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C. Shell Development Company a 0".ision o' Shen Oil Comoanv One Sftefl Plaza P O Sox 4320 Houston. Texas 77210 August 27, 1985 FROM: F.B. THOMAS, ACTING CHAIRMAN, PS-7 TASK FORCE TO: MEMBERS, API MBSO EXECUTIVE COMMITTEE SUBJECT: OVERVIEW OF API BENZENE RESEARCH PROGRAM Appended for your information and approval is an overview * of benzene toxicology prepared by the API PS-7 Task Force. This document is being sent directly to you at the request of Dr, Scala, in order that approval can be solicited from the API MBSD Executive Committee prior to the next meeting of HESC (September 5, 1985). I understand that a telephone survey of the members of the Executive Committee will be made short!y. As a separate item, jl have been asked by Dr. Craig to send to you a copy of a draft statement which will be sent as a formal communication1 from Mobil to HESC. This document, which has not yet been reviewed by the PS-7 Task Force, outlines Mobil's position concerning the need for a chronic low dose study of benzene in the rat. No action by the API Executive Committee has been requested by Dr. Craig, and the document is being sent to you at this time for your information. cc (w/a11achment): Members, PS-7 Task Force C. DiPerna--MobiI J . Sul 1ivan--Amoco M. Beauchamp--API N.K. Weaver--API C.E. Hoidsworth--API OVERVIEW OF BENZENE TO XI API PS-7 TASK F Version of 8/26 INTRODUCTION: The U.S. Occupational Safety & Health Administration (OSHA) is expected in the near future to issue regulations concerning the use of benzene in the workplace, establishing a not-to-be-exceeded Permissible Exposure Limit (PEL) for this compound of 1 ppm, a Short Term Exposure Limit (STEL, 15 min) of 5 ppm, and an action level of 0,5 ppm. OSHA will justify this regulation on the basis of quantitative estimates of human cancer (e.g., leukemia) risk derived from epidemiological studies of populations exposed to benzene. * Data from animal studies are cited by OSHA as further support for the need of such regulation. The California Air Resources Board (CARB) has also developed quantitative estimates of human cancer risk from benzene based on tumor data in laboratory animals seen in a cancer bioassay sponsored by the National Toxicology Program. CARB has concluded that human cancer risks from even ambient benzene levels of 4-5 ppb are not negligible, and may use their estimate in support of California's listing of benzene as a hazardous air pollutant. The present document is not intended to provide a detailed review of the epidemiological and toxicological basis of the OSHA and California regulations. Rather this document identifies those issues surrounding benzene where it is believed that toxicological data may make a contribution. The PS-7 Task Force believes that the major benzene issues of relevance to the occupational use of this compound continues to revolve around hematotoxicity and the development of leukemia. While of concern, other biological endpoints of benzene toxicity (e.g., solid tumors, cytogenetics, micronuclei, etc.) are poorly understood and are of unknown significance to human health. The PS-7 Task Force has identified the following issues where toxicological research programs might be considered by the Industry:1 1. RELEVANCE OF RODENT DATA TO MAN: The major question affecting the development of reasonable workplace exposure 7imits for benzene is the relevance of findings in rats and mice to human health. It is known from the API/CMA research programs that mice are significantly more sensitive to the hematotoxic effects of benzene than are rats. Lacking, however, are definitive data for the relative sensitivity of man to the toxic effects of benzene on the blood-forming organs. This GOODIE MOD issue was in fact recognized previously by the PS-7 Task Force who initiated pilot studies at the Brookhaven National Laboratory (BNL) in 1985. Sammett et a 1. (J Toxicol Environ Health 5: 785- 592 , 1979) reported that rats subjected to partial hepatectomy were significantly less sensitive to the hematotoxic effects of benzene, suggesting that the liver may play a key role in metabolizing benzene to a pretoxic derivative which may be subsequently activated in the bone marrow. This program is developing a method of culturing rodent and human bone marrow in chambers implanted into the peritoneal cavity of a host animal which is exposed to benzene. Thus, all marrow samples will be exposed to the same milieu of benzene and benzene metabolites, so that a direct comparison can be made of toxic effects seen in marrows across species. To date, BNL investigators have demonstrated that human marrow can in fact be grown in the body cavity of rodents, and they hope to identify certain cytokinetic parameters (e.g., the growth of specific bone marrow cell populations, etc.) which will allow a measure of the relative sensitivity of mouse, rat and human bone marrows to the toxic effects of benzene. If useful cytokinetic parameters are not found by BNL, the Task Force anticipates that analysis of covalent benzene-DNA adducts and/or other endpoints may be considered as crude measures of benzene toxicity. In this regard, it should be noted that the Task Force is presently reviewing data from a recent report (submitted for publication) from the Chemical Industry Institute of Toxicology CIIT) finding increases in micronuclei and sister chromatid exchanges in rats and mice exposed in a single 6-hour exposure to benzene vapor. Pharmacokinetic and metabolite identification studies are ongoing by NTP at Lovelace. Interim findfns will be available this year; when this information Is available, the need for further pharmacokinetic studies can then be better assessed. The PS-7 Task Force recommends examination of prior CIIT work In this area and notes that the current CIIT approach on 1,3-butadiene (i.e., immune response, oncogenes, retrovirus activation) may also be relevant to benzene research. As mentioned earlier, the first phases of this research program are presently on-going at BNL, and it is estimated that the entire program will require approximately 18-24 months more to complete. While it must be stressed that this effort must be character!zed as highly experimental, the Task Force believes that a number of important benefits may be derived from this exercise: MOD 000015828 '= g? j a. The data on the relative sensitivities of the bone marrow samples from various species may provide a basis for scaling in risk modelling. b. Such data may also give a basis of selecting the most appropriate test species for further research on benzene. c. Development of the implanted marrow model provides the Industry with a unique tool to evaluate the different degrees of benzene toxicity which might result from gavage vs. inhalation, pulse vs. continuous exposures, gavage in oil vs. gavage in water. d. Such data contribute substantially to our understanding of the mechanisms of benzene hematotoxicity. 2. PERCUTANEOUS ABSORPTION: The API Toxicology Committee has been sponsoring a complex program examining the absorption of benzene through the skin. This program is nearing completion and a final report is anticipated by the end of 1985. 3. REPRODUCTIVE TOXICITY: The PS-7 Task Force has been informed that a report of reproductive toxicity associated with benzene was recently presented by investigators at New York University to the 25th Annual Meeting of The Teratology Society. While details of the NYU findings are not available at this time, the Task Force understands that this information is presently under review by one API member company, and further information is being sought. It should be noted that reproductive toxicity was not seen in a previous study of benzene sponsored by API (Report No. 28-31212). 4. CARCINOGENICITY: In 1977, Maltoni and Scarnato (Gli Ospedali della Vita 4: 111-113, 1977) reported that the daily oral administration of benzene in olive oil to Sprague-Dawley rats for 52 weeks resulted in the appearance of a number of highly diverse solid tumors. This was subsequently confirmed in a bioassay sponsored by the National Toxicology Program (NTP) in which benzene in corn oil was administered orally to F344 rats and B6C3F1 mice on a daily basis (NTP, 1983). Maltoni et al. subsequently reported that Zymbal gland carcinomas were seen in rats exposed chronically to benzene vapor. In this latter study pregnant Sprague-Dawley rats were exposed to 200 ppm of benzene vapor, 4 hours/day, 5 days/ week from gestation day 12 to delivery. The offspring were then exposed to 200 or 300 ppm of benzene vapor, 4 or 7 hours/day, 5 days/week for up to 104 weeks. At 104 weeks, 8 of 137 rats had developed Zymbal gland carcinomas compared to none in the concurrent controls. ocoo^ .B29 page -i Various investigators have found that some strains of mice respond to benzene exposure with increased incidences of thymic lymphoma and related tumors. However, these same strains of mice are known to harbor a virus (Murine Leukemia Virus) which is believed to play a critically important role in their developing such tumors. Consequently, the human health significance of the occurence of thymic lymphoma in these specific strains is not clear. The PS-7 Task Force has considered two proposals for carcinogenesis bioassays on benzene: a. CARCINOGENESIS BIOASSAY IN CBA/Ca MOUSE: Recent data from investigators at BNL indicate the mice of the CBA/Ca strain exposed to 300 ppm of benzene vapor (6 hr/day, 5 day/wk, 16 weeks) appear to develop an increased incidence of Acute Myelogenous Leukemia (AML). This is the histological type of leukemia most commonly associated with benzene exposures in man. Further, according to the BNL investigators, this strain of mouse apparently does not harbor Murine Leukemia Virus, leading BNL to suggest that the CBA/Ca strain may be an appropriate animal model for benzene 1eukemogenesis. The Task Force has conducted a search of the common toxicological databases for information on the development of AML in this strain of mouse, but did not identify any published information. For this reason, the Task Force does not endorse a cancer bioassay in the CBA/Ca mouse at this time. However, as additional information becomes available on this strain, the Task Force will reevaluate the merits of conducting studies in the CBA/Ca mouse. b. CARCINOGENESIS BIOASSAY IN THE RAT: The API Health, Environment & Safety Committee (HESC) has asked the PS-7 Task Force to review a proposal submitted by Mobil Research and Development Corporation (Letter J.E. Penick to W.J. O'Keefe, 6/19/85) suggesting that the Industry consider sponsoring a low-dose benzene inhalation study in the rat In an effort to define a no-effect level for solid tumor development. Several benefits have been suggested to justify such a study: (1) Mr. Penick's letter notes that the finding of solid tumors in rodents exposed to high oral doses of benzene (diluted with vegetable oil) raises a new basis for concern beyond the workplace--the possibility of unwarranted class action suits claiming damages for all 3^.3 oOv o Pace 5 types of cancer allegedly caused by benzene emissions from industrial facilities and operation of vehicles. (2) Mobil notes that California has used the NTP data to conclude that health risks associated with 4-5 ppb ambient levels of benzene are not negligible. The California Air Resources Board is evaluating various strategies for reducing levels, including lowering the benzene and/or aromatics content of gasoline. (3) According to Mr. Penick's letter, OSHA may use the NTP data to justify a further lowering of their proposed benzene standard from 1.0 ppm to even lower levels. Mobil suggests that without animal data showing a no-effect dose level, extrapolation based on studies at high doses will continue to be used to calculate worst-case human risks, and almost any exposure level could be alleged to cause cancer in man. (NOTE: The draft OSHA benzene standard reviewed by the PS-7 Task Force bases its regulation of benzene on risk assessments using epidemiological data, not animal data). (4) The PS-7 Task Force believes that the development of additional tumor data via the inhalation route may shift regulatory modelling of human risk from ambient and workplace exposures to benzene vapor (e.g., CARS) away from the gavage data reported by NTP and Maltoni. (NOTE: Questions about benzene as a groundwater/drinking water contaminant are still impacted by the gavage data .) The benefits suggested above (i.e., regulatory risk assessment and litigation) are the purview of other groups within API. For this reason, the PS-7 Task Force will not address these issues, except where specific technical comments are believed to be approprlate. However, the PS-7 Task Force has identified a number of technical concerns which should be considered fully by the Industry before sponsoring a low-dose benzene inhalation study as proposed by Mobil . (1) It is understood that the CARS risk estimate is based on the incidence of preputial gland tumors in the B6C3F1 mouse and not in the F344 rat. Thus, if there is concern about solid tumor data being used in risk calculations, the API may want to consider a study using both rats and mice. Similarly, the Task Force believes that defining a no-effect level only in the rat (i.e,, the less sensitive of the rodent species would be subjected to 000015831 MCI) technical criticisms. (2) The Task Force reviewed an analysis of the likely effect of various assumed no-effect levels upon risk estimates derived from the "Global 82" model which was performed by 8ob Sielken on behalf of Mobil. Although Sielken concludes that such data can have significant impact on the maximum likelihood estimates of risk, he notes that the data would have little effect on the 95% confidence limits; these limits are presently used by regulatory agencies as their basis for decision-making. It should be noted that Sielken's analysis makes no allowance for error and also presupposes that only one tumor type is identified as a basis rather than total tumors. In addition, his analysis shows that if the no-effect level is determined to be 30 ppm instead of 50 ppm, even the maximum likelihood estimate would be little affected. (3) The study design as proposed includes 200 to 1000 rats per dose to improve the statistical significance of the results. PS-7 had hoped to utilize Dr. Sielken as a consultant to determine the statistical power to be derived from the size of the experimental groups, as well as other statistical design considerations. Unfortunately, Dr. Sielken is not available until early September. However, based on discussions with statisticians from within the Industry, the Task Force believes that conducting a "mega-rat'* study using 1000 ani ma 1 s / group would not yield significantly better data than a study using 300 anima1s/group. (4) Related to the question of group size above, the Task Force notes that large numbers of animals could necessitate that as many as 10 exposure chambers be employed for each treatment group, greatly increasing the complexity of the statistical evaluation of this experiment. (5) It was suggested that API consider sponsoring the proposed low-dose study at Or. Cesare Maltoni's laboratory in Bologna, Italy. However, Dr. Maltoni uses Sprague-Dawley rat In his studies, so that data from such an experiment would do little to refute the observations of NTP in the F344 rat and B6C3F1 mouse. In addition, Mobil has noted that Dr. Maltoni lacks the computer facilities to analyze the volumes of animal observations which would accumulate from such a study. Thus a third-party would have to be involved for data analysis. MOD 0000 (6) The proposed study design involves exposures to benzene vapor for 6 hr/day, 5 day/week , for approximately two years. This exposure schedule is considered by the Task Force as being more appropriate for mimicking occupational exposures, than for the consumer exposures which are of litigious concern (see Penick letter). (7) Similarly, if the intent of the proposed study is to refute the tumor observations of the NTP bioassay, the route of exposure should be the same as that used by NTP (i.e., gavage in corn oil, not inhalation). (8) As noted above, previous data developed by API and CMA indicate that the mouse is substantially more sensitive to the hematotoxic effects of benzene vapor than is the rat. The Task Force is concerned, therefore, that in a low-dose study involving rats and mice, that the no-effect level determined in mouse may be substantially lower than the 25 to 50-ppm no-effect level predicted by Mobil in the rat. This outcome would, of course, raise once again the basic question of the relevance of rodent data to human health. The PS-7 Task Force hopes this discussion, in combination with the inputs of API's regulatory and legal experts, will provide an adequate basis for putting into perspective the overall direction and content of the Industry's research program on benzene* ENZENE DF^rT MTE- h UJ Jr ^ Will W i, HESC MELE. Th* >wT ^ API P`5 -7 wU ^rc^P THE CARCINOGENICITY OF BENZENE Mobil believes tiiet csrcinugsnicity has been and will continue to be, the primary factor which drives benzene regulation. Further, Mobil believes that -future regulations will be based upon a -formal process o-f m evaluation, i.e., quantitative assessment of risk. Industry has the responsibility to conduct its own assess.nents, including psrticularlv the development of valid and credible scientific data upon which an unbiased evaluation of e::posur e/r i sk can be -founded. Although many other aspects are significant, c1ear1/defined cose response curve is the central requirement cf a risk assessment. For assessments which use animal data to predict human risk, other important requ:rsnents include appropriate experimental design, and other factors for minimizing the significance of species differences. As a generality, the latter factors are derived from metabolic and kinetic studies. Without a well-defined dose response curve based on an applicable experimental design, be no valid risk assessment can be made. It 1= rsccQni^sd thaz mreriTiation may cone f rcir> a Vcfi st y ct sourcsi , but It c iz * I b;^l 1 svss that t h3 1T1 Qat =icr:ric=;'.t data in the future will come from animal models o.: benzene c arc 1 rogsnesi 3, i.e., the rat and .the mouse. Both sexes of both scecies predict a o =roino genio response in man and therefore must be regarded, in a. general sense, as applicable models. m No current 1v available data provide a satisfactory basis for risk assessment of benzene csrcinccaresis. Recent epidemiology studies of workers exposed to benzene several decades ago have been flawed by speculative (probably highly underestimated; exposure values. The several inhalation care:nocenicity studies in rats and mice conducted in the last two decades have been cf the screening type, designed to reveal whether a carcinogenic hazard exists, and conducted at levels of l'I'O ppm =.rd above. An oral carcinogenicity study in rats arc mice conducted bv the- National Toxicology' Program (NTP) used high rates of a.dm i .n i strati on (25 me 'kc-'day and Greater) . Every ecss-d grzup of both sexes of both scc-cies experienced a significant carcinogenic responsei 0000l5835 VIC'D  ooo rC (5` l/l n rr t. 0 a J-- m a in * iG 33 O n fll ni 3 ID a a n *h 0 03 3a ft r cr h r it *-* ft O ir +i rt 3 ID Ui ID *- 3 rti in ft Q ft* rt M n 3 in 3 rt 77 Hi 3 fl* rt it a C* d HI in __i ri 111* 3 l`l 77 0 3 -I-. t- II rt u> zs I-- m fll T xi b~i n a* cr --' lit it u < it u. ft* :r Ill 3 id ?: !* L'l *-< 11 r 3 O in rt 3 ID n in 3 in rt Id rc TJ a Hi * i*i 3 in H G Hi it* cr III H -* t-- III Hi ;; cr it it Cl "T 3 i-- (ll a* D in 3 III in in in XI o rr n n H- x> it - G IT in n fli -* it IT - ft H 3' _i ID ft "N 2 t. n o -- t. 3 Js !i *- if a _T in B* hi it M- u pi 3 fill 3 n a 0* ID y. cr Ll n "1 Hi ID 3 III -* cr Hi it cr `a ft* id cr in lj I* H-, Ci ft n in t. 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III n i- in m rt 3 XI cr ft* Cl lu Hi *-- Cl it in III n ID ib r ;; -* 1 3 TJ tl 0 TJ D n r 3 0 Ul < 3 (D 3 ID 3 + ID n cr 0* in it u> IT i-- -- in cr rt cr ID ft* it ft* d rt Cl u* na 3 -ii rr ij cr i H* III in ni rlT ~ iC a ft* < Ul III III Ill Ul ill f+ = o I'll Cl O it 0 < H- -1 a rr m ID *i in rt a jC 0 n. in 01 n G Cl ri id 3 it T fji ,t G 3 in cr id .t r 0i id j ri Hi 1 G ft* 3 a in rr ID : i G Ul r XI f-* n Tl an n Ul a ru Hi in Hi n G 1" Cl cr ID < rt to ID 1 * Ul Ul jC it c 3 III H' 13 ft O ft* Ul cr i-- CD ru O t. cr iii n4 n Ul 1 01 i-- D rr ~T ID 3 ft* "7 rt n cr f-*ft - O t CT i ID Ul n XI u *'l 3G a XI rO n Ul ii ID ni Cl a ft* CT I"* Cl 3 3 Cl "f 1 ft* ft -- ID ft* 3 it 3 *-> O ul 3 rt C ft* a ft < o -h m ir 1--: ,f III a fit 3 G 3 rn[^r cr fli fll 3 N 'U 111 3 m 1 l" HI B -t. 3 it- 3 * 01 ru n ?. III n -Ti u.i 01 f'l fl* - 3 in i *h 3 3 hi n ft O ni f-* ft i 0 3 Cr fl* rt, 0 n 3 m !-- *n ~T Q3 it D* fl* n !-* *-- rr Cl 3 i n fl* H Hi Kl hi 3 it 0 M II i. ill 3 ID -K 0 n Cl H- 3 Oi f. 3 3 Ul rt n ID rr -- it ft 3 3 3 < cr M- tD fl* --1 Hi 111 ft r~ id 77 - III v' *1 n G G 0l M- Ci 3 a --1 in 3 3 III 77 Ci rt rt ,t I-- G 3 fli ~r r ID III Hi III ID i--* in G in Hi m 13 3O ft D CL XI '1 3 111 iQ a *- rt n cr i r ft* .t rr H H' cr -H Hi Tl n a a* in i--* ri -* ft * r. IT tj Tl 3 *1 ft* 3 n Cl rt ID a 3 ~r m Cl 0i 01 'i 3 ti - fl* r[ G 01 t. Ul ID ni 3> Ul n a I-*- m rt 3 -1 Ul H-. cr 3 On Ul 3 hobil hc.= not proposed tne conduct of parallel 2 t '_ c i 5 * in. the itcu s e boo a. use or recent developments concerning t h a. t species at 'r oof har en Laboratory. In screening studies at ICO pern and above, the CBA/ca strain qt mouse nas been shewn tc develop myeloid 1 eu.l-:e:Tii a.. a type of cancer observed in workers e:: posed to mgr. concentrat 1 ons of benzene in t.ne air. The Beqzer.e To;i 1 col cev Task Pores has the responsibility ot dstor;t: r 1 no whether the CE'A/ca mouse snculd be regarded as a. specific iiiccai of human benzene 1 sukemooenesi 3. If it is concluded that if the mocei appears applicable, studies in tne CEA/cs. mouse should be considered. 3 00 oo^ American Petroleum Institute 1220 l Street. Northwest Washington, DC 20005 202-682-8000 tjf- .............. Toxtootog 1st 202/682-6J42 TO: FROM: DATE: SUBJECT: PS-7/TRTG Task Forces Thomas H. Keenan July 24, 1985 Meeting Minutes The Minutes o the June 13, 1985 Meeting are enclosed for your information. Please review the minutes and inform me of any additions/corrections. xc: C.E. Holdsworth An taual opportunity omployor e-6-^ American Petroleum Institute Medicine and Biological Science Department PS-7/TRTG Task Force Meetng Minutes API Offices, Room 1273 Thursday, June 13, 1985 1*4 p.m. Attendees P. Craig (Mobil) M. Lakin (Chevron) S. Cragg (ARCO) R. Nair (Monsanto) Others J. Amsel (API) M. Bird (Exxon) C. Blank (API) PS-7 Task Force P. Garvin (AMOCO) B. Thomas (Shell) TRTG R. Kociba (Dow) C. Stack (CMA) T. Slone (DuPont) K. Bristol (API) E. Cronkite (Brookhaven) J. Rodricks (Environ) ? Keenan (API) I. Dr. Cronkite's Benzene Research. Dr. Cronkite presented evidence for his purported benzene leukemogenesis model. The experimental design consisted of exposing animals via inhalation to 100 or 300 ppm benzene 6 hr/d, 5d/wk for 16 weeks. Two strains of mice were used (i.e., C57B6 and CBA/Ca). The lymphomas/leukemias observed with the C57B6 strain are roughly analogous co human acute lymphoblastic leukemia; however, the lymphomas produced are associated with a retrovirus. Acute myelogenous leukemia (AML) is induced in CBA/Ca. The spontaneous incidence of AML is low; there is no evidence for the existence of a retrovirus (Personal communication to Dr. Cronkite: Ester Hays (UCLA) and Robin Mole). The results as of April 4, 1985 are summarized in the attached tables and the data is presented in the figures. General conclusions as presented by Dr. Cronkite are: C57B6: a shortened latent period and a more rapid increase in tumors is observed with animals exposed to benzene or radiation. CBA/Ca; benzene or radiation induces an increased incidence of leukemia. This strain is more responsive than the C57B6 strain. II. Cl IT Manuscripts. A preprint of a manuscript released by CUT concerning SCE and micronucleus formation in mice and rats was discussed. The results indicated that a single 6 hr exposure of benzene induced statistically significant increases in SCE in peripheriai blood lymphocytes and micronuclei in polychromatic erythrocytes in mice (10 ppm SCE and MN) and rats (3 ppm - SCE; 1 ppm - MN). III. Developmental Project (Dr. Cronkite). The feasibility of growing bone marrow cells in Plasma clot Diffusion Chambers in mice and rats is being determined. The data (table attached) indicate that human bone marrow cells grow better in mice than in rats. The PS-7 Task Force will review this information and deter mine if the second phase of the project will be funded. The experiments of the second phase will compare the eryth ropoietic responses of human, rat, and mouse bone marrow cells following benzene exposures. IV. TRTG Meeting. Dr. Snyder's review of the recent benzene literature used by OSHA has been distributed. Task Force members are requested to review the manuscript and be prepared to comment by the next meeting. i^O oV^ oO STRAIN SEX C57B6 M M M M F F F F F F CBA/Ca M M H M M H F F F F MORTALITY, LEUKEMIA, AND TOTAL TUMOR INCIDENCE IN TWO STRAINS (C57B6 AND CBA/Ca) IN A BENZENE INHALATION EXPERIMENT EXPOSURE BENZENE EXPOSURE TIME X I2 CONC. DURATION ON STUDY MORTALITY LEUKEMIA 300 ppm sham 300 ppm sham 300 ppm sham 300 ppm sham 300 ppm sham 16w 450d 450d 8w 430d 430d 16v 1023d 1023d 8w 230d 230d 16v , 540d intermittent 540d 43 35 0-- 55 0-- 95 50 35 55 2 NA, 8 NA3 0-- 300 ppm sham 300 ppm sham 100 ppm sham 300 ppm sham 100 ppm sham 16w 16w 16w 16v 16w 505d 505d 520d 520d 480d 480d 505d 50Sd 480d 480d 50 17 0 48 NA3 0-- 0-- 0-- 35 10 0-- 0-- 0-- X TOTAL TUMORS NA3 NA3 -- 75 NA^ NA^ NA, NA3 -- 20 NA3 -- -- -- 25 -- -- -- Exposures were 6 hr/d, 5d/wk. Thymic mod nonthymic lymphomas In C57B6* Acute myelogenous leukemia in C3A/Ca. NA, not available* Exposure were for 2 weeks on, then 2 weeks off for a total of 16 weeks exposure* MORTALITY, LEUKEMIA, AND TOTAL TUMOR INCIDENCE IN TWO STRAINS (C57B6 AND CBA/Ca) IN A RADIATION EXPERIMENT STRAIN C57B6 CBA/Ca TIME ON SEX TREATMENT STUDY M Bonlrraddlated M 525r-single dose M 175r-3 times 84 Intervals M 5.25r/d,5d/vk to total 525r lOOOd lOOOd lOOOd 720d M Nonlrradlated 300r 250r 200r lOOr 50r 1050d 1050d 10504 1050 MORTALITY 80 80 90 20 LEUKEMIA 26 38 50 NA2 TOTAL TUMORS 35 45 65 NA2 85 3 95 27 100 28 35 10 6 NA2 35 48 Total tumors 1c the CBA/Ca excludes hepatomas. This strain has a high spontaneous incidence of hepatomas. NA, not available. Treatment Croup 1. 550 Rads KUMAR BONE MARROW CROWN IN DirrUSION CHAMBERS WITH MICE AND RATS AS HOSTS Host Experiment Dey 7 cru-E ---c-r-u----E------ 14 BFU-E* BNLC mice 1 2 84.7*14.9 55.7*14.7 61.3*24.6 22.5* 6.7 4.0*1.8 1.0*0.6 2. 550 Rads and FHZd 3. PHZd Hypoxia* 4* 550 Rads and Rypoxlo* 5. 550 Rads and Hypoxia* 6. 600 Rads gr 7. 600 Rads and V Hypoxia* BNhc mice BNLC mice BNLe mice C57BI/6J mice SpragueDavley Rats SpragueDavley Rats 1 2 1 2 1 2 3 l 2 3 1 1 *7.7*21.1 57.5*14.7 81.6*19.3 26.2*11.0 44.3* 9.6 22.2* 6.2 97.8* 41.9 7.2* 2.2 22.3* 7.8 80.0*13.6 22.5*11.0 56.5*20.6 e 36.0* 4.7 9.3* 2.9 94.3*18.9 114.0*14.7 49.3* 9.8 54.0* 3.5 2.3* 1.4 9.5*4.9 e 0 0 9.5*3.0 17.7*4.0 8.243.3 6.541.2 0 0.8* 0.5 57.8*14.4 11.2*3.6 Inoculum - 2,5 x 105 separated bone narrow cells (LSMmethod) per chamber, Colony forming units - erythroid (CFU-E). Htan colonies (8 to 64 erythroid cells) * standard error, b Burst forming units - erythroid (BFU-E). Mean bursts (64 erythroid cells or a dust' of 3 colonies) dr standard error. c Randomly bred white mice of the Brookhaven (Hale/Stoner) strain. d PhenyIhydrazine Hydrochloride (PHI) 50 eng/kg body weight l.P. 2 hours prior to lnplat chambers* e Host mice in this treatment group died before day 14* * Hypobarlc chamber 6 hours a day, 7 days week (starting 24 hours post implant of chambers) tfCA) 00 e (B8) C57 F. 16.MK BENZENE (300 PPM 6HR/D 50/WK) ILeukemia ncidence in Sham Group c ZZ LO CD CO or U_ O- (X r- LO =r O U_ O cn CO CO a: MOD 0Q0015846 OO'COl 00'06 t.OOC C0`04 oo`09 .,,o<rrfs oc'ooi Gbdu blow'lNb 4 no-o'c OC *C3 CO 0 v CO (B9) C57 F, 8WK BENZENE (300 PPM 6HR/D 5D/WK) 05 OF 4 RPR 85 cc ~ cc x 0 Xa CL 0 tn X x >- cc m UJ <x s c- >- __1 *- CL tn cc UJ 0X cc UJ z X UJ =) in *-- atf 0 c J w CL 0 3E cc UJ _J >Z UJ < + St 0^^o.1 oV &S) & ll(l 00* otfi co'cs oc*p's oo*Si m o'sOo3Goai'o'lsbrtlKooo*Loh oo*o'e 00*02 00 c\ e c (B14) C57 M, 16HK BENZENE (300 PPM 6HR/D 50/WK) H5 OF y RPR 05 <N0 DEATHS IN SHAMGROUP) nn fto.OQ M D.00 5 0 .0 0 6 0 .0 0 7 0 . DO (lO .00 PO.OO 1 0 0 .0 0 1 1 0 .0 0 ttO .O O P O .O O ( CD IP CD S cc X LD X CL. Q. O < O CO LU X UJ rvi UJ CD DsC 3 CD rin LJ CD CD r rT " ,(B12) C57 F, 16WK BENZENE (300 PPM 2WK"0N 2WIT0FF (RS OF 4 RPR 85 no deaths in sham group) an no fin 0(1 . ( 1 01 0 0 .0 0 MO.OO U 0 .0 0 J >0 IS C .00 150.00 lpO.QO 30.DC 30.00 o (B13) CBR F, 16WK BENZENE (300 PPM SHR/D 50/WK) * HS OF n RPR 85 (no DEATHS IN SHM group) MORTALITY A ALL NEOPLASMS + ALL NEOPLASMS OTHER THAN HEPATOMA X LEUKEMIAS/LYMPHOMATA * EXPOSURE PERIOD Xac>t o o vO--*' CD CJ A ~YW 7p,C1 i l . 0 5;1.00 7. ANIMAL OEPD6 *;J00 30.00 iC.QC 20.00 o L SO 00 CO.00 70.00 00.00 00.00 100.00 I (0.00 UO.OO l*'0.00 mo.oo I 50.00 r\ > CB13) CBR M, 16WK BENZENE (300 PPM 6HR/D 5D/MK) RS OF 4 RPR 85 (no DEATHS IN SHAM GROUP) zx ? 9 MORTAL ITT I9t* A all neoplasms 99 + ALL NEOPLnSMS OTHER THAN HEPATOMA O X LEUKEMIAS/LVMPHOMATfl 99 a. * EXPOSURE PERIOD 3 to* cr z0 0 s cc crQ-_r lii XX 10 z (X X 0CL t0d Oy O5 CO CO sr 2UJ {/) X UJ M 2! yj O. UJ 2 CQ >- -cJr c 0z to CzcOr COL Lzi ~J cr X>- cr Leci X H* O -- X OX to to c-J fi. >az-. V. to a L0i X Z -J -aJ ZLi XL_JI 00 eLCeLi Li CC Xto cax. Li X 2 CO 0 < + X* W-* in CD m X CC 0. cr cr CO 0 3* IL in O CD in w cr 0'001 OO'ds OO'H OO dt 00*0*9 CO'jfh Go3u i'lewifco X 00`G 00*0* 00'0 IpO.OQ ^ t\ # (B21) CBR F. 1GWK BENZENE (100 PPM GHR/D 5D/WK) RS OF 4 RPR 05 MALE(no deaths in group) O MORTAL ITT A ALL NEOPLASMS + ALL NEOPLASMS OTHER THAN HEPRTOMR X LEUKEMIfiS/LYMPHOMRTfl * EXPOSURE PERIOD XE Sp.03 /p.OQ gp.UO 5,0.OQ fep.00 20. DO Hp.QJ gp.CO 4*b aaao- * too.00 110.00 120.00 no. oo t\o.on no.oo 10-33