Infected animals exposed to 25 parts per million of nitrogen dioxide for 2 hours showed an increased mortality rate and decreased survival time. This effect was evident up to 72 hours after infection. Exposure to 2.5 parts per million of nitrogen dioxide for 2 hours did not produce any apparent changes in susceptibility to infection.

Freeman and Haydon 43 in a continuing study of groups of rats exposed to concentrations of 12.5, 25, 50, and 100 parts per million of nitrogen dioxide respectively observed that after 213 days at 12.5 parts per million about 10 percent of the rats died of pulmonary complications with strikingly voluminous lungs (emphysema) such as is produced more abundantly by the higher exposure concentrations. The body weights of the survivors averaged about 20 percent less than controls of the same age. The respiratory rates for these animals averaged about 60 per minute with a wide range compared to rates of about 40 per minute for control animals. Pathological studies of rats exposed continuously to 25 parts per million of nitrogen dioxide were performed. Half the rats, the controls, were sacrificed; the other half, which died between 146 and 157 days after start of exposure were examined. The latter group exhibited strikingly voluminous lungs at autopsy which were anatomically characteristic of emphysema. Examination of the lung sections revealed moderate hypertrophy and hyperplasia of the bronchial and bronchiolar epithelium. The major bronchi contain increased numbers of active goblet cells.

Exposure of guinea pigs to concentrations of nitrogen dioxide of 5 parts per million and above has been shown to alter the lung protein in the exposed animals, making it antigenic.49

When such lung homologosate was injected to guinea pigs not previously exposed to nitrogen dioxide immunological studies revealed the development of abnormal proteins presumably antibodies. Lead

Effects on humans.-Recent review and study of the concentrations of lead emissions from auto exhaust as a source of community atmospheric pollution suggest that there has been little change in the atmospheric lead concentration over the past 10 years. Since atmospheric concentrations may vary significantly from year to year because of source factors and meteorological conditions, principally the latter, it is not possible to establish trends on the limited amount of atmospheric air monitoring data available. It can be demonstrated however that lead concentrations of blood and urine samples show the effects of environment. Data on lead concentrations in blood and urine samples of humans in the general population indicate these to be in the range presently defined as "normal."

Carbon monoxide

Effects on humans.-In a recent study 50 of the effects of exposures of healthy males to an atmosphere of 100 parts per million of carbon monoxide for varying lengths of time, it was determined that impairment of function due to carbon monoxide was detectable at levels of carboxyhemoglobin in the blood of the subjects below 5 percent. The degree of impairment increases with increasing concentration of the carboxyhemoglobin in the blood.

VEHICLE USE TRENDS

With the population increasing, and the number of automobiles also increasing, air pollution, unabated, will worsen. Recent automotive population and use trends are indicated in the following table:

Compared to the rate of population increase, the rate of increase of vehicular pollution has been greater and is expected to continue to be greater. The ratio of persons aged 20 and over per vehicle has decreased from an average of 3.13 in 1940 to 1.86 in 1960 and is predicted to further decrease to 1.26 by 1980.53

RECOGNITION BY STATE GOVERNMENTS

State governments in general are showing more concern for the preservation of air quality. Some States have taken steps to control automotive air pollution or are appraising the problem as a preliminary to taking control steps.

California

The State of California leads in the establishment of standards for the regulation of automotive pollutant emissions. The acute smog problem in metropolitan Los Angeles forced the control of exhaust carbon monoxide and hydrocarbons and crankcase blowby emissions. Continued surveys by California of vehicular emissions and laboratory investigations of emission sources indicated that the original standards would not return clean air to California and, on October 23, 1964, the California State Board of Public Health held an open hearing to consider the adoption of revised and additional motor vehicle emission standards.54 In this hearing:

1. The board adopted more restrictive standards for automobile exhaust hydrocarbons and carbon monoxide to become effective. January 1, 1970. The new standards limit hydrocarbons to 180 parts per million by volume (compared to the current limit of 275 parts per million) as measured with nondispersive infrared spectrophotometer sensitized with hexane, and limit carbon monoxide. to 1 percent by volume (compared to the current limit of 1.5 percent) as measured by nondispersive infrared spectrophotometer.

2. The board adopted more restrictive standards effective immediately for crankcase emissions-0.1 percent hydrocarbons by weight of the supplied fuel, compared to the 0.15 percent previously established.

3. The board adopted standards effective immediately for fuel tak emissions-6 grams per day of hydrocarbons-and carburetor hot soak emissions-2 grams hydrocarbons per soak.

4. The board issued a policy statement indicating that standards for nitrogen oxides are needed, and that the board will consider adoption of an exhaust standard for oxides of nitrogen in 1965. Continuing studies probably will lead to the adoption of hydrocarbon standards expressed in terms of the reactive hydrocarbons and standards for diesel exhaust odor.

Colorado

House bill No. 1050, approved March 18, 1964, requires the Colorado State Board of Public Health to keep informed on automotive air pollution with a view toward developing legislative recommendations. In addition, House Joint Resolution 1022, adopted February 23, 1964, requires that the Colorado Department of Revenue include crankcase emission controls in the items to be inspected on cars if the devices were factory installed.

District of Columbia

The Department of Motor Vehicles of the District of Columbia is charged with the responsibility of inspecting motor vehicles in accordance with traffic and motor vehicle regulations that prohibit motor vehicle emissions as dark as or darker than Ringelmann No. 2.

Illinois

The Illinois Air Pollution Control Act, passed August 19, 1963, defined motor vehicles as air contaminant sources and required the Governor to appoint a nine-member air pollution control board. On October 26, 1964, the board directed its technical secretary to prepare a report on the steps necessary to evaluate the automotive air pollution problem in Illinois and on the feasibility of such an evaluation. Indiana, Kansas, New Hampshire

Laws in these States require that the engine and power mechanism of every motor vehicle be equipped and adjusted to prevent the escape of excessive fumes and smoke.

New Jersey

On September 21, 1964, the New Jersey Air Pollution Control Commission, an agency of the New Jersey Department of Health, accepted a number of recommendations included in a report by the commission's motor vehicle committee. These recommendations are:

1. the commission urges that the State department of health to provide as quickly as possible information about the effect of motor vehicle pollutants on the air over New Jersey;

2. the commission and the State department of health are to urge the U.S. Public Health Service to approve and assist in a comprehensive air pollution survey of the New York-New Jersey metropolitan area as previously proposed by an interstate committee;

3. the commission requests the State department of health to provide detailed information on crankcase ventilation devices and their effectiveness and whether they affect negatively the operations of an automobile;

4. the commission urges the department to proceed with final development of its device for measuring the "smokeability” of gasoline-burning engines; and

5. the commission urges the department to hire a person with the training requisite to make the studies indicated."

On May 5, 1964, the State of New Jersey passed a resolution to create a motor vehicle air pollution control study commission to study

and report on air pollution and smog conditions resulting from motor vehicle fumes.

New York

Effective June 30, 1963, the New York State Legislature required all new motor vehicles, with certain exceptions, registered and manufactured or assembled in the State, be equipped with a crankcase ventilating system of a type approved by the air pollution control board.s Effective with the manufacture or assembly of all 1965 and subsequent vehicles, with certain exceptions, criteria specify that the crankcase emission control system shall prevent the emission to the atmosphere of at least 80 percent of the mode weighted blowby at the seventh decile of the vehicle blowby population (70 percent of the vehicles produce blowby equal to or less than this value).

Pennsylvania

The State of Pennsylvania, on May 8, 1962, appointed a panel of technical advisers on automotive air pollution. The panel's report acknowledges automotive vehicles as a major source of air pollution, states that reasonable controls are justified, and that a control program undertaken now will tend to alleviate present conditions and to prevent an increase in severity of the problem as the automobile density increases in the future.57 Among the panel's recommendations were

1. That atmospheric surveys of pollutants in selected localities be conducted;

2. That crankcase emission controls be required on new cars effective January 1, 1964;

3. That a program be initiated to determine the effectiveness of regular maintenance on emission reduction;

4. That, subject to the results of the study on maintenance, semiannual safety inspections be expanded to include condition of blowby devices and engines (ignition, carburetion, and air cleaner);

5. That the motor vehicle code be amended to cite vehicles operating on highways with continuous visible emissions other than water vapors.

PROGRESS IN THE RESOLUTION OF THE PROBLEM

Technical papers published by the Society of Automotive Engineers and other technical organizations document much of the air pollution control investigative activities of the automotive vehicle manufacturers.58 Progress of the device and vehicle manufacturers in developing controls are evidenced in the general use since 1963 of crankcase emission control devices and in the California approval of five devices or systems for controlling exhaust hydrocarbons and carbon monoxide. Promises to California by the automobile manufacturers that 1966 high-volume production cars will be equipped with built-in exhaust controls indicate further progress.

EXHAUST EMISSION CONTROL

Hydrocarbons and carbon monoxide

The California Motor Vehicle Pollution Control Board on June 17, 1964, approved four exhaust control devices for installation on new

passenger cars. Pursuant to the California law, new 1966 vehicles for which controls are available must be equipped with exhaust controls to be eligible for California registration.

One of the devices, a direct-flame afterburner, was approved also for used cars. Mandatory installation on used cars will not be required until a second device is approved,

Prior to the control board action the Automobile Manufacturers Association, on March 10, 1964, had announced that 1967 cars produced for California would be equipped with exhaust emission control systems which would meet California standards. The motor vehicle pollution control board action apparently stimulated the car manufacturers to speed their activities; on August 12 the manufacturers individually reported their progress to the board and described engine modifications that were commercially practicable and would enable vehicles to comply with the State standards. The manufacturers advised that the high-volume production 1966 cars delivered for sale in California would be equipped with the yet-to-be approved systems. One of these systems has since demonstrated its ability to comply with the California standards and criteria, and, on November 18, was approved for factory installation on new 1966 model cars produced by the manufacturer for sale in California. Other systems are now undergoing tests at manufacturers' proving grounds and in California. Road emission studies conducted in Cincinnati and Los Ageles have shown that under normal traffic conditions exhaust hydrocarbon and carbon monoxide emissions are inversely proportional to vehicle average speed.107

One new approach to hydrocarbon and carbon monoxide exhaust control that is presently being investigated uses timed-port fuel injec tion.59 60 Preliminary results show satisfactory vehicle operation at leaner air-fuel ratios through improved cylinder distribution, show exhaust emission reductions of 25 to 50 percent under road conditions and show an overage overall increase of 7 percent in the engine power developed. The method has an inherent advantage in that it markedly reduces the normal carburetor running and hot soak losses.

Oxides of nitrogen

Investigations have revealed possible methods of controlling the emission of oxides of nitrogen in gasoline engine exhaust. The applicability to and effectiveness of these control measures on the vehicle population have not yet been determined.

Studies of exhaust gas recirculation to reduce oxides of nitrogen emissions have produced conflicting results. One investigation indicated effectiveness without serious engine performance deterioration.61 Others have indicated significant reductions in emissions at the sacrifice of engine performance (which perhaps could be restored by extensive modifications of fuel metering and distribution equipment).62 63 64

Water injection has been found to effect a degree of control of oxides of nitrogen in exhaust gases.62 63 Water injection, however, has been said to promote engine wear and oil sludging under light load conditions,65 and in cold climates necessitates the use of an antifreeze solution with attendant operational cost increases.

An independent research organization recently disclosed the development of a catalyst for nitrogen oxides reduction. The catalyst.