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Bai, K. S.; Martell, A. E. J. Znorg. Nucl. Chem. 1969, 31, 1697. Zepp, R. G. In The Handbook of Environmental Chemistry; Hutzinger, O., Ed.; Springer-Verlag: Berlin, 1982; Vol. 2, Part B, pp 19-41. Evans, J. E.; Yue, C. D. Environ. Toxicol. Chem. 1988, 7, 1003-101 1. Muralidharan, S.; Ferraudi, G. Znorg. Chem. 1981, 20, 2306-231 1. Gray, R. D. J. Am. Chem. Soc. 1969,91, 56. Zuberbuhler, A. Helv. Chim. Acta 1970, 53, 473-485.
Colombo, M. F.; Austrilino, L.; Nascimento, 0. R.; Castellano, E. E.; Tabak, M. Can. J. Chem. 1987,65,821-826. Thurman, E. M. Organic Geochemistry of Natural Waters; Martinus Nijhoff/Dr. W. Junk Publishers: Dordrecht, The Netherlands, 1985. Mohl, W.; Motschi, H.; Schweiger, A. Langmuir 1988, 4, 580-583.
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SOC.1987, 109, 3665-3669. Received for review August 6,1990. Accepted February 20, 1991. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the U.S. Environmental Protection Agency. This research was supported in part by a Senior Research Associateship from the National Research Council.
Chlordane Accumulation in People Mark A. Dearth and Ronald A. Hltes’
School of Public and Environmental Affairs and Department of Chemistry, Indiana University, Bloomington, Indiana 47405 Human breast adipose tissues were examined for 13 Components and metabolites of technical chlordane. The geometric mean concentrations of heptachlor epoxide, oxychlordane, and trans-nonachlor were 48, 88, and 120 ng/g of fat, respectively. These concentrations increased with the subject’s age, but were not much different from 1970-1980 values. The nanochlors and the pentachlorocyclopentene chlordanes are the most highly retained compounds in people, when compared to their abundances in technical chlordane. Chlordane accumulation in people was compared to its accumulation in other mammals, in fishes, and in invertebrates by using a calculated parent/metabolite ratio. The sources of chlordane exposure were evaluated, and it was concluded that exposure to chlordane in indoor air was an important source of these components to the U S . population. Introduction Chlordane is a pesticide used to control termites around homes. While its use has stopped in the United States (I) and in Japan (21,consumption in other countries continues (3). More than 70000 tons of this mixture were produced and used in the United States, mainly between 1960 and 1988 ( 4 ) . Because chlordane’s half-life in the environment is at least 5 and possibly 15 years, people could be exposed to this toxic and persistent mixture for another generation (4). 0013-936X/91/0925-1279$02.50/0
The major components of technical chlordane are a-and y-chlordane (aCL and gCL; see Chart I for structures and abbreviations), cis- and trans-nonachlor (cN9 and tN9), and heptachlor (not shown in the chart), which is a pesticide in its own right. The chlordanes all have eight chlorine atoms, the nonachlors have nine, and heptachlor has seven. In almost all organisms, these compounds are metabolized to two, persistent epoxides: heptachlor epoxide (with seven chlorines) and oxychlordane (with eight chlorines); see HEP and OXY in the chart. There are, however, vast differences in the extent of metabolism. We noted that fish, for example, do not seem to metabolize these compounds well, but rats do. We were interested to see where people fit into this spectrum and if the degree of metabolism could be related to such factors as age and type of exposure. Our first step in this study was an exhaustive analysis of technical chlordane itself; this is published elsewhere (4). Second, a preliminary study showed that certain trace compounds containing up to 12 chlorine atoms were preferentially accumulated from technical chlordane into human adipose tissue (5). The accumulation of these highly chlorinated compounds gave us some hints about the mechanisms of accumulation of chlordane compounds. Third, the depuration of various chlordanes was examined by dosing rats with technical chlordane. An analysis of the isomeric configurations that influence the depuration rate of the chlordane compounds was reported (6). In this
0 1991 American Chemical Society
Environ. Sci. Technol., Voi. 25, No. 7, 1991
1279
Chart I CI
cN9
c
CI
CI
&o
CI
c4 tN9 CI
CI
C
HEP
0
OXY CI
C
CI
CI
MC6
aCL
MC7
CI CI
CI gCL CI
paper, we will present the results of the analysis of 23 human breast adipose tissue samples. We will compare the relative human bioaccumulation of these compounds to one another and to other biota, elucidate the effect of the subject’s age on their body burden, and analyze the relative significance of various pathways of chlordane exposure. Experimental Section Sample Source and Selection. Twenty-three human adipose tissue samples were obtained from the pathology department of Bloomington Hospital, Bloomington, IN. All of the tissues were preserved in formalin and were stored in polyethylene containers at room temperature. The time between collection and analysis was generally less than 3 months. The tissues were removed from the subjects during surgery for breast cancer or fibrocystic disease. Two samples were obtained from breast reduction procedures. The diseased tissues were removed for pathological examination prior to our receipt of the tissue sample; thus, we analyzed lipids normally associated with surrounding, healthy breast tissues. The subjects were chosen to ensure 1280 Envlron. Sci. Technol., Vol. 25, No. 7, 1991
a statistically significant sample in the three age groups 19-40, 40-60, and 60-90. Only samples with more than 30 g of adipose tissue were accepted for analysis. Nonlipid tissues were removed, and the lipids were homogenized. Sample Extraction and Workup. The extraction and workup of the breast tissues is essentially the same as for the rat adipose tissue samples published elsewhere (6). Briefly, the tissues were homogenized with Na2S04,spiked with an internal standard, and Soxhlet extracted for 24 h with a 1:l mixture of hexane and acetone. Total lipids in the extract were determined after solvent removal. A volume equal to 1 g of lipid was used to separate, by gel permeation chromatography, the organochlorine contaminants (7). Further column chromatography was performed using Sep-pack Florisil cartridges. (Waters ASSOC., Milford, MA), following procedures recommended by the manufacturer. Analysis. Analytical methods have been previously described (6) and will only be summarized here. Octachlorobiphenyl (PCB congener 204) was used as the internal quantitation standard. A method blank was run with each set of five tissue samples analyzed. Measured recoveries were better than 90% through the entire sample preparation and analysis procedure. All mass spectral analyses were conducted on a Hewlett-Packard 5985 gas chromatographic mass spectrometer (GC/MS) operating in the electron capture, negative ionization mode. Typical capillary GC/MS conditions have been previously described (6). Our analyses included compounds in technical chlordane for which there are no standards. For quantitation purposes, response factors for the octachloro compounds were assigned the average of the a- and y-chlordane response factors. For the nonachloro compounds the average of the response factors of cis- and trans-nonachlor was used. Response factors were determined by the analysis of a standard of pure chlordane compounds including hexachloro compounds (chlordene, isomer 2 chlordene, and a-, p-, and y-chlordene), heptachlor0 compounds (heptachlor and heptachlor epoxide), octachloro compounds (a- and y-chlordane, compound K, and oxychlordane), and nonachloro compounds (cis- and trans-nonachlor). Response factors were averaged from two analyses, one a t the beginning and one at the end of each day. Statistics. All statistical procedures were done using the Statistical Analysis System (SAS Institute Inc., Cray, NC) running on various VAX computers. Univariate analysis showed that the data were log-normally distributed; thus, Pearson correlation coefficients were calculated with log-transformed data. Results and Discussion Table I gives the concentration data (in nanograms per gram of extracted fat) for 13 compounds in 23 breast tissue samples. The column labeled “sum” is the total of the columns to the left. The geometric mean is listed at the bottom of each column. The analyses are listed in order of increasing age. Compounds U81, U82, and U83 correspond to peaks 44,49, and 56 given in ref 6. These compounds all have a pentachlorocyclopentene moiety as ring 2, and they have three chlorines on ring 1;we will call these “5 + 3 types”. Other compounds are those with a hexachlorocyclopentene moiety as ring 2 and either two or three chlorines on ring 1; these are called “6 + 2” or “6 + 3 types”.
@-$; 3a
4
3
Table I. Concentrations of Chlordane8 in Women from Bloomington, IN,1987-1988’’ sample
age, yr
tN9
OXY
HEP
cN9
MC6
19 20 22 30 32 38 39 46 52 52 53 53 53 54 55 56 56 65 69 69 73 83 89
45 59 60 180 64 67 66 150 54 89 99 140 210 140 130 140 200 140 120 290 83 370 310 120
50 57 51 110 49 49 55 81 42 82 71 87 160 110 100 87 120 94 120 200 64 200 260 88
25 85 72 65 26 72 16 79 25 24 62 66 63 18 85 47 56 64 28 140 7 170 120 48
4 5 6 15 6 7 6 26 5 7 13 14 17 14 14 15 24 14 12 24 9 29 25 12
5 5 6 26 7 7 8 10 5 8 8 12 17 10 10
3540 22 4033 3510 3199 4108 34 33 6 18 7 16 28 30 13 8 17 11
27 14 31 10 29 Geo mean
11
13 12 9 25 8 40 22 11
compoundsb U82 MC5 aCL 0.4
1 2
0.4 1.3 1.0 1.2 0.6 0.8 0.5 3.3 0.5 1.4
3
1.7
4
1.9 2.1 2.7 2.0
1.3 2.7 1.9 2.2 0.9 0.8 1.0
1 3 2 5 1
2 1
5
5 6 3 2 7 3 2
6 1 11 5 3
1.1
3.9 0.9 0.9 2.1 0.8 2.9 1.9 1.3
1.1 1.1
1.6 0.3 0.5 0.6 3.1 0.5 1.1
1.1
0.8 2.3 1.0 3.7 6.8 1.2
gCL
US1
MC4
U83
MC7
sum
0.3 0.9 0.9 0.8 0.3 0.5 0.9 1.4 0.3 0.9 0.6 2.2 1.1
0.2 0.2 0.2 1.0 0.3 0.3 0.2 2.0 0.2 0.4 0.2 0.5 0.8 0.6 0.5 0.4 0.4 0.6 0.5 1.2 0.3 1.9
0.1 0.4 0.4 1.0 0.1 0.3 0.2 1.0 0.1 0.3 0.5 0.7 0.9 0.9 0.5 0.4 1.1 0.5 0.4 1.0 0.2 2.2 0.8 0.5
0.2 0.3 0.2 0.7 0.2 0.2 0.2 0.4 0.2 0.3 0.3 0.6 0.9 0.6 0.3 0.4 0.5 0.5 0.4 1.0 0.2 1.5 0.9 0.4
0.1 0.2 0.1 0.2 0.1 0.1 0.1 0.5 0.1 0.2 0.2 0.3 0.2 0.4 0.1 0.2 0.4 0.1 0.1 0.3 0.2 0.5 0.3 0.1
130 220 200 410 150 210 160 360 130 220 260 330 480 310 350 300 430 330 290 690 180 830 760 290
1.1
0.6 0.4 0.9 0.3 0.6 1.1 1.0 1.9 3.4 0.8
1.1
0.5
a All values are in nanograms per gram of fat. *Abbreviations: tN9, trans-nonachlor; OXY, oxychlordane; HEP, heptachlor epoxide; cN9, cis-nonachlor; aCL, a-chlordane; gCL, y-chlordane. The “MC” compounds have no trival names; see the chart for structures. The structures of the “U” compounds are unknown; see ref 4 for details.
Table 11. Relative Accumulationa of Chlordane in People compdb
type
accum factor
compdb
type
accum factor
tN9 MC6 cN9 U83 U81 U82
6+3 6+3 6+3 5+3 5+3 5+3
240 100 85 80 80 42
MC4 MC5 aCL MC7 gCL
5+3 5+3 6+2 5+3 6+2
20 6.1 1.5 1 1.00
Average concentration of each compound in the 23 human adipose tissue samples divided by the concentration of that compound in technical chlordane; the resulting ratios were then normalized to unity for y-chlordane. bSee footnote b in Table I for abbreviations.
Relative Bioaccumulation. Figure 1 shows mass chromatograms of the octachloro chlordanes in human fat (upper trace) and in technical chlordane (lower trace). The obvious differences between these two plots highlight the degree of alteration this complex mixture undergoes between its application as a pesticide and its accumulation in human adipose tissue. We can estimate the relative effectiveness with which these compounds accumulate in people by dividing the average relative abundance (gCL set to 1.00) of each compound in human breast tissue by ib average relative abundance (gCL set to 1.00) in technical chlordane. We obtained the “accumulation factors” listed in Table 11. The accumulation of the various components of chlordane is dependent on the configuration of the chlorines on ring 1. With the exception of MC7, all of the compounds with three chlorines on ring 1have accumulation factors greater than 6. Furthermore, those compounds with nine chlorines (6 + 3 types) are more highly accumulated than those with eight chlorines: The nonachloro compounds all have accumulation factors greater than 85; this class includes the most well retained compound, tN9. The group MC6, cN9, U83, and U81 all accumulate to
b QCL
1~
1
U82
MC4
RCL
1
1
I\, 1 1
I
i
I \ IN9
MC7
U ’ ‘ dL - L L
Flgure 1. Selected-ion-monitoringtraces of the octachloro chlordane compounds in human breast adipose tissue (upper trace) and in technical chlordane (lower trace). Individual peaks are labeled with their abbreviation; see the chart. Both mass chromatograms were obtained under identical GUMS conditions: m / z 410 (C,oH,35C1,37CI,) was monitored.
about the same extent; these compounds all have three chlorines on ring 1. The groups aCL, MC7, and gCL are not accumulated. The preferential accumulation of nonachloro- and pentachlorocyclopentene compounds (the 5 + 3 types) in these samples suggests that people are unable to effectively metabolize these isomers. The hexaand heptachlor0 chlordane compounds do not accumulate in people. Effects of Age. A correlation matrix showed that the human tissue concentrations of all of the compounds Environ. Sci. Technol., Vol. 25, No. 7, 1991 1281
1,000 h
i
m
h
800-
Humans
\ hc v M
2
Marine main.
1.8
600-
0
400 -
0
2
4
6
8
10
12
14
16
P/M ratio
Flgure 3. Average parent (gCL, aCL, tN9, and cN9) to metabolite (HEP and OXY) concentration ratios for chlordane compounds in the tissue, blood, or milk from several different species.
200 -
0” 0
20
40 60 Age of s u b j e c t
80
J
100
Flgure 2. Total concentration of chlordane compounds in human tissue samples (see Table I) plotted as a function of age.
(except heptachlor epoxide) were correlated with each other and with the summed concentration at the 98% (and frequently a t the 99.9% ) level. Given this high interrelationship among the measurements, this discussion will focus on the summed chlordane concentration. Figure 2 is a plot of this variable as a function of the age of the subject a t the time of tissue removal. Note that the regression line passes very near the origin, as it should. Although there is some scatter, the correlation between the summed concentration of chlordane compounds in the subject’s tissue is highly correlated with the subject’s age; the correlation coefficient (9) is 0.443, which is significant a t the 99.9% level. A correlation analysis of each compound as a function of age found a significant correlation in each case, except for heptachlor epoxide. This strong correlation between age and human pesticide concentration has also been noted by other workers (8-11). For example, there is a strong dependence of the concentration of p,p’-DDE in blood with the age of the subject (11). The cause of this age dependency is not known, and it is contrary to the exposure history of the different age groups. Since organochlorine pesticides were not in common use before 1946, all exposure started at this time, and anyone born before this date should have (on average) the same exposure. Since we observe continuously increasing concentrations in the adipose tissues of people born before this date, we conclude that, although exposure may have been constant, other factors affect the human body burden of chlordane. For example, older people may not be able to metabolize and excrete these compounds as readily as younger people. There may also be other, unknown, confounding variables that affect the older population.
Species Variations in Chlordane Metabolism. Chlordane has often been found in biota that had not been intentionally exposed. A summary of these data is given in Table 111. The literature is varied and often conflicting in nomenclature, compounds reported, method of reporting concentration (i.e., lipid adjusted or wet weight), and measurement technology used. In some cases, this somewhat limits the usefulness of many of these data. After a preliminary principal components analysis, we determined that the best way to compare the data in Table I11 was by taking the ratio of the summed concentration of the “parent” compounds (gCL, aCL, tN9, and cN9) to that of the “metabolite” compounds (HEP and OXY). We will call this ratio the “parent to metabolite ratio” (P/M); it is given in the last column of Table 111. This ratio would 1282 Environ. Sci. Technol., Voi. 25, No. 7, 1991
be very high if chlordane had not been metabolized, because of recent exposure to fresh material, for example. P/M would be less than unity if the concentrations of the metabolites exceeded those of the unmetabolized compounds. From an examination of Table 111,we note a few things: (a) Although the range of the P / M ratios for the human data was large (0.32-3.2) (certainly much of this variability can be attributed to the different analytical techniques employed and to the different tissues sampled in the various studies), there are no consistent differences between those who were known to have significant exposure to unaltered technical chlordane (2,19-21,23) and those who were unexposed. (b) Although the P/M ratio is about twice as high for people from Japan and Canada as compared to the United States, this difference is not statistically significant. Given observations a and b, we will treat all of the human data similarly. (c) Fishes and invertebrates have much higher P / M ratios than other species. Clearly, these species are not adept at metabolizing these compounds. We averaged the P / M ratios for the various types of species, and these data are shown in Figure 3. We have also shown the P / M ratio for the U.S. human diet. These data were calculated from Food and Drug Administration ”market basket survey” data from 1977 to 1984 (32-35). It is remarkable that the human adipose tissue P / M ratio (0.98) is 7 times higher than that of the US. food supply (0.14). It is difficult to imagine a process by which this ratio could increase from food to tissue: Metabolism of chlordane components present in food would cause this ratio to decrease not increase. This peculiar result can best be explained if there was an important source of human exposure in addition to food. Thus, we considered other sources. Sources of Human Exposure. We considered two routes of human exposure: ingestion from food and inhalation from air. The doses by ingestion were estimated by the U.S. Food and Drug Administration, who estimated that 840 ng/day chlordane and its metabolites are ingested; of this, only 160 ng/day are unmetabolized chlordane compounds (32-35). We calculated the average human dose of chlordane by inhalation using the following approach: The fraction of absorption by inhalation is dependent on lipophilicity and on dose (36). For chlordane, we have assumed a 66% fraction of adsorption, a value obtained for the absorption of styrene in people (36). Since people spend over 80% of their time indoors, we used indoor air concentrations for our calculations of exposure by inhalation. These data were obtained from Anderson and Hites (37), who measured organochlorine contaminants in residential housing with routine pesticide treatment histories and from a study of 500 Air Force houses that had differing levels of
Table 111. Ambient Levels of Chlordane in Human Tissue, Milk, and Blood and in Biota" sample
ref
date
HEP
OXY
compounds gCL aCL
tN9
cN9
120
12
P/Mb
Indiana University, Human Tissue Samples geometric means
1986-1988
8 8 8 8 8 8 8 8 12 13 14
ambient ambient ambient ambient ambient ambient ambient ambient normal serum levels poisoning by ingestion Florida citrus workers
1974 1975 1976 1977 1978 1979 1980 1981 1981 1983 1985
15 15
indigenous people Canndian national survey
1987 1987
16 16
KingstonC Ottawae
1986 1986
17 18
unexposed, milk fat unexposed, fat tissued
1986 1989
unexposed controls 2-yr exposure group 3-yr exposure group
1988 1988 1988
48
88
0.8
1.2
0.99
U.S. Human Adipose Tissues 77 80 80 70 70 70 80 90 60 2600 2.2
110 60 130 100 120 120 140 110 350 1900 2.7
0.57 0.32 0.68 0.59 0.67 0.71 0.70 0.61 1.4 0.61 0.64
12 19
36 19
1.1 0.96
18 16
115 86
14 9.5
1.4 1.4
3.1
16 120
4 33
0.78 1.9
2.1 6.0 7.7
26 68 135
6.4 18 28
0.90 1.5 1.4
115 110 110 100 110 100 120 90 190 510 2
Canadians, Human Milk 35 35
11 13
3 8
Canadians, Adipose Tissue 48 33
59 47
Japanese, General Population 20 35
11 45
1.2
Japanese, Exposed to Contaminated Indoor Air 2 2 2
21 44 83
19 22 53
JaDanese. Pest Control ODerators' 19 20 21 22 23 23
pco's whole blood pco's whole blood pco's whole blood unexposed whole bloode pco's controls
1982 1982 1986 1986 1990 1990
24 25 25 26 26
Weddell seal seal polar bear Weddell seal porpoise
1984 1988 1988 1988 1988
26 26 27
murre penguin gull
1988 1988 1989
28 28 28 28 7 29 25 30 30 26 26 27
scabbard fish scorpion fish pike carp fish, Saginaw Bayf lake trout arctic cod lake trout8 whitefish# walleye antarctic chum alewife
1984 1984 1984 1984 1985 1986 1988 1988 1988 1988 1988 1989
26 26 26 31
squid antarctic krill zooplankton mayfly larvae
1988 1988 1988 1990
1.5 5.9 14 (DCO'S)
1.5
1.6 1.7 0.29
2 0.29 0.22 0.59 0.35
0.43 0.22
Blood SamDles 0.1 0.29
0.35 0.65
0.1 0.25 0.48
0.05 0.19 0.23
2.7 4.6 0.55 0.08 1.4 0.89
0.03 0.46 0.22
1.0 1.5 0.95 1.2 2.3 3.2
Marine Mammals 64 200
11 170 1600 13 250
5.9 9.2 28 6.8 440
4.6 28 0.05 63
36 120 170 41 1800
7.3 14 28 8.3 270
4.5 0.63 0.14 4.3 10
10 1.7 10
0.19 1.1 0.65
Birds 82 16 29
19
0.05 0.05
2.8 0.91
2.7 15 21
Fishes
16 38 0.08 58 170 3
20 2 3 0.1 14 25 0.18 73 160 8.3 2.5 2
80 0.1 4 0.1 93 40 0.4 17 5.2
250 3 14 13 130 80 0.35 420 260 44 9.5
8.1 0.51 13 11
15 0.58 19 10
245
10 2.1 8
29 3.0 10 210 18 5.1 5.8 7.6 2.1 16 14 6.2
2.4 0.22 5.1 13
36 19 18 3.3
3 12 8 320 135 0.63 570 450 62 17 23
68 0.13
Aquatic Invertebrates
16
1.2 0.11 2.9 18
18 0.8 14 78
"Values are in nanograms per gram of extracted fat, except for whole blood data which is in nanograms per gram of blood. *Sum of trans-nonachlor, cis-nonachlor, a-chlordane, and y-chlordane divided by the sum of oxychlordane and heptachlor epoxide. e Both a composite sample and the geometric mean of 91 people were reported, but only for some compounds. The higher of the two values is reported here. dValue of HEP reported here is the geometric average of data reported; other values were calculated from data given in text of ref 18. eThe averages of reported male and female means are reported here. 'Nonachlors were quantitated individually but then summed and reported as "nonachlors". 8 Individual chlordanes and nonachlors were summed into congener classes and reported as single compounds. Environ. Sci. Technol., Vol. 25, NO. 7, 1991 1283
chlordane treatment (38). Unfortunately, Anderson and Hites did not report total chlordane concentration as we have done in Table I. Thus, to determine the total chlordane dose, we assumed that y-chlordane accounted for 12% of the toal mixture and divided the average ychlordane concentration reported by Anderson and Hites by 0.12 to get the total chlordane value. The indoor air concentrations are 110 ng/m3 in Bloomington and 1200 ng/m3 for the “untreated” Air Force houses. The daily dose by inhalation was calculated by multiplying these concentrations by the resting respiration rate of an average adult (8.5 L/min; see ref 36) and by the fraction of dose absorbed (0.66). The resulting doses are 890 ng/day in Bloomington and 9700 ng/day for the Air Force houses. None of this dose was metabolites. These doses are conservative estimates; we did not assume maximum values in any step of the calculations, but chose the best estimates available (for instance, indoor concentrations have been reported as high as 260 000 ng/m3 in the Air Force study). It is clear that doses from the inhalation of indoor air (890-9700 ng/day) are equal to or in excess of doses from the ingestion of food (840 ng/day), and 5-60 times greater if we consider only the parent compounds and not the metabolites. On the basis of this comparison, we believe that indoor air is an important source of exposure to technical chlordane in the United States, even for people living in untreated houses. Food remains the most significant souce of exposure to the metabolites heptachlor epoxide and oxychlordane. However, inhaled a- and ychlordane and heptachlor would be quickly metabolized to the epoxides and would act as an additional, internal “source” of the epoxides. On the basis of the use history of chlordane and its known persistence, we conclude that indoor air exposure is likely to be a widespread phenomenon and a significant source of these compounds to the general population and that remediation of homes with high levels of chlordane may be prudent. A more thorough survey of the concentrations of chlordane in the air of residential housing, in both treated and untreated homes, is warranted. Trends Over Time. The levels of chlordane compounds in people are not declining. The mean levels in our sample population were 48, 88, and 120 ng/g of fat, for heptachlor epoxide, oxychlordane, and trans-nonachlor, respectively. The same compounds were measured in the National Human Adipose Tissue monitoring program from 1974 to 1982, and their concentrations were 70-90,90-120, and 60-140 ng/g of fat for the same compounds, respectively. With the possible exception of heptachlor epoxide (which might be coming from a different pesticide formulation), there has been no measurable decline in these concentration levels even after 10 years of regulation. For a similarly persistent compound, p,p’-DDE, significant decreases in environmental and human adipose tissue concentrations were seen as little as 3 years after regulation began (8). After 8 years of regulation, p,p’-DDE concentrations in human adipose tissue had dropped from a mean value of 4.9 ppm in 1972 to 2.3 ppm in 1980. It is possible that the restrictions on the use of chlordane have had no real effect on the general population’s exposure. Acknowledgments We thank Ilora Basu, whose efforts contributed greatly to the success of this project, and Anthony Pizzo of the Bloomington Hospital for the tissue samples. Registry No. aCL, 5103-71-9; gCL, 5566-34-7; cN9,5103-73-1; tN9, 39765-80-5; HEP, 1024-57-3; OXY, 27304-13-8; MC4, 1284
Envlron. Sci. Technol., Voi. 25, No. 7, 1991
98255-11-9; MC5,31503-681; MC6,9831&97-9;MC7,133496-94-3; CL, 12789-03-6.
Literature Cited (1) Fed. Regist. 1987, 52, 42145-42149. (2) Taguchi, S.; Yakushiji, T. Arch. Enuiron. Contam. Toxicol. 1988, 17, 65-71. (3) Velsicol Chemical Co., Chicago, IL, personal communication, 1990. (4) Dearth, M.; Hites, R. Enuiron. Sci. Technol. 1991, 25, 245-254. (5) Dearth, M.; Hites, R. J. Am. SOC.Mass Spectrom. 1990, I , 99-103. (6) Dearth, M.; Hites, R. Enuiron. Sci. Technol., in press. (7) Jaffe, R.; Stemmler, E.; Eitzer, B.; Hites, R. J. Great Lakes Res. 1985, 11, 156-162. (8) National Human Adipose Tissue Survey, Office of Pesticides and Toxic Substances, Washington, DC. (9) Adeshina, F. Organochlorine Compounds in Human Adipose Tissue and Carcinogenic Risk: a Case Study of Chlordane/Heptachlor. Thesis, University of Texas a t Dallas, 1988. (10) Ansari, G.; James, G.; Hu, L.; Reynolds, E. Bull. Enuiron. Contam. Toxicol. 1986, 36, 311-316. (11) Kreiss, K.; Zack, M.; Kimbrough, R.; Needham, L.; Smrek, A.; Jones, B. J . Am. Med. Assoc. 1981, 245, 1926-1930. (12) Barquet, A,; Morgade, C.; Pfaffenberger, C. J . Toxicol. Enuiron. Health 1981, 7, 469-479. (13) Olanoff, L.; Bristow, W.; Colcolough, J.; Reigart, J. J . Toxicol. Clin. Toxicol. 1983, 20, 291-306. (14) Griffith, J.; Duncan, R. Bull. Enuiron. Contam. Toxicol. 1985, 35, 411-417. (15) Davies, D.; Mes, J. Bull. Enuiron. Contam. Toxicol. 1987, 39, 743-749. (16) Lebel, G.; Williams, D. J.-Assoc. Off. Anal. Chem. 1986, 69,451-58. (17) Tojo, Y.; Wariishi, M.; Suzuki, Y.; Nishiyama, K. Arch. Enuiron. Contam. Toxicol. 1986, 15, 327-332. (18) Kashimoto, T.; Takayama, K.; Mimura, M.; Miyata, H.; Murakami, Y.; Matsumoto, H. Chemosphere 1989, 19, 921-926. (19) Kawano, M.; Wakimoto, T.; Ohkoda, T. Nippon Nogei Kagaku Kaishi 1982,56, 531-536. (20) Kawano, M.; Tatsukawa, R. Nippon Nogei Kagaku Kaishi 1982,56, 923-929. (21) Saito, I.; Kawamura, N.; Uno, K.; Hisanaga, N.; Takeuchi, Y.; Ono, Y.; Iwata, M.; Gotoh, M.; Okutani, H.; Matsumoto, T.; Fukaya, Y.; Yoshitomi, S.; Ohno, Y. Znt. Arch. Occup. Environ. Health 1986, 58, 91-97. (22) Wariishi, M.; Suzukim, Y.; Nishiyama, K. Bull. Enuiron. Contam. Toxicol. 1986, 36, 633-643. (23) Wariishi, M.; Nishiyama, K. Arch. Enuiron. Contam. Toxicol. 1989, 18, 501-507. (24) Kawano, M.; Inoue, T.; Hidaka, H.; Tatsukawa, R. Chemosphere 1984, 13, 95-100. (25) Muir, D.; Norstrom, R.; Simon, M. Enuiron. Sci. Technol. 1988,22, 1071-1079. (26) Kawano, M.; Inoue, T.; Hidaka, H.; Tatsukawa, R. Environ. Sci. Technol. 1988, 22, 792-797. (27) Braune, B.; Norstrom, R. Enuiron. Toxicol. Chem. 1989, 8, 957-968. (28) Kramer, W.; Buchert, H.; Reuter, U.; Biscoito, M.; Maul, D.; Le Grand, G.; Ballschmiter, K. Chemosphere 1984,13, 1255-1267. (29) Price, H.; Welch, R.; Scheel, R.; Warren, L. Bull. Enuiron. Contam. Toxicol. 1986, 37, 1-9. (30) Swackhamer, D.; Hites, R. Enuiron. Sci. Technol. 1988,22, 543-547. (31) Standley, L., Stroud Water Research Center, Avondale, PA, personal communication, 1990. (32) Gunderson, E. J.-Assoc. Off. Anal. Chem. 1988, 71, 1200-1209. (33) Gartrell, M.; Craun, J.; Podrebarac, D.; Gunderson, E. J.-Assoc. Off. Anal. Chem. 1985,68, 862-873. (34) Podrebarac, D. J.-Assoc. Off. Anal. Chem. 1984, 67, 176-185.
Environ. Sci. Technol. 1091, 25, 1285-1289
(35) Gartrell, M.;Craun, J.; Podrebarac, D.; Gunderson, E. J.-Assoc. Off. Anal. Chem. 1986,69,146-159. (36) Ramsey, J.; Anderson, M. Toxicol. Appl. Pharmacol. 1984, 73, 159-175. (37) Anderson, D.;Hites, R. Atmos. Environ. 1989, 23, 2063-2066.
(38) Bennett, G.;Ballee, D.; Hall, R.; Fahey, J.; Butts, W.; Osmun, J. Bull. Environ. Contam. Toxicol. 1974,11,64-69. Received for review August 6, 1990. Accepted March 4, 1991. This work was supported by Grant 87ER60530 from the US. Department of Energy.
High-Temperature Removal of Cadmium Compounds Using Solid Sorbents Mohit Uberolt and Farhang Shadman" Department of Chemical Engineering, University of Arizona, Tucson, Arizona 85721
rn Emission of cadmium compounds is a major problem
Table I Composition of Sorbents Used (wt % )
in many combustors and incinerators. In the present work, the use of solid sorbents for removal of cadmium compounds from high-temperature flue gases is investigated. The sorbents tested were silica, alumina, kaolinite, emathlite, and lime. Compounds containing aluminum oxide show high cadmium removal efficiency. In particular, bauxite has the highest rate and capacity for cadmium capture. The overall sorption process is not just physical adsorption, but rather a complex combination of adsorption and chemical reaction.
SiOz A1203 FezO, TiOz CaO MgO K,O NazO
bauxite"
kaoliniteb
emathlitec
limestoned
11.0
52.1 44.9 0.8 2.2
73.4 13.9 3.4 0.4 5.0 2.6 1.2 0.1
0.7 0.3 0.3
84.2 4.8
97.2 1.5
"Paranam bauxite from Alcoa Corp. bBurgess Pigment Co. Mid-Florida Mining Co. Pfizer Inc.
Introduction
Cadmium compounds are considered to be among the most toxic trace elements emitted into the environment during fuel combustion and waste incineration. Cadmium and cadmium-compounds are primarily used in the fabrication of corrosion-resistant metals. Cadmium is also used as a stabilizer in poly(viny1 chlorides), as electrodes in batteries and other electrochemical cells, and for numerous applications in the semiconductor industry (1). Due to this wide range of applications, cadmium is present in many municipal and industrial wastes. Cadmium is also present in coal in trace quantities (2). Consequently, emission of cadmium compounds is a problem in many waste incinerators and coal combustors. The chemical form and concentration of these compounds depend on a number of factors including feed composition and operating conditions (3). The increased use and disposal of cadmium compounds, combined with their persistence in the environment and relatively rapid uptake and accumulation in living organisms, contribute to their serious environmental hazards. The present technology is inadequate to meet the expected cadmium emission standards. Therefore, new and effective methods need to be developed and investigated for controlling the emission of cadmium and other toxic metals in combustors and incinerators. A promising technique for the removal of metal vapors from high-temperature flue gases is through the use of solid sorbents to capture and immobilize the metal compounds by a combination of adsorption and chemical reactions. The sorbent can be used in two ways: a. I t could be injected as a powder (similar to lime injection) for in situ removal of cadmium compounds. b. The cadmium-containing flue gas could be passed through a fixed or fluidized bed of sorbent. The sorbent could be used in the form of pellets, beads, or monoliths (for high dust applications). Previous studies by us and other investigators indicate that solid sorbents can be very effective in removing alkali Present address: W. R. Grace & Co., Research Division, 7379 Route 32, Columbia, MD 21044. 0013-936X/91/0925-1285$02.50/0
and lead vapors from hot flue gases (4-7). In the present work, a number of potential sorbents were screened and compared. for their effectiveness in removing cadmium compounds from hot flue gases. Details of the sorption mechanism were investigated. for the selected sorbents. E x p e r i m e n t a l Section
Materials. In the first part of this study, several model compounds and naturally available materials were evaluated as potential sorbents for removal of gaseous cadmium compounds from hot flue gases. The model compounds included silica (MCB grade 12 silica gel) and a-alumina (Du Pont Baymal colloidal alumina, technical grade). The naturally available materials included kaolinite, bauxite, emathlite, and lime. The composition of these sorbents is given in Table I. Cadmium chloride was used as the cadmium source. For the screening experiments, the sorbents were used in the form of particles, 60-80 mesh in size. For the kinetic and mechanistic study the sorbents were used in the form of thin flakes (disks). The flake geometry is easy to model and characterize by analytical techniques. All the sorbents were calcined at 900 "C for 2 h and stored under vacuum until used. All the experiments were conducted in a simulated flue gas atmosphere containing 15% COz, 3% 02, 80% N2, and 2% HzO. Equipment and Procedures. Screening Experiments. The main components of the experimental system were a Cahn recording microbalance, a quartz reactor, a movable furnace, and analyzers for determining the composition of the gaseous products. This system has been previously used for screening of sorbents for removal of lead compounds. Therefore, only the salient features of the system are described here. Details can be found in a previous publication ( 4 ) . The cadmium source was suspended by a platinum wire from the microbalance, which monitored the weight change during the experiments. A fixed bed of the sorbent particles was made by placing 100 mg of the sorbent particles on a 100-mesh stainless-steel screen in a quartz insert. All experiments in this study were performed with the source at 560 "C and the sorbent at 800 "C. This method ensured that the concentration
0 1991 Amerlcan Chemical Society
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