Document GmE9nz1D6wLbMa6XbrDr12XNN

MEMO TO S. G. Colliai J. G. NasSif R. S. Nelson L. J. O'Neill Here's a draft of a presentation for AichE National Meeting in September. I'd appreciate any comment!, 1*> enclosure j. H. Craddock 7/9/82 FROM MONS 214475 WHAT WE KNOW ABOUT HEALTH EFFECTS OF PCB'S H. P DBy John Craddock, h Monsanto Company St. Louis, Missouri Presented Before Summer National AIChE Meeting August 30, 1982 Cleveland, Ohio Symposium On PCB"Engineering Solutions to the Problem" MOMS 21*476 WHAT WE KNOW ABOUT HEALTH EFFECTS OF PCB'S PCB' ,Polychlorinated biphenyls, s have received considerable atten tion OVER THE PAST DECADE BECAUSE OF INCREASING CONCERNS ABOUT THEIR POSSIBLE EFFECTS ON HUMAN HEALTH AND THE ENVIRONMENT, AS A CLASS OF CHEMICALS PCB'S ARE ONE OF THE MOST MISUNDERSTOOD, MOST FEARED AND MALIGNED GROUPS OF CHEMICALS KNOWN TO MAN. THEY HAVE BEEN SINGLED OUT IN THE CONGRESS, LEGISLATURES AND NEWS MEDIA OF THIS COUNTRY AS POSING A GENERAL THREAT TO HUMAN HEALTH, CERTAIN ENVIRON MENTALISTS, REGULATORY OFFICERS, LAWMAKERS AND THE MEDIA HAVE DUBBED PCB'S AS "DEADLY TOXINS", "HUMAN AND ANIMAL CANCER-CAUSING AGENTS* AND "LIFE THREATENING CHEMICALS." THIS HAS RESULTED IN AN UNWARRANTED PCB'SPUBLIC PERCEPTION THAT EVEN THE SLIGHTEST PRESENCE OF REPRESENT A SIGNIFICANT HAZARD TO HEALTH AND THE ENVIRONMENT. PCB'S ARE THE ONLY CHEMICAL SUBSTANCE WHICH CONGRESS SPECIFICALLY EPATARGETED FOR IMMEDIATE REGULATORY ACTION BY THE ADMINISTRATOR. PCB EPA'The Ban Regulations are premised on s belief that any exposure PCB'SOF HUMANS TO IS SIGNIFICANT AND MAY PRESENT AN UNREASONABLE RISK. Today many scientists believe that substantial evidence does exist to PCB'SSUPPORT THE CONCLUSION THAT LOW-LEVEL EXPOSURES TO DO NOT PRESENT A RISK TO HUMAN HEALTH OR THE ENVIRONMENT. HONS 216477 Page 2 Much new information has been published on the health effects of PCB'S SINCE EPA PROMULGATED ITS BAN REGULATIONS IN 3976, A RECENT SEARCH OF THE PUBLISHED LITERATURE SHOWS THAT OVER 5,000 SCIENTIFIC AND TECHNICAL PAPERS ON PCB'S HAVE BEEN PUBLISHED FROM 1976 TO 1981. A EPASeptember, t most. Congress and had available i_ess than 2,800 SCIENTIFIC ARTICLES WHICH WERE PUBLISHED DURING THE 10-YEAR PERIOD PRIOR TO 1976, INCLUDING ONLY ONE HUMAN EXPOSURE INCIDENT, UPON PCB'S,WHICH TO BASE THEIR FINDINGS OF ADVERSE HEALTH EFFECTS OF EPAOn THIS BASIS ALONE, OF SHEER NUMBERS OF PUBLICATIONS, THE SHOULD EVALUATE THE NEW SCIENTIFIC INFORMATION AND REASSESS THE POSITION PCB'STHAT ANY EXPOSURE TO IS SIGNIFICANT. Of PARTICULAR SIGNIFICANCE IN THE NEWLY PUBLISHED SCIENTIFIC REPORTS ARE THOSE RELATING TO HUMAN EXPOSURE (EPIDEMIOLOGY) STUDIES. WITHIN 12-24 PCBTHE LAST MONTHS A LARGE NUMBER OF HUMAN EXPOSURE STUDIES PCBHAVE BEEN PUBLISHED WHICH SHED SIGNIFICANT NEW LIGHT ON THE HEALTH EFFECTS PROBLEM. In PCBaddition, in conjunction with the new rulemakings being EPA DCCONDUCTED BY UNDER MANDATE OF THE FEDERAL CIRCUIT COURT, SEVERAL INDEPENDENT GROUPS OF SCIENTISTS (ABOUT SIX AT LAST COUNT) PCBHAVE RECENTLY RE-REVIEWED THE TOTAL BODY OF HEALTH AND TOXICITY LITERATURE WITH PARTICULAR EMPHASIS ON THE HUMAN EXPOSURE STUDIES. Their independent conclusions, which are supportive and consistent WITH EACH OTHER, ARE SUMMARIZED AS FOLLOWS: HONS 216478 r Page 3 1, PCB'S GENERALLY DO NOT POSE ANY SERIOUS RISK OF INJURY TO HUMAN HEALTH. 2, PCB'S ARE NOT HUMAN CARCINOGENS. 3. PCB'S HAVE NOT BEEN SHOWN TO ADVERSELY AFFECT HUMAN REPRODUCTION OR CAUSE BIRTH DEFECTS. PCB'S ARE NOT MUTAGENS OR TERATOGENS. 4. The only proven adverse human health effects resulting from PCB's ARE TWO SKIN CONDITIONS; DERMATITIS AND CHLORACNE, WHICH ARE REVERSIBLE AFTER DISCONTINUANCE OF EXPOSURE. - I SHOULD EMPHASIZE THAT THESE CONCLUSIONS ARE NOT NEW OR STARTLING PCBTO SCIENTISTS WHO HAVE BEEN INVOLVED IN STUDIES OVER THE PAST decade. However, the weight of the new evidence upon which they're BASED SHOULD REINFORCE THE BEDEVABILITY AND, HOPEFULLY, RESOLVE THE PCBISSUE OF HEALTH CONCERNS. AS RECENTLY AS 1979, THE NATIONAL RESEARCH COUNCIL OF THE NATIONAL PCB's. IAcademy of Sciences reviewed the subject of n the report PREPARED BY THE COMMITTEE ON THE ASSESSMENT OF POLYCHLORINATED Biphenyls in the Environment, the NAS group concluded with respect PCBto Assessment of Hazard; PCB"An analysis op data compiled following the criteria of FIFRA TSCAand proposed guidelines, leads to the conclusion PCB'sTHAT ARE PERSISTENT, AND ARE LIKELY TO ACCUMULATE. PCB'S DO NOT APPEAR PARTICULARLY TOXIC FOR SHORT-TERM EXPOSURE, BUT RESULTS ARE SUBJECT TO INTERPRETATION.* The most recent 1981-1982 reviews were conducted independently by SEVERAL GROUPS OP SCIENTIFIC EXPERTS WHICH INCLUDED THE FIELDS OF CHEMISTRY, TOXICOLOGY, PATHOLOGY* EPIDEMIOLOGY, INDUSTRAL HYGIENE AND MONS 214479 Page 4 MEDICINE, INCLUDING OCCUPATIONAL MEDICINE, TO NAME A FEW, THE DATA AND CONCLUSIONS FROM THESE STUDIES HERE RECENTLY SUBMITTED TO THE (J.S. EPA FOR THEIR USE IN DEVELOPING NEH PCB REGULATIONS. In EPA 1982addition, in May of sponsored a two-day symposium of leading WORLD SCIENTISTS AT BETHESDA, MARYLAND, TO REVIEW AND DISCUSS "The Recent Advances in Exposure, Health and Environmental Effects PCB' .*Studies of s However, there is little public awareness of THESE SIGNIFICANT STUDIES, THEIR REVIEWS AND THEIR IMPLICATIONS. In ESSENCE, THESE CONCLUSIONS FROM ALL OF THE REVIEWS TO-DATE DEMONSTRATE AND STATE IN "LEGALESE" TERMS THAT: 1, PCB'S PER SE DO NOT REPRESENT AN UNREASONABLE RISK TO HUMAN HEALTH AND THE ENVIRONMENT. 2. PCB'That any exposure to s is not significant. - I'd briefly like to discuss in more detail what we do know about the PCB'S (1)HEALTH ASPECTS OF FROM THE LABORATORY STUDIES ON ANIMALS, (2) THE NOW AVAILABLE AND MORE MEANINGFUL RETROSPECTIVE STUDIES ON HUMAN EXPOSURE, I.E., EPIDEMIOLOGY STUDIES, AND (3) SOME ENVIRONMENTAL CONSIDERATIONS. Laboratory Studies The probability that a chemical will result in an adverse effect is A FUNCTION OF EXPOSURE TO THE COMPOUND AND ITS INHERENT TOXICITY. PCB'SFORTUNATELY, ONE OF THE KEY PHYSICAL PROPERTIES OF WHICH MADE IT A VALUABLE INDUSTRIAL CHEMICAL, THE LOW VAPOR PRESSURE, ACTUALLY , MINIMIZES THE POTENTIAL FOR EXPOSURE EVEN AT CONCENTRATIONS OF SEVERAL MONS 216480 Page 5 PCB'STHOUSAND PPM. ANIMAL TOXICITY LITERATURE DOCUMENTS THAT ARE NOT A HIGHLY TOXIC COMPOUND. UTILIZATION OF STANDARDIZED CRITERIA PCB'SFOR ACUTE TOXICITY CLASSIFIES AS ONLY SLIGHTLY TOXIC TO NON TOXIC (Table 1). This ranking is based in part on the fact that the DOSES REQUIRED TO PRODUCE SHORT-TERM TOXIC EFFECTS IN' SOME TEST SPECIES ARE SO HIGH THAT THE DOSE NECESSARY TO CAUSE SIMILAR EFFECTS IN HUMANS WOULD EXCEED ONE QUART. A COMPARISON OF THE ACUTE TOXICITY PCB'S 2.OF WITH OTHER COMMONLY KNOWN CHEMICALS IS SHOWN IN TABLE PCB COMPOUNDS HAVE BEEN EVALUATED FOR MUTAGENIC POTENTIAL IN SEVERAL SYSTEMS* RANGING FROM BACTERIAL TEST SYSTEMS TO INTACT ANIMAL studies. They have been found to be negative in the Ames test with THE EXCEPTION OF A POSITIVE MUTAGENIC RESPONSE FOR ONLY ONE COMPOUND, the 4-chlorobiphenyl congener* This early study has not been CONFIRMED; DESPITE REPEATED ATTEMPTS TO DUPLICATE THE RESULTS. This LACK OF REPRODUCIBILITY IN THE EARLY FINDINGS CAN ONLY LEAD TO THE CONCLUSION THAT THE POSITIVE RESULT IS UNFOUNDED. Chlorinated biphenyls are found to exhibit negative responses in the * DOMINANT LETHAL TEST <A TEST FOR HERITABLE DAMAGE LEADING TO EMBRYOTOXICITY) AND ARE NOT CLASTOGENIC (CAPABLE OF CAUSING GROSS OR MORPHOLOGICAL DAMAGE TO CHROMOSOMES OF BLOOD; SPERM CELLS OR RATS OR CULTURED HUMAN BLOOD CELLS). COLLECTIVELY; THE RESULTS OF THESE STUDIES INDICATE THAT LOW-LEVEL EXPOSURE TO CHLORINATED BIPHENYLS DO NOT PRESENT A MUTAGENIC RISK. PCB'S HAVE PRODUCED EMBRYOTOXICITY AND SPONTANEOUS ABORTIONS IN LABORATORY ANIMALS; BUT ONLY AT DOSES WHICH ARE HIGH ENOUGH TO PCB'SPRODUCE MATERNAL TOXICITY. ARE NO MORE TOXIC TO THE FETUS THAN MOMS 216481 Page 6 Table 1 TOXICITY RATING CHART Probable Oral Lethal Doae for Humans* Rating Animal LD^q 1. Nontoxic 2. Weakly Toxic 3. Moderately Toxic 4. Toxic 5. Extremely Toxic 6. Super Toxic 15,000 mg/kg 5,000-15,000 mg/kg 500-5,000 mg/kg 50-500 mg/kg 5-50 mg/kg 5 mg/kg Expected Human Dose 1 Pint-1 Quart 1 Ounce-1 Pint 1 Teaspoon-1 Ounce 7 Drops-1 Teaspoon Less Than 7 Drops * Average Adult of 70 leg Adapted from Caaarett and Doull'ii Toxicology: The Basic Science of Poieona (2nd edition) Macmillan Publishing Co., Inc., New York (1990) MOMS 216462 Page 7 Table 2 ACTUAL TOXICITY AND THE TOXICITY RATING CHART Or SOME SELECTED CHEMICALS Agents PCBs Alcohol Table Salt Iron DDT Strychnine Nicotine TCDD Botulinus toxi Animal LDjQ (mg/kg) 14.000 10.000 4,000 1,500 100 2 1 0.001 0.00001 Expected Human Dose* 1 Quart 1 Pint-1 Quart 1 Pint 1 Ounce-1 Pint 1 Teaspoon-1 Ounce 4 Drops 1 Drop Less Than 1 Drop Less Than 1 Drop * Average Adult 70 kg Adapted from Casarett and Doull's, Toxicologyt The Basic Science of Poisons 12nd edition) Macmillan Publishing o., inc., New York (1980) HONS 216483 Page 8 most chemicals when given at toxic doses to the maternal animals, The Chemical Manufacturers Association (CMA) contracted with the INDEPENDENT CONSULTING FIRM ECOLOGY AND ENVIRONMENT, INC. (EiE), TO PREPARE A REVIEW OF THE LATEST HEALTH EFFECTS INFORMATION ON PCB's. I E&E'st is "independent professional opinion that 'any EXPOSURE TO PCBVDOES NOT POSE A SIGNIFICANT HEALTH RISK TO E&EHUMANS." CONCLUDED "THAT PCB'S DO NOT REPRESENT A CARCINOGENIC (GENOTOXIC/INITIATOR) RISK AND THAT, EVEN IF THEY POSSESS ONCOGENIC (EPIGENETIC/PROMOTING) ACTIVITY, THE RISK AT LOW EXPOSURES IS INSIGNIFICANT," Numerous studies involving both mice and rats have been reported, PCB'sBUT TO-DATE, ONLY ONE STUDY EXISTS WHICH SUGGESTS THAT MAY CAUSE AN INCREASE IN HEPATOCELLULAR CARCINOMA (LIVER CANCER). TWO OTHER CHRONIC TESTS IN RATS, AS WELL AS TESTS IN THE MOUSE, DID NOT REVEAL A STATISTICALLY SIGNIFICANT INCREASE IN LIVER CANCER OR ANY OTHER PCB'S. ACANCER FROM EXPOSURE TO RECENT BIOASSAY PERFORMED BY THE National Cancer Institute did not demonstrate that PCB's produced CANCER IN THE RAT, COMPARING THE ONE POSITIVE STUDY WITH THE LARGE NUMBER OF NEGATIVE TESTS AND CONSIDERING OTHER IMPORTANT CONTRIBUTING FACTORS (SUCH AS THE SPONTANEOUS RATE OF LIVER INJURY AND LIVER REGENERATION WHICH CAN LEAD TO ABERRANT HEPATOCELLULAR GROWTH), PCB'SSUPPORT THE CONCLUSION THAT DO NOT REPRESENT A CANCER RISK TO HUMANS, A PCB'st worst, at high or elevated doses in laboratory animals meet SOME OF THE CRITERIA FOR A CHEMICAL PROMOTER, I.E., THEY ENHANCE TUMOR PCB'SGROWTH THROUGH EPIGENETIC MECHANISMS. DO NOT INDUCE NEW TUMOR MONS 21648* Page 9 A PCB'sGROWTHS. t MOST/ HAVE BEEN SHOWN TO POSSESS ONLY A WEAK PROMOTING ACTIVITY, THEREFORE/ THE THRESHOLDS BOTH PROPOSED IN THEORY AND OBSERVED IN ANIMAL STUDIES SUGGEST THAT THERE ARE SAFE EXPOSURE LEVELS FOR PCB's, It SHOULD BE EMPHASIZED THAT TWO FACTORS CONFOUND ISSUES RELATING TO THE HEALTH EFFECTS OF PCB'S. FIRST OF ALL/ THE EFFECTS OF PCB'S VARY GREATLY WITH THE DEGREE OF CHLORINATION OF THE BIPHENYL MOLECULE. SECONDLY/ MOST OF THE TOXICITY STUDIES AVAILABLE HAVE UTILIZED PCBCOMMERCIAL MIXTURES, THESE MIXTURES FREQUENTLY CONTAIN CONTAMINANTS WHICH MAY BE TOXIC THEMSELVES AT HIGH EXPOSURE LEVELS. Epidemiology The most meaningful information for assessing a chemical's chronic HEALTH EFFECTS CAN BE DERIVED USING HUMAN DATA FROM PROPERLY DESIGNED EPIDEMIOLOGY STUDIES. EPIDEMIOLOGICAL STUDIES ARE OFTEN POSSIBLE IN SITUATIONS WHERE PEOPLE HAVE BEEN EXPOSED FOR MANY YEARS. A RECENT REVIEW OF TWENTY-ONE EPIDEMIOLOGY STUDIES FOUND THAT DURING PCB'SOCCUPATIONAL EXPOSURE/ CAN CAUSE TEMPORARY SKIN PROBLEMS. YET/ THERE ARE NO CLINICALLY OBSERVABLE LONG-TERM HUMAN HEALTH EFFECTS, INCLUDING THE OCCURRENCE OF CANCER. STUDIES OF NON-OCCUPATIONALLY EXPOSED POPULATIONS FOUND NEITHER DERMATITIS NOR OTHER CLINICAL EVIDENCE OF EXPOSURE-RELATED EFFECTS. Many of the recent epidemiology studies include data on large numbers OF INDUSTRIAL WORKERS WHO/ OVER MANY YEARS/ WERE OCCUPATIONALLY s MOMS 21*445 Page 10 PCB' .exposed to s These occupational exposures, in host cases, PCBinvolved chronic exposure levels which were orders of magnitude greater than any which can reasonably be foreseen under existing Aregulations. comparative review of these occupational-exposure PCB'SSTUDIES REVEALS THAT, LIKE OTHER CHEMICALS, CAN CAUSE ADVERSE HEALTH EFFECTS, BUT IN MOST RESPECTS THESE EFFECTS HAVE BEEN MINIMAL. While dermatitis and chloracne have been noted, these skin disorders WERE REVERSIBLE AFTER DISCONTINUING THE EXPOSURE. In SPITE OF OVER 50 YEARS OF USE, NO CAUSAL RELATIONSHIP HAS BEEN ESTABLISHED FOR ANY SPECIFIC TYPE OF CANCER, NOR HAS IT BEEN PROVEN THAT THE INCIDENCE OF PCBCANCER MORTALITY HAS INCREASED FROM EXPOSURE. A RECENT STUDY BY THE NATIONAL INSTITUTE OF OCCUPATIONAL SAFETY AND (NIOSH)Health focused on 2,500 electrical equipment manufacturing workers. Over half of the cohort was occupationally exposed in PCB'SEXCESS OF 20 YEARS. SOME OF THE WORKERS WERE EXPOSED TO FOR AS LONG AS 40 YEARS. THE STUDY FOUND NO EXCESS IN TOTAL MORTALITY, NOR IN MORTALITY DUE TO CANCER, CARDIOVASCULAR DISEASE OR NEUROLOGICAL disorders. Since this study failed to demonstrate an excess cancer RATE IN A HIGH-EXPOSURE POPULATION, IT PROVIDES SOME REASSURANCE THAT IT IS UNLIKELY THAT FUTURE STUDIES WILL SHOW ANY INCREASED RISK OF PCB'S.CANCER FROM As ADDITIONAL DATA HAVE BEEN ACCUMULATED ON THE YUSHO INCIDENT, IT APPEARS THAT IT WAS NOT THE PCB'S WHICH WERE RESPONSIBLE FOR THE ADVERSE HEALTH EFFECTS OBSERVED BUT THE EXTRA ORDINARILY HIGH LEVELS OF IMPURITIES IN THE JAPANESE COMMERCIALLY PCBMANUFACTURED MIXTURE. HONS 216486 Page 11 The conclusions reached by all of the epidemiologic studies are in DISTINCT CONTRADICTION TO STATEMENTS APPEARING IN THE PRESENT COURT "PCB'of Appeals Decision that s are extremely toxic to humans", and THAT "EPIDEMIOLOGY DATA AND EXPERIMENTS ON LABORATORY ANIMALS PCB'SINDICATED THAT POSE CARCINOGENIC AND OTHER RISKS TOHUMANS." Environmental Considerations Although most recent scientific literature reviews have focused on HUMAN HEALTH EFFECTS STUDIES, RECENT PUBLICATIONS ON THE EFFECT OF PCB'SENVIRONMENTAL CONTAMINATION BY DO NOT SUPPORT THE CONCLUSIONS PCB'STHAT HAVE EXHIBITED A SIGNIFICANT IRREVERSIBLE EFFECT ON THE PCB'SECOSYSTEM. EARLY REPORTS DOCUMENTED THAT ARE BOTH PERSISTENT IN THE ENVIRONMENT AND THAT THEY BIOACCUMULATE IN SOME SPECIES. PCBScientists agree generally that the heavily chlorinated homologs ARE PERSISTENT AND BIOACCUMULATE TO SOME DEGREE. HOWEVER, CURRENT AVAILABLE SCIENTIFIC EVIDENCE DOES NOT SUPPORT THE ALLEGED HEALTH AND ENVIRONMENTAL EFFECTS. EPAFear of dire ecological consequences caused the Administrator o> f PCB'STO FIND "THAT ANY RELEASE OF INTO THE ENVIRONMENT WILL EVENTU ALLY RESULT IN WIDESPREAD EXPOSURE OF WILDLIFE, INCLUDING SOME OF MAN'S FOOD SOURCES AND HUMANS, AND THAT SUCH EXPOSURE MAY HAVE ADVERSE EFFECTS." IN 1976, EPA PRESENTED DATA ON PCB CONTAMINATED 1973*1975 3).food for the years (Table These data clearly indicate PCBA SIGNIFICANT DOWNWARD TREND IN LEVELS, INCLUDING A DECLINE IN THE HIGH CONCENTRATIONS FOUND IN FISH. THESE DOWNWARD TRENDS IN CONCENTRATION LE*VELS ARE THE RESULTS OF VOLUNTARY INDUSTRY ACTIONS HONS 21648? Page 12 Product! Fiah Milk 998 Cheeae Feed component! Animal Feed Proceaaed Fruit Baby Food Meata, Poultry Table 3 PCBa IN FOOD 1973 60.4 3.2 1.1 0.9 12.7 7.2 4.5 1.1 1.9 1974 44.0 2.6 4.2 2.6 0.0 0.0 0.0 0.0 1.2 1975 17.9 0.7 0.0 0.0 0.3 0.0 0.0 0.0 0.3 Maximal Concentra tion (SOppm) 123.0 2.3 11.0 2.9 9.0 199.5 19.2 trace 5 ppm Adapted from Jelinek, C. F. and Corneliuaaen, P. ., Level! of PCBa in the O.S. Food Supply. National Conference on Polychlorinatedbiphenyl! (EPS-560/6-75-004) pp. 147, (1976) HONS 216488 Page 13 TAKEN IN 1971 TO REDUCE USAGE AND POSSIBLE EXPOSURE TO PCB'S, THESE RESPONSIBLE INDUSTRY ACTIONS WERE TAKEN PRIOR TO PROMULGATION OF TSCA 1976 PC8IN AND CERTAINLY MUCH EARLIER THAN THE ACTUAL REGULATIONS WHICH BECAME EFFECTIVE IN MID-1979, Very recent data on contamination of fish and natural bodies of water PCBFROM COMMERCIAL MIXTURES HAVE SHOWN THAT ENVIRONMENTAL LEVELS ARE STILL DECREASING AT A SIGNIFICANT RATE. LEVELS IN FISH IN THREE DIFFERENT AREAS OF THE UNITED STATES (GREAT LAKES, NEW YORK STATE AND ALABAMA-GEORGIA) WERE IN THE RANGE OF ] TO 5 PPM IN 1980*81, AS CONTRASTED WITH THE DATA WHICH RANGE FROM 60 PPM IN 1973 TO 18 PPM IN 1975, In addition, at least two recent publications demonstrate that THE EARLIER PREDICTION OF EXTREME PERSISTENCE OF THE HIGHER CHLORINATED PCB HOMOLOGS IN THE ENVIRONMENT IS NOT OF THE ORDER OF A HUNDRED 40-50YEARS BUT IS MEASURABLE AND IS,ON THE AVERAGE,IN THE RANGE OF PCB'months, These data are based upon half-life values of s in the TISSUES OF FISH ENVIRONMENTALLY EXPOSED. In ADDITION, RECENT DATA (1979)PUBLISHED BY THE NATIONAL RESEARCH COUNCIL HAVE SHOWN A PCBSIGNIFICANT REDUCTION OF CONCENTRATIONS IN AIR OVER THE NORTH Atlantic Ocean, These data have demonstrated an order of magnitude DECREASE IN PCB CONCENTRATIONS IN AIR RANGING FROM 0.760,55 NG/M3 IN 1973 TO 0,074*0.099 ng/m3 in 1977. Thus, a thorough evaluation of the toxicological and, to a lesser EXTENT, THE ENVIRONMENTAL LITERATURE SUBSTANTIATES THE CONCLUSION PCB'$THAT UNDER MOST CONDITIONS OF EXPOSURE HAVE NOT BEEN DEMONSTRATED TO BE HAZARDOUS TO THE PUBLIC AND THAT LOW EXPOSURES HONS 216489 Page 14 EPAWILL NOT LEAD TO HARMFUL CONSEQUENCES. HOPEFULLY, THE AND Government scientists will totally review the recent data and PUBLISHED LITERATURE AND REACH SIMILAR CONCLUSIONS TO THOSE OF THEIR OTHER SCIENTIST COLLEAGUES. HONS 216490 t