Document yk03pVMzw7YqxBK0qOnvMr4Qr

Table C-1. APPENDIX C. BIOAVAILABILITY OF DIOXIN Page Summary of Data on the Bioavailability of 2,3,7,8-TCDD Following Ingestion of Environmental M atrices ...................................................................................... C-14 DRAFT - DO NOT QUOTE OR CITE APPENDIX C. BIOAVAILABILITY OF DIOXINS C.1 Bioavailability Data Um breit et al. (1985 , 1986a,b) conducted experim ents in guinea pigs, adm inistering 2,3,7,8-TC D D in corn oil, 2,3,7,8-TC D D added to chem ically decontam inated soil, or soil from tw o industrial sites in Newark, New Jersey (a m anufacturing site and a salvage site) contam inated w ith CDDs. 2,3,7,8-TC D D w as the principal low er chlorinated isomer (dioxin or furan) present in the soil from the m anufacturing site (for w hich a chemical analysis w as presented). Soil from the manufacturing site was found to have 1,500 to 2,500 ppb 2,3,7,8-TC DD under soxhlet extraction; release under am bient tem perature manual solvent extraction w as much lower, reported as " > 2 . 5 ppb." The soil from the salvage site w as reported as approxim ately 180 ppb 2,3,7,8-TCDD under soxhlet extraction. In this study, groups of tw o or four male and tw o or four female guinea pigs received single gavage doses of the test materials and were observed until death or sacrifice at 60 days. 2,3,7,8-TC D D in corn oil or in recontam inated soil (6 g/kg in both) proved highly to xic, w ith o u t similar to x ic ity being observed in animals treated w ith up to tw ic e this dose of 2,3,7,8-TC D D in the soil from the m anufacturing site. The limited data on 2,3,7,8-TC D D levels in the liver showed much higher levels follow ing adm inistration of recontaminated soil versus contaminated soil from the manufacturing site. Um breit et al. (1986a) thus dem onstrated th a t gavaged 2,3,7,8-TC D D containing soil from the m anufacturing site was substantially less toxic than equivalent doses of 2,3,7,8-TC D D in corn oil. However, quantitative comparison of the effective doses in this study is d ifficu lt. Approaches to a quantitative com parison are outlined below. (1) Guinea pigs receiving 12 ug/kg 2,3,7,8-TC D D in contam inated soil experienced no deaths, w hile five out of eight guinea pigs receiving 6 ug/kg 2,3,7,8-TC D D in corn oil died, w ith no groups tested having low er doses in corn oil. Other authors have provided data on the to xic e ffe cts of 2,3,7,8-TC D D in corn oil w hich could aid in the comparison. McConnell et al. (1984) observed one out of six animals dying at 1 ug/kg and six out of six animals dying at 3 ug/kg. S ilkw orth et al. (1982) observed three out of six animals dying at 2.5 ug/kg and no deaths out of six at 0 .5 ug/kg. Comparing these data directly w ith the Umbreit et al. results w ould suggest th a t the 2,3,7,8-TC D D in the Newark m anufacturing site soil w as less e ffe ctive, by a facto r of 10 or greater, in producing C-1 DRAFT - DO NOT QUOTE OR CITE to x ic ity than 2,3,7,8-TC D D in corn oil. (2) Um breit et al. reported a "slig h tly reduced" w e ig h t gain in guinea pigs receiving 6 ug/kg of 2,3,7,8-TC D D in Newark m anufacturing site soil, and a "greater reduction" at the 12 ug/kg dose. No other signs of to x ic ity were noted in these groups. The animals receiving 6 ug/kg 2,3,7,8-TC D D in corn oil, in contrast, exhibited a marked loss of body w e igh t and showed to x ic ity and m ortality. S ilkw orth et al. (1982) also provided data on w eights of guinea pigs receiving 2,3,7,8-TC D D in corn oil. Those receiving 2.5 ug/kg exhibited a marked reduction in w e igh t gain among three out of six survivors, while those receiving 0.5 ug/kg showed a w eight gain comparable to vehicle controls. Comparison of this weight data w ith that of Umbreit et al. suggests th a t the 2,3,7,8-TC D D in corn oil was more than 5 tim es but less than 25 tim es as potent as 2,3,7,8-TC D D in the Newark soil. This comparison assumes that the effect of the Newark manufacturing site soil on w e ig h t gain was due to 2,3,7,8-TC D D as opposed to other com pounds in the soil. Numerous other dioxin and furan com pounds and other chem icals have been identified in this soil (Umbreit et al., 1987a). It has not been established th a t 2,3,7,8-TC D D is the sole or prime source of to x ic ity in the soil. (3) Um breit et al. presented liver concentrations of 2,3,7,8-TC D D after death or sacrifice at 60 days following gavage. Much lower concentrations of 2,3,7,8-TC D D were found in the livers of animals receiving soil from the m anufacturing site compared w ith those receiving the dose in corn oil. There are, how ever, tw o factors th a t lim it the conclusions than can be drawn from this comparison. First, the corn oil group experienced major to x ic ity and w e igh t loss, particularly complete loss of body fat. These changes may have affected the partitioning of 2 ,3 ,7 ,8 TCDD w ith in the body, leading to a higher concentration in the livers of the animals experiencing to xicity. Second, the animals gavaged w ith corn oil died early--half were dead by 26 days, w hile all of the guinea pigs treated w ith soil survived to 60 days (w ith the exception of one gavage death). The U.S. EPA (1985c) reported a half-life for 2,3,7,8-TC D D elim ination of 30 + 6 or 22 to 43 days from tw o studies in guinea pigs. A dditionally, the U.S. EPA (1985c) stated th a t elim ination in the guinea pig may fo llo w zero-order kinetics. Differences in elim ination due to differences in periods of survival are likely to have affected the relative quantities of 2,3,7,8-TC D D found in the livers of the test groups. C-2 DRAFT - DO NOT QUOTE OR CITE Perhaps a more appropriate com parison can be made w ith the four animals receiving 0 .3 2 ug/kg of 2,3,7,8-TC D D in contam inated soil from the Newark salvage site. These animals experienced no reported to xic signs (w e ig h t data not presented) and survived the full 60-day experiment. A pproxim ately 6% of the gavage dose was found in the liver of these animals, w hile only about 0 .0 6 % of the gavage dose w as found in the livers of guinea pigs in the 12 ug/kg group receiving the Newark m anufacturing site soil. This w ould suggest th a t the 2,3,7,8-TC D D in the m anufacturing site soil w as 100 tim es less bioavailable. H ow ever, given the different doses used and the fa ct th a t only a single pooled sample w as analyzed for 2,3,7,8-TC D D in each group, caution m ust be used in interpreting this comparison. The 2,3,7,8-TC D D in soil from the salvage site was substantially bioavailable, based on the single liver tissue analysis. Approxim ately 6% of the administered dose was recovered from the livers of these animals at 60 days. This can be compared w ith data on hamsters given 2,3,7,8-TC D D in corn oil by McConnell et al. (1984 ), where approxim ately 8% of the 2,3,7,8-TC D D could be recovered in the 1 ug/kg dose group among survivors at 30 days. McConnell et al. (1984) treated Hartley guinea pigs (2.5 weeks old) w ith single gavage doses of either 2,3,7,8-TC D D or dioxin contam inated soil from tw o sites in Missouri. The 2,3,7,8-TC D D concentrations from the tw o sites were reported at 700 and 8 80 ppb respectively; total tetrachlorodibenzofurans (TCDF) concentrations in the soil were 40 to 80 ppb, and polychlorinated biphenyls (PCB) concentrations were 3 to 4 ppm. Taking into account the relative toxicities, the authors concluded that to xicity from the other com pounds was likely to be small compared w ith th a t from 2,3,7,8-TC D D . Livers were analyzed for 2,3,7,8-TC D D at death or sacrifice at 30 days follow ing treatm ent. Treatm ent deaths occurred between 5 and 21 days post-gavage. Guinea pigs that died exhibited severe loss of body fat, markedly reduced thym us and testicle size, and adrenal hemorrhage. No adverse affects were noted in animals treated w ith decontam inated soil. For 2,3,7,8-TC D D in corn oil and for both contam inated soils, there were clear dose-responses in m ortality. The calculated LD50 values for the tw o soil types were low er than the LD50 for 2,3,7,8-TC D D in corn oil by a facto r of three to four. There was a dose-response between the liver concentration of 2,3,7,8-TC D D and the gavage dose; the details of this relationship are com plex. Anim als dying during the experim ent had liver concentrations a facto r of 1.4 to 3.2 higher than animals in the same dose groups who survived 30 days. This observation makes quantification of the dose-response relationships d iffic u lt (all or m ost of the animals in the low-dose groups C-3 DRAFT - DO NOT QUOTE OR CITE survived the experim ent, w hile all of the animals in the high-dose groups died). W hen the liver concentrations of 2,3,7,8-TC D D in animals dying early at the middle and high-dose groups are com pared, there appears to be a greater-than-linear increase in liver concentration w ith dose for the Times Beach and Minker Stout soil groups, w ith a 3.3-fold increase in dose producing a 10- to 13-fold increase in liver concentration. Liver concentrations of animals in the different dosing groups can best be compared among groups that experienced similar m ortality. (1) Anim als in dose groups in w hich all animals died w ith in 30 days: 2 ,3 ,7 ,8 TCDD in corn oil, approxim ately 2 0 % of the administered dose was in the liver. For the soil-treated groups, 13% and 11% of the doses, respectively, were in the liver. Comparison of these data suggest th a t 2,3,7,8-TC D D was approxim ately tw ice as available through corn oil as through soil. (2) Anim als surviving the 30-day experim ent (in groups where at least 4 out of 6 survived): For 2,3,7,8-TC D D in corn oil, 7.5% of the administered dose w as in the liver. For soil-treated animals < 3 .6 , 1.3, < 4 .2 , and 2.0 % of the doses, respectively, were in the liver. Comparison here w ould suggest th a t 2,3,7,8-TC D D was approxim ately four tim es as available through corn oil as through soil. The authors note th a t the differences in liver concentrations observed in the study may reflect varying partitioning of the 2,3,7,8-TC DD among internal organs, since dying animals suffered major loss of body w e ig h t and fa t content. In addition, surviving animals w ould have had greater opportunity to metabolize and excrete 2,3,7,8-TC D D due to a longer lifetime. Um breit et al. (1986a) reported additional chemical analyses of the Times Beach soil. Soxhlet extraction of the Times Beach soil yielded a similar quantity of 2 ,3 ,7 ,8 TCDD to the solvent extraction reported by McConnell et al. (1984). This is in contrast to the Newark m anufacturing site soil used in the Um breit et al. (1987a) experim ents, where only a small fraction of soxhlet-extractable 2,3,7,8-TC DD was extractable by the solvent extraction m ethodology used by McConnell et al. (1984). McConnell et al. (1984) also reported an experim ent in w hich groups of six Sprague-Dawley rats were given single gavage doses of 2,3,7,8-TC D D in corn oil or dioxin-contam inated soil from the Minker site. Induction of aryl hydrocarbon hydroxylase (AHH) in the rat livers was measured at sacrifice 6 days after dosing. Experimental doses ranged from 0 .4 to 5.0 ug/kg 2,3,7,8-TCDD. Measured AHH induction was similar for groups receiving 2,3,7,8-TC D D in corn oil or receiving contam inated soil containing nearly equal doses of 2,3,7,8-TC D D . For example (based on the rate of form ation of 3- C-4 DRAFT - DO NOT QUOTE OR CITE hydroxybenzo[a]pyrene), AHH a ctivity was measured at 1,269 pmole m in-1 m g-1 for the group receiving 5 ug/kg 2,3,7,8-TC D D in corn oil and at 1,230 pmole m in-1 mg-1 for the group receiving 5.5 ug/kg 2,3,7,8-TC D D in contam inated soil. For the five dose groups, the AHH a ctivity for the soil group ranged from 50% to 110% of the a ctivity in the corn oil group. The McConnell et al. (1984) rat data indicate th a t the bioavailability of 2 ,3 ,7 ,8 TCDD from the Minker site soil was at least 50% of that of equivalent doses of 2 ,3 ,7 ,8 TCDD in corn oil. Lucier et al. (1986) provided additional inform ation on the induction of hepatic enzymes in rats by the 2,3,7,8-TC D D contam inated soil from the M inker site tested by McConnell et al. (1984). AHH induction w as similar for the groups of rats receiving 2,3,7,8-TC D D in corn oil and contam inated soil (w ithin a factor of tw o ) over a broader range of doses (0 .0 1 5 ug/kg to 5 ug/kg) than reported by McConnell et al. (1984). In a second enzyme assay using the same animals, UDP glucuronyltransferase a ctivity was found to be slightly higher in groups receiving 2,3,7,8-TC D D in corn oil than groups receiving equal doses in contam inated soil. Liver concentrations of 2,3,7,8-TC D D for the rats were also reported. For the corn oil vehicle the liver concentrations were 4 0 .8 + 6.5 ppb at the 5 ug/kg dose and 7.6 + 2.5 ppb at the 1 ug/kg dose. Assuming that the liver comprises 4.0% of body w eight, the retention rates for the 5 and 1 ug/kg doses were 33% and 3 0 % , respectively. In rats receiving 2,3,7,8-TC D D in contam inated soil, the 5.5 ug/kg group had liver concentrations of 2 0 .3 + 12.9 ppb, and the 1.1 ug/kg group had concentrations of 1.8 + 0.3. Thus, retention rates for the 5.5 and 1.1 ug/kg groups are estim ated at 14% and 7% , respectively. These data indicate th a t liver retention in the soil group w as 20% to 4 0 % of th a t in the corn oil vehicle groups. Um breit et al (1986b) report additional studies of m ortality in guinea pigs treated w ith soil containing 2,3,7,8-TC D D from Newark (m anufacturing site) and Missouri (Times Beach) previously tested by Umbreit et al (1985 , 1986a) and McConnell et al. (1984), respectively. Guinea pigs received a single gavage dose of a soil suspension and were observed for 60 days. A fte r autopsy, deaths were classified as w hether or not they appeared to be due to TCDD to x ic ity . Substantial m ortality (25% overall) from conditions not attributed to TCDD w as observed across all groups. The data for both the Newark and Missouri sites are similar in trend for the previous data on these sites; and clearly indicate the greater to x ic ity of the Newark soil for given equal administered doses of 2,3,7,8-TC D D . W ith larger groups of guinea pig studied, a toxicity-related death was observed in both the 5 and 10 m g/kg dose groups for C-5 DRAFT - DO NOT QUOTE OR CITE Newark soil w hile no deaths were observed in corresponding dose groups (6 and 12 mg/kg) w ith few er animals in Umbreit et al. (1986a). Comparing groups w ith in this study, similar m ortality (1 or 2 deaths in 10 to 16 animals) was seen in both the 5 and 10 ug/kg Newark groups and the 1 and 3 ug/kg Missouri groups. These results suggest th a t the to x ic ity of these materials differs by an order of m agnitude or less. As noted above, the degree to w hich to x ic ity from these soils can be attributed to 2,3,7,8-TC D D in the presence of numerous other related to xic com pounds is not know n. 2,3,7,8-TC D D tissue concentrations were not reported in this work. In another com parative study Umbreit et al. (1987b) compared the Newark m anufacturing site and Times Beach soils in the induction of aryl hydrocarbon hydroxylase (AHH) in rats. W hile the use of only single dose levels prevents detailed analysis, the tw o soils proved quite similar in their ability to induce AHH. The explanation for the difference in this finding from those observed in the to x ic ity studies discussed above is not clear, but may relate to the presence of other toxic and/or AHH inducing compounds. Um breit et al. (1987a) report a reproductive to x ic ity study w ith soils from the Newark m anufacturing site and salvage yard previously studied by Umbreit et al. (1986a). Female mice were treated thrice weekly w ith soil from these sites, w ith treatm ent continuing through fertilization to weaning of pups. The total doses of 2,3,7,8-TCDD received by the mice were 720 ug/kg in m anufacturing site soil, and 86 ug/kg in salvage yard soil. A corn oil vehicle group and a recontam inated soil group received a total of 225 ug/kg. Deaths in animals show ing "classic signs" of TCDD to x ic ity were observed in the corn oil and recontam inated soil groups, and indicate appreciable bioavailability of 2 ,3 ,7 ,8 TCDD. Deaths were also observed in animals receiving m anufacturing site soil but the authors did not observe "classic signs" of TCDD to x ic ity . Fewer live pups born and few er pups surviving until weaning were observed in the m anufacturing site soil group compared w ith those receiving decontam inated soil. TCDD com pletely blocked reproduction in the corn oil and recontam inated soil groups. The results of this study dem onstrate acute and reproductive e ffe cts occurred in animals receiving m anufacturing site soil. However, these e ffe cts were of a lesser m agnitude than those seen in animals treated w ith 2,3,7,8-TC D D in corn oil at a dose three fold lower. The authors note the presence of substantial quantities of other to xic substances in the m anufacturing site soil (chemical analyses presented). No to xic e ffe cts were noted in animals treated w ith salvage site soil, w ho received a much smaller 2,3,7,8-TC DD dose. The data does not allow a quantitative evaluation of the bioavailability of 2,3,7,8-TCDD. C-6 DRAFT - DO NOT QUOTE OR CITE Kaminski et al. (1985) and S ilkw orth et al. (1982) reported the results of a series of studies on the to x ic ity of soot containing dioxin and furan com pounds from a fire involving transform er fluid containing PCBs. Hartley guinea pigs (500 to 6 00 g) received single oral doses of soot in an aqueous vehicle, a soxhlet extract of the soot in the same vehicle, or 2,3,7,8-TC D D in either an aqueous vehicle or corn oil. The soot w as reported to contain 2.8 to 2.9 ppm 2,3,7,8-TC D D and 124 to 273 ppm 2,3,7,8-TCDF. The total polychlorinated dibenzofuran content was estimated at 5 ,0 0 0 ppm. Animal w e igh ts and m ortality were recorded for 42 days, at w hich point the survivors were sacrificed and LD50 values were calculated. Blood chem istry and a pathologic examination were performed at sacrifice. S ilkw orth et al. (1982) noted th a t the LD50s for contam inated soot and soot extract were similar at 4 1 0 and 3 27 equivalent ug/kg, indicating th a t the m atrix had only a small e ffe ct on to xicity. If expressed in term s of the content of 2,3,7,8-T C D D , the LD50 from soot is 2.5 ug/kg, w hich is a facto r of seven below the LD50 for 2,3,7,8-TC D D in an aqueous vehicle, suggesting that other compounds contributed to the toxicity of the soot and soot extract. The authors stated th a t they adopted an aqueous vehicle in these experim ents because it was nontoxic and provided a stable suspension of soot; they regarded this vehicle as more appropriate for modeling of human exposure conditions than an oil vehicle. The data from these experim ents also dem onstrate th a t use of an oil vehicle leads to substantially greater 2,3,7,8-TC D D to x ic ity than does an aqueous vehicle. Comparison of m ortality and w e ig h t loss in groups of female guinea pigs receiving 500 ug/kg of soot or the equivalent amount of soot extract suggests that the extract may be som ew hat more to xic; how ever, all six animals died in the 1,000 ug/kg soot group, w hile four out of five died in the 500 ug/kg extra ct group. Taken together, these data indicate th a t the soxhlet extract of soot in an aqueous vehicle was between one and tw o tim es as to xic as the soot itself. It is likely th a t a larger difference in to x ic ity w ould have been observed if the soot extract was in an oil vehicle. Van den Berg et al. (1983) fed small groups of male W istar rats fly ash from a municipal incinerator (pretreated w ith HCl) containing dioxins and furans, a soxhlet extract of the fly ash, or a purified extract of the ash th a t was obtained using column chrom atography. 2,3,7,8-TC D D was present as 3 .3 % of the TCDD isomer group in the fly ash extract. (The authors did not specify whether this reference was to crude or purified extract.) 2,3,7,8-TC D F w as present as 17.9% of the tetra-CDF isomer group in the extract. The rats were fed 2 g/d fly ash mixed w ith diet or the residual from 2 mL/d extract after the extract was mixed w ith diet and the solvent was evaporated. The animals C-7 DRAFT - DO NOT QUOTE OR CITE were exposed to the treated diet for 19 days, and then sacrificed, and the liver tissue was analyzed for the presence of dioxins and furans. A pproxim ately 1% of the 2,3,7,8-TC D D dose from fly ash w as retained in the liver, and approxim ately 4% of the dose of this isomer from fly ash extract was so retained. The corresponding percentages for 2,3,7,8-TC D F are 0 .3 and 1.0. Data on the retention of isomer groups in adipose tissue were presented for the extract-treated groups b u t not for the fly ash-treated group. The concentrations of the various isomers in adipose tissue are comparable to , or less than, the concentrations in liver tissue. The U.S. EPA (1985b) reported a half-life for elim ination of 2,3,7,8-TC D D in the rat of 20 days at high dose. If a similar half-life is assumed in this experim ent, the quantities of 2,3,7,8-TC D D in the animals at the end of the 19-day feeding experim ent w ould be significantly less than the absorbed dose, but still of the same order of m agnitude. H ow ever, the recovery percentages in this study are low for both the fly ash and fly ash extract groups in com parison w ith other studies in w hich 2,3,7,8-TC D D was administered to rats. Fries and M arrow (1975) fed rats diets containing 7 or 20 ppb of 2,3,7,8-TC D D for a period of up to 42 days. A fte r 14 days of feeding, the rat livers contained an average of 32% of the cum ulative administered dose; at 28 days, 21% of the dose; and at 42 days, 18% of the dose. Thus, in the van den Berg et al. (1983) study, the liver retention of 2,3,7,8-TC D D for the fly ash extract group is a facto r of five to eight below w h a t could be anticipated for the Fries and M arrow (1975) data, and the liver retention in the van den Berg et al. (1983) group fed soot is a facto r of 20 to 30 low er than th a t seen by Fries and M arrow (1975). Data from Kociba et al. (1976 ), Rose et al. (1976 ), and Kociba et al. (1978) lead to similar conclusions to those from the Fries and M arrow (1975) data regarding the fraction of cum ulative 2,3,7,8-TC D D dose retained in the rat liver. An explanation of the low level of recovery for the animals receiving the soxhlet extract of soot is not apparent. It is possible th a t the presence of m ultiple com pounds affected absorption or m etabolism in the rats fed soot and soot extract. A second approach to the van den Berg et al. (1983) data is to compare the ratios of liver concentrations for dioxins in fly-ash-treated animals to the concentrations in extract-treated animals. These ratios, based on measurements in small numbers of animals, indicate a substantial bioavailability of dioxin and furan com pounds from the tested fly ash. This availability varied among the different isomers w ith the value of 0.3 for 2,3,7,8-T C D D , indicating th a t this isomer was three tim es as available from fly ash extract as from fly ash. Van den Berg et al. (1985) fed fly ash (pre-treated w ith HCl) to W istar rats, guinea pigs, and Syrian golden hamsters. Fly ash was mixed w ith standard laboratory diet at C-8 DRAFT - DO NOT QUOTE OR CITE 2.5% by w e ig h t, and animals were allowed to eat ad libitum . The am ount of fly ash consumed by each group of five rodents was determined by the authors. For each species there were three groups of animals each fed fly ash for approxim ately 32 days (group I), 60 days (group II), or 94 days (group III). C oncentrations of dioxin and furan isomer groups in the food were presented, and include 1.4 ng/g TCDD com pounds and 2.1 ng/g TCDF compounds. The authors presented calculated recovery percentages for the cum ulative dose of specific isomers in the rodent liver. For 2,3,7,8-TC D D in guinea pigs, 3 .7 % , 0 .9 % , and 1.4% of the administered dose w as recovered in the liver in groups I, II, and III, respectively. The 32-day (group I) recovery percentage is som ew hat higher than seen in the low er dose groups receiving 2,3,7,8-TC D D contam inated soil in McConnell et al. (1984). The value in hamsters was approxim ately 2% (only reported for group II), and analytical problems prevented this determ ination in rats. No other TCDD com pounds were quantified. Similarly, for 2,3,7,8-TCDF, guinea pigs showed retention of 4 .7 % , 2.2% , 2.5% of the administered dose in groups I, II, and III, respectively. For both 2 ,3 ,7 ,8 TCDD and 2,3,7,8-TC D F the recovery percentages in guinea pigs at 32 days were approxim ately a factor of 4 to 15 higher than th a t observed in the van den Berg et al. (1983) study in rats. Other TCDD compounds that were present showed comparable or somewhat lower retention, averaging 1% to 2% over the animals groups. No TCDD or TCDF compounds were detected in hamster liver or analyzed for in rat liver. Higher chlorinated congeners m ost typically showed retention in the range of 2% to 5% in rat liver and 1% to 3% in guinea pig liver, w ith the exception of 2,3,4,7,8-PeC D F (9 .8 % , 8 .3 % , and 11.3% in the hamster groups). Few other com pounds were found in hamster liver, but 2 ,3 ,4 ,7 ,8 PeCDF was found w ith a recovery of 5% to 8% and 2,3,4,7 ,8-H xC D D w as found at 3% to 7%. A s w ith other experim ents in w hich the retention of dioxins in the liver has been determined, these percentages place a lower bound on the bioavailability of the dioxins but, because not all dioxin is localized in the liver, do not perm it bioavailability to be estim ated w ith o u t know ledge of the elim ination of the administered dose over tim e and the quantity of dioxins in the remainder of the organism. No positive control group receiving 2,3,7,8-TC DD was included for comparison. Poiger and Schlatter (1980) conducted several experim ents in Sprague-Dawley rats (180 to 220 g) in w hich liver concentrations of tritiu m label from 2,3,7,8-TC D D were determined using various doses and vehicles. All experim ents consisted of a single gastric intubation of 2,3,7,8-TCDD-containing material, followed by animal sacrifice at C-9 DRAFT - DO NOT QUOTE OR CITE predetermined times. The doses used were well below the LD50 in the rat (the maximum dose applied was 5 ug/kg), and no deaths or to xic e ffe cts were reported. In a prelim inary experim ent, rats were treated w ith 14.7 ng/rat 2,3,7,8-TC D D in ethanol. The results indicate substantial localization of 2,3,7,8-TC D D in the rat liver, w ith a decrease of a factor of tw o in the fraction of the dose in the liver between 1 and 4 days. Poiger and Schlatter (1980) conducted all further studies w ith sacrifice at 24 hours to maximize the recovery of 2,3,7,8-TC DD from the liver. In a second experim ent, the authors administered 2,3,7,8-TC D D doses in ethanol ranging from 15 to 1,070 ng/rat to groups of six rats. They found a graded increase in percentage retained in the liver from 37% + 1% at the 15 ng dose to 51% + 4% at 280 ng. A t the high-dose point, the percentage may have fallen (42% + 10% at 1,070 ng). In a further experim ent, 2,3,7,8-TC D D w as administered at low dose in a series of vehicles. These data dem onstrate th a t adm inistration of 2,3,7,8-TC D D in soil reduced the retention of the dose in the liver to 6 6 % , or 4 4 % of the retention seen w ith 2 ,3 ,7 ,8 TCDD in ethanol. The low er value, 4 4 % , was obtained for soil th a t w as aged for 8 days at 3 0 -40 oC follow ing addition of 2,3,7,8-TC D D . This observation is consistent w ith the findings of other studies reported here that 2,3,7,8-TC D D from environmental soil (naturally aged) was generally less available than 2,3,7,8-TC D D freshly added to clean samples of these soils. The aqueous suspension of 2,3,7,8-TC D D in activated carbon showed little evidence of bioavailability; this is supported by the authors' measurements showing that 2,3,7,8-TCDD was only slightly extractable from the activated carbon matrix by various solvents. In contrast, 58% to 70% of 2,3,7,8-TC D D could be recovered from soil samples by washing w ith hexane/acetone (4:1 v/v). Poiger and Schlatter (1980) also presented results from several skin application experim ents w ith TCDD-containing m aterials using rats and rabbits (not reviewed here). Bonaccorsi et al. (1984) reported the results of a study of gut absorption of 2,3,7,8-TC D D from soil taken from the Seveso, Italy accident site. Soil containing 81 + 8 ppb 2,3,7,8-TC D D from the "highly contam inated" area in Seveso was administered to albino male rabbits (2.6 + 0 .3 kg) in daily gavage doses for seven days. Additional samples of clean soil were spiked w ith 2,3,7,8-TC D D in the laboratory to yield 10 and 40 ppb contam ination levels and were administered to rabbits follow ing the same protocol. For com parison, rabbits were also treated w ith 2,3,7,8-TC D D in solution in acetonevegetable oil (1:6) or alcohol-water (1:1). Rabbits were sacrificed on the day after treatm ent stopped and liver concentrations of 2,3,7,8-TC D D were measured. The authors did not remark on the presence or absence of to x ic ity in the treated rabbits. EPA (1985a) C-10 DRAFT - DO NOT QUOTE OR CITE reports values for the single dose LD50 of 2,3,7,8-TC D D in rabbits of 115 and 275 ug/kg. The total doses received by the rabbits in this study were approxim ately 54, 107, and 215 ug/kg over seven days. Based on this com parison, there is a likelihood th a t to xic e ffe cts occurred in the Bonaccorsi w o rk, and as noted above, to x ic ity has the potential to a ffe ct the tissue concentrations of 2,3,7,8-TC D D . For this reason, the m ost appropriate com parisons among these data are between groups show ing similar liver concentrations of 2,3,7,8-T C D D , w hich may then be inferred to have experienced similar to xic effects. That this method of comparison is desirable can also be seen from the Bonaccorsi et al. (1984) data, where both solvent vehicle groups and the spiked soil groups show an increase of the fraction of the dose in the liver at the higher administered doses. However, it should be mentioned th a t use of tw o d ifferent solvent vehicles com plicates interpretation. Similar liver concentrations of 2,3,7,8-TC D D were seen in the 40 ug/d solvent vehicle and 80 ug/d Seveso soil groups. Comparing the percentage of liver retention in these tw o groups indicates absorption from Seveso soil was 4 0 % of th a t from the solvent vehicle. Using the same approach, comparison of the 80 ug/d solvent vehicle and 160 ug/d Seveso soil groups indicates th a t absorption from the soil w as 4 1 % of that from the solvent. The same approach can be used to compare absorption from the solvent vehicle and from the spiked soil. In this case the 40 ug/d solvent vehicle group had the liver concentrations closest to either the 40 or 80 ug/d spiked soil groups. Comparison of the percentage of dose in the liver indicates absorption from spiked soil is 6 8 -7 3 % of that from the solvent vehicle. Bonaccorsi et al. (1984) conducted w o rk w ith either aged or non-aged spiked soil but do not present data to allow a comparison of these groups. Shu et al. (1987 , as cited by Leung and Paustenbach, 1987) studied 2,3,7,8-TC D D from the Missouri site tested by McConnell et al. (1984). Their paper reports an oral bioavailability of approxim ately 4 3 % in the rat dosed w ith environm entally contam inated soil from Times Beach, Missouri. This figure did not change significantly over a 500-fold dose range of 2 to 1450 ng 2,3,7,8-TC D D per kg of body w e ig h t for soil contam inated w ith approxim ately 2, 30 or 60 ppb of 2,3,7,8-TC D D . The data from this study is not now available to the Exposure Assessm ent Group of EPA for review. C.2 Summary of Bioavailability Table C-1 C-11 DRAFT - DO NOT QUOTE OR CITE C-12 DRAFT - DO NOT QUOTE OR CITE C-13 DRAFT - DO NOT QUOTE OR CITE C-14 DRAFT - DO NOT QUOTE OR CITE summarizes data th a t are pertinent to the bioavailability of 2,3,7,8-TC D D from environm ental m atrices. Studies of bioavailability, w h ich examined soil samples, soot, and fly ash, have utilized three methodologies: measuring acute to xicity, retention of 2,3,7,8TCDD in the liver, and induction of hepatic enzymes. A m ong the five samples of soil from contam inated sites th a t have been tested, three have shown substantial bioavailability, e.g., 25% to 50% , when compared w ith 2,3,7,8-TC D D in corn oil gavage. A fourth soil sample w as compared w ith 2,3,7,8-TC D D administered in a solvent vehicle, and fell in this range. The fifth soil, tested by Um breit et al. (1986 a,b ; 1987a,b) showed bioavailability substantially less than the other soils tested. W hile d iffic u lt to gauge quantitatively, dioxin from this fifth soil may be an order of m agnitude less available than from the other soils. A d ditio nally, three samples of soil spiked w ith 2,3,7,8-TC D D have been tested for bioavailability, including one sample in w hich the 2,3,7,8-TC D D was incubated w ith soil at C-15 DRAFT - DO NOT QUOTE OR CITE C-16 DRAFT - DO NOT QUOTE OR CITE C-17 DRAFT - DO NOT QUOTE OR CITE an elevated tem perature. The 2,3,7,8-TC D D added to these soil samples proved to be highly available (e.g., 40% to 70% ). In one study, soot from a transform er fire containing dioxins and furans proved sim ilarly to x ic to a soxhlet extract o f the soot in an aqueous vehicle. H ow ever, the soot extract may have proved more to x ic if delivered in corn oil, as w a s 2,3,7,8-TC D D in the soil studies. The availability o f 2,3,7,8-TC D D and other dioxins and furans from incinerator fly ash have been addressed by van den Berg et al. (1983 , 1985) in extended feeding studies. In these studies, liver retention of 2,3,7,8-TC D D from either fly ash or fly ash extract proved lo w , w ith availability from fly ash being approxim ately 25% of that from the extract. The individual studies reviewed have a variety of lim itations, as discussed in the preceding text. A notable lim itation w as that some experiments were conducted using highly toxic doses of 2,3,7,8-TC D D , so that determ ination of bioavailability was com plicated by w asting and early death of the te st animals. It should also be noted that, w hile the relative retention of 2,3,7,8-TC D D in the liver can serve as an appropriate indication of differences in bioavailability between samples, the percentage of dose found in the liver only places a low er bound on absorption. This is particularly relevant to experim ents where animals have been maintained for many weeks after dosing and an undetermined quantity of 2,3,7,8-TC D D has been excreted. Finally, to xicity data for mixtures for w hich both to xicity and bioavailability of individual com pounds may vary are d iffic u lt to interpret quantitatively in term s of bioavailability. As presented in U.S. EPA (1 985 c), Rose et al. (1976) determined gut absorption of 2,3,7,8-TC D D in a 1:25 m ixture of acetone to corn oil (by volume) in the rat. In both single dose and m ultiple dose experim ents, measured absorption was approxim ately 85% . Assuming th a t absorption from pure corn oil is sim ilar to th a t from this m ixture, and assuming th a t absorption in other species for w hich data are not available is sim ilar, the 85% facto r can be applied to the data presented here to obtain an approxim ate range for typical 2,3,7,8-TC DD absorption from soil. Using this factor, the estimated relative bioavailability of 2,3,7,8-TC D D from soil is 25% to 50% and, when compared w ith corn oil, provides an estim ate of gut absorption of 20% to 4 0 % of ingested 2,3,7,8-TC D D in soil. This estim ate is comparable w ith the 20% to 26% absorption from 2,3,7,8-TC D D treated soil from the w o rk of Poiger and Schlatter (1980). Recognizing these lim itations, the weight of evidence indicates that 2,3,7,8-TCDD is often highly available from environm ental materials. H ow ever, in one tested soil sample the compound w as substantially less bioavailable. W hile the data are too sparse to allow C-18 DRAFT - DO NOT QUOTE OR CITE a prediction as to w hether a particular environm ental sample w ill prove more or less bioavailable, one im portant suggestion has emerged. In the tw o samples that have proved least bioavailable (the Umbreit et al. (1986a) m anufacturing site soil sample, and 2 ,3 ,7 ,8 TCDD on activated carbon tested by Poiger and Schlatter (1980)) the 2,3,7,8-TC D D was largely resistant to solvent extraction. This was not the case for more bioavailable materials. Further research, using short-term experim ents in w hich animals are handled under identical conditions and are fed dioxins in d ifferent media, is needed for an improved comparison of absorption between different environmental samples. Acutely to xic doses should be avoided to ensure th a t tissue concentrations are directly interpretable. Experiments studying both tissue retention and enzyme induction should prove valuable for this research. W hole-body levels of 2,3,7,8-TC D D need to be related to liver concentrations, and the e ffe cts of m etabolism need to be addressed. The vehicle of adm inistration has been show n to a ffe ct acute 2,3,7,8-TC D D to x ic ity , and vehicle effects need to be considered in designing experiments. C.3 Distribution Ryan et al. (1985) examined the distribution of 2,3,7,8-TC D D in tw o humans at autopsy. On a w e ig h t basis, there were 6 ppt of TCDD in fa t, 2 ppt in liver and below levels of detection in kidney and muscle. They reported th a t on a per lipid basis the levels were similar between tissues. It is im portant to note th a t one of these subjects suffered from a fa tty liver syndrom e, possibly resulting in higher levels in the liver than m ight norm ally be found in healthy individuals. Poiger and Schlatter (1986) estim ated th a t about 90% of the total body burden of 2,3,7,8-TC D D w as sequestered in fat. Levels of 2,3,7,8-TC D D averaging 5-10 ppt have been reported for background populations in St. Louis, MO, by Graham et al. (1986 ), and in A tlanta, GA, and Utah by Patterson et al. (1986). These data are consistent w ith the lipid bioconcentrations assum ptions made in calculations of daily intakes (vidae supra). Patterson et al. (1987) developed a high resolution gas chrom atographic/high resolution mass spectrom etric analysis for 2,3,7,8-TC D D in human serum. A high correlation was reported between adipose tissue and serum concentrations when adjusted for total lipid content. The reader is referred to other docum ents (U.S/ EPA, 1993; Schlatter, 1991; Schecter, 1991) for more details on the distribution and elim ination. C-19 DRAFT - DO NOT QUOTE OR CITE References Bonaccorsi, A .; diDom enico, A .; Fanelli, R.; M erli, F.; M otta, R.; Vanzati, R.; Zapponi, G.A. (1984) The influence of soil particles adsorption on 2,3,7,8-tetrachlorodibenzo-p-dioxin biological uptake in the rabbit. Arch. Toxicolo. Suppl. 7 :4 3 1 434. Brewster, D.W .; Elwell, M .R.; Birnbaum, L.S. (1988) T o xicity and disposition of 2 ,3 ,4 ,7 ,8 pentachlorodibenzofuran (4PeCDF) in the rhesus monkey (Macaca m ulatta). Toxicology and Applied Pharmacology 9 3 :2 3 1 -2 4 6 . Fries, G.F.; M arrow , G.S. (1975) Retention and excretion of 2,3,7,8-tetrachlorodibenzo-pdioxin (TCDD) by rats. J. Agric. Food Chem. 23:265 -2 69. Graham, M.; Hileman, F.D.; Orth, R.G.; W endling, J.M .; W ilson, J.W . (1986) Chlorocarbons in adipose tissue from a Missouri population. Chemosphere 15:1595-1600. Huetter, R.; Phillipi, M. (1982) Studies on microbial m etabolism of TCDD under laboratory conditions. Pergamon Ser. Environ. Sci. 5 :8 7-93. Kaminski, L.S.; DeCapiro, A.P.; G ierthy, J.F.; S ilkw orth, J.B .; Tum asonis, C. (1985) The role of environm ental m atrices and experimental vehicles in chlorinated dibenzodioxin and dibenzofuran to xicity. Chemosphere 1 4 :6 8 5 -6 9 5 . Kociba, R.J.; Deeler, P.A.; Park, C.N.; Gehring, P.J. (1976) 2,3,7,8-Tetra-chlorodibenzo-pdioxin (TCDD): results of 13-w eek oral to x ic ity study in rats. Toxicol. Appl. Pharmacol. 3 5 :5 5 3 -5 7 3 . Kociba, R.J.; Deyes, D.G.; Beyer, J.E., et al. (1978) Results of a tw o year chronic to x ic ity and oncogenic study of 2,3,7,8-tetrachlorodibenzo-p-dioxin in rats. Toxicol. Appl. Pharmacol. 4 6 (2 ):2 7 9 -3 0 3 . Luceir, G .W .; Rumbaugh, R.C.; M cCoy, A .; Haas, R.; Harvan, D.; Albro, P. (1986) Ingestion of soil contaminated w ith 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) alters hepatic enzyme activities in rats. Fund. Appl. Toxicol. 6: 3 6 4 -3 7 1 . McConnell, E.E.; Lucier, G .W .; Rubaugh, R.C.; et al. (1984) Dioxin in soil: bioavailability after ingestion by rats and guinea pigs. Nau, H.; Bab, R.; Neuber, D. (1986) Transfer of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) via placenta m ilk, and postnatal to x ic ity in mouse. Arch. Toxicol. 59:36-40. Nessel, C.S.; Am oruso, M .A .; Umbreit, T.H.; Gallo, M.A. (1990) Hepatic aryl hydrocarbon hydroxylase and cytochrom e P450 induction follow ing the transpulm onary absorption of TCDD from intratracheally instilled particles. Fund. Appl. Toxicol. 15:500-509. Patterson, D.G.; Holler, J.S.; Lapez, C.R., Jr. (1986) High resolution gas chrom atographic/high resolution mass spectrom etric analysis of human adipose tissue for 2,3,7,8-tetrachorodibenzo-p-dioxin. Anal. Chem. 58:705 -7 13. Patterson, D.G.; Hampton, L.; Lapeza, C.R., Jr. (1987) High resolution gas C-20 DRAFT - DO NOT QUOTE OR CITE chrom atographic/high resolution mass spectrom etric analysis of human serum on w hole w e igh t and lipid basis for 2,3,7,8-tetrachlorodibenzo-p-dioxin. Anal. Chem. 59:2000-2005. Perdew, G.H.; Hollenbeck, C.E. (1990) Analysis of p h o to a ffin ity labeled aryl hydrocarbon receptor heterogeneity by tw o dimensional gel electrophoresis. Biochem istry 29: 6210-6214. Philippe, M .; Drasnobagew, V .; Zeyer, J.; Huetter, R. (1981) Fate of 2 ,3 ,7 ,8 tetrachlorodibenzo-p-dioxin (TCDD) in microbial cultures and soil under laboratory conditions. FEMS Symp. 1 2 :2 2 1 0 -2 2 3 3 . Poiger, H.; Schlatter, C. (1980) Influence of solvents and adsorbents on dermal and intestinal absorption of TCDD. Food Cosmet. Toxicol. 18:477-481. Poiger, H.; Schlatter, C. (1986) Pharmacokinetics of 2,3,7,8-TC D D in man. Chemosphere 15(9-12):1489-1494. Rose, J.Q .; Ramsey, J.C.; W entzler, T.H. (1976) The fate of 2,3,7,8-tetrachlorodibenzo-pdioxin follow ing single and repeated oral doses to the rat. Toxicol. Appl. Pharmacol. 3 6 :2 0 9 -2 2 6 . Ryan, J.J; Schecter, A .; Lizotte, R.; Sun, W .F.; M iller, L. (1985) Tissue distribution of dioxins and furans in humans from the general population. Chemosphere. 14(6/7): 929-932. Schecter, A. (1991) Dioxins and related chem icals in humans and in the environm ent. In: Biological Basis for Risk Assessm ent of Dioxins and Related Compounds; Gallo, M .; Scheuplein, R.; Van Der Heijden, K. eds.; Banbury Report 35, Cold Spring Harbor Laboratory Press. Schlatter, C. (1991) Data on kinetics of PCDDs and PCDFs as a prerequisite for human risk assessment. In: Biological Basis for Risk Assessment of Dioxins and Related Compounds; Gallo, M .; Scheuplein, R.; Van Der Heijden, K. eds.; Banbury Report 35, Cold Spring Harbor Laboratory Press. Shu, J.; Paustenbach, D.; Murray, F.J. (1988) Bioavailability of soil bound TCDD: oral bioavailability in the rat. Fund. Appl. Toxicol. 1 0 :6 4 8 -6 5 4 . S ilkw orth, J.; M arti, D.; DeCapri, A .; Rej, R.; O'Keefe, P.; Kaminski, L. (1982) Acute to x ic ity in guinea pigs and rabbits of soot from a polychlorinated biphenylcontaining transform er fire. Toxicol. Appl. Pharmacol. 6 5 :4 2 5 -4 3 9 . Stanley, J.S.; Boggess, K.; Onstot, J.; Sack, T.; Remmers, J.; Breen, J.; Kutz, F.W.; Robinson, P.; M ack, G. (1986) PCDDs and PCDFs in human adipose tissues from the EPA Fy 82 NHATS repository. Chemosphere 1 5 :1 6 0 5 -1 6 1 2 . Umbreit, T .J.; Patel, D.; Gallo, M.A. (1985) Acute to xicity of TCDD contam inated soil from an industrial site. Chemosphere 1 4 :9 4 5 -9 4 7 . Um breit, T.H .; Hesse, E.J.; Gallo, M .A. (1986a) Bioavailability of dioxin in soil from a 2.4.5.-T manufacturing site. Science 2 3 2 :49 7-499. Umbreit, T.H.; Hesse, E.J.; Gallo, M.A. (1986b) Comparative to x ic ity to TCDD C-21 DRAFT - DO NOT QUOTE OR CITE contam inated soil from Times Beach, M issouri, and Newark, New Jersey. Chemosphere 15(9-12):2121-2124. Umbreit, T.H.; Hesse, E.J.; Gallo, M.S. (1987a) Reproductive to x ic ity to female mice of dioxin-contam inated soils from a 2,4,5-trichlorooxacetic acid m anufacturing site. Arch. Environmental Contam ination and Toxicology 16: 4 6 1 -4 6 6 . Umbreit, T.H.; Hesse, E.J.; Gallo, M.S. (1987b) Differential bioavailabilty of 2 ,3 ,7 ,8 Tetrachlorodibenzo-p-dioxin from contaminated soils. American Chemical Society Symposium Series No. 3 3 8 , "S olving hazardous w aste problems: Learning from dioxin. U.S. Environmental Protection Agency (1985a) Compilation of air pollutant emission factors, Vol 1. Research Triangle Park, NC: O ffice of Air Q uality Planning and Standards. U.S. Environmental Protection Agency (1985b) Rapid assessment of exposure to particulate emission from surface contam ination sites. W ashington, DC: O ffice of Solid W aste and Emergency Response. E P A -600/8-85-002. U.S. Environmental Protection Agency (1985c) Health assessment document for polychlorinated dibenzo-p-dioxins. Research Triangle Park, NC: O ffice of Air Planning and Standards. E P A-600/8-84-014F. U.S. Environmental Protection Agency (1993) Health assessment for 2 ,3 ,7 ,8 tetrachlorodibenzo-p-dioxin (TCDD) and related com pounds. W ashington, DC: O ffice of Health and Environmental Assessment. van den Berg, M .; Ollie, K.; Hutzinger, O. (1983) Uptake and selective retention in rats of orally administered chlorinated dioxins and dibenzofurans from fly-ash and fly-ash extract. Chemosphere 12:537-544. van den Berg, M .; Vroom , A .; van Greevenbroek, M .; Olie, K.; Hutzinger, O. (1985) Bioavailability of PCDDs and PCDFs adsorbed on fly ash in the rat, guinea pig, and Syrian golden hamster. Chemosphere 14:865-869. C-22