increase. Any risk to the population should be commensurate with the benefit resulting from the use of nuclear energy. Guides have been established to assist in maintaining radiation exposures at reasonable levels. 80, 81

(3) Relative importance as air pollutants

To put the various sources of radiation exposure in some perspective, the Federal Radiation Council estimates the radiation exposures to the U.S. population resulting from all past nuclear tests at 110 millirem (the conventional unit of measurement) for whole body exposure over a 30-year period and at 465 millirem for bone exposure over a 70-year period. These amounts are only percent and 5 percent, respectively, of the corresponding figures (3,000 millirem and 9,000 millirem) for exposure to naturally occurring radioactive materials in the environment. Expressed in another way, the U.S. population having the highest exposure has received an exposure from the radioactive fallout of all past nuclear tests about equal to that from natural radiation in this country in one year. Of course, this exposure is in addition to that from natural sources. 1. Pesticides.-Airborne hazards from pesticides have largely been related to occupational exposure on the part of persons concerned with their application. There are some instances in which pesticides applied by aircraft have drifted from the intended area to another area, with troublesome consequences, but on the whole, the evidence of adverse effects on members of the general population from the inhalation of airborne pesticides is minimal.83

On the other hand, pesticides not only provide an example of the many new chemicals which in their production and use are potential air pollutants but also constitute a class of products which, by virtue of their toxicity and widespread use, require special consideration in any program to anticipate and ameliorate the harmful effects of atmospheric pollution.

Sales of organic pesticidal chemicals by primary producers increased 15.7 percent in 1961 and another 14.4 percent in 1962, when they amounted to $346,441,000. In the report cited above, the President's Science Advisory Committee pointed to increasing volume of use, persistence of some chemicals in the environment, observed effects on wildlife, and indications that at least two insecticides are accumulating in man, as evidence of the need to obtain more data on the present levels of pesticides in our environment and to increase our efforts to understand their longterm effects.

SULFUR OXIDES

The sulfur oxides that are of concern as atmospheric pollutants are sulfur dioxide, sulfur trioxide, and their acids and acid salts. Fossil fuels, such as coal and petroleum, contain elemental sulfur, and when the fuel burns, the sulfur is converted to sulfur dioxide and to a lesser degree, sulfur trioxide. Since fossil fuels are burned abundantly in the United States to heat buildings and to generate electric power, pollution of the atmosphere with the oxides of sulfur is widespread and is especially prevalent in cities. Petroleum refineries, smelting plants, coke processing plants, sulfuric acid manufacturing plants, coal refuse banks, and refuse burning activities are also major sources of sulfurous pollution. Effects of Sulfur Oxides on Man

The evidence is considerable that sulfur oxide pollution aggravates existing respiratory disease in humans and contributes to its development. Sulfur dioxide gas alone irritates the upper respiratory tract; adsorbed on particulate matter, the gas can be carried deep into the respiratory tract to injure lung tissue. Sulfuric acid when inhaled in a certain particle size can also deeply penetrate the lung to damage tissue.

In the documented air pollution disasters-Meuse Valley, Belgium, 1930; Donora, Pennsylvania, 1948; New York City 1953 and 1963; London, 1952 and 1962-large numbers of people became ill and many died. All episodes had common factors; they occurred in heavily industrialized areas during relatively brief

Federal Radiation Council. Background Material for the Development of Radiation Standards. Washington. Report No. 1. 1960 and Report No. 2 1961.

1 Federal Radiation Council. Background for the Development of Radiation Protection Standards. Washington. Report No. 5, 1964. Federal Radiation Council. Estimates and Evaluation of Fallout in the United States from Nuclear Weapons Testing Conducted Through 1962. Washington. Report No. 4,

1962.

Interagency Coordination in Environmental Hazards (Pesticides): Hearings before the Subcommittee on Reorganization and International Organizations of the Committee on Government Operations. United States Senate, Part I (May, June 1963): U.S. Government Printing Office, Washington, 1964.

periods of anticyclonic weather conditions; and sulfur dioxide levels were excessively high as were levels of other gaseous and particulate pollution. Although the pattern of effects was not perfectly uniform in all these episodes, generally speaking, the elderly, the very young, and those with preexisting cardiorespiratory disease were most affected.

Epidemiological and clinical studies substantiate this evidence that certain portions of the population are more sensitive to sulfur oxide pollution. For examples: prolonged exposure to relatively low levels of sulfur dioxide has been associated with increased cardiovascular morbidity in older persons; prolonged exposures to higher concentrations of sulfur dioxide has been associated with an increase in respiratory disease death rates and an increase in complaints by school children of non-productive cough, mucous membrane irritation. and mucus secretion; the residual air in the lungs of emphysema patients has been significantly reduced when the patients breathed ambient air that had been filtered of pollutants; and the most important single factor to correlate (inversely) with the feeling of well-being in chronic bronchitis patients has been the level of smoke and sulfur dioxide pollution.

Sulfur oxides pollution can also adversely affect the more robust portions of the population. Experiments in which healthy human volunteers were exposed to sulfur dioxide concentrations several times higher than the taste threshold concentration indicate that such exposures will produce pulmonary function changes including increased respiration rates, decreased respiratory flow rates, and increased airway resistance. The impairment of function is greater when the sulfur dioxide gas is administered together with particulate matter.

In other experiments in which healthy human subjects were exposed to sulfur oxides, effects were observed but a complete interpretation of effects could not be made; for examples, concentrations of sulfur dioxide below the taste threshold produced cortical conditioned reflexes. and concentrations at the taste threshold desynchronized the predominant wave in electroencephalograms and increased the sensitivity of the dark adapted eye.

Clinical-epidemiological studies on humans in community atmospheres

Clinical-epidemiological studies on the acute and chronic effects of community atmospheres containing oxides of sulfur at various concentrations have been undertaken by numerous investigators. It should be noted that these atmospheres contained other pollutants as well and, that although sulfur dioxide is the measure of sulfurous pollution in the studies, also present were an undetermined amount of sulfuric acid mist and sulfate salts. It has been shown by numerous investigators that the effects related to a given amount of sulfur dioxide in community air can be expected to be greater than in laboratory experiments in which sulfur dioxide was the only pollutant.

Spicer made daily observations over a period of several weeks of air pollution and pulmonary function of a group of normal individuals and a group of subjects with chronic obstructive airway diseases. In general the airway resistance and other measures of pulmonary function of the two groups changed together from week to week, and persons within either group changed together from day to day. An analysis of individual persons revealed that some responded to changing concentrations of one component of air pollution, others responded to changing concentrations of another component, and still others responded to many things. The data seem to indicate increasing airway resistance in patients with chronic obstructive lung diseases when exposed to as little as 0.05 parts per million (ppm) sulfur dioxide in ambient air. Sulfur dioxide concentrations averaged over 2-hour periods ranged from nearly zero up to 0.5 ppm during the period of the study. Further studies are needed to substantiate these observations.

Lawther and Waller and Pemberton studied groups of patients with chronic bronchitis over several winters. Lawther's group consisted of about 1000 patients with established bronchitis who recorded daily whether they felt better or worse than on the preceding day. The percentage of those who felt worse than on the preceding day was then calculated. Fluctuations in this index followed closely the daily variations in air pollution, and when smoke rose above 300 g/m2 and sulfur dioxide above 0.21 ppm the health of the groun deteriorated. The authors concluded that air pollution as measured by smoke and sulfur dioxide was the most important factor affecting the day to day well-being of the subjects.

McCarroll et al studied a large number of families (approximately 1000 people) in New York City and correlated the symptoms of upper respiratory tract and eye irritation with sulfur dioxide concentrations. In two air pollution episodes occurring in the period November through December of 1963, in which the daily average sulfur dioxide concentration exceeded 0.2 ppm for 4 days and reached maximum 1 to 2 hour average concentrations of 0.9 to 1.5 ppm, there were significant increases in the incidence of rhinitis, sore throat, cough, and eye irritation.

Anderson and Ferris found that, after controlling for age, height, sex, and smoking habits, one second forced expiratory volume and Wright peak expiratory flow rates were greater for persons living in a town with less pollution (0.05 mg sulfur trioxide/100 cm3/day; 10 tons/mi2/mo dustfall) than for persons living in a more polluted town (0.4 mg sulfur trioxide/100 cm3/day; 35 tons/mi2/mo dustfall). In both towns air pollution was measured only during August and September, months of generally low pollution in the United States and Canada. Prindle, et al observed greater airway resistance in persons who lived in the more heavily polluted of two towns where sulfation rates (3.7 mg sulfur trioxide/100 cm3/day) and dustfall (83 tons per square mile per month) were respectively 6.2 and 3.2 times greater in the one town than the other. Gaseous sulfur dioxide averaged 0.09 and 0.01 ppm in the high and low polluted towns respectively. The major source of pollution was a coal fired power plant.

Epidemiologic studies of morbidity within cities

Diseases which seem to be of the most concern from the standpoint of sulfur oxides pollution are chronic bronchitis and/or chronic disabling respiratory diseases, cardiac diseases, and respiratory diseases due to infection.

Martin studied daily hospital admissions in London during the periods 1958 to 1959 and 1959 to 1960. The hospital admissions were separated into three categories: (1) diseases from all causes; (2) cardiac diseases, and (3) respiratory diseases. For each category a daily morbidity index was determined as the deviation in number of admissions from the 15 day moving average. The separate daily morbidity indexes were than correlated with daily measures of smoke and sulfur dioxide. Correlation coefficients of morbidity from all causes with smoke and sulfur dioxide were significant only in 1958 to 1959. Correlation coefficients of respiratory morbidity with smoke and sulfur dioxide were essentially equal-0.25 in 1958 to 1959 and 0.34 in 1959 to 1960. Correlation coefficients of cardiac diseases with smoke were 0.28 in 1958 to 1959 and 0.22 in 1959 to 1960; with sulfur dioxide they were 0.20 in 1958 to 1959 and 0.23 in 1959 to 1960.

Burn and Pemberton observed that up to four times as many bronchitis attacks were reported than were expected during five smog periods in Salford, England during 1958. Daily average sulfur dioxide concentrations during these periods were between 0.5 and 1 ppm, and daily average smoke concentrations were above 1 mg/m3. During the year period, bronchitis attacks ranged from 130 percent of expectation in the most severely polluted area to 60 percent in the least polluted area. Average daily sulfur dioxide concentrations in the more heavily polluted areas were approximately 0.25 ppm; in the less polluted areas average daily sulfur dioxide concentrations were approximately 0.10 ppm. Average daily smoke values were approximately 500 μg/m3 in the more severely polluted areas and 350 μg/m3 in the less polluted areas.

In a Detroit, Michigan/Windsor, Ontario study, greater morbidity was observed in areas with higher pollution than in areas with lower pollution. Sulfur dioxide concentrations were about twice as high in the more polluted areas (0.04 to 0.10 ppm annual average) as in the lesser polluted areas. In the more highly polluted areas suspended particulates were found to be 1.2 to 1.8 times greater (193 to 281 μg/m3 annual average) than in the lesser polluted areas. absolute differences in pollution between otherwise comparable areas increased, greater increases in sickness rate between the areas were noted.

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Zeidberg, et al studied morbidity among 9.313 individuals in 2.833 households in Nashville, Tennessee. The major part of the analysis was confined to the middle socioeconomic class households representing 6,393 individuals. A direct correlation between morbidity and pollution could not be shown with any consistency except for those 55 years of age or older. In this older age group cardiovascular morbidity among the white population progressed as either the soiling index or sulfur dioxide concentration in the residential area increased. Cardiovascular morbidity was approximately twice as high in the

most polluted areas (annual average-Cohs 0.831 or more, sulfur dioxide 0.01 ppm or more) as in the least polluted areas (Cohs 0.330 or less, sulfur dioxide 0.005 ppm or less). The annual averages are geometric means which can be approximately converted to arithmetic means by multiplying by 1.5. Relationships between air pollution and morbidity rates for cancer, respiratory diseases, and gastrointestinal diseases could not be demonstrated.

Epidemiologic studies of morbidity between cities

Dohan studied the incidence of respiratory illnesses lasting more than 7 days in female employees in 5 cities. The results of this study showed a very high correlation (0.964) of the average concentration of suspended sulfate in the air in these cities with the rate of respiratory illnesses. The average sulfate concentrations for the cities ranged from 5 to 20 μg/m3. During the noninfluenza epidemic years the incidence of respiratory disease was more than twice as great in the city with the highest surface concentration as in the city with the lowest sulfate concentration.

The incidence of total respiratory disease during the 1957 to 1958 Asian influenza epidemic was greater than in the same cities during non-epidemic years. In the city with the lowest concentration of suspended sulfates there was approximately a 20 percent increase in the incidence of respiratory illness during the epidemic year, whereas, in the city with the highest concentration of suspended sulfate there was approximately a 200 percent increase in the incidence of respiratory illness. During the influenza year the incidence of respiratory diseases in the city with the highest pollution was more than 5 times as high as in the city with the least pollution. The author could not demonstrate correlations between respiratory disease rates and the mean concentrations of benzene soluble organic matter, acetone soluble organic matter, nitrates. copper, or zinc. However, the mean concentrations of nickel and vanadium (measured in 4 cities) increased along with increase in incidence of respiratory disease.

Epidemiologic studies of morbidity associated with air pollution episodes

Increased illness rates associated with the acute air pollution episodes which occurred in the Meuse Valley in 1930, Donora in 1941, New York City in 1953 and 1962, and London in 1952 and 1962, and in which high concentrations of sulfur oxides were present have been reported.

In the Meuse Valley, Belgium during a period of anticyclonic weather in December, 1930, a dense fog enveloped the valley. By the third day many of the residents developed throat irritation, hoarseness, productive and non-productive cough, shortness of breath, and sense of chest constriction. Some individuals also developed nausea and vomiting. The most severely affected were elderly people and individuals who had previous cardiorespiratory disease. No measurements of air pollution were made at the time of the episode, but subsequent investigations indicated that the oxides of sulfur were the principle irritant.

In Donora, Pennsylvania in October, 1948 a similar meteorological condition occurred which lasted 4 days. By the third day 42.7 percent of the population (5910 persons) developed mild to severe symptoms of irritation characterized by burning of the eyes, tearing, nasal discharge, sore throat, non-productive cough, nausea, vomiting, and diarrhea. No age group was spared but the incidence rate of illness increased with age. Regardless of age the most sensitive individuals were those with pre-existing heart and lung disease. Retrospective studies indicated that sulfur dioxide levels may have reached 0.5 to 2.0 ppm and that large numbers of other airborne particulates and gases were present.

Ciocco and Thompson restudied the Donora population 10 years after the incident. Among the persons surviving in 1957 who could be questioned (80 percent of the total study group) there was no evidence that those who smoked tobacco in any form prior to October, 1948 became ill during the episode at a higher rate than those who did not smoke. The essential findings were that persons who reported acute illness at the time of the smog episode subsequently demonstrated higher mortality and higher prevalence of illness than the other persons living in the community at that time.

Abercrombie reported that the normal number of weekly applications for emergency bed service during the month of December in London was approximately 1000. In 1952 when a severe smog developed between December 5 and December 9 the weekly total number of applications was more than 2500. The increase in illness was larger in cardiorespiratory disease. The illness rate did not return to the normal statistical rate for approximately 2 to 3 weeks. Sulfur

dioxide measurements during the smog reached peak levels of 1.3 ppm and the general average during the episode was 0.7 ppm.

Greenburg, et al. reported that during the period of high air pollution in New York City in November, 1953 pediatric and adult clinic visits for upper respiratory illnesses and cardiac diseases rose above normal in all of the 4 hospitals studies. Sulfur dioxide ranged between 0.07 ppm and 0.86 ppm from November 12 to November 24, and hospital admissions were clearly elevated by November 16 at which time concentrations had not exceeded 0.25 ppm.

From November 27 through December 4, 1962 a condition of atmospheric stability occurred in New York City during which sulfur dioxide concentrations ranging up to 1.4 ppm and Cohs values ranging up to 9 were observed. Greenburg. et al studied visits during this period for upper respiratory infections, cardiac conditions, and asthma at five emergency clinics in the major city hospitals, four old-age homes, an employee clinic at the Chase National Bank, and visits recorded by the Blue Shield Health Insurance Plan. The average daily visits at each of the installations were compared with the period prior to and subsequent to December 1 through 7. No significant change was found in the records of any of the facilities with the exception of the four old-age homes. significant rise in upper respiratory illness was found in all 4 of the old-age homes, and the incidence of illness did not return to normal until after December 14.

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Acute illnesses then, of epidemic magnitude developed after 24 hour average sulfur dioxide concentrations of approximately 0.5 ppm, during which peak hourly averages of 0.75 ppm or more occurred, and when suspended particulate matter concentrations of 1000 μg/m3 or higher or when Cohs values of 8 or more were attained. Increased hospitalization and outpatient clinic visits were primarily attributed to cardiorespiratory illnesses. In severe episodes accompanied by fog, nausea and vomiting occurred in addition to the usual symptoms of respiratory irritation. Secondary complications frequently develop in individuals of all age groups, but the elderly individuals and the individuals with preexisting cardiorespiratory disease are especially susceptible. From one study it was determined 10 years after the episode that individuals who became ill during the outbreak had a less favorable morbidity and mortality experience than those who were not so affected.

Epidemiologic studies of deaths among cities

Studies of differences in death rates between different cities of the United States as they relate to air pollution have not been made. However, several such studies have been made in England. Very high correlations have been obtained between various measures of air pollution containing sulfur oxides and respiratory disease deaths. Bronchitis death rates relate strongly to indices of air pollution from domestic coal consumption, lead peroxide candle sulfation rates, and to pH of the precipitation. Pneumonia death rates increase from 40 per 100,000 to 60 per 100,000 as sulfate in the dustfall increases from 1.4 to 7 tons/ mi2/mo. Bronchitis death rates increase by a factor of about 1.5 as lead peroxide candle sulfation rates increase from 0.75 to 2.25 mg/100 cm2/day. Epidemiologic studies of deaths during air pollution episodes

Numerous reports of increased deaths during air pollution episodes exist. In London, annual average sulfur dioxide concentrations are about 0.10 ppm, but fogs are frequent, and air pollution episodes occur in varying degrees almost every year. In the most notable episode, that occurring in 1952, there were 4000 excess deaths. During this episode sulfur dioxide averaged 0.7 ppm during the 4-day period and reached a peak of 1.3 ppm for a "short period". In the United States only a few such incidences have been recorded, but an intensive search for their occurrence has not been made.

In the 4 day air pollution episode at Donora, Pennsylvania in October, 1948, 17 persons died on the third day and 3 other deaths were ascribed to fog. Normally at Donora in the period 1948 to 1948 about 100 persons died per year or 1 person every third day. The ages of the 20 persons who died during the episode ranged from 52 to 84 years. Pre-existing disease of the cardiorespiratory system appeared as a single factor among the fatally ill, although in four cases no history of any chronic disease was obtained. Autopsies of three persons who died during the smog showed acute changes in the lungs characterized by capillary dilation, hemorrhage, oedema, purulent bronchitis, and bronchiolitis. Chronic cardiovascular disease was a prominent feature in the autopsies.