Concentrations of some trace elements in hair, liver and kidney from autopsy subjects — relationship between hair and internal organs

Concentrations of some trace elements in hair, liver and kidney from autopsy subjects — relationship between hair and internal organs

The Science of the Total Environment, 76 (1988) 29-40 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands 29 CONCENTRATIONS O...

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The Science of the Total Environment, 76 (1988) 29-40 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

29

CONCENTRATIONS OF SOME TRACE ELEMENTS IN HAIR, LIVER AND KIDNEY FROM AUTOPSY SUBJECTS -- RELATIONSHIP BETWEEN HAIR AND INTERNAL ORGANS

Y. MURAMATSU* and R.M. PARR International Atomic Energy Agency, P.O. Box 100, A-1400 Vienna (Austria)

(Received January 13th, 1988; accepted February 4th, 1988)

ABSTRACT Autopsy samples of hair, liver and kidney cortex from 30 Swedish subjects (Caucasian) were analysed for Ag, Co, Cr, Hg, Sb, Se and Zn by neutron activation analysis (NAA). The following elements were observed to have higher concentrations in hair than in liver and kidney cortex: Ag, (Co), Cr and Hg (on a dry weight basis). Selenium was highly concentrated in kidney cortex, and Fe in liver. The observed concentrations of most of the elements were very variable for each tissue. In particular, Co values for hair showed more than a 5000-fold difference. However, Se values for hair were relatively constant. A highly significant positive correlation was observed between Hg concentrations in hair and kidney cortex. Somewhat weaker correlations were found between Hg in kidney cortex and liver and Se in hair and kidney cortex. The concentration of Co in liver correlated with that in kidney cortex. It was concluded that, with the exception of mercury, and to a lesser degree selenium, hair analysis did not provide a useful measure of the trace element status of the subjects included in this study. INTRODUCTION A large number of hair analyses have been made during the last decade. However, serious uncertainty still exists as to the meaningful interpretation of h u m a n h a i r m i n e r a l d a t a i n e n v i r o n m e n t a l h e a l t h s t u d i e s . T h i s is m a i n l y d u e to a lack of knowledge as to whether trace element levels in hair can be used to measure human body burdens, in particular whether there are meaningful correlations between trace element levels in hair and in internal organs. A a l b e r s a n d H o u t m a n (1985) a n d A a l b e r s a n d d e G o e i j (1984) r e p o r t e d t r a c e e l e m e n t c o n t e n t s i n h u m a n h a i r a n d i n t e r n a l o r g a n s o f a b o u t 200 a u t o p s y subjects collected from different areas in the Netherlands. They reported that no correlations between hair and a number of internal organs could be estab l i s h e d f o r s e v e r a l t r a c e e l e m e n t s (Cd, Cu, F e , P b , Zn, etc.). H o w e v e r , m o r e analytical data with different concentration ranges and data for additional elements are needed to confirm the validity of these conclusions. *Present address: National Institute of Radiological Sciences, Isozaki 3609, Nakaminato-shi, Ibaraki 311-12, Japan.

0048-9697/88/$03.50

© 1988 Elsevier Science Publishers B.V.

30 The International Atomic Energy Agency (IAEA) started a Co-ordinated Research Programme in 1984 on the significance of hair mineral analysis as a means for assessing internal body burdens of environmental mineral pollutants. This programme includes the following three studies: (i) elemental analysis of hair and internal organs (autopsy samples) from human subjects, (ii) animal experiments on mineral absorption, distribution and excretion of selected toxic elements, and (iii) the use of multiparametric mathematical methods to interpret the analytical results. Presently there are 11 participants in this programme. As a part of this programme we have analysed autopsy samples of hair, kidney cortex and liver by neutron activation analysis. MATERIALSAND METHODS Autopsy samples of scalp hair, liver and kidney cortex were collected from 30 subjects (Caucasian male) in Sweden as a part of an earlier WHO/IAEA co-ordinated research programme on trace elements in cardiovascular diseases (Masironi and Parr, 1979). The samples were frozen and stored in the IAEA's own laboratory. The storage time was relatively long (---6 years). However, since they were packed in closed polyethylene bottles and kept at about - 20°C, it was thought unlikely that the concentrations of any elements analysed would have changed (at least not when expressed on a dry weight basis). To remove external contamination of the frozen liver and kidney cortex samples, the surfaces were cut off. A titanium knife was used in order to avoid contamination with any of the elements of interest. About 4 g (wet weight) of each sample was then freeze-dried. The dried samples were then cooled in liquid nitrogen and homogenized in a Teflon container by the brittle fracture technique, i.e. by shaking with a micro-dismembrator (B. Braun, Melsungen, F.R.G.) (Iyengar, 1976). Hair samples were washed once in acetone, thrice in water and once more in acetone (IAEA recommended procedure, Ryabukhin 1978). During each wash, the samples were allowed to stand at room temperature for 10min; the supernatant liquid was then poured off and fresh solvent was added. Finally, the hair samples were dried and also homogenized by the brittle fracture technique. Approximately 100mg amounts of each sample (for hair, somewhat less), together with suitable reference materials, were sealed in pure quartz ampoules (Suprasil) and irradiated in the ASTRAReactor of the Forschungszentrum Seibersdorf, Austria, at a neutron flux density of 8 x 1013ncm-2s-1 for ~ 48 h. Known amounts of each element were sealed in quartz ampoules and irradiated at the same time for use as standards. A f t e r a cooling time of ~ 6 weeks the gamma-ray spectra of the samples, standards and reference materials (IAEA: hair, animal muscle and horse kidney; NBS: bovine liver; NIES: hair) were recorded with a Ge(Li) detector. Duplicate analyses were carried out for most samples. Analytical results for reference materials agreed well with the certified values given in the literature. Mercury and Se in some of the liver samples with very low Hg (or Se) levels were determined using a simple radiochemical method developed by the

31 present authors (Muramatsu et al., 1988). This was done by heating the irradiated sample to 1000°C in an oxygen stream in a quartz tube with two charcoal traps. The evaporated Hg and Se were collected in the first charcoal trap. This trap was then heated to ~ 750°C in a nitrogen stream to separate the Hg by propelling it into the second charcoal trap, while Se was retained in the first trap. RESULTS AND DISCUSSION

The elements Ag, Co, Cr, Fe, Hg, Sb, Se and Zn were measured. However, Ag, Cr and Sb were not detected in hardly any of the liver and kidney samples. The concentration ranges of most of the elements analysed are very wide in each sort of tissue. Table 1 summarizes the ranges, median and mean values of the analysed samples for each element. (Individual analytical results and other information about the subjects, e.g. age, weight, working place and smoking habits, are available from the authors on request.) In order to compare our results with analytical data for each tissue reported by other authors, normal values for hair, kidney and liver were collected from the literature and are listed in Table 2. Commonly occurring values for element concentrations in hair and liver established by Iyengar (1985) and values for Standard Reference Man by ICRP (1975) are also included in this table. Concentrations of some trace elements in hair, kidney cortex and liver Silver The mean Ag concentration comparable to the mean values Table 2. Silver concentrations below the limit of detection ( ~

(0.56 mg kg-1) in hair observed in this study is reported by the different authors mentioned in in most of the kidney and liver samples were 0.03 mg kg 1 on a wet weight basis).

Cobalt A difference of more than 5000-fold was observed in Co values for hair samples (range 0.005-3.6mgkg-1). Only two samples showed extremely high values of > 1 mg k g - ' . Since liver and kidney samples of these subjects showed no particular enrichment of Co, the high value indicates possible external contamination. The concentration of Co is higher in liver than in kidney cortex. Cobalt is known to occur as a central atom of the vitamin B12 molecule. However, the concentration of Co in organs may not indicate the status of vitamin B,2 (~ 4% Co), because Co probably also occurs in other chemical forms in the body. Chromium The range of Cr concentration in hair observed in this study is also very wide. The highest concentration (4.5 mg kg -1) must be due to external contamination. High Cr values in hair (> 1 0 m g k g - ' ) have also been reported by

32 TABLE 1 S u m m a r y of the analytical r e s u l t s for 30 a u t o p s y subjects (mg kg -1) Element

Organ

Ag

Hair

Dry

Kidney

Co

Cr

Fe

Hg

Sb Se

Zn

Minimum

Median

Maximum

< 0.1

0.2

3.1

Dry Wet

< 0.1 < 0.02

< 0.1 < 0.02

0.33 0.065

Liver

Dry Wet

< 0.1 < 0.03

< 0.1 < 0.03

0.28 0.085

Hair

Dry

0.005

0.028

3.6

0.19 _+ 0.67

Kidney

Dry Wet

0.029 0.0057

0.060 0.013

0.33 0.074

0.072 +_ 0.053 0.015 _+ 0.012

Liver

Dry Wet

0.031 0.011

0.14 0.038

0.84 0.17

0.16 + 0.16 0.045 _+ 0.034

Hair

Dry

0.11

0.35

4.5

0.57 _+ 0.82

Kidney

Dry Wet

< 0.2 < 0.03

< 0.2 < 0.03

0.39 0.12

_a -

Liver

Dry Wet

< 0.2 < 0.06

< 0.2 < 0.06

4.9 1.8

-

10.4

27.4

M e a n _+ SD 0.56 + 0.72 a -

Hair

Dry

4.6

Kidney

Dry Wet

303 53.4

516 97

738 219

515 +_ 120 107 _+ 37

11.7 + 6.1

Liver

Dry Wet

370 103

945 262

1800 583

967 + 400 275 _+ 130

Hair

Dry

0.20

1.04

4.29

1.26 + 0.89

Kidney

Dry Wet

0.16 0.036

0.73 0.14

4.42 0.98

1.08 + 0.99 0.22 i 0.21

Liver

Dry Wet

0.041 0.0087

0.24 0.062

1.01 0.26

0.34 + 0.24 0.096 + 0.069

Hair

Dry

0.004

0.064

0.80

0.12 +_ 0.18

Hair

Dry

0.21

0.44

0.63

0.42 _+ 0.10

Kidney

Dry Wet

1.79 0.36

3.8 0.77

5.46 1.29

3.81 + 0.82 0.78 _+ 0.19

Liver

Dry Wet

0.32 0.082

1.28 0.33

1.92 0.64

1.19 + 0.41 0.33 i 0.12

Hair

Dry

31.3

Kidney

Dry Wet

Liver

Dry Wet

142

231

137 _+ 51

121 22.9

232 44.0

716 132

259 _+ 135 52.9 + 26.9

34,2 12.7

215 55.4

848 204

243 _+ 160 66.2 _+ 41.0

a , Since Ag and Cr c o n c e n t r a t i o n s in most of the kidney and liver samples were below the limits of detection, m e a n values are not given,

33 other authors (e.g. Qureshi et al., 1982; Kim et al., 1985). Chromium concentrations in most of the liver and kidney samples in this study were below the limit of detection ( ~ 0.05 mg kg 1 on a wet weight basis). However, one liver sample showed a very high Cr concentration of 1.8mgkg -1 (wet), which cannot be explained.

Iron Iron concentrations in hair are obviously lower than those in liver and kidney cortex. The mean Fe value for hair in this study ( l l . 7 m g k g -1) is somewhat lower than that of the literature values mentioned in Table 2, whereas those for liver and kidney are comparable to the literature values.

Mercury Mercury is the most important toxic element in this study. The concentrations of Hg show a large variability in each sort of tissue. This element is more highly concentrated in hair and in kidney cortex than in liver on a dry weight basis. The mean concentration of Hg in hair in this study is comparable to values obtained in the U.S.A., Korea and Pakistan; however, it is much lower than t h a t in J a p a n (see Table 2). This may be due to the fact that the consumption of marine products by Swedes is much lower than that by Japanese. The relationship between fish consumption and Hg concentrations in hair has been pointed out by several authors. Wide variations in Hg concentrations in hair in this study may also be explained mainly by the fish consumption of the subjects, if no atmospheric contamination existed. Mean values of Hg both in liver and kidney cortex obtained in this study are similar to the literature values in Table 2, excluding those of Yukawa et al. (1980) for the organs collected in Japan. This might be due to the high intake of Hg through marine products in Japan.

Antimony Antimony concentrations in hair observed in this study range from 0.004 to 0.80 mg kg 1. Because of interference from the Cs peak, the analytical accuracy for Sb in hair was not very high, and this element was not detected in liver and kidney cortex.

Selenium Selenium is also one of the most important elements in this study. In spite of its known toxicity at higher concentrations Se is essential for animals and humans. Concentrations of Se are low in hair but high in kidney cortex. Selenium levels in hair in this study are relatively constant. One subject had Se concentrations which were the lowest values recorded for all three tissues. Several papers in the scientific literature refer t o a possible relationship between Se deficiency and a concomitant increased death rate from cardiovascular disease. Most of the samples analysed in this study were collected from subjects who suffered from this disease. Selenium concentrations in hair in this

30 28~40

Sweden Belgium Netherlands G.D.R. Italy U.S.A.b Canada India Pakistan Korea Japan Frequent value

30 5 8 7

Sweden Sweden Sweden Yugoslavia U.K. U.S.A. Japan Japan Reference man

113 18~23 6

n

Location (Type of value)

0.013

0.01

0.015 0.004 0.001

Co

120 86.7 74

107 79 79

Fe

0.07 0.33 0.48 0.038

0.68 0.47

0.39

0.13 0.03-0.045

0.19 0.128

Co

1.1

0.56 0.8

Ag

(b) Kidney (mg/kg wet weight basis)

30-57 49 330 110 260 105 44 300

na

Location (Type of value)

0.83 2.1

0.22 0.12 0.091 0.14

Hg

0.46 1.42 2.33 0.82

4.0 1.3-1.7

0.57

Cr

38 39.6 48

48

0.2 1.5

52.9 31 25

Zn

0.78 0.79 0.70

Se

60 51.1 152 35 30~0

203

11.7 40 10

Fe

0.12 0.15 1.6 0.101

0.36 0.26 0.07&.25

(0.12) 0.15

Sb

1.18 0.5-1.0

1.4 0.58-1.2 0.5 1.28 1.03

0.42 0.80

Se

This study Brune et al. (1979) Brune et al. (1980) Kosta et al. (1975) Hamilton et al. (1972) Mottet and Body (1974) Yukawa et al. (1980) Shiraishi et al. (1986) ICRP

Author

1.73 1.88 4.2 0.5-2.0

2.4 1.7-2.2 2.0

1.26

Hg

200 138 255 215 183 150-250

137 180 165 148 208

Zn

This study Tomza and M a e n h a u t (1984) Aalbers and De Goeij (1984) Wiesener et al. (1979) Clemente et al. (1979) Gordus et al. (1974) Chatt (1985) Arunachalam et al. (1979) Qureshi et al. (1982) Kim et al. (1985) Takeuchi et al. (1979) Iyengar (1985)

Author

Literature values for trace element concentrations in hair, kidney and liver in comparison with the results of this study (a) Hair (mg/kg dry weight basis)

TABLE 2

30 5 8 8 5 11 113 35 11 ~15 15 7

Sweden Sweden Sweden Yugoslavia Belgium U.K. U.S.A. U.S.A. New Zealand Japan Japan Japan Reference man Frequent value

Fe

275 274 246 195

230 120 212 180 150-250

Co

0.045 0.13 0.013

0.031

0.042 0.15 0.06

0.061 0.06~.15 0.03~}.15

0.26 0.086 0.16 1.6 0.23

0.096 0.10 0.037 0.030 0.074

Hg

0.25~.4

0.50 0.30 2.30

0.25 0.30

0.33 0.29 0.19

Se

75 48 63.8 47 40-60

53

53-66 75.8

66.2 46 41

Zn

This study Brune et al. (1979) Brune et al. (1980) Kosta et al. (1975) Lievens et al. (1977) Hamilton et al. (1972) Mottet and Body (1974) Zeisler et al. (1984) J o h n s o n (1976), J o h n s o n et al. (1976) Yukawa et al. (1980) Kitamura et al. (1978) Shiraishi et al. (1986) ICRP Iyengar (1985)

Author

Mean values (in a few cases, median or range) for samples from non-contaminated areas are reported. a n = number of samples. bRange of mean values of sub-groups (hair values in U.S.A.).

n

Location (Type of value)

(c) Liver (mg/kg wet weight basis)

36 study (mean 0 . 4 2 m g k g 1) are s o m e w h a t low c o m p a r e d with the l i t e r a t u r e values. H o w e v e r , the differences m a y be within the r a n g e of v a r i a b i l i t y for n o r m a l values. Selenium levels in liver and k i d n e y are in a g r e e m e n t with l i t e r a t u r e values. Zinc Zinc is one of the most i m p o r t a n t essential t r a c e elements for h u m a n s and animals. This e l e m e n t is a c o n s t i t u e n t of m a n y m e t a l l o e n z y m e s and proteins. C o n c e n t r a t i o n s of Zn i n h a i r observed in this study are r e l a t i v e l y constant; however, levels in k i d n e y c o r t e x and liver are v e r y variable. T h e results o b t a i n e d for hair, k i d n e y c o r t e x and liver are c o m p a r a b l e to the l i t e r a t u r e values.

Relationship between concentrations of elements in hair and internal organs It is widely assumed ( p a r t i c u l a r l y by p u r v e y o r s of c o m m e r c i a l h a i r analysis services) t h a t h a i r analysis is a useful tool for assessing the i n t e r n a l body burdens of toxic and t r a c e elements. Several papers h a v e suggested t h a t h a i r reflects e n v i r o n m e n t a l c o n t a m i n a t i o n a n d / o r n u t r i t i o n a l status of some t r a c e elements. H o w e v e r , t h e r e exist only v e r y few a n a l y t i c a l results for b o t h h a i r and i n t e r n a l o r g a n s from the same subjects. In this context, we made a n a l y s e s of t h r e e tissues, i.e. hair, k i d n e y and liver, from a u t o p s y subjects. The correlation coefficients b e t w e e n different pairs of tissue are shown in Table 3. T h e r e was a highly significant positive c o r r e l a t i o n between Hg in h a i r and k i d n e y c o r t e x (see Fig. 1). T h e c o r r e l a t i o n coefficient (r) for h a i r - k i d n e y for all 30 samples is 0.61. If we exclude only one sample with an u n u s u a l Hg value, the c o r r e l a t i o n coefficient of h a i r - k i d n e y becomes m u c h b e t t e r (r = 0.81). However, only a w e a k c o r r e l a t i o n was found b e t w e e n Hg in h a i r and liver (r = 0.40, see also Fig. 2), and a slightly s t r o n g e r one between Hg in k i d n e y c o r t e x and liver (r = 0.55). By m e a n s of animal experiments using radioisotopes, K o l l m e r (1985) observed t h a t Hg was t r a n s f e r r e d to growing h a i r in l a r g e r a m o u n t s t h a n o t h e r TABLE 3 Product momentum correlation coefficients (r) of elemental concentrations in each pair of tissues for 30 samples. Values indicating significant correlations (at P/> 95%) are underlined

Co Fe Hga Se Zn

Hair-kidney

Hair-liver

Kidney-liver

0.09 0.02 0.61 (0.8-'-'~) 0.55 0.15

0.07 0.42 0.40 (0.42) 0.23 0.06

0.80 0.23 0.55 (0.55"---) 0.40 0.36

a Correlation coefficients for Hg excluding one unusual sample are shown in parentheses.

37

~3 o~ E

• °•i • ° i

o

.c c~1 "1-

*

. . .

( r - 0.801

|oB •



i~,

i 1

I 2

n 3 Hg in Hair

i 4 (mg/kg)

i 5

6

Fig. 1. Relationshipbetween Hg in hair and kidney (on dry weight basis) (Correlation coefficient (r) excludingone unusual sample is shown in parentheses.) A

E .> .J ¢•o) "1-

3

2 r- 0.40

1 •

°

• ° ~ • • t.

00



1





°



2

• °

I

l

!

3

4

5

6

Hg In Hair (mg/kg)

Fig. 2. Relationshipbetween Hg in hair and liver (on dry weight basis). toxic elements such as Cd and As, and that Hg accumulated much more in t h e kidney t h a n in liver. Ohmori and Hashimoto (1985) found a high accumulation of Hg in kidney in comparison with other tissues through experiments using guinea pigs administered HgC12. Matsubara and Machida (1985) reported, on the basis of their radio-tracer experiments with mice, that hair might be a reasonable indicator of Hg, as this element was readily deposited into hair and has a long biological half-life. The results of these animal experiments agree with our findings regarding the possible relationship between Hg in hair and kidney cortex and a high Hg accumulation in kidney cortex. Thus it would appear t h a t hair may be used as a rough indicator for assessing the internal body burden of Hg. However, since the life span of hair is much shorter than that of internal organs, it is expected that hair may not reflect well the level of Hg in the body over a long time scale. The results for one subject, which showed a high Hg content in kidney (4.4mgkg 1, dry) but not in hair (1.1 mgkg-1), may perhaps be explained by this reason. In contrast, Hg levels

38 in hair may be elevated by atmospheric contamination without increasing the levels in internal organs. It is known that Se concentrations in hair are influenced by the dietary intake of this element. Low concentrations of Se (mean value 0.074mgkg 1, Zhu, 1981) have been found in the Keshan area of China (known as a region of Keshan disease caused by Se deficiency), whereas relatively high levels (mean value 1.56, Br~itter et al., 1984) have been reported in Venezuela (known as a high Se region). Therefore, we expected a significant positive correlation between the concentrations of this element in hair and internal organs. However, Se contents of hair in this study were fairly constant and only rather weak or almost no correlations were observed between Se concentrations in hair and internal organs (hair-kidney, r = 0.55; hair-liver, r = 0.23). It should be noted that there was a relatively good correlation (r = 0.80) between Co concentrations in kidney cortex and liver (see Fig. 3), although there appeared to be no relationship between hair and organ concentrations of this element. However, if we exclude one sample with high Co contents in both kidney and liver, the correlation coefficient becomes obviously lower (r = 0.40). Therefore, more data are necessary to confirm this relationship. Also, no correlations were found between concentrations of Fe and Co in hair and the internal organs included in this study. Aalbers and Houtman (1985) and Aalbers and de Goeij (1984) also found no correlations for Zn, Fe, Cu, Cd and Pb between human hair and internal organs. Kollmer and Berg (1985) reported, on the basis of their animal experiments, that Zn levels in hair and other tissues (with the exception of tibia) collected from animals fed a Zn-deficient diet were almost the same as those from animals fed a normal diet. It was concluded that, with the exception of mercury, and to a lesser degree selenium, hair analysis did not provide a useful measure of the trace element status of the subjects included in this study. 0.9 0.8 0.7 0.6 0.s

.~ 0.4 ..1

._c 0 . 3 0

o 0.2

0.1

e~ee

/..s ",

J 0.1

i

i

i

0.2 0.3 0.4 Co In kidney {mg/kg)

0.5

Fig. 3. Relationship between Co in liver and kidney cortex (on dry weight basis).

39 ACKNOWLEDGEMENTS T h e a u t h o r s w o u l d l i k e t o t h a n k M s R. O g r i s a n d M s F. R e i c h e l f o r t h e i r h e l p in analysing the autopsy samples. REFERENCES Aalbers, Th.G. and J.J.M. de Goeij, 1984. Levels of magnesium, manganese, iron, copper, zinc, cadmium and lead in human hair: Can and do they reflect tissue levels? Working paper for the first Research Co-ordination Meeting on the Significance of Hair Mineral Analysis as a Means for Assessing Internal Body Burdens of Environmental Mineral Pollutants, IAEA, Vienna. Aalbers, Th.G. and J.P.W. Houtman, 1985. Relationships between trace elements and atherosclerosis. Sci. Total Environ., 43: 255-283. Arunachalam, J., S. Gangardharan and S. Yegnasubramanian, 1979. Elemental data on human hair sampled from Indian student population and their interpretation for studies in environmental exposure. IAEA Symp. Nuclear Activation Techniques in the Life Sciences, Vienna, 1978. IAEA/STI/PUB/492, pp. 499-513. Br~itter, P., V.E. Negretti and U. RSsick, 1984. Effects of selenium intake in man at high dietary levels of seleniferous areas of Venezuela. In: Trace Element Analytical Chemistry in Medicine and Biology, Vol. 3. Walter de Gruyter & Co., Berlin. Brune, D., G.F. Nordberg, P.O. Wester and B. Biveered, 1979. Accumulation of heavy metals in tissues of industrially exposed workers. IAEA Symp. Nuclear Activation Techniques in the Life Sciences, Vienna, 1978. IAEA/STI/PUB/492, pp. 643~55. Brune, D., G. Nordberg and P.O. Wester, 1980. Distribution of 23 elements in the kidney, liver and lungs of workers from a smeltery and refinery in north Sweden exposed to a number of elements and of a control group. Sci. Total Environ., 16: 13-35. Chatt, A., 1985. Personal communication. Clemente, G.F., L.C. Rossi and G.P. Santaroni, 1979. Trace element composition of hair in the Italian Population. IAEA Symp. Nuclear Activation Techniques in the Life Sciences, Vienna, 1978. IAEA/STI/PUB/492, pp. 527-543. Gordus, A.A., C.C. Maher and G.C. Bird, 1974. Human hair as an indicator of trace metal environmental exposure. Proc. 1st Annu. NSF Trace Contaminants Conf., Oak Ridge Natl. Lab. Conf. 730802, pp. 463-487. Hamilton, E.I., M.J. Minski and J.J. Cleary, 1972. The concentration and distribution of some stable elements in healthy human tissues from the United Kingdom. Sci. Total Environ., 1: 341-374. ICRP Task Group of Committee, 2, 1975. Report of the Task Group on Reference Man. ICRP Publication 23. Pergamon Press, Oxford. (Values in Table 2 were converted from mg/organ to mg/kg by G. Tanaka, 1984. Concentrations of elements in human body. In: M. Saiki (Ed.), Environmental Radioactivity. Soft-Science Co., Japan, pp. 529-533 (in Japanese).) Iyengar, G.V., 1976. Homogenized sampling of bone and other biological materials. Radiochem. Radioanal. Lett., 24: 35. Iyengar, G.V., 1985. Concentrations of 15 trace elements in some selected adult human tissues and body fluids of chemical interest from several countries: Results from a pilot study for the establishment of reference values. KFA Report Jii1-1974, F.R.G. Johnson, C.A., 1976. The determination of some toxic metals in human liver as a guide to normal levels in New Zealand (Part 1). Anal. Chim. Acta, 81: 69-74. Johnson, C.A., J.F. Lewin and P.A. Fleming, 1976. The determination of some toxic metals in human liver as a guide to normal levels in New Zealand (Part 2). Anal. Chim. Acta, 82: 79~82. Kim, N.B., H.W. Chung and K.Y. Lee, 1985. Trace element analysis of human head hair by neutron activation technique. In: Health-related Monitoring of Trace Element Pollutants using Nuclear Techniques. IAEA-TECDOC.330, pp. 169-174. Kitamura, S., K. Sumino, K. Hayakawa and T. Shibata, 1978. Contents of heavy metals in hair of the inhabitants in Nara Prefecture, Japan. J. Hyg., 33: 101.

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