Document 0gLpJKLDJbajKqnEM2Qa6dq0V

I f\ PCB RESIDUES: THEIR SIGNIFICANCE TOANIMAL AGRICULTURE C. F. FRIES POLYCHLORINATED biphenyls, more com mon!) known as PCD's, arc chlorinated hydro not recognized as widespread environmental con taminants until 1966. The major use of PCB's has carbon comjxiunds that have a variety of industrial been as a dielectric in transformers and capacitors. use; Residues of these compounds have been found Other significant uses have included heat transfer to be widely distributed in the environment. and hydraulic fluids. Minor uses, making up less These residues have occurred in a number of than 6 percent of sales, have included such items as foods bin oiore frequently in seafoods than any other surface coatings, plasticizers, sealants, adhesives, food pmduct Contamination of animal product* and printing inks. has not been widespread, but several significant The sole producer of PCB'i in the United States localized problems have arisen with poultry and is the Monsanto Chemical Co1 whose production of dairy pioducts these compounds peaked in 1970 at about 36,500 It is niy purpose to review the known incidents tons. The company has restricted sales of PCB's to of poultiy and milk contamination by PCfl's and to use in sealed products such as a dielectric in trans discuss future problems that may arise formers and capacitors Foreign producers of PCB'i Bad*pound Pcil's have been produced since 1930 but were 'Trad* Mbtn are a*cd 1 tfaf* wMf for lb* of provUtAg specific UfoniatlMi trad* ****** dan Mt cnnitliut* fwaranlr *r warranty tf tb pratfuti by lb*- U.S, prptnmtnt *f Ayrkrnl* tnr* *r *n a^doraetnent * n nihrt pwlvclt art mrnttonfd Third Quarter 1972 4 HONS 208536 ,iti' nrii . vifymlu.ini fartoi in L'S us.tgr but .m impoiMnt wlii'n loiiMiltring global contamination pioblems ' p0hi liloruniud biphenyl* null polychlonnaU d mplicnyb <ite sold by Monsanto undei the tiadc name Area lot 'Ihcy arc described b) a Four digit mimln-t The first two dibits indicate tlie chemical stincline of the material, while the second two thgus indicate ihc percent chlorine llrat the material contains for example, Arodor 1254 it a polychlonnated biphenyl containing 54 perreni dilonne At oclors an- mixtures but do not contain all of the 210 theoretically possibly polychlorinated bi phenyl compounds A single Formulation may con tain as many as 40 individual PCB's Chemically and biologically, PCB's are similar to other chlorinated hydrocarbon compounds PCB's can be isolated by the same analytical procedures used in online surveying for chlorinated hydrocar bon pesticides Some components have the same gas clnomotographic retention times as chlorinated hydrocaibon peiticidet These interferences led to the discoieiy and identification of PCB's in the environ ment Some values listed m the literature as DD l pi ior to J 966 may have been PCB's. PCB's persist in the environment and resist degra dation by organisms However, in some species the less chlorinated components are degraded and con verted to w ater soluble compounds. PCB's a re stored in the body fat of animals where the concentrations undergo biological magnification Thus, animals at the higher levels of the food chain vvill have the highest residue levels 1 he toxicological significance of PCB residues has not been determined. The only clinical experience with acute human exposure occurred in Japan in 1968, About 1,000 persons had eaten rice oil con taminated with PCB's. They developed darkened 'Kins, eye discharge, severe acne, and symptoms of what came to be called Yusho disease Average intake was 2 grams of PCB, with symptoms appear ing at a minimum dose of 0.5 g. A variety of subarute effects at much lower in takes have liecn observed in many other species. I he long-term significance of these effects and their implications for human health has not been deterniiiK d Toximlogu al evaluation of PCB's is difficult ber.itiM- iliev all arc mixtuicv Proportions of the com p >ni-niv :i 11- (tiflneni among the larioin. At odors 20 One cannot cvaluaic a single formulation aod a*surnc that the icsult applies to other foi mutations 1 line is also cv idenre that PCB v, particularism ihovt of r.uiopinu ami Japanese manuFjctutf, may rniiUin highly toxic impurities such as dibcniofunns Tin I'Cll piobhius in the L'liilw! State- involvmi; animal agtu nlltuc have been of two distinct tvpov The pimliry incidents were short-tenn, high-level exposures cruising not only high residues in the prod uct but also adverse effects on the birds *lhe milk incidents were chronic exposures involving only residues. Milk Residues PCB residues tn milk were first detected in 1970 in Ohio. The source was traced to a sealant used on the inside vs alls in the manufacture of concrete stave silos Aroclor 1254 was included in the formula of this sealant which was used extensively by one company. All incidents of milk contamination have involved the silos of this company and its successors Other companies have in ihetr files formulas for PCB-containing sealants. It has not been deter mined whether or not any of these were produced and used. However, no contaminated silos originat ing from other companies have been detected The sealant containing PCB's was developed in the 1930's and used until about 1968. Estimates of the number of silos in which it was used are not available In addition to Ohio, contaminated stlo> exist in Kentucky, Tennessee, and adjacent Stales Scrapings from silo walls contain as much as 1 to 2 percent PCB While PCB's are not very solu ble in water, their concentrations as high as 100 ppm in the silage dry matter can occur adjacent to the wall Levels drop rapidly-as the distance from the wall increases and significant residues are seldom found more than 2 or 3 feet from the wall. The diffusion towaids the center isgreaterat lower levels in the silo Despite the relatively low transfer of PCB from the wall to the silage, there are two fartors In addition to the high-wit! concentrations that con tribute to the milk residue problem. First, it w imprariicat to separate thr high-residue silage ad jacent to the viall from the other silage and second, PCB's are transferred very efficiently from the silage to the cows' milk We sttAcyfd a number of farms that were living i nnlamlnnu-d silo> la-srls of PCB residue* m milk Afirituftvrnf Settntr /?i HONS 200537 fat vine approximate!' 10 pp.m when the silage uas fed Oilifi workers ha'e found individual farms with residue Itvcla as high as 20'p pin. The Fowl ami Ding \dminisiianou (FD\> guideline for maximum PCB lcsiduc is equivalent to 2 5 ppm. in milk fat J.cm-Ietcl silage feeding non Id theorem rail) allots production of milk within the guide lines, bin the level is too low to be practical We hate studied the metabolism of PCB's by cotes both in the field and undei ion trolled condi tions in the laboratory. Tiansfei of PCB's from the feed to the milk fat and body fat is very efficient Rates of transfer are approximate!} equal to the rates for DDL, the most |>ersistenl metabolite of DDT. Hie tola! diet of the cott must contain less than 0 5 ppm PCB in order to present milk from exceeding FDA guidelines. If excessive residues occur in milk the time re quired to return the herd to a marketable condi tion may be quite long. PCB's are removed from die hod} fat at a rate pioportional to the con centration in the bodt fat. It takes approximately G to H weeks to reduce the concentiotioii in milk fat by onr-half. Thus, if the PCB concent ration in milk fat is 10 ppm. (four times the FDA Hindi line), ii tv HI take approximate)} IGwrcks from the tinic the contaminated feed is removed fiorn the eon's diet for the milk to be uiilnn the guideline. Since the PCB concentration in the bodv fat is closely related to that in the milk fat, cons exceed ing the guideline for niilk nould also exceed the guideline for meat If the cons aie producing milk with excessive PCB levels, one can either destroy the animal or wail until ihc residue lex cl In milk returns within the guideline In cither case the loss to the dairxman can be substantial. `I he number of contaminated silos delected by trgulatoiY activity has been small compared to the rttiin.-iicd number of contaminated mIos This is l.nitrlv due to problems of analysis anti surve; tech niques that arc followed bv i-egnliitorx .urcneics. Ornetoils the lower level of detection has been about 1 p p.m m milk fat. 1 bus. if die milk supply it vut et eel using nmipoMte sample* of many farms, it tumid lie difficult to tlcii'i t an individual farm uuh ronltiinuiriitd milk if the min f.mns in the sample pnxbin-d clean milk I he amount of PC B-contamin.iti d milk pi odm ed it l< butch smalt ronip.itcil to (tir- lotal milk supply of the couiutt The hums pirxhirtm. contaminated V turrf QutfiIrr MH milk are scaueicd and it is greatly dilutrd by clean milk Thus, there is no reason to be pjiticularly concerned about tile efTicts of the icsidues oil ibe health of the general public However, there is one segment of the population that could receive significant exposures from this soul re: Faim families who drink milk from their own cows fed oil contaminated silage. Using typical esidur and milk consumption levels, intakes of PCB foi over 15 to 20 years would approximate the level of short-term intakes that caused serious effects in Japan. However, the problem is probably not as serious as implied since a dose consumed over a long period may be less serious than the same dose consumed in a very short period Also the PCB in the con taminated silos was more chlorinated than the Jap anese product which also may have contained highly toxic contaminants. Thus, the situations are not duectlv comparable. Silo Dirontamination _ A.NY method devised to correct the PCB problem in milk should have two desirable characteristics: Effectiveness and economy Because of the high efficiency of transfer of PCB's from a cow's diet to its milk ihcie is no known effective remed) shoit of elimination of most PCB from die cow's diet The most effective and most costly method of elimi nating the problem would be complete abandon ment of the contaminated silos Several alternatives to complete abandonment have been suggested and partially tested. The sug gestions generally involve rescaling the silo to block the diffusion of PCBY from the silage. In some cases the icsealing may be preceded by partial removal of the PCB's Partial lcmoval of PCB has been attempted b' cither sandblasting the surface or tv ashing the suvfaec with a suitable solvent. Sandblasting followed b* rescaling has been triyd but no studies of its effec tiveness hate been made. The cost of this ptocedtirc is greatei than half the cost of a new silo and mat exrcerl the dopteriated value of the silo Sandblastingh.is v'mtrquciu.es that bate not lieen full; cxpltiicd The opciaiion i* dusty and lints it is possible that othei aieas of the farm could be (onl.niuii.ilcd The PCB's also jH-ncirate quite tlccplt mm (oiKiete. It i not known bow ninth of the sntf.icc would hate to lx* letnotcrl to rom|ilotc!t' 21 MONS 2OBS30 remove or reduce ihe PCB's to a satisfactory level Solvent washing has been tried on a few silos, but the cost of the procedure is not established Pre sumably it Mould be similar to the cost of sandblastini' In field experiments we have found that the prorrss of solvent washing and rescaling has not bren effective. Whether this was due to the specific piocedure used has not been determined. Rescaling the silo without prior treatment would be a desirable method because of us lower cost. For this method to be effective the PCB should not pene trate the new sealant and the new sealant must ad here to the walls for the remainder of the silo's life Several materials have been tested and some show ptotnise. However, the work that has been reported has only covered the first yean' experience. It is not known how well these materials will continue to seal. Temporary expedients have been attempted on a few farms where contaminated silos were iden tified by regulatory agencies. Lining the interior of the silo with plastic was effective enough to keep the residue levels near the guideline. Discarding the silage within about 6 inches of the wall was less effective Neither method is compatible with mech anized unloading of the silo and neither eliminates the problem. Poultry SOME of the most spectacular and publicized incidents of PCB contamination have involved poultry. In the past 2 years there have been serious incidents in North Carolina, New York, Maine, and Minnesota. Ihe source ol contamination was not established in all cases. , 1 he North Carolina incident was the most exten sive and is the best documented. A large poultry producer noted a severe decrease in hatchability of eggs. The problem was tracked to fishmeal con taminated by Arodor 1242. The fishmeal was con taminated during processing when the PCB leaked from a corroded heat exchanger. In addition to this incident, contaminated feed from the same source had been shipped to 11 other States before the situ ation Mas hi ought under control. Significant num bers of broilers and eggs had to be destroyed because of the high residues. Lowered hatchability ii one of the more impor tant toxicological effet ts of PCB's in birds In con trast to some of the chlorinated hydrocarbons such 22 as DDT, PCB's apparently have little or no effect on eggshell thickness. The effect on liatrhahihty mav occur at levels as low as 10 p.pm in the diet Grn> nail), there is full development of the embno hut die clinks aie unable to break the shell Siibdrnnal edema is die most frequent abnormality. Only the Arodors with intermediate degrees of chlorination affect hatchability We found that A roclor 1232 has some effect, while the most severe effects are encountered with Arodors 1242 and 1248. In contrast, Arodors 1221 and 1254 have no effect at levels as high u 20 p p.m, in the diet No significant effects of PCB's on mammalian embryo development have been reported. This may indicate a species difference. However, most mammalian studies have used the more highly chlorinated PCB's and it is possible such effects could be obtained with the less chlorinated compounds. The FDA has recently prohibited use of PCB's in feed plants and the use of recycled paper for feed HONS 208519 containers, Presumably these restrictions should t limiu.uf shyit-temi exposures of die type that have orcuncd with poultry, Howe'er, since PCB's have been so widely used and all of their possible uses have not been established, it is conceivable that a ft" incidents of this type will occur in the future. Oi/rcr Animal Products Pen contamination of poultry and dairy products suggests that contamination of other animal prod' ucts may have occurred. How ever, there are circum stances that minimise its significance and chances for detection. It is possible that some cattle raised for beef have received silage from contaminated silos. However, silage, particularly during fattening, is not as im|>ortani a component of beef rations as it is of dairy rations. From levels in milk contamination, it can be assumed that some carcasses of surplus dairy animals have residue levels exceeding the FDA guideline. However, surplus dairy animals account for a small part of the meat supply. There would only be a small chance for a carcass of either type to be selected for routine analysis. The incidents involving poultry suggest that con. lamination of feeds for other livestock could also have occurred. Some of the fishmeal from the North Carolina incident may have been used for pigs, yet residues in pork hate not been reported. Some of the fishmeal also was ultimately destined for catfish food. 'I v date there have been no severe losses of species other than poultry due to PCB's. This could indicate that other species are not as sensitive to PCB's as jiouhry and if exposure occurred, there was no noticeable effect on productivity. l)i mansion PCB residues have been accumulating for 40 years hut were not detected until 6 years ago. It can be assumed that other undetected contamination exists ll usually comes to light by one of two ways One is the release of high levels of a material and tubieeiuciit ohreiv alien of scveic problems, as illustrated by the jmultry incidents. 1 he other, and more fre quent, it the development of nnalvhcat instruments and methods capable of detecting smaller residues than was previously possible, as illusiraird by the m l incidents. Thhi) Qvmrrr J97? PCH's have the two characteristics of a compound most likely to cause contamination problems These are resistance to degradation and solubility in fat. Water soluble compounds, even if not degradable, would tend to disperse in the environment and would be of less potential hazard. The poultry feed and silo problems also illustrate some practical problems associated with regulatory activities. With the poultry feed there was no ques tion of the severity of the problem. Through an intensive short-term effort, regulatory agencies lo cated alt of the contaminated feed and products which were then removed from food marketing channels The situation involving silos is considerably dif ferent. Mixed samples of milk from several farms rarely show significant residues. Thus, only a small percentage of the affected farms have been identi fied in routine surveys. In otder to completely eliminate the problem it would be necessary to sample individual farms. This would involve a very large sample load and is prob ably beyond the capability of most regulatory labora tories This problem could be overcome to a large extent if a preliminary survey was made and the individual samples were limited to the farms having the suspected type of silo. To my knowledge only Ohio is following such a program at the present time. Regulatory efforts that are not completely effec tive raise a number of questions. The first is whether or not the undetected fanns pose a threat to public health. Tlfey probably do not because dilution would reduce the residues to a negligible level How ever, the "dilution principle" has not been accepta ble to many regulatory agencies. The second question is whether or not the oc casional removal of a contaminated dairy from the market provides a sufficient incentive for other dairymen to determine whether they have silos that are contaminated and to correct the problem if it exists. Removal fiom the market is a major eco nomic loss but the cost of correcting the problem without market loss can also lie substantia] If a dairyman feels the chances of being delected arc very small he mav take the chance and ignore the possibility that he has contamination. Problems arc also posed for others, such oj re search and extension personnel, who may be aware 23 HONS 208540 of the nature of the situation hut who have no direct responsibility fur its revolution. They should not condone the pioduction of milk with residue levels above the guidelines On the other hand, it is diffi cult to recommend a laigc economic outlay tc* a dairyman unless it prevents a larger outlay in the future Also confusing the isvne >< the determination of r< ipnnsibiliiy for the contaminated silos Litigation involving dairymen, the silo builder, and the PCI! niatmfariun'r is now in progress When responsibil ity is established, it should be easier to decide upon and to implement a course of action ON ANSWERING "WHAT ARE YOU DOING, MR. RESEARCHER?" sometimes imagine myself discussing my own I have worked out a method for rapid identification 1 (research) project with several kinds of people of heat-tolerant individuals within a breed. These and they each ask the question, "What are you individuals should have better feeding efficiency in doing." our climate, thus making your business more profit Let us say that this question is asked by a fellow able." scientist, a Texas beef cattle producer, a man in To the man in the street I would say, "I am the street, and a member of the legislative Appro* working on a scheme which, if successful, will give priations Committee. the consumer better beef at lower cost." To my fellow scientist I would say, "I have a To the legislator I would say, "Texas cattle theory based partially on a feedback control model feeders can use this information to their economic that the regulation of internal temperature in cattle advantage and thus contribute further to our indus can be studied by treating the hypothalmus as a trial economy." sensor-controller amenable to testing. To achieve Now I know all of this sounds kind of awful. . . . such tests I have to install a camula permanently trying to be everything to everybody, but every word in the anterior hypothalmus to permit repeated entry. Thus the tissue can be heated artificially to of what I said, I think, is true and illustrates the idea that if the researcher cannot discuss these put_a step input into the controller or I can measure matters with people having all shades of opinion, its temperature change in response to a step change then maybe he shouldn't be doing that kind of work. in environmental temperature. In either case the R. F. Stewart, data for entering the control model can be secured Distinguished Professor of Enginetrins;, and from this the thermal time constant can be Ttxas A cfc M University derived. Thus a small advance in our knowledge (From n talk at a workshop on research planning of bovine temperature regulation might be made." and derision making held in Washington, D C by To the beef cattle producer I would say, *`I believe the Cooperative State Research Service ) 24 Afrtcvltvrel Seitnee Review HONS 208541