272, passed late in 1965, requires that the Secretary of Health, Education, and Welfare promulgate national standards for emissions from motor vehicles. The current expectation is that the first standards will take effect on 1968-model cars.

In preparation for the expected deadline, the Public Health Service and the automobile industry are testing the California-type emission control devices in various sections of the United States to determine their effectiveness under the wide variations in climate, weather, altitude, and topography which prevail in the United States. To further meet the need for information on which to base vehicular emission standards, the Public Health Service is emphasizing in its program the development of compliance testing methods and of simplified sampling and analytical techniques.

Work is continuing for further development of chassis-dynanometer driving cycles: one for certification of devices; another for field surveillance to determine the effectiveness of control techniques after extended periods of use. In addition, instrument manufacturers have been apprised of the need for simplified analytical instruments for use in compliance and surveillance testing.

The types of engine modification systems developed by the automotive industry have been found to meet California standards. One introduces air under pressure to the exhaust manifold near each exhaust valve and is accompanied by minor changes in carburetion. The additional air at the high-temperature location oxidizes some of the unburned exhaust hydrocarbons and carbon monoxide. All but one of the country's car makers are expected to use “manifold air oxidation."

The other type of engine modification system is achieved by a combination of the following changes :

(1) Leaner carburetor calibration under idle and road load conditions. The leaner fuel-air mixture promotes a more complete combustion.

(2) Slightly earlier choke release. Since time is reduced during which a rich fuel mixture is fed to an engine, the amount of unburned hydrocarbon exhausted is reduced.

(3) Increased closed-throttle air flow. This provides a leaner mixture while idling.

(4) Retarded ignition at idle. This provides more complete combustion of the leaner idle mixture and minimizes the effect of increased air flow on idle speed.

(5) A vacuum advance control valve. Retarded ignition timing produces increased hydrocarbon emission during deceleration. The control valve senses the higher intake manifold vacuum associated with deceleration and advances the timing to normal.

None of these engine modifications decreases the emissions of oxides of nitrogen. Some may even increase them. Complete combustion of the hydrocarbons produces higher combustion temperatures; and the higher the combustion temperature, the greater the oxidation of the nitrogen in the combustion air. The Public Health Service is evaluating techniques for reducing oxides of nitrogen. Two specific techniques now under study are exhaust gas recirculation and water injection; both of these techniques reduce peak combustion temperatures.

The measures so far described can be applied in a relatively short time to ameliorate vehicular air pollution. Studies of new-type engines for long-range application are also being conducted, since it may be that neither add-on devices nor minor engine modification will achieve the desired degree of abatement. One such long-range study seeks to achieve lean-mixture operation through use of the stratified charge techniques. Stratified charge operation presents to the spark plug at its firing time a small preliminary "starter dose" of rich fuel-air mixture which is easily ignited and propagates its flame to the rest of the leaner fuel-air mixture, which might otherwise be too lean to ignite. This method permits an excess of oxygen to be available for more complete combustion without affecting the efficiency of ignition. To achieve this type of operation, cylinder heads and combustion chambers would have to be redesigned.

The gas turbine passenger car has been presented by one American car manufacturer to a limited number of people to determine its market appeal and roadability. Other manufacturers have produced some gas turbine trucks. No test data on the air pollution potential of these turbine vehicles have been published, although some initial tests of a gas turbine passenger car have been made in the PHS Laboratory in Cincinnati, Ohio. Since the gas turbine operates with an extremely lean mixture, its emissions may be expected to be relatively low in hydrocarbons and carbon monoxide. Since a relatively nonvolatile leadfree fuel is used, fuel evaporative losses should be minimal and the exhaust will be free of lead. A further advantage is that there is no crankcase to ventilate. The gas turbine offers promise of reduced pollutant emissions but it is too early to tell whether or not it will ever replace the piston-type engine.

Since no let-up is in sight in the worldwide increase in the number and use of motor vehicles, the U.S. Department of Health, Education, and Welfare is also deeply interested in even more radical solutions to the problem of vehicular emissions. These include possible replacement of the internal combustion engine with alternative power sources, such as fuel cells or electric batteries; and alternative means and patterns of transportation in and between our biggest cities, such as rapid transit lines. Among the possibilities of still longer range, urhan rebuilding to permit smaller population concentrations, each with work. residential, shopping, and recreation areas in close proximity, has been suggested

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