Document 93wwxkqk8Z1gaoyzqOan9NZx7

feature PCB's-prevalent and persistent Intensified research is needed to minimize their dangers Carl G. Gustafson, Federal Water Quality Administration, Athens, Ga. I during the past three years, a special class of compounds, called polychlorinated biphenyls (pcb's), has claimed the attention of ecologists and pesticide analysts in this country. These compounds were not discovered in the environment until 1966 in Swe den and 1967 in the U.S., despite the fact that they have been available com mercially for 40 years. Interest in pcb's has arisen because they are frequently found in fish, bird, water, sediment, and other environmental samples when such samples are examined for chlori nated pesticide residues. That a wide variety of samples containing pcb's has been collected from England, Scandi navia, The Netherlands, Antarctica, Central America, and many different parts of the U.S. makes them truly ubiquitous pollutants. Polychlorobiphenyls are made by substituting chlorine atoms for one or more of the hydrogen atoms at the The Monsanto Co. stated recently in a letter to Congressman William F. Ryan of New York that as of August 30, it would no longer sell pcb's to , customers for use in general plasticizer operations where disposal of the endproducts cannot be controlled. After some lag period--the time it takes to eventually dispose of the products made from pcb's and currently in processor's inventories--the quantity of pcb's getting into the environment may be substantially reduced. If Monsanto's former customers look for PCB substitutes, rather than purchasing pcb's from manufacturers in Japan and Europe, the projected decrease could become a reality. Carl G. Gustafson 814 Environmental Science & Technology numbered positions of the biphenyl structure. In the process of replacing hydrogen atoms with chlorine atoms, a large number of substitution combinations arise. For example, three monochlorobiphenyl isomers are possible, 12 dichlorobiphenyl isomers, 21 trichlorobiphenyl isomers, and so on. Theoreti cally, 210 compounds can be prepared by this substitution process; a typical example would be 2,4,6,2'4'-pentachlorobiphenyl. Whenever aromatic hydrocarbons such as biphenyls are chlorinated, the product is a mixture of compounds, in cluding isomers. It is quite difficult to synthesize single, specific chlorobiphenyl compounds in the laboratory unless involved procedures are em ployed. Consequently few of the indi vidual compounds have been prepared in the pure form for study. In the commercial process for pcb manufacture, biphenyl is chlorinated with anhydrous chlorine in tall cy lindrical towers with either iron filings or ferric chloride as the catalyst. The by-product is hydrogen chloride; the product is a mixture of several pcb's. The degree of chlorination is deter mined by measuring the specific gravity of the mixture or, when the product is more viscous, the ball-and-ring soft ening-point test is used. The whole pro cess takes from 12 to 36 hours. In the U.S., the sole manufacturer of pcb's is the Monsanto Co., which markets them under the trade name Aroclor. pcb's are also manufactured in Europe and Japan, under trade names such as Phenochlor and Clophen. The various Aroclors are dif ferentiated by a four-digit number, with the last two digits indicating the percentage of chlorine in the mixture. Properties The three most important physical properties of the pcb's are low vapor pressures (they have high boiling points), low water solubility, and high dielectric constants. They are mis cible with most organic solvents and compatible with many types of poly mers. Although some individual polychlorobiphenyl compounds are crys talline, the Aroclor mixtures are either liquids or resins. The chemical properties that make pcb's desirable industrial materials are their excellent thermal stability, their strong resistance to both acidic and basic hydrolysis, and their general in ertness. They are quite resistant to oxidation. Monsanto reports, in a tech nical bulletin on pcb's, that they can be heated to 140 C. under 260 p.s.i. of oxygen pressure "without showing any evidence of oxidation as judged by de velopment of acidity or formation of sludge." The physiological properties of the pcb's make them potentially significant contaminants of the environment. For any pollutant, two factors are involved: acute toxicity, which is immediately evident because of a high death rate or other maiming effect; and chronic tox icity, which is the result of a slow ac cumulation of the poison in the body and is a sublethal effect. Whenever acute toxicity is high, a pollutant will be readily recognized and appropriate remedial actions will be introduced. If, on the other hand, acute toxicity is low, DSW 223273 STLCOPCB4053441 chlordane, dieldrin, and pcb's, activate enzymes in the liver which transform estrogen into a more water-soluble compound that is readily eliminated from the bird's body. This means that when estrogen levels are low, calcium reserves will also be low, and there fore very little calcium will be avail able for strong eggshell production. Dieldrin and pcb's are more effective than ddt in this type of enzyme-induc tion activity. Aroclor 1262 has an es tradiol degrading potential four to five times that of p,p'-dde or technical grade ddt. The ability of the female bird to deliver calcium to her oviduct during the last 20 hours, when the eggshell is being formed, is related to the func tioning of the enzyme carbonic anhydrase. When birds that have ex hibited the ability to lay normal eggs are injected with a metabolite of ddt (dde) just prior to the formation of the eggshell, they will lay thin-shelled eggs. This indicates that ddt also in hibits the activity of carbonic anhydrase, the enzyme that controls the flow of calcium from the blood stream of the bird into its oviduct. Since dieldrin seems to have no effect on carbonic anhydrase, we may assume that neither do the pcb's. How ever, these compounds delay breeding time significantly. Many ornithologists feel that late breeding has a stronger influence on the reduction of bird populations than does the laying of thin-shelled eggs. If this is true, pcb's are a more potent threat than ddt to our declining bird populations, es pecially for predatory birds that ac cumulate fairly high levels of pcb's be cause they eat smaller animals that al ready have concentrated pcb's in their own tissues. Other investigators have produced evidence to show that pcb's are simi lar to ddt in their activity. Dr. Joseph Street at Utah State University has shown that when pcb's accumulate in the liver, they induce microsomal en zyme activity by bringing about more rapid metabolism of drugs, insecticides, and other foreign compounds. He fed rats a diet containing 50 p.p.m. of Aroclor 1254 or Aroclor 1260. After 10 days on this diet, the test animals were administered hexobarbitol at a dose of 100 p.p.m. to induce sleep. In comparison with a control group, the sleeping time for these rats was reduced by 65 to 80%. Street also found that Aroclor, when fed at the 816 Environmental Science & Technology same level, will reduce dieldrin stor age in adipose tissue by 90 to 95 %; in crease aniline oxidation by 200 to 300%; and increase epn detoxication by 430 to 470%. In addition, the pcb's cause activation of organothiophosphate compounds, which adversely af fect the system. This latter effect coun terbalances the detoxification of diel drin. Normally, when a substrate activates an enzyme, it is converted to a watersoluble form that will be eliminated from the system; however, this is not the case with pcb's. Because they re main in the system for prolonged pe riods of time, their enzyme induction activity is always present. In this way the normal concentration of important body chemicals may be lowered to the point of bringing about malfunctions in the system. For example, Street be lieves that the pcb's bring about steroid degradation, which can lead to altered, endocrine relationships. The chronic toxicity to man is as follows: Like the chlorinated naphthalenes, the chlorinated diphenyls have two distinct actions on the body, namely, a skin effect and a toxic action on the liver. The lesion produced in the liver is an acute yellow atrophy. This hepato-toxic action of the chlorinated di phenyls appears to be increased if there is exposure to carbon tetrachloride at the same time. The higher the chlorine content of the diphenyl compound, the more toxic it is liable to be. Oxides of chlorinated diphenyls are more DSW 223275 STLCOPCB4053442 toxic than the unoxidized ma terials. The skin lesion is known as chloracne, and consists of small pimples and dark pigmentation of the exposed areas, initially. Later, comedones and pustules develop. In persons who have suffered systemic intoxication, the usual signs and symptoms are nausea, vomiting, loss of weight, jaundice, edema, and abdominal pain. Where the liver damage has been severe, the patient may pass into coma and die. Sax, N. Irving, "Dangerous Prop erties of Industrial Materials," 3rd ed.. Van Nostrand-Reinhold, New York, 1968. The ubiquity of pcb's is related to the wide spectrum of applications that have been found for them. The largest single use of pcb's is related to their electrical properties--as coolant-insu lation fluids in transformers. For this purpose the Aroclors are also sold under such trade names as Chlorextol (Allis-Chalmers Mfg. Co.), Dykanol (Federal Pacific Electric Co.), Inerteen (Westinghouse Electric Co.), Noflamol (Wagner Electric Co.), Pyranol (General Electric Co.), and Therminol (Monsanto Co.). Other uses of pcb's include formula tion into ballasts for fluorescent fix tures; impregnation of cotton and as bestos for braided insulation of elec trical wiring; a plasticizer in wire and cable coatings; capacitors and askareltype transformers; and plasticizers of vinyl chloride polymer films. Because of their thermal stability and fire re sistance, the pcb's also find application in high-pressure hydraulic fluids, spe cialized lubricants and gasket sealers, heat transfer agents, and machine tool cutting oils. Miscellaneous uses in clude: formulation into some epoxy paints; protective coatings for wood, metal, and concrete; adhesives; and in carbonless reproducing paper. One of the primary manufacturers of carbon less reproducing paper also sells Aro clors in an encapsulated form. Generally the kinds of applications described above mean that the pcb's will be in many types of products that eventually find their way to the domes tic market. When used in manufacture of ballasts for fluorescent fixtures they will be found in kitchens, bathrooms, stores, and offices throughout the coun try. Wherever office forms are used that do not use carbon paper, one may find pcb's formulated into the micro capsules of dye that comprise the re Gas chromatogram A is of a standard pesticide mixture, B is typical of Aroclor 1254, and A + B is the chromatogram of a 50 : 50 mixture of both. The concentration of Aroclor 1254 is approximately 10 times those of the pesticides in A, hence it is un derstandable why PCB's were not readily recognized in pesticide chromatograms. Gas chromatograph (Packard 7620) conditions: gas flow 80 ml./min. nitrogen; tem peratures--oven, 210 C., inlet, 230 C., detector, 218 C.; Ni" electron capture detector; 5' x Vs" glass column packed with 8% SE-30 on Chromosorb Q 80-90 mesh- DSW 223276 producing layer of the business form. pcb's have also been found on the transparent receipts used in credit card charge forms. As plasticizers they can be expected to appear in many con sumer plastics. Since the chronic toxicities are so significant, it becomes important to know just how extensively the pcb's are distributed in the ecosystem, and just how they find their way into the environment. Rainwater in En gland, brown seals off the coast of Scotland, white-tailed eagles in Swe den, cod in the Baltic Sea, mussels in The Netherlands, adelie penguin eggs in the Antarctica, brown pelican eggs in Panama, Arctic terns, shrimp in Florida, river water in Japan, waters in the Great Lakes, human hair, and human adipose tissue--samples of all these have been found to contain pcb's. STLCOPCB4053443 thus making them a class of widely T dispersed pollutants. Readily absorbed The properties of pcb's that make them industrially useful are the same properties that cause them to persist in the environment. These in clude thermal stability, resistance to oxidation and hydrolysis, solubility in a wide range of organic solvents, water insolubility, high dielectric constant, and compatibility with many types of macromolecules. Their resistance to oxidation and hydrolysis also makes pcb's more stable and persistent than ddt. Consequently, they could even tually accumulate to a higher concen tration than ddt, especially if the use of ddt is sharply curtailed in the U.S. The solubility of pcb's in nonpolar solvents explains why they are readily absorbed into fatty tissue and into the liver. Their resistance to oxidation or other types of chemical degradation explains their persistence in the en vironment and accumulation in animal tissue. The latter effect is enhanced both by their insolubility in water and solubility in organic solvents. Their chemical inertness and resistance to metabolism account for their low acute toxicity. But as they slowly build up in a living system their con centration approaches toxicity levels, at which point chronic effects make themselves evident. It has been established that fish-eat ing birds will accumulate large concentiations of pcb's, as in the case of the white-tailed eagle, which has been found to have as much as 14,000 p.p.m. of pcb's. Peregrine falcons, taken off the coast of California, were found to have as much as 2000 p.p.m. in their lipid tissue. When shrimp were exposed to 10 p.p.b. of Aroclor 1254 for 48 hours, they accumulated 1300 p.p.b. of pcb's, which represents a 130-fold con centration in a very short time. Oysters, exposed to an identical concentration of Aroclor 1254 for 96 hours and then placed in pcB-free water for four days, still had a concentration of 33,000 p.p.b. of pcb's, which constitutes a 3300-fold concentration. This means that even though the concentrations of pcb's are in the parts-per-billion range in the environment, their high lipid solubility causes them to collect in fatty tissues of lower animals and marine life. Therefore, species at the top of a food chain will also accumulate pcb's in their bodies, particularly in their lipid tissue and liver, in much the same way as they accumulate ddt and other chlorinated pesticides. Because of the low solubility of pcb's in water, when a solution or dispersion of them is discharged into a river or lake, they will accumulate on the sedi ment in relatively high concentrations. Subsequently, they will redissolve very slowly in the water as conditions change. Therefore, it will usually take a long time to flush out a contaminated area. Accidental occurrence The reason that pcb's have not been found in the ecosystem as extensively as ddt, and are not present in environ mental samples at as high a concen tration as ddt, is that pcb's find their way into the environment accidentally. ddt is deliberately spread because this is the only way its insecticidal proper ties can be utilized, pcb's are not in tended to get into the environment, but they do because their unique chemical properties prevent them from being de stroyed by our usual waste disposal methods. Thus, they inadvertently es cape and become widely dispersed. In Sweden, where the use of ddt has been banned, and where the main power source is hydroelectric, investi gators find that the concentration of pcb's in the environment is as high as that of ddt. There are several ways by which pcb's get into the ecosystem. One of these is by incineration. Products con taining pcb's, such as carbonless re producing paper in business forms, plastics (especially polymer film and sheeting that contain pcb's as plasti cizers), spent ballasts from fluorescent light fixtures, and objects coated with PCB-formulated coatings, all find their way to the city dump or incinerator for burning. The pcb's do not burn but are vaporized. They are then carried into the atmosphere, where they collect on particulate matter and are subse quently returned to the surface of the earth, into the rivers, lakes, and oceans. In this way they become widely dis tributed throughout the global environ ment. Another source is probably land run-off from industrial wastes and dumps. A third source is the point of manufacture and the plants where pcb's are processed into other products. They can escape through the plant ven tilation and exhaust systems into the atmosphere and through its waste treat ment system into sewers or directly into waterways. DSW 223277 STLCOPCB4053444 It is interesting to note that the inci dence of pcb's in environmental sam ples is highest in industrialized and ur banized areas. Birds whose primary habitat is the San Francisco Bay area have a larger concentration of pcb's per unit of body weight than those lo cated in Baja, Calif., which is com pletely rural. Aquatic life in the Archi pelago of Stockholm, the most indus trialized area of Sweden, were found to have a higher concentration of pcb's than fish samples taken from the west ern coast of Sweden, a less developed .trea. Sediment samples taken from southern portions of Lake Michigan have a higher concentration, of pcb's ;han those from other parts of the lake. Monsanto states that until a recent change in marketing policy (see inset, page 814), sales of Aroclors were in creasing at the rate of 8% per year. While this increase does not seem sig nificant, it may be important if the in creased consumption was in consumer products and thus would find their way into our normal solid waste disposal systems. Such an occurrence would mean a definite increase of pcb residues in the environment, and therefore a marked increase in their chronic tox icity effects. Detection pcb's were not discovered in environ mental samples until very recently for several reasons. First, as indicated above, they have not been deliberately distributed about the ecosystem. Sec ondly, because of their relatively low acute toxicities, their presence was not immediately evident. Finally, they are difficult to detect analytically. The pcb's were first detected as in terfering peaks in the gas chromato graphic analysis (gc) of environmental samples being analyzed for chlorinated pesticide residues. When pcb's are pres ent in a sample they give a pattern of several gc peaks, whose retention times are similar to those of dieldrin, ddt, dde, aldrin, and heptachlor oxide. Be cause the peaks were not large or sharp, investigators tended to ignore them until S. Jensen, in Sweden, and R. Risebrough, at the University of California at Berkeley, identified them as corresponding to common constitu ents of environmental samples being analyzed for persistent pesticides. The problem of the interferences of pcb's with the analysis of other chlori nated pesticides has been largely over come by prior treatment of the sam- nlo Qatrarn I iniracfmotArc hoxra nra/1 column chromatography to separate pcb's from chlorinated pesticides. At a recent meeting, sponsored by the fwqa's National Water Quality Lab oratory, Duluth, Minn., a general pro cedure was recommended for separa tion of pcb's from pesticides. In this procedure for biosamples, the sample is extracted with hexane as in regular pesticide analysis. It is then partitioned with acetonitrile to remove fats, the cleaned-up extract is passed through a Fluorisil column and then through a silicic acid column. Finally, the sample is analyzed by gas chromatography, with a chloride-specific detector. In this way the pesticides are retained on the silicic acid column for later elution and identification. Research needs To assess fully the significance of pcb's as environmental pollutants, ad ditional research is needed. No one really knows the extent of the chronic effects of these chlorinated hydrocar bons. Some problems that need to be considered are: Although pcb's are known to ac cumulate in human organs we do not know at what concentration they will begin to exhibit toxic effects. Will these chronic effects be similar to those shown in animals--microsomal en zyme activity, calcium metabolism in hibition, and so on? What are other possible chronic effects? Which of the many pcb com pounds in the commercially available mixtures are responsible for their tox icity? Can commercial pcb mixtures be modified to eliminate the toxic com ponents? Pure samples are required to answer these questions. At the present time work is continuing at the fwqa's Southeast Water Laboratory to sep arate each of the Aroclor mixtures into its many components, and to identify each component. We need to know all the uses for the pcb's. What is the annual produc tion of pcb's? Our knowledge of these facts is limited and needs to be ex panded. These facts should be known if we are to accurately determine how they get into the environment, and take steps to prevent further environmental contamination by them. In view of the complexity of the isolation and accurate quantitative analysis of pcb's in chlorinated resi dues, a straightforward, unambiguous measurement of them needs to be de i ral Ana/1 What is the fate of pcb's in nat ural waters? More needs to be known of their partition coefficients between bottom sediments and water. This is vital if we are to estimate how long it will take for a river bed to clean itself of contamination. It will also be useful when assessing the effects of pcb's on marine life that feed on the bottoms of lakes, rivers, and estuaries. We should also learn more about pcb solubility in water of various ionic strengths. Are present waste treatment sys tems adequate to handle pcb's? Do spe cial measures need to be taken when pcb's are part of the waste effluent be ing treated? By trying to get some of these an swers now, we may find that we are in a position to control the escape of pcb's into the environment before ad ditional damage is done. So frequently, action is taken only after it is evident that massive damage has resulted from a particular pollutant. In the case of the pcb's we may have an opportunity to resolve the situation before that happens. Additional Reading Hubbard, H. L.; "Chlorinated Biphenyl and Related Compounds," Encyclo pedia of Chemical Technology, 2nd ed., 5, Interscience Publ., New York, N.Y., 1964, pp. 289-298. Reynolds, L. M., Bull. Environ. Contam. Toxicol. 4, 128 (1969). Risebrough, R. N., et. al.. Nature 220 (1968). Carl G. Gustafson, chairman of the Department of Chemistry of King's College, Briarcliff Manor, N.Y., re ceived a Ph.D. in organic chemistry from the University of Delaware in 1957. During the 1969-70 academic year, he was on leave at the fwqa Southeast Water Laboratory in Athens, Ga., where he studied trace organic analysis in waste effluents. As a mem ber of the National Water Contami nants Characterization Research Pro gram, he worked with pcb\t and pulp /im/7 n/in^p yyiilf oPHtiontf STLCOPCB4053445