Atmospheric Pollution PHILIP DRINKER Harvard School of Public Health, Boston, Mass. Atmospheric pollution implies abnormal concentrations of some substance in air. Excess nitrogen, carbon dioxide, or minute amounts of chlorine are evidences of pollution just as much as is common smoke. The polluting agent may be a gas, liquid (mist), solid, or even emanations as from radium. No hard and fast rules can’be set as to what concentrations constitute pollution, but any departure from normal air is presumed to be evidence of pollution. The polluting agent may be harmful to plant and animal life, it may be a nuisance and dirty our clothes and buildings, it may form explosive mixtures with air, it may be harmful to machinery or to a manufacturing process, or it may be detrimental to human health. Pollution is usually man-made (e. g., stack gases) but can be simply the result of natural phenomena (fogs or dust storms). Stack pollution
N UNUSUAL concentration of any substance in the at-
A
mosphere means pollution. Pollution may be caused by an excess of a normal constituent such as nitrogen, by a foreign gas such as ~ u l f u rdioxide, by a natural fog alone or accompanied by artificially produced smoke particles, by a vapor from a liquid such as benzene, by the effluent from chemical or metallurgical stacks, or by dust generated by grinding, blasting, or drilling of rock. If breathed in sutficient amounts for long periods, some of these polluting agents may be harmful, but as met by thd average man they are nuisances rather than health hazards. It is regrettable that most polluting agents are not worth the cost of recovery. There are exceptions, and the advocates of smoke control are quick to cite them. Cottrell’s first precipitator was installed to catch sulfur trioxide because the plant emitting it was a nuisance to the neighborhood. The fact that enough acid was recovered to be of financial interest was a welcome but unexpected sequel. We have all heard of recoveries of valuable metal fumes, but we get no such tales of the cash value of fly ash recovered from plants burning powdered coal or of sulfur dioxide from stack gases. Some years ago a large manufacturer near Boston offered to buy all the fine granite dust from the local granite cutters and use it as a filler in one of his processes. It soon became apparent that the dust collected in a month would not last the manufacturer more than a day. This is a typical example of the fact that trifling amounts of polluting agents are often the cause of trouble. The amounts loom large as a health matter but aw industrially trivial. The chemist will look in vain for analogies in these atmospheric suspensions to his true colloids. Most of our atmospherio suspensions are unstable, and it is fortunate that the slightest atmospheric disturbance, such as a change in wind, pressure, temperature, or relative humidity, upsets the equilibrium and generally changes the entire picture. The properties of the polluting agents which are of most importance to us are those which help in controlling them. Thus, sulfur dioxide creates a nuisance because of its corrosive
is preventable and appropriate control measures can be enforced. Fog control is still in the experimental stage. Some pollution problems have been solved in order to prevent the loss of valuable material. Others are controlled because the manufactured product is improved by freeing it from contaminants. But many instances of needless pollution are ignored until expensive damage suits force control. Industrial chemists are often required to estimate the concentration of these various contaminants. Concentrations range from grams per liter to micrograms per cubic meter. Some of the contaminants can be recorded automatically; others must be sampled as often as conditions dictate. Examples of various types of contaminants are given, together with methods for estimating and controlling them.
or destructive action which, in turn, is a function of its solubility. It is removed from air or other gases by treatment with suitable solvents, such as alkaline water. Katural fogs reduce visibility, which fact is used in measuring their intensity, while their comparative instability renders them susceptible to slight changes in temperature, pressure, or turbulent air motion. It is important to understand the magnitude of concentrations of the polluting agents as they are met in industrial life today. Sulfur dioxide is measured in parts per million by volume; dangerous concentrations of carbon monoxide are given in parts per ten thousand; flammable mixtures of gasoline with air are reported in per cent. Particles of lead fume in air are generally reported in milligrams per cubic meter, a dust such as silica is given in particles per cubic foot or per cubic centimeter, and a flammable dust, like starch, is reported in grams per liter. We deal, therefore, with concentrations for gases, mists, and dusts which vary over this enormous range.
Measurement of Pollution The duty of the chemist is to devise ways of measuring atmospheric pollution. If assigned such a task, he will seize at once upon the outstanding physical or chemical property of the polluting agent and try to adapt his concentration measurement to permit the use of this special property. Thus, the most important factor in pollution by natural fog is loss of visibility. The same is true of man-made smoke, as from chimneys. Visibility through smoke can be recorded or measured by eye or by appropriate photoelectric means. Sulfur dioxide is measured and recorded automatically by virtue of purely chemical reactions. Carbon monoxide is recorded by measuring the heat evolved from the oxidation of carbon monoxide to carbon dioxide. I n general, results from all such recording instruments are empirical and require careful calibration against known concentrations. The chemist naturally prefers such measurement to results of samples taken from time to time. Fur1316
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found that the trifling concentrations of sulfur dioxide in Washington, D. C., were enough to cause the deterioration of book paper and book bindings. At present there are no general ordinances in the United States specifically requiring control of sulfur dioxide in stack gases. If a condition is to be remedied, the usual method is to build a stack of sufficient height and sufficient capacity to ensure adequate dissipation of the gases. According to Pollution by Gases Monkhouse (12) a British investigating committee reported that if a chimney is over two and one half times as high as The most important gaseous contaminants are the sulfur gases. Recent surveys by the Air Hygiene Foundation (6) the surrounding buildings it offers reasonable assurance that the gases emitted will not come in contact with the earth. But have shown that concentrations of sulfur dioxide in industrialimagine building such a stack in the business district of New ized cities such as Pittsburgh, where much soft coal and oil York! Wells (19) showed that high stacks (200 to 450 feet) are burned, may reach 2.266 p. p. m., as compared with nondiluted to innocuous concentrations the sulfur gases from industrial Washington with maximum concentrations of large sulfide roasters and thus did away with a vexing pollu0.29 p. p. m. tion problem. In British power plants, according to Nonhebel (IS),sulfur dioxide concentrations of 0.05 to 0.2 per cent are treated with cleaning efficiencies of the order of 99.7 per cent. Nonhebel states that corrosion troubles in the scrubbing towers are eliminated if the pH of the scrubbing liquor is kept fairly close to 6.3. In air-conditioning apparatus for removing from 0.009 to 0.29 p. p. m. of sulfur dioxide from the air of the National Archives a t Washington, Kimberly (11) recommended that the wash water be kept a t pH of 8.5 to 9, a t which sulfur dioxide recovery is excellent. , 0 OTHER SULFURGASES. Hydrogen sulfide can be smelled I 4 MILES ‘FROM” STACK in comparatively low concentrations, about 0.34 p. p. m., and is very toxic to animals; it ranks with hydrogen cyanide in RELATION BETWEEN HEIGHT OF STACK that respect. At fairly high concentrations it is readily ab(IN FEET)AND SULFUR DIOXIDE CONsorbed by ferric hydroxide, but at low concentrations, which CENTRATION AT VARIOUSDISTANCES FROM THE PLANT (19) may be harmful to health, quantitative absorption is difficult. Low concentrations (parts per million or less) of foulsmelling sulfur compounds, such as carbon disulfide or the Burdick and Barkley (4) summarized various data from mercaptans, can be eliminated best if first oxidized to sulfur all over the world on sulfur compounds in city air. I n several dioxide. In certain industrial processes carbon disulfide is typical American cities, concentrations were found as shown recovered by absorption in activated carbon, but in terms of in Table I. true atmospheric pollution, wasteful concentrations of carbon disulfide rarely, if ever, are emitted from stacks. Carbon TABLE I. SULFUR DIOXIDE CONCENTRATIONS IN 0-5 MILE ZONE (P. P. M.) -~ PhiladelphiaSt Louis: disulfide is very toxic; Massachusetts Pittsburgh Camden Washington E St. Louis Detroit suggests 15 to 20 p. p. m. as the upper Av. Max. Av. Max. Av. Max. Av. Max. Max. Season Av. limit for continuous exposure to man. It Winter 0.093 0.897 0.041 0.354 0.014 0.290 0.261 2.266 0.051 0.370 Summer 0.060 o 828 0.030 0 . 4 2 4 0.003 0.086 0.111 1.080 o 023 o 228 is also flammable at 1per cent by volume Entire year 0,078 0.897 0.035 0 . 4 2 4 0,009 0.290 0.186 2.266 0.037 0.370 in air (I) so that there is a double reason for preventing its escape into the air,
thermore, one must always remember that the mere word ‘Lpollution” conjures up the unwelcome vision of damage suits or punitive action of some sort from local authorities. The best defense against such action and the best proof of proper conditions, is found in a continuous series of records of conditions. They are acceptable in court and their significance can be made clear to lay juries.
These authors also reviewed the literature on the effects of sulfur compounds on various materials, such as cement, stone, metals, paint, leather, paper, and cloth (3). Data are available on the effects of various concentrations under laboratory conditions in which temperature and humidity were controlled and under outdoor conditions, taken as they came. SULFURDIOXIDE.This gas is not particularly dangerous to man because it is irrespirable in toxic concentrations. All chemists know the violent coughing that a whiff or two of air containing a little sulfur dioxide will induce. Contrast this effect with that of breathing a few parts per million of some of the most successful war gases which are nonirritating in dangerous concentrations. Plant life generally is damaged by continuous exposure to concentrations of sulfur dioxide over 1 p. p. m. (19),but low concentrations are apparently without effect (17). Kimberly (11)
NOON
A M
SULl?UR
DIOXIDE CONCENTRATIONS TO
P.M.
12, 1936,
IN VARIOoS CITfiS, OCTOBER
APRIL25, 1937
Samples were taken at the street from the 0-16 b i l e limit ‘T%).
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CARBONMONOXIDE. I n the general atmosphere carbon monoxide means incomplete combustion. It is of no consequence in the gases from power plants, as their oombustion efficiency is so high. It does occur frequently in stack gases of locomotives or stationary engines when forcing combustion for a heavy pull and was an important factor in brineins about the electrification of railroad tunnels and subways. In the life of the average man today, carbon monoxide is associated either with leakage of manufactured gas into a room or with automobile exhaust gas. As engineers we do not tolerate more than a fraction of a per cent of carbon monoxide in the stack gases of the modern power plant, but we all drive motor cars emitting anything from 3 to 10 per cent of carbon monoxide-mute testimony to inefficient combustion. With carbon monoxide in exhaust gases we always find a certain amount of dirty carbonaceous smoke. Admitting that the modern passenger bus or fast 10-ton t r u c k operates a t a higher combustion efficiency than the average pleasure car, the average motorist hurries past the heavily Courlcw. R. n. McCIourin loaded truck PAaTICLES OF FLYASH, &ALL SPHERES WZTE VARYING AMOUNTS OF UNBURNED which he knows will s h i f t gears CARBON CAUSING PARTICLES TO PASS FRO= TRANSPARENT TO OPAqUE BLACK part way up the next hill and blast him with as foul a mess of odors as he is likely to meet. It is time we adopted the suggestions made long ago by Fieldner, Henderson, and others that motor cars and trucks exhaust their waste gases vertically through the roof, instead of horizontally close to the ground. Furthermore, it would not seem unfair to penalize heavyduty vehicles which emit foul-smeUing gases. We would not tolerate such smells from our neighbor's chimney, so why should we breathe them on our highways? I
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Industrial Mists and Fogs From December 1 to 5, 1930, a thick fog covered a considerable area along the valley of the Mense in Belgium. A large number of people were injured, many were attacked by acute respiratory troubles, sixty-three died on the fourth and 6fth days, after very short illnesses, and many head of cattle were killed or had to be slaughtered. On the sixth day the fog disappeared and with it went the respiratory troubles. At the time this catastrophe excited great interest, and it is surprising that no gas analyses were made. Therefore, it is a matter of chemical guesswork to 6x upon the specificpolluting agent responsible. Firket (6) points out that in the Li6ge district during the last thirty years fogs lasting more than three days have occurred five times, always in winter. I n all cases the various works in the district were in active production. The symptoms of those affected were acute gassing, similar to those from the lethal agents used in chemical warfare. A few parts per million of a powerful gas, such as phosgene or chlorine, can cause just such accidents, particularly to old
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accentuates natural fog. Recently Houghten and Radford (7) studied natural fogs with a view particularly to their partial elimination for airplane landings. Fog particles average about 40 p in size, and their density or concentration is approximately 100 to 200 mg. per cubic meter (8). For comparison a cloud of dry magnesium oxide sufficient to interfere seriouslv with visibilitv is of the order of 20 to 60 mg. per cubic mete;. Houghteu i n d Radford point out that natural fogs can be temporarily or locally reduced by electrical precipitation of the droplets (Cottrell process), by spraying charged sand particles into the atmosphere as from a plane, or by a combination of heat and air motion. Bearing in mind the huge volumes of air to be treated if conditions on the modern foggy landing field are to be momentarily remedied for landing or other purposes, Houghten and Radford believe that the circulation of carefully controlled currents of warm air offer the most promising approach and the least expensive in money or power. When we consider the growing importance of airplane transportation, it seems more than likely that some measure of fog control will soon be realized. In the prevention of natural fogs, however, we are as far from our objective as we are in all other forms of outdoor climatic control.
Dust and Fumes Dnst coneentrations in the midst of the Dust Bowl storms of a few years ago and dust storms in the desert regions of North Africa have reached concentration levels of sign%-
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cance to human health, but these concentrations are of short duration. It is perhaps of some interest to consider how far some of the sources of pollution can travel in ordinary air. In severe volcanic eruptions such as that of Krakatao in 1883, minute particles are thrown high into the air with such violence that they ultimately reduce solar radiation all over the earth. At the height of some of our midwestern dust storms particles of dust were collected in Boston and identified as coming from the districts in question. The surprising fact mas that many of these dust particles were as large as 20 to 30 p. In the case of the volcanic dust, particle size causing the solar halos was calculated to be 1.85 p (9). Next to fog, the commonest polluting agent is carbon in the form of soot, minute coal particles, or oily particles from incomplete combustion of one sort or another. The man i n the street does not worry about the distinction between a blast of black exhaust from a passenger bus and that from a faulty oil burner in the neighboring apartment house. H e has every right to have both corrected, and it is not necessary that he prove that concentrations reaghed levels dangerous to health. Routine smoke inspections are generally made in large but rarely in small cities, and practically never on streets or highways. The modern power plant emits little black smoke; the combustion efficiency is always extremely high, and pollution by visible particles or colored effluent is insignificant. It is true, EFFECTIVENESS OF MODERN AIR-CONDITIONING PLANT IN REMOVING POLLEN however, that most power plants have short FROM AIR (IO) periods during which they may cause conStation A is in Louisville, Ky., and station B in the suburbs of Louisville. siderable pollution-for example, by fly ashbut the tendency today is to control even these periods. those which in winter months cause respiratory troubles, such When smoke abatement campaigns are initiated in any as asthma, and in summer months, hay fever. The chronic community, it is usual to turn to the health authorities and asthmatic or the hay fever sufferer gets great relief from a urge that they appear before the committee and state that complete change in climate. We can prevent hay fever the health of the community is a t stake. The engineer is too (10) by the simple expedient of eliminating plant pollens a p t to indulge in the fallacious theory that a little inhaled from the inhaled air. Pollens are about 10 to 40 p i n diameter smoke or soot must be injurious since it is admitted that and are removed successfully by an air-conditioning plant. overwhelming doses are harmful. Unfortunately there is a Similarly, they can be caught effectively by the modern inlaw in physiology which states that a stimulus has to reach a dustrial dust respirator, or by drawing outdoor air through an certain level (usually unpredictable) before any reaction reappropriate filter and discharging it into a room which is then sults. A little dust or a little smoke, or even a little of some kept a t a slight positive pressure. Prevention of these respoison, may be completely without effect, whereas a dose piratory troubles by supplying clean air is naturally the of threshold intensity or greater produces a characteristic remethod the engineer or the chemist advocates. sponse. The question from the standpoint of public health really is, then, what is the threshold concentration of city Air-Borne Diseases and Air Conditioning smoke, and not whether a certain city is smoky or not. This is a hard question to answer. We cannot experiment Attention is being focused now upon air-borne bacterial and upon man, and experiments upon animals for the forecasting virus infections. If physicians define the causative agent in of slight or subtle reactions to man are unreliable. We must certain diseases as bacteria of definite size and shape, it is not have data on humans. The British have compiled the most particularly difficult for the engineer or chemist to devise complete records available on smoke pollution (1.4). In means for killing the bacteria. For instance, ultraviolet America, the city of Pittsburgh has been the most consistent light (& the I) addition , of suitable bactericidal agents to the i n studying its smoke problem. Recently Schnurer (16)rewater of air washers (5),or special masks (18) will ensure the ported upon a considerable series of autopsy records from wearer of adequate protection. hospitals in the Pittsburgh district. Comparing the evidence It has been shown beyond reasonable doubt that ultraviolet of persons suffering lung damage with that of persons who were light will kill dry, air-borne bacteria and probably air-borne not city dwellers, Schnurer feels that the effects of coal smoke viruses (those substances which pass easily through filters and and dust upon lungs cannot be ignored. cause diseases such as infantile paralysis, yellow fever, and The dusts of greatest interest to the general community are influenza). Admitting, for the sake of argument, that engi-
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neem can free indoor air of such contaminants by various airconditioning methods, it remains to be shown that the population at large will be benefited by breathing only such sterilized air while indoors. It is a refinement which may prove needless and, conceivably, can even prove harmful. When it was first applied, the air washer was intended to do just what its name implies. The realization soon came that it was only moderately effective as a cleaner but very useful for dew point control. Today it is used for dew point control and little else. If special air cleaning is needed, as is usually the case in cities, it is done by filters which are cleaned from time to time or else thrown away. Little attention has been paid t o the possibility of adding to the wash water substances that will increase wetting power and thus let us catch fine particles which now pass through the washer. No chemist who has followed the remarkable progress in flotation of the nonmetallic minerals during the last few years will deny that the outlook for improvement in air washing is likely. The air-conditioning industry needs such improvement badly and would welcome the interest and cooperation of chemists in that field. Sometimes we need air for industrial purposes which is absolutely free from particulate matter. Tyndall thought that expired air from humans was dust-free, but improved analytical methods have shown that he was wrong. It is difficult to measure degrees of pollution which are less than those we would find on the top of a mountain. However, we can prepare such air today and can measure its cleanliness. It
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seems likely that further uses for dust-free air will be found and that it will be comparatively common in the future.
Literature Cited (1) Air Hygiene Foundation of America, Preventive Eng. Series, Bull. 2,pt. 8 (Jan., 1939). (2) Air Hygiene Foundation, Special Research Series, Bull. 1 pt. i (Sept. 1, 1937),pt. ii (Jan. 20, 1938). (3) Burdick, L. R., and Barkley, J. F., U. S. Bur. Mines, Circ. 7064 (1939). (4) Ibid.. 7066 (19391. (5) Carswell, T: S., boubly, J. A., and Nason, H. K., IND. ENQ. CHEM.,29, 85 (1937). (6) Firket, J., Trans. Faraday SOC.,32, 1192 (1936). (7) Houghten, H. G.,and Radford, W. H., Papers in Phusical Oceanography and Meteorology, 6, No. 3 (1938). (8) Ibid., 6 , No. 4 (1938). (9) Humphreys, W.J., “Physics of the Air”, Philadelphia, Lippincott Co.. 1920. (10) Kendal, T:A., and Weidner, G., Trans. Am. SOC.Heating Ventilating Engrs., 40, 229 (1934). (11) Kimberly, A. E., and Emley, A. L., U. S. Bur. Standards, Misc. Publ. 142, (1933). (12) Monkhouse, A. C.,Chemistry & I n d u s t r y , 58, 596 (1939). (13) Nonhebel, G.,Trans. Faraday SOC.,32, 1291 (1936). (14) Owens, J. S., Ibid., 32, 1234 (1936). (15) Roholm, K.,J . Indus. Hyg. Toxicol., 19,126 (1937). (16) Schnurer, L., Ibid., 20, 14 (1938). (17) Setterstrom, C . , Zimmerman, P. W., and Crocker, W., Contrib. Boyce Thompson Inst., 9,179 (1938). (18) Tolman, R. C., et al., J . Infectious Diseases, 24,637 (1919). . , 640 (1917). (19) Wells, A. E., J. IND.ENG.C H ~ N9, (20) Wells, W. F., and Wells, W. W., J . Am. Med. Assoc., 107, 1698, 1805 (1936).
Legal Aspects of the Industrial Wastes Problem JAMES A. TOBEY American Institute of Baking, New York, N. Y.
vv
‘HEN legal principles are applied to the perennial problem of industrial wastes, they involve the right of every individual to the reasonable enjoyment of life, liberty, and property, and the power of the state to regulate persons and property in the interests of the common good and the general welfare. The legal aspects of this vexatious problem are concerned, therefore, with both private law and public law. However, the mere invocation of that omnipotent force known as The Law is not a panacea for such technological and sociological maladies as industrial wastes. Neither legislation nor judicial action, alone or together, can solve a problem that also requires for its solution such important elements as investigation and research, the application of new and established technical procedures, the education of industry and the mobilization of public opinion, and the provision for financial and economic aid where necessary. Legislation, law enforcement, and litigation may, nevertheless, be potent factors in helping to correct abuses due to the waste products of necessary industrial processes. The magnitude of this problem is indicated by the fact that food, textile, chemical, metallurgical, paper, and other industries whose products are valued a t 18 billion dollars, and who employ some 3 million workers, are now discharging wastes
into streams, the air, and the soil (1). I n addition, mining waste is coming from nearly twenty-eight thousand active and abandoned mines and oil fields in this country. It is estimated that an expenditure of approximately 2 billion dollars a year over a period of 10 to 20 years would be necessary on the part of American municipalities and industries t o abate the more objectionable pollution.
Industrial Wastes as Nuisances Whenever industrial wastes pollute the soil, the atmosphere, or waters so as to cause harm and annoyance to individuals, they constitute a nuisance. Legal redress in such matters is therefore governed by the American jurisprudence that has been established with respect to public and private nuisances (2). Industrial wastes that cause trouble usually are both public and private, or mixed nuisances. Such wastes may be detrimental to the comfort, security, and possibly to the health of one or more individuals, and they may also affect the welfare of a considerable number of persons in a community. An individual is entitled to suitable legal action for injuries caused by a private nuisance of this nature, although he cannot proceed against a public nuisance that does not directly
