Document 91zyvve1XDXRoLKxoROoO3Yrq

The Toxicity of the Vapors of Aroclor 1242*and Aroclor 12540 J. F. TREON, Ph.D., F. P. CLEVELAND, M.D., J. W. CAPPEL. and R. W. ATCHLEY Tha Kettering Laboratory, Department of Preventive Medicine and Industrial Health College of Medicine, University of Cincinnati Reprinted from American Industrial Hygiene Association Quarterly 17:2, 204*213, June 195(3. ' (Copyright, 1956, American Industrial Hygiene Association) MGNS 096370 The Toxicity of the Vapors of Aroclor 1242*and Aroclor 1254* J. F. TREON, Ph.D.. F. P. CLEVELAND, M.D., J. W. CAPPEL, and R. W. ATCHLEY Tha Kattaring Laboratory, Department of Preventive Medicine and Industrial Health College o.f Medicine. University of Cincinnati nvestigation of the physiological re* Aroclor 1242 per liter of air is equivalent I sponse of animals to the inhalation of to 96.9 ppm by volume. two Aroclors, namely 1242 and 1254. was Aroclor 1254, which corresponds to penta* undertaken because in the earlier literature1 chlorobiphenyl, is a light, straw-colored, dealing with the toxic effects of Aroclors, viscous liquid. The positions of the chlorine no distinction has been drawn between the atoms have not been established. The mo toxic effects of chlorinated biphenyls and lecular weight of pentachlorobiphcnyl is those of chlorinated naphthalenes, despite 326.445, of which 54.3% is chlorine. Ben the differences in the chemical composition, ignus has reported that Aroclor 1254 con physical characteristics, and industrial ap tains 55.0 0.5% of chlorine. Bulletin No. plications of these classes of compounds. In O-P-115 describes Aroclor 1254 as having a the case of the chlorinated biphenyls, at specific gravity at 25",25C of 1.538 to least, further toxicological investigation and 1.548; a distillation range of 365* to 390'C, consideration were required to demonstrate a refractive index (D-line at 20C) of 1.639 the relationship between the extent of their to 1.G41, and a Saybolt Universal viscosity chlorination and their toxicity. at 100 F of 1,800 to 2,500 seconds. The vapor pressure at 150C is about 1.3 mm, Properties and at 200*C is about 9 mm. The material A ROCLOR 1242 is a light, straw-colored, mo* is soluble in most organic substances, but it bile liquid. According to Benignus, of is insoluble in water and glycerine. At 745 Monsanto Chemical Company, it contains mm of mercury and 25'C the concentration 42.0 A 0.5% of chlorine, an amount which of 1 mg of Aroclor 1254 per liter is equiva corresponds to a chlorinated biphenyl with lent to 76.5 ppm by volume. three chlorine atoms in unassigned posi tions. The physical and chemical properties Experimental Method are given in Monsanto Application Bulletin Exposure TO the vapor: In a preliminary No. O-P-115. Its specific gravity at 25*/ experiment (No. 1) with the vapor of 25*C is 1.378 to 1.388; it has a distillation Aroclor 1242, a group of animals was con range of 325* to 360"C; a refractive index fined for seven hours on each of five days (D-Hne at 20*C) of 1.627 to 1.628; a Saybolt per week in a rectangular plywood chamber Universal viscosity at 100'F of 80 to 93 (volume 600 liters), of which the inner seconds, and a flash point (Cleveland Open metal lining was coated with a baked chemi Cup) of 176*-180*C. Its vapor pressure is cally resistant plastic, through which was about 4 mm at 150*C and about 30 mm at passed a stream of air laden with Aroclor 200*C. Although-insoluble in water and gly 1242 in a known concentration. The stream cerine, it is soluble in most organic sub of air, conditioned with respect to tempera stances. At 745 mm of mercury and 25C, ture (75* a: 3*F inside the chamber), dust the concentration of 1 mg of the vapor of and humidity, entered the chamber through Pr*Btr4 *t the Svnt**nth Annum! Mettinff of th American iNousrniAL Hyoiens AmtocuTtoN, Philadelphia. April M, im. an "Anemostat," located at the center of its top, at the rate of 500 liters per minute, as measured by an inclined manometer attached MQNS 4)96371 to the Aroclors, in another cham ber supplied only with condi tioned air. A second set of experiments with each of the Aroclors at lower concentrations was con ducted in the same chambers. In the third experiment with Aro clor 1242, which was heated to 56" to 60*C, the air passed over the liquid at the rate of 800 liters per minute. In the second ex periment with Aroclor 1254, the liquid was maintained between 115 and 125C while 700 liters of air per minute passed over its surface before entering the chamber. The animals exposed in each of these experiments, as well as a second group of controls, Seh*m*lic dUgrtm of qu'pmtnt for voUtilliing Aroeior, chmbr, ond quipmont for combutHon and collection of amploi, were confined in separate GOO liter chambers during a seven hour period on each of five days per week during the week pre to a venturimeter (Fig. 1). The air was ceding the initial exposure of the test ani withdrawn by suction from the chamber mals to the vapor of the respective Aroclors. through an exit tube located on the rear In all experiments, the period of exposure wall near the floor, equidistant from the or confinement (controls) was seven hours sides. ' per day on five days per week for several Aroclor 1242 was volatilized from a weeks. In all instances, the original group heated glass well maintained at 132 to consisted of one cat, 9ix guinea pigs, ten 138C. The air passed over the surface of mice, four rabbits, and ten rats. Among the liquid before entering the chamber both the experimental and control groups, (Fig. 1). several animals died from extraneous causes In a second similar experiment performed during the course of these experiments and on the same Aroclor (No. 2), the tempera were replaced very soon thereafter. In the ture of the liquid was kept at 100* to 105C. second experiment with Aroclor 1242, in While the second experiment with Aroclor the first experiment with Aroclor 1251, and 1242 was in progress, an experiment involv in the comparable group of controls, repre ing the vapor of Aroclor 1254 (No. 1) was sentative animals were killed throughout the carried out in a second chamber similar to experiment. the first except for the absence of a plastic Method for the determination of the inner lining. The rate at which air flowed aroclors IN AIR: These materials were de over liquid Aroclor 1254, which was main termined quantitatively by virtue of the fact tained at 130* to 135*C, was 400 liters per that, on thermal decomposition, they yield minute. - hydrochloric acid which with silver nitrate, In order to accustom the animals to the forms a suspension, the density of which experimental procedure, they were kept in could be measured by means of the Beckman their respective chambers for seven hours spectrophotometer at 500 mu. on each of four consecutive days during the On each day, two samples of air from each week prior to the introduction of the Aro chamber were collected by passing air at the clor vapor into the chamber. For purposes rate of one liter per minute (for 15 min of control (No. 1), a third group of animals utes in the case of the higher concentrations was confined, throughout a like period be and for 45 minutes in case of the lower con fore and during the period of the exposure centrations) through a fused silica combus- X MGNS 096312 Ftq. 3. Sampling fowtrt. (Midgtt BubbUrs) tion furnace, and then through two midget bubblers, in series, each containing 10 ml of 0.1 N sodium hydroxide. A quartz tube (13 mm outside diameter, 7 mm inside diameter and 16.25 inches in length) contained sev eral strips of folded platinum foil. The mid dle nine inches of the tube were wrapped with a heating unit. The heating unit of the furnace (Fig. 2) consisted of 20 feet of B. and S., gauge 22, nichrome wire (1 ohm per foot), and was covered with as bestos cement. The sample of air was hu midified by a cotton wick saturated with water placed 0.5 inch upstream from the quartz tube. With the furnace maintained at 850*C, the Aroclor was decomposed in the presence "of H:0 to form HCl; this was absorbed in 0.1 N sodium hydroxide in midget bubblers (Fig. 3) equipped with fritted-glass bubblers (Mine Safety Ap pliance Company No. 43867). The 0.1 N sodium hydroxide was pre pared by dissolving 4.0 g of pellets (ACS specifications 0.01 (c Cl) in about 50 ml of double-distilled water. To this were added 10 g of arsenic trioxide (chloride-free) dis solved in water and filtered through What man No. 42 filter paper. The combined solu tions were diluted to 1,000 milliliters. The sample was transferred to a 25 ml graduated cylinder to which one drop of a solution of phcnolphthalein was added (1 g of phenolphthalein dissolved in 100 ml of CP methanol). The solution was neutralized with 3N nitric acid (190 ml CP concen trated nitric acid diluted to 1,000 ml with double-distilled water) and diluted to 23 ml with double-distilled water. One ml of 3X nitric acid was added to obtain a pH of 1. After adding 1 ml of a solution of silver nitrate (3 g of AgXO;< diluted to 1,000 ml with double-distilled water), the sus pension was mixed by inversion. After standing 30 minutes, the transmission of wave-length 500 m,n was measured in a 50 cm cell by means of a Beckman spectropho tometer which was set against a correspond ing cell containing a reagent blank. The amount of Aroclor was estimated by means of a standardized curve prepared from known quantities of sodium chloride. A curve presenting the transmission values at 500 m,u of suspensions prepared from sodium chloride ranging from 5.0 to 120 micrograms per 25 ml of final suspension is shown in Fig. 4. On the basis of 42.0(<? of chlorine in Aroclor 1242 and 55.0rc in Aroclor 1254, one micvogvam of sodium chloride is equivalent to 1.442 micrograms of Aro clor 1242 or to 1.1028 micrograms of Aro clor 1254. Experimental Results jJroRTALiTY--AROCLOR 1242: No signs of A intoxication were observed in any of the members of a group of 31 animals (Ex periment No. 1), all of which survived throughout a period of 24 days, on 17 of which they were subjected to the inhalation of air bearing 8.6 micrograms of Aroclor 1242 per liter (0.83 ppm) for seven hours (Table I). One cat, four guinea pigs, six mice, two rabbits, and eight rats survived without HONS 096373 signs of intoxication throughout their exposure (Experiment No. 2) for seven hours on each of 82 days over a period of 120 days to air bearing the vapor of Aroelor 1242 in the concentration of 6.83' micrograms per liter (0.66 ppm). Certain other survivors (two guinea pigs, three mice, one rab bit, and two rats) were subjected to fewer periods of exposure (cf. Table 1). The deaths from ex traneous causes among the ex posed animals were fewer than those which occurred among the' corresponding group of controls (No. 1, Table I). One cat, three mice, three guinea pigs, three rabbits, and eight rats survived following confinement for seven hours on 84 days over a period of 122 days, in a chamber in Fl. 4. Standard eurva for th* determination of Aroelar 1242 and Aroelor I2S4. which the air, conditioned with respect to In another experiment (No. 3, Tabic I-A) dust, humidity and temperature, contained in which animals were exposed to air bear no vapor of either Aroelor. Ten more survi ing Aroelor 1242 in the concentration of 1.0 vors (three guinea pigs, four mice, one rab micrograms per liter (0.18 ppm) for seven bit, and two rats) were subjected to fewer hours per day on 160 days over a period of periods of confinement (cf. Table 1). 214 days, the incidence of mortality among Table I. Summary of Data on Mortality Amonc Animals Exposed TO THE Vapor OF Aroclor 1242 OR AROCLOR 1254 in Am (Higher concentrations) Number of Animal* that Survived Material of Exposure Guinea y/l ppm (hour*) Cat* Flp* Mle* Rabbit* Rate No. Aroelor 1340 Aroelor 1243 Aroelor 12S4 Control ts.in 6.63 6.40 0 0.63 0.66 0.41 0 17 a 7 82 x 7 88 a 7 84 * 7 1, 1 1 1 10 O'.V 10'.* 7V 4 l> 4>. 4* 10 10'. 10* 10*.* 1 2 1 l 'On* of th* animal* was exposed on only 68 to 77 day* On* of th* animals wai exposed on only 41 to 61 days On* of th* animal* was *xpo**d on only 20 to 88 day* `Five of th* mic* w*r* *xpo**4 on only 74 day* 'Three of th* rale* were exposed on only 14 to IS dsya "On* of th* rabbit* was exposed on inly IS day* Table I-A. Summary of Data on Mortality Among Animals Exposed TO THE Vapor of Aroclor 1242 or aroclor 1254 in Air (Lower concentrations) Number of Animal* that Survived Materia! Aroelor 1242 Aroelor 1264 7/1 i.SO 1.60 ppm 0.18 0.11 of Exposaro (hour*) 168 x 7 160 X 7 Cat* i l Pufii a* Px* 6' 7*.',' Mk* 8'.' Rabbit* 8.M 4 Rate 10* 11* No. 6 t 'On* of th* animal* w* exposed on only IS to 1? day* 'On* of th* animal* was exposed on only 41 to 55 day* Ob* of th* animal* "* xpo**d on only ISO to ISO day* 'On* of th* animat* ** exposed on only 6 te It Say* 'On* of th* animal* vii exposed on only 10? to ISO day* 'On* moua* *# expesed on only 00 day* MUMS 0963 74 the various species, with the exception of the rabbits (which died during an epidemic of pneumonia), was no greater than that en countered among a similarly constituted control group (Experiment No. 2, Table I-A). One cat, five guinea pigs, six mice and nine rats survived throughout the entire period of their subjection to the vapor of Aroclor 1242. Seven Additional survivors (one guinea pig, two mice, three rabbits, and one rat) were exposed intermittently to the vapor of Arocior 1242 over a shorter period of time (cf. Table l-A). Among the group of controls (Experiment No. 2, Table I-A), one cat, five guinea pigs, four mice, two rabbits, and nine rats survived through out the entire period of confinement, for seven hours on each of 150 days over 213 days in a chamber supplied with condi tioned air. Eleven other control animals (one guinea pig, six mice, three rabbits, and one rat) survived during a shorter total period of intermittent confinement (Table l-A). No signs of intoxication were ob serve^ among experimental or control ani mals. Mortality--aroclor 1254: One cat, three guinea pigs, four mice, two rabbits, and nine rats survived throughout their expo sure, for seven hours on each of 83 days over a period of 121 days, to air containing Aroclor 1254 in the concentration of 5.40 micrograms per liter (0.41 ppm). Certain other animals (three guinea pigs, six mice, two rabbits, and one rat) were killed for examination after 33 to 74 periods of expo sure (Table I). The incidence of mortality from extraneous causes among the exposed and control animals (Experiment No. 1), with the exception of the rabbits, was com parable (Table I). One cat, four guinea pigs, six mice, four rabbits, and 10 rats survived (Experiment 2, Table I-A) following their exposure for seven hours on each of 15Q days over a period of 213 days to air containing Aroclor 1254 in the concentration of 1.5 micrograms per liter, (0.11 ppm). Eight other animals (three guinea pigs, four mice, and one rat) survived through 30 to 139 periods of ex posure. The incidence of fAtalities among the exposed group was slightly less than that encountered among the controls (Ex periment 2, Table l-A). Table II. orThe Average Changes in Weight Experi mental and Control animals (Higher concentrations) Specie* of Animal Number of Animal* Av*ra*a Chan** In Weight Avereta Expree.ed a* Initial Wei*ht Percent*** of (k*i laltlal Weight Aroclor 1242 - 9.60 1/1 - Experiment No. 1 Cat Guinea PI* Mouse Rabbit Rat 1 10 4 10 2.666 0.646 0.024 6.001 0.921 + 9.1 - 2.0 + 7-1 + 1.1 Aroelor 1942 6.63 i/l Experiment No. 2 Cat Guinea PI* Mouie Rabbit Rat 1 3 10 2.271 0.404 0.021 1.(97 0.212 +22.2 +21.2 4(0.9 + 17.( A roelor 12(4 . (.40 1/1 . Experiment No. \ Cat Guinea Pi* Mouee Ri.bbit Rat 1 6 10 4 10 2.120 0.409 0.021 2.72* 0.227 +22.1 +40.7 +26.6 +34.1 + . ' Conditioned Air Control* Experiment No. 1 Cat Guinea PI* Mouae Rabbit Rat ^ 1 6 7 4 10 2.991 0.419 0.022 2.704 0.211 + 64 +16.0 + 17.4 +44.9 +16.4 Table II-A. The Average Changes in Weight of the Sur vivors AMONG THE OKICINAL GROUPS (Lower Concentrations) Specie* of Animal Average Chang* is Weight Number Average Exprmaeil aa of Initial Weight Percentage of Animal* (kgl Initial Weight P Aroclor 1242 . 1.9 v/l . Experiment No. 3 Cat Gulnoa PI* Mouao Rat 1 A 1.710 0.S14 0.023B 0.214 +116.0 + 41.1 + 21.9 + 39.9 -- >0.05 >0.09 ->0.115 Aroclor 12(4 - 1.3 >/] - Experiment No. 2 Cat Guinea PI* Moua* Rabbit Rat 1 4 6 4 10 2.9(9 0.497 0.0243 2.469 0.222 + U1 + 12.( + 17.0 + 44.4 + 21.7 -- >0.09 >Q.0( >0.09 -> 0.0S Conditioned Air Control* Experiment No. 2 Cat Guinea Pi* Mouae Rabbit Rat l ( 9 4> 0 (.324 0.(00 0.02(7 2.622 0.219 'Include* two early replacemente. - 7.4 + (4.7 + 11.2 + 62.2 + (3.7 -- -- -- -- MGNS 096375 No general or specific signs of intoxica tion were noted among the experimental animals during or after their exposure. Growth: The pertinent data relating to the changes in weight of the animals of the various groups are presented in Table II and II-A. Although comparable controls were not weighed during the first experiment with Aroclor 1242 (17 x 7.0 hrs.--8.60 micro grams per liter) all of the animals, except the guinea pigs, appeared to gain normal ly in weight during the period of exposure. Despite a small net loss by the guinea pigs in this experiment, they were actually gain ing weight at the termination of the period of exposure. The animals exposed to the vapor of Aro clor 1242 in the concentration of 6.83 micrograms per liter (Experiment No. 2) or to Aroclor 1254 in the concentration of 5.40 mierogrnms per liter (Experiment No. 1), with the exception of the guinea pigs that,were exposed to the vapor of Aroclor 1264, grew equally as well as the controls (Experiment No. 1, Table II). The growth of the surviving experimental animals in the groups initially exposed to the lower concentrations of the vapor of Aroclor 1242 (Experiment No. 3, 1.9 micro grams per liter) and Aroclor 1254 (Experi ment No. 2, 1.5 micrograms per liter) was unaffected. No significant differences in the average change in weight of the experi mental and the control groups were found by the use of the "t" test (Table 1I-A). Weight of liver and kidneys: The weights of the livers and kidneys and the relationships of their weights to the body weights (expressed as grams per 100 grams of body weight) of the animals that sur vived following exposure to the vapor of Aroclor 1242 in the concentration of 6.83 micrograms per liter, are shown in Table III, which also gives the corresponding data on the controls. Comparison by the "F" test of the variances of the ratios of the livers or kidneys to the body weights of rats, guinea pigs and rabbits exposed to the va por of Aroclor 1242 (6.83 mierogrnms/ liter), with those of the controls, revealed no significant differences (P>0.0o) ex cept in the case of the livers of the rnts. Application of the *`tM test to the mean values (Table III) revealed no significant differences between the test and control groups of guinea pigs, rats, and rabbits. Comparable values for rats, guinea pigs and rnhj>its exposed to Aroclor 1254 in the concentration of 5.40 micrograms per liter Table ill. Summary or the Data on the Relationship of the Weight of the Liver on the Kidneys to the Body Weight op Animals Exposed to the Vapok of Aroclor 1242 on Aroclor 1254 Aroclor 1242 - 6.83 y/1 - 82 x 7 hrs. Aroclor 1251 6.40 y/1 - 83 x 7 hrs. Controls 0 yi 84 x 7 hrs. Compound Aroclor 1242 Aroclor 1242 Aroclor 1242 Aroclor 1284 Aroclor 1284 Aroclor 1284 Aroclor 1242 Aroelor 1242 Aroclor 1342 Aroclor 1284 Aroclor 1284 Aroclor (284 Control Control Control Control Control Control Orfcn Liver Liver Liver Liver Liver Liver Kidney* Kidney* Kidney* Kidney* Kidney* Kidney* Liver Liver Liver Kidney* Kidneys Kidney* Specie* of Animal Ret Guinee Pit R*bb(t Ret Guinea Pit RsbMt Ret Guinee Fit Rabbit Hat Guinee Fir Rebblt Ret Guinee Pig Rebblt Ret Guinee Pig Rebblt n 10 10 10 10 Average Onren Weight (f) 11.2 20.6 122.0 12.8 28.9 120.0 1.88 6.0 18.4 11 4.8 18.8 0.0 80.8 102.3 2.0 4.8 19.6 Average Weight (g) 240 840 4.028 239 661 a.sa7 240 640 4.028 239 661 8.837 243 268 8.993 243 688 8.903 Ratio of Weight of Organ x 100 to Body Weight 4.84 4.68 8.04 8.34 4.81 8.88 0.773 0.805 0.461 0.770 0.808 0.464 4.16 4.61 2.SI 0.807 0.781 0.604 1.7181 0.4291 1.6085 1.3192 0.0000 1.0183 0.5642 0.7257 0.4177 0.4109 0.5411 0.3108 --_ -- -- -- - P O.iU-D.JO ->0.50 O.HM.JO <0.01 ->0 50 ->0.50 >0 50 0.40.0.50 >0-80 >0 so >0.50 >0.50 --_ -- -- -- -- MQNS 096376 are also given in Table III. Application of the "t" test to the differences in the mean values which characterized the experimental and control animals (Table III) shows that the weights of the livers of the exposed rats were significantly greater than those of the controls, the ratio of the liver to the body weight of the former being 5.34 g per 100 g of body weight, that of the latter being 4.15 g per 100 grams. In all other instances tested (livers and kidneys of both guinea pigs and rabbits and kidneys of rats) the differences were statistically insignificant. The organs of the animals exposed to the lesser concentrations of the vapor of the Aroclors were not examined in this manner because of the borderline character of the results associated with the higher concen* trations. Liver function; Data were obtained as to the apparent prothrombin activity of the blood (measured by the method of Kato5) of certain animals that had been exposed (1) to the vapor of Aroclor 1242, in the. con* centration of 6.83 micrograms per liter; (2) to the vapor of Aroclor 1254 in the concen tration of 5.40 micrograms per liter; and (3) to conditioned air alone. In Table IV the percentile relationships of the clotting power have been calculated arbitrarily by dividing 100 times the average clotting time of the blood of the control animals by the clotting time of the blood of the experi mental animals on the same day. No dimin ution in the clotting poiver of the blood, as a measure of the impairment of the function of the liver, was induced by the exposure of the animals to the vapor of Aroclor 1242 in air in the concentration of 6.83 micro grams per liter, or to the vapor of Aroclor 1254 in the concentration of 5.40 micro grams per liter. This functional test was not applied to animals subjected to the lower concentra tions, because of the negative results ob tained when the animals were subjected to the higher concentrations. Hematological results : Determina- Table IV. The Effect of Exposure to the Vapor of Aroclor 1242 o* Aroclor 1254 in Air for Seven Hours Per Day on Five Days Per Week Over a Period of Several Months Upon the Ap parent Prothrombin Content of the Blood of Cat3 and Rabbits Relation of "I'lothi umLii Timv" of Control and Expoee Animate Expreaeed Arbitrarily In Term* of Percentage Change in Clotting Time of Blood Time of Sampling In Relation to Period of Before of Period After Clotting Time of Qlood of Expoted Animal* Aroclor 1242 6.83 v/1 - Experiment No. 2 Cat A-416 Rabbit* (Average) 100.0 00.8 118.6 101.1 07.4 118.8 89.8 03.8 105.1 9.0 08.0 103.7 101.5 100.0 Aroclor 1884 6.40 -,/l . Experiment No. 1 Cat A-444 RabblU (Average) 100.0 100.0 u HI.4 101.8 08.8 00.0 17.1 6.0 01.0 00.0 90.8 103.0 112.1 07.0 06.4 06.8 100.0 'Determlaatlon made IS day* alter 82nd period of exposure. 'Determination made 14 d*>'i after 83rd period of expoeure. Period 3 2 8 2 Wee Drawn 10 10 48 60 82 ' 10 16 10 12 46 60 68 HONS 096377 Tablx V. The Average Numbers op Erythrocytes and Leucocytes Afro the Average Concentration op Hemoglobin in the Peripheral Blood of Experimental and Control Animals Compound Aroclor 1Z4 2 Aroclor 1264 Control* Concentration <v/l> 6.83 1.40 0 Eiperiment Number 2 t 1 Specie* of Animal Guinea Pl Rabbit Gulnw P!| Rabbit Ouinw Pit Rabbit Erythrocyte*: (Thousand*) 5.701 6.086 6.886 6.486* B.T2B 6.809 Leucocyte*: per mm* 9.766 10.611 12.124 11.690 Hemoglobin: f/100 ml 11 4s 14 6* Value aifnincantlv In* thnn that yielded by control*. 'Value *(gniflrantly greater than (Hat yielded by control*. tions of the numbers of erythrocytes and leucocytes and of the hemoglobin content in the peripheral blood of the guinea pigs and rabbits subjected to inhalation of the vapor of Aroclor 1242 in the concentration of 6.83 micrograms per liter, are given in Table V, which also includes comparable results on control animals. Application of the "t" test to differences in the mean values for the experimental and control animals yielded borderline evidence of significant differ ences in the number of leucocytes and In the concentration of the hemoglobin in the blood of the guinea pigs. These differences were small and of opposite sign (the num bers of leucocytes in the blood of the test animals were low, while the hemoglobin con tent was high), as well as being subject to individual variations, and they cannot be regarded as of physiological significance. Somewhat comparable results were ob tained when guinea pigs and rabbits were subjected to Aroclor 1254 in the concentra tion of 5.40 micrograms per liter. No physi ological significance is attached to the slightly elevated hemoglobin content of the guinea pigs. Pathological findings: In all of the ex periments, animals were killed from one to 15 days after the final period of exposure. In the first experiment with Aroclor 1242 (8.60 micrograms per liter), all of the ani mals were examined postmortem, and since gross examination of the viscera did not reveal any Significant alterations, the tis sues of only representative animals (one cat, four guinea pigs, six mice, four rabbits and six rats) were sectioned and examined microscopically. No abnormalities were found in the viscera of these animals. In the second experiment with Aroclor 1242 (6.83 micrograms per liter), and in the first experiment with Aroclor 1254 (5.40 micrograms per liter), which were carried out simultaneously, the deaths that occurred among the test and control animals were the apparent result of an appreciable in cidence of pneumonia. The lesions of cer tain of the animals were those of frank pneumonia; in others such lesions were not fully developed. Degenerative changes in the viscera were usually found, in varying de grees of severity, in association with the pneumonia, but in certain animals, test and control alike, the degenerative changes were more evident than the pneumonia. The similarity of the lesions in test and control animals, and the lack of characteristic evi dence of chemical pneumonitis, led to the reasonable, but not altogether certain, con clusion that all of these fatalities resulted from intercurrent disease among the ani mals, and not from the effects of their ex posure to the Aroclors. For practical pur poses, this conclusion was subjected to the critique of further experiments involving more prolonged exposure of animals to some what lower concentrations. Except in the case of the rats exposed to Aroclor 1254, the survivors subjected to the higher concen tration of either Aroclor had normal vis cera. All of the animals exposed to the vapor of Aroclor 1242 In the concentration of 1.9 micrograms per liter w'ere examined post mortem, and the viscera of most of them w'ere examined microscopically. The few deaths among the exposed group were at tributed to incidental infectious pulmonary disease. All exposed survivors, except two rabbits that had hepatic lesions of coccidiosis, had normal viscera. The control animate (Experiment No. 2) that died were found to have had pneumonia. Of those that sur- MOMS 096378 vlved, one rat, two guinea pigs, and one mouse had focal or diffuse cytoplasmic vacuolation of the hepatic cells. The remaining control animals had normal viscera. All of the animals exposed to the vapor of Aroclor 1254 in the concentration of 1.5 micrograms per liter were examined post* mortem, and the viscera of most of them were examined microscopically. A guinea pig that died exhibited chronic pyelone* phritis, pulmonary hyperemia and edema, and degenerative lesions in the brain and liver. The visceral lesions were related, no doubt, to the renal Infection. The deaths of four mice were attributable to acute bron chitis and pneumonia. The viscera of the cat that survived were norma). Of the seven guinea pigs that were living when the ex* periment was terminated, three had normal viscera and four had slight alterations of hepatic cells characterized by cytoplasmic vacuolation. Ten mice survived, and of these six had normal viscera and four had slight degenerative changes in the liver. Four rab* bits killed one to 15 days after the last I>xiod of exposure had diffuse hepatic de itineration. The character of the lesions varied from cloudy to hyaline or hydropic degeneration and included varying degrees of fatty metamorphosis. The other viscera of these animals were normal. All of the rats were examined and found to have slightly to moderately severe degenerative lesions of the liver. The lesions of greatest severity were found in the rat that was killed and examined on the first day after the last period of exposure. Two rats had chronic pyelonephritis, and the remainder had alight degeneration of the renal tubules. Discuasion: In terms of mortality, growth (except that of guinea pigs) and non-occur rence of pathological changes, the vapor of Aroclor 1242 in the concentration of 8.6 micrograms per liter (approaching satura tion) appeared to be non-injurious to ex perimental animals subjected thereto for seven hours on each of 17 days over a peri od of 24 days. Experimental animals subjected to but a slightly lower concentration of Aroclor 1242 (6.83 micrograms per liter) for seven hours per day on each of 82 days over the period of 120 days suffered no injury on the basis of any of the following criteria: mor tality, growth, pathology, organ enlarge ment, liver function or hematological changes. More prolonged exposure of animals to a lower concentration of Aroclor 1242, (1.9 micrograms per liter) over the period of seven months was likewise without harm in terms of growth, mortality and the absence of pathological changes. In view of this evidence it is suggested that the tentative allowable concentration of the vapor of Aroclor 1242 should be at least two micrograms per liter (2 mg per cu meter), which is twice that recommended by the American Conference of Govern mental Industrial Hygienists3 for a chlorin ated diphenyl of unstated chlorine content. The exposure of animals to the vapor of Aroclor 1254 in the concentration of either 5.40 or 1.5 micrograms per liter failed to induce harmful effects in the form of re tardation of growth (except in the esse of guinea pigs exposed to the higher concen tration), or of mortality, but histopatho logic evidence of apparently reversible hepatic cellular injury was found in the animals. These findings cannot certainly be attributed to the effects of Aroclor 1254 be cause of the appreciable incidence of pneu monia among both experimental and con trol animals. When these nonspecific toxic changes in the viscera of the animals were associated with pneumonia, they were readi ly explained thereby, but they were al^o found in animals that had been exposed to the vapor of Aroclor 1254 and were free of pneumonia. That these may have repre sented toxic effects of exposure to Aroclor 1254 finds support in the fact that the livers of the exposed rats (5.40 micrograms per liter) were significantly heavier in relation to their body weight, than were those of control rats. It would appear that this ma terial, which is reported to contain 55% of chlorine, is somewhat more toxic than is Aroclor 1242, which contains only 42% of chlorine. Therefore it is suggested thAt the threshold concentration of 1 mg per cu meter of air recommended tentatively for safe in dustrial practice by the American Confer ence of Governmental Industrial Hygien ists3 is reasonable. It should be noted that it was necessary to heat these Aroclors in order to increase the rate of volatilization sufficiently to at tain the concentrations maintained in these HONS 096379 t I experiments. To the extent that their indus sponsored by the Monsanto Chemical Com trial usage is carried out at ordinary tem pany, whose Anancial support is gratefully peratures, the hazard of their inhatation acknowledged, as is also their assistance in may well be slight or entirely absent. supplying the materials for investigation. Summary PROLONGED intermittent exposure of ani*mals to the vapor of Aroclor 1242 (1.90 to 8.63 micrograms per liter) demonstrated no injury. Prolonged exposure to compa rable concentrations of Aroclor 1254 re sulted in reversible degenerative changes in certain viscera. The work described in this article was References 1. DRINKW. C. X.: Further Observation* oa Uio Foe. ibl Systemic Toxicity of Certain of the ChlorlaaMd Hydrocarbon* with Suftoatlona for Pormlaatblo Concen tration* in th* Air of Workroom*. J. Ind. Hwt- 4 Too.. 21:1SS. IMS. I. Kato, K.sMIero.prothrombin Toit with Capillary Whole Dleod; Modification of Quick'* Quantitative Meth od. Amtr. J. Clin. Path., 10:14T, 1*40. S. American Conference of Governmental Industrial RycienUta. Threshold Unite for IMS. AUA Arab. (ntf. H*altk. lS|. L HONS 096380