CADMIUM, ZINC, COPPER AND METALLOTHIONEIN LEVELS IN THE K I D N E Y AND L I V E R OF H U M A N S F R O M C E N T R A L P O L A N D * EWA M. BEM, BRONISLAW W. K A S Z P E R t, CZESLAW ORLOWSKI, JERZY K. PIOTROWSKI, G A B R I E L A WOJCIK and EWA Z O L N O W S K A
Department of Toxicological Chemistry, Institute of Environmental Research and Bioanalysis, Medical University, 90-151 Lodz, Muszyhskiego 1, Poland. (Received: August 1991)
Abstract. Cd, Zn, Cu, and metallothionein (MT) levels have been determined in the renal cortex and liver of 70 persons who died in Lodz and its surroundings in the years 1985-1989. The mean concentrations were: 44.9-4-28.6 #g Cd/g, 52.04-16.7/zg Zn/g, 2.44-1.0 #g Cu/g, 0.794-0.40 #mol Hg/g, and 3.54-1.8 #g Cd/g, 66.74-30.5/zg Zn/g, 4.94-2.1 #g Cu/g, 0.504-0.38/zmol Hg/g wet tissue in renal cortex and liver, respectively, with mean age 54.04-13.8. Smokers showed 2.4 times higher levels of Cd in the renal cortex than non-smokers. The mean body burden of Cd was 33.44-17.3 mg. Smoking increases it twofold from 22.0 mg in non-smokers to 41.8 mg in smokers.
1. Introduction
Cadmium is a toxic metal of great concern. In the environment cadmium can be found everywhere: in the soil, water, air, as well as in food and cigarettes. Cadmium production, which started only in the nineteenth century, had, by the seventies of the present century, amounted to 15 000-18 000 tons y-1 [1]. Therefore anthropogenic sources of atmospheric cadmium emissions are almost 20-fold higher than the emissions from natural sources [2]. This has caused an almot 5-fold increase in cadmium body burden in humans [3]. The biological half-life of cadmium is about 20 y and the element accumulates mainly in the renal cortex and the liver, which jointly contain 50% of the total amount of cadmium in the organism (the kidney alone contains one third [4]). The kidney is the critical organ in long-term, low-level (environmental) exposure, and cadmium concentration in the renal cortex (CdK) grows with age, reaching its maximum at c a . 50 years of age [4]. From the fact that cadmium accumulation in humans may result from a variety of sources it follows that the best way of cadmium exposure evaluation and risk assessment is biological monitoring. CdK is a source of information on cadmium accumulation during a lifetime and the most certain source for cadmium exposure evaluation for the general population. Monitoring investigations of CdK levels have been carried out in Belgium, China, India, Israel, Sweden, the USA, and Yugoslavia as part of a UNEP/WHO programme started in 1978. The results were published in 1982 [5]. The project drew the attention of many investigators to the problem of environmental cadmium This work was supported by the grant CPBR 11.12(C-56/86) from the Institute of Rural Medicine, Lublin, Poland. Deceased.
Environmental Monitoring and Assessment 25: 1-13, 1993. (~) 1993 Kluwer Academic Publishers. Printed in the Netherlands.
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EWA M. BEM ET AL.
exposure of general populations in many countries. Many papers on that subject have followed [6-22]. Data conceming environmental exposure to cadmium in Poland are only flagmentary [23-30]. The aim of the present paper was to collect monitoring data conceming environmental cadmium exposure of central Poland's general population.
2. Materials and methods 2.1. SUBJECTS The investigations were carried out on people who died in the years 1985-1989, as inhabitants of Lodz or its close surroundings. The autopsy was performed at the Department of Pathology, Medical University, Lodz, 384-13.6 hours after death, on average. Renal cortex and liver samples were collected from persons with no occupational exposure to cadmium and with no history of liver or kidney diseases. No macroscopic lesions were found in these organs at autopsy. Information about the patient (taken from the case history) was included in a questionnaire concerning the sex, age, body weight, the mass of the kidney and the liver, profession, dwelling place, and smoking history. Unfortunately, full information was not always available. The samples were obtained from 70 persons (25 women, 7 of them smokers and 9 non-smokers, and 45 men - 28 smokers and 4 non-smokers), mean age 544-13.8. Data for subjects (13 men and 9 women) whose smoking habits could not be identified were not included in the analysis of smokers/non-smokers. 2.2. AREA Lodz (population 800 000) is the second largest city in Poland and is a centre of the textile industry, but with no heavy industry. Mean cadmium concentrations in the air have changed during the last decade from 0.005 #g/m 3 in 1971 [31] to 1-10 #g/m 3 in 1980 [32]. Mean cadmium concentrations in the blood of the inhabitants of this region were: 3.01 #g Cd/1; in non-smokers 1.93 #g/1 and in smokers 4.63 #g/1 [32]. Urine Cd concentrations were 1.12 #g/l; in non-smokers 0.72 #g/1 and in smokers 1.73 #g/1 [32]. 2.3. SAMPLE PREPARATION
Samples (ca. 20 g) of tissues were collected from the lower left pole of the kidney after separating the cortex from the medulla, and from the upper part of the left lobe of the liver, and then placed in acid washed (10% HNO3 - 48 h) polyethylene containers, which were then closed tightly and frozen at -20°C, and thus stored until analysis.
CADMIUM IN HUMAN KIDNEY AND LIVER
3
2.4. ANALYTICAL METHODS
Metals (Cd, Zn, Cu) were measured by flame AAS (Pye-Unicam SP-192) with deuterium background correction after tissue digestion with a mixture of acids (HNO3, HCIO4, H2SO4, Merck, Suprapure) as described in [33]. Three samples were always prepared from each tissue. The detection limits were: 0.02 #g Cd/ml, 0.01 #g Zn/ml, and 0.04 #g Cu/ml. The relative standard deviation for 10 determinations at 0.2 #g/ml was 5%, 2% and 5 % for Cd, Zn and Cu, respectively. Metallothionein (MT) was determined in full homogenates using the 2°3Hg method [34] giving a relative standard deviation of 5%. Levels of MT were expressed in #molHg/g wet tissue to enable easy comparison with MT levels determined by different methods. 2.5. ANALYTICAL QUALITY ASSURANCE
All the analyses were performed under strictly defined conditions alongside samples of internal laboratory control based on a CL- 1 standard (lyophilized cabbage leaves) supplied by AGH (Poland) with certified metal levels. To further assure the accuracy of our determinations we participated in the interlaboratory analytical quality control program conducted by the Institute of Veterinary Science (Poland) with the cooperation of experts from the EC and the United States Department of Agriculture. In three received samples our results were: 0.991, 0.989 and 0.983 #g Cd/g. The correct values were: 0.9974-0.0610, 0.9764-0.0854, and 1.014-t-0.0589 #g Cd/g, respectively. 2.6. STATISTICAL ANALYSIS
All the determined values revealed log-normal distributions. All the parameters for each distribution are given in Table I along with the arithmetic mean and standard deviation for easier comparison with the results of other authors. Student t-tests were used to evaluate statistical differences between groups. 3. Results and discussion The concentrations of cadmium, zinc, and metallothionein in the renal cortex (CdK, ZnK, and MTK) and in the liver (CdL, ZnL, and MTL) for the whole investigated population, as well as Cd levels in relation to smoking and gender are given in Tables I and II. The dependence of CdK on age is shown in Figure 1. A very wide range of concentrations (4.0-133.0 #g/g) was observed, with levels increasing up to about 50 years of age and decreasing thereafter (Table III), which is in agreement with previous observations of other authors [4,5,7,9,10,13,17,18,20]. CdK levels found in this study for individuals who had had no occupational exposure (GM 35.5 #g/g) are among the highest in Europe (Belgium 30.5 #g/g, Sweden 13.1 #g/g, Jugoslavia 24.2 #g/g [5], FRG 12 and 19 #g/g [11], 25.7 #g/g [ 13], 17.1 #g/g [20], CSFR 18.7 #g/g [20]). Higher levels were only found in Japan
4
EWA M. BEM ET AL.
TAB LE I Statistic characterization of the population investigated and monitoring parameters determined.
Age
Kidney Cortex Cd Zn MT /zg/g /zg/g #mol Hg/g
Cd /zg/g
Liver Zn MT #g/g /zmol Hg/g
Total
n x SD GM GSD Median 90-percentile
70 54.0 13.8 52.0 1.3 49.2 71.9
70 44.9 28.6 35.5 2.1 31.6 82.0
70 52.0 16.7 49.6 1.4 49.2 73.7
63 0.79 0.40 0.68 1.78 0.63 1.31
70 3.5 1.8 3.0 1.8 2.9 5.9
70 66.7 30.5 61.6 1.5 65.0 106.4
63 0.50 0.38 0.40 1.86 0.44 0.99
Smoker
n x SD GM GSD Median
35 51.9 9.2 51.1 1.2 50.4
35 62.5, 26.1 57.5 1.5 57.1
35 55.5 15.2 53.4 1.3 54.0
29 1.01. 0.39 0.92 1.6 0.87
35 4.2 1.7 3.8 1.6 3.6
35 72.7 34.6 66.8 1.5 67.3
29 0.59 0.47 0.46 2.00 0.47
90-percentile
63.9
96.4
75.3
1.52
6.3
117.6
1.21
Nonsmoker
n x SD GM GSD Median 90-percentile
13 47.9 16.7 44.5 1.6 45.9 69.7
13 26.2* 17.4 20.2 2.3 19.8 48.9
13 49.1 18.0 46.1 1.5 45.5 72.5
12 0.49* 0.26 0.42 1.85 0.42 0.83
13 2.9 2.4 2.3 2.1 2.3 6.0
13 62.0 17.7 59.6 1.4 59.3 85.0
12 0.41 0.16 0.38 1.50 0.40 0.62
Females
n x SD GM GSD Median 90-percentile
25 51.8 15.5 49.4 1.4 48.4 71.9
25 39.5 28.2 30.3 2.2 29.9 76.1
25 52.6 18.1 49.9 1.4 49.2 76.2
22 0.72 0.43 0.60 1.95 0.57 1.28
25 3.7 2.1 3.1 1.9 3.0 6.4
25 61.2 19.4 58.7 1.3 58.8 86.4
22 0.44 0.34 0.37 1.78 0.36 0.88
45 69.8 35.1 63.3 1.5 65.6 115.3
41 0.53 0.40 0.43 1.90 0.46 1.05
n 45 45 45 41 45 x 55.2 47.9 51.7 0.82 3.4 SD 12.7 28.6 16.0 0.39 1.7 GM 53.6 38.7 49.4 0.73 3.0 GSD 1.3 2.1 1.4 1.70 1.8 Median 51.7 35.7 49.3 0.70 19.4 90-percentile 71.8 85.2 72.5 1.30 5.7 x = mean, SD = standard deviation, G M = geometric mean, GSD = geometric standard deviation; • = p < 0.001.
Males
CADMIUM IN HUMAN KIDNEY AND LIVER
5
TABLE II Cadmium levels (/zg/g wet weight) in kidney cortex and liver in relation to smoking and gender. Total
Females
Males
70 54.04-13.8 44.94-28.6
Kidney Cortex 25 51.84-15.5 39.54-28.2
45 55.24-12.7 47.94-28.6
35
7
28
Age x4- SD
51.94-9.2 62.54-26.1.
44.9-4- 9.8 62.44-31.6. * *
53.74- 8.3 62.54-25.2**
Nonsmoker
n Age a:4- SD
13 47.94-16.7 26.24-17.4.
9 50.74-14.5 29.24-18.4. * *
4 41.84-22.0 19.54-14.9.*
Total
rz Age x4- SD
70 54.04-13.8 3.54- 1.8
Liver 25 51.84-15.5 3.74- 2.1
45 55.24-12.7 3.44- 1.7
Smoker
n Age z4- SD
35 51.94- 9.2 4.24- 1.7
7 44.94- 9.8 4.64- 1.4
28 53.74- 8.3 4.04- 1.7
Nonsmoker
n Age z4- SD
13 47.9-4-16.7 2.94- 2.4
9 50.74-14.5 3.34- 2.7
4 41.84-22.0 2.24- 1.3
Total
Smoker
n Age x4- SD n
* = p < 0.001; ** = p < 0 . 0 0 5 ; * * * = p < 0.02.
(56.2 #g/g [5], 90.1 #g/g [10], 91.37 #g/g [21] and 93.4 #g/g [12]). It is known that smoking markedly affects the cadmium levels in the organism [4,5]. The information concerning smoking was available for part of the population only. It has been found that smokers (62.5 #g/g) show c a . 2.4 times (Tables I and II) higher CdK than non-smokers (26.2/,g/g), with only a slight age difference between both groups (51.9 and 47.9 years, Tables I and II). Considering all age groups the CdK ratio for smokers and non-smokers is c a . 2 for women and c a . 3 for men (Table II). Similar values for heavy smokers have been given [6,13,16] while the other data [5,1 l, 18,20] point only to several dozen per cent growth. The high mean CdK level (44.94-28.6/,g/g) is the result of the smoking habits of a large part of the population investigated. Tobacco produced in Poland, like that of the GDR and Switzerland, contains high amounts of cadmium: 1.3-3.20 #g Cd/cigarette [35,36].
6
EWA M. BEM ET A L
TABLE Ill Cadmium, zinc and metallothionein concentrations* in kidney c o ~ x and liver in relation to age and smoking. 20-40 yr Total
n Age Cd Zn MT
11 36.14- 3.4 52.04-38.6 60.14-19.2 0.894-0.50
41-60 yr > 61 yr Kidney Cortex 34 23 52.04- 5.9 68.74- 5.6 53.4±26.2 31.9-t-21.0 52.54-14.4 48.64-18.0 0.864-0.41 0.694-0.34
Smoker
n Age Cd Zn MT
5 37.04- 2.6 81.14-33.5 65.54-18.2 1.14-0.54
24 52.04- 5.9 60.44-25.1 53.74-15.1 0.97+0.41
Nonsmoker
n Age Cd Zn MT
2 35.8 17.4 64.0 0.56
6 3 52.34- 5.3 66.74- 3.5 3 8 . 8 - 4 - 1 5 . 8 17.24-11.5 55.04-11.2 34.74-11.2 0.634-0.27 0.374-0.23
Total
n Age Cd Zn MT
11 36.14- 3.4 3.84- 1.8 66.74-27.6 0.444-0.46
Liver 34 52.04- 5.9 3.74- 1.7 68.14-28.3 0.544-0.35
23 68.74- 5.6 3.44- 2.0 65.74-36.7 0.494-0.40
Smo~r
n Age Cd Zn MT
5 37.04- 2.6 4.94- 0.8 79.84-35.6 0.584-0.74
24 52.04- 5.9 4.0+ 1.6 70.24-31.7 0.594-0.41
6 64.04- 3.1 4.14- 2.3 76.64-48.9 0.624-0.56
6 64.04- 3.1 55.6+20.4 55.9+12.0 1.14-0,16
n 2 6 3 Age 35.8 52.34- 5.3 66.7q- 3.5 Cd 2.3 2.8-t- 1.9 4.7-4- 3.9 Zn 57.7 70.54-14.0 52.04-26.5 MT 0.33 0.484-0.14 0.374-0.26 * Metals (Cd,Zn) are expressed as #g/g wet weight (mean-4-SD), MT is expressed as/zmol Hg/g wet weight (mean+SD).
Nonsmoker
7
CADMIUM IN HUMAN KIDNEY AND LIVER
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AGE(YEARS) Fig. 1. Cadmium in kidney cortexin relation to age in deceasedpersons from central Poland.
These amounts are higher than the cadmium levels in imported cigarettes sold on the Polish market. These amounts are: 1.18-1.73, 0.91-1.96, 0.5-1.10 and 0.850.91 #g/cigarette for FRG, American, Finnish and Cuban cigarettes, respectively [36]. However, for economic reasons, smokers prefer Polish cigarettes. No effect of sex on CdK level has been found (Tables I and II), and small differences are statistically insignificant. The average mean CdK found in this study is lower than the generally accepted (on the basis of data from occupational exposure) critical concentration of 200 #g/g [4]. However, CdK corresponding to 90% is already 82 #g/g, which for a part of the investigated population is responsible for a safety factor of only 2 (for nonsmokers 90% makes up 48.9 #g/g and the safety factor is 4). The results of recent investigations [37] on renal effects caused by cadmium in the general population in Belgium led to the conclusion that renal risk can be observed after renal excretion has exceeded 2 #g Cd/24 h. This occurred in 10% of the population. Such excretion corresponds to a CdK concentration of c a . 50 #g/g [37]. Furthermore, Lindqvist [38] claims that the critical CdK concentration should be much lower than that accepted at present, and suggests the value of 30 #g/g. It is worth noticing that CdK for non-smokers in the age range 41-60 years is 38.8 #g/g (Table III). Thus, even in non-smokers for whom the only source of Cd is food, the safety margin is not great, even with the now commonly assumed critical value of 200 #g/g. CdK levels for non-smokers in general (26.2 #g/g) are close to comparable values in Belgium [5]. The levels should reflect daily cadmium intake with food.
8
EWA M. BEM ET AL.
TABLE IV Correlation coefficients in kidney cortex and liver of the subjects studied. N
/g
Regression equation
Kidney Cortex Cd - Zn
70
0.40,
Zn(#g/g) = 0.23
C d - MT
63
0.82,
MT(/zmol Hg/g) = 1.32
Cd(#g/g) + 41.6
Zn - MT Zn - Cu
63 70
0.52* 0.40*
MT(/zmol Hg/g) = 0.85 Zn(/zmol/g) + 0.12 Cu(/zg/g) = 0.024 Zn(#g/g) + 1.17
Z n - MT
63
0.79,
MT(#mol Hg/g) = 0.618
Cu - age
70
-0.29, • •
C d K - CdL ZnK-ZnL
70 70
0.58* 0.61,
M T K - MTL
63
0.38**
Cd(#me!/F) ~ 0.2 '~
Liver Cu(#g/g)=-0.044
Z n ( # m o l / g ) - 0.135
Age (years) + 7.32
Kidney/Liver CdL(#g/g) = 0.037 CdK(#g/g) + 1.84 ZnL(#g/g) = 1.11 ZnK(#g/g) + 8.88 MTL(#mol Hg/g) = 0.352
MTK(/zmol Hg/g) + 0.222
* = p < 0.001; ** = p < 0.005; * * * = p < 0.02.
Such data for Poland are available, but quite divergent e.g. 20 #g [39] and 65/,g [40], and only partially reveal a violation of the ADI. In Belgium the daily cadmium intake is 15 #g [41]. However, CdK levels in non-smokers are not always a simple reflection of the daily cadmium intake. For instance, in the FRG intakes are 30-55 #g Cd/day [39], while CdK levels in non-smokers are markedly lower than those observed in our study and amount to 13.3 #g/g [20], c a . 16.5 #g/g [13], and 11.7 #g/g [11]. Similarly low levels (13.9/,g/g) have been found in non-smokers in England [18] with daily intakes in the range 8.6-35 #g [39]. It is known that cadmium in the human kidney is bound mainly to metallothionein [42], a protein induced by heavy metals, whose level has been suggested as a marker of exposure to these metals [9]. MTK levels found in this study are in the range 0.1-2.01 #molHg/g. The dependence of MTK on age is similar to cadmium - the levels grow up to about 55 years and then decrease (results partly shown in Table III), which is in agreement with the results of refs. [9,43]. The mean MTK level was 0.79-t-0.40 #mol Hg/g and is almost three times higher than that in Canada [9], similar to the CdK mean. No statistically significant differences in MTK levels between men and women have been found (Table I). In accordance with the fact that MT in humans is a Cd,Zn protein [42], high correlations in the renal cortex between MT and Cd levels and between MT and Zn levels have been observed (Table IV). Similarly to the CdK findings, smoking increases the MTK level by a factor of two (Table I). MT levels are not easy to compare directly for several reasons. It has been
CADMIUM IN HUMAN KIDNEY AND LIVER
9
found recently [44] that due to postmortem changes in tissue cadmium binding at room temperature, MT decomposition follows, with further cadmium release. The cadmium is then bound to high molecular weight proteins. The process is not observed, however, even after seven days, if the tissues are stored at - 9 ° C (refrigerator freezer) or - 4 0 ° C (dry ice). Therefore the time between death and autopsy is an important factor affecting MT levels in humans. It is known that alcohol consumption increases MTK in humans [43]. Stress may be also expected to affect the levels, as has been found in rats [45]. An additional factor complicating the comparison of MT levels obtained in various laboratories is the nonspecificity of the different analytical methods used [46]. That is why we think that only trends conceming the MT levels and not their absolute values can be compared, and therefore MTK levels are of limited monitoring value. Similarly to CdK levels, zinc levels in the renal cortex (ZnK) show great scatter of individual values (26.5-106.0 #g/g) (Tables I and III). Although zinc in the renal cortex is only partly bound by Zn,Cd-MT, similar changes of cadmium and zinc levels with age are revealed in the clear correlation between them (Table IV). No effect of smoking on ZnK has been found (Table I) as opposed to the results of Blanusa et al. [16] who observed a ca. 40% ZnK increase in smokers. The mean ZnK level 52.0+16.7 #/g is slightly higher than that observed in Canada (40.1+3.2 #g/g [9]) and India (36.044-9.22 #g/g [17]). The Cd]Zn weight ratio reaches the maximum value (1.02) in the 41-60 age group (Table III), which confirms the results of other authors [9,17]. Values of the Cd/Zn ratio found in these studies are low, which is connected with lower levels of cadmium. Though it is known that the kidney is a critical organ in the case of long-term cadmium exposure, when CdK exceeds 200 #g/g the concentration of cadmium in the kidney decreases, despite the further growth of exposure. The value of 200 #g/g in a normal kidney corresponds to 30 #g/g in the liver [8]. Roels et al. [8] suggest that cadmium levels in the liver grow with exposure, even after exceeding the critical value. The results of Honda and Nogawa [12] confirm this hypothesis, and thus CdL levels have become interesting for monitoring purposes. CdL, ZnL and MTL concentrations observed in the population investigated are shown in Table I. All the data are in accordance with our preliminary data published earlier [26] as well as with other data for that region [32,47]. The mean CdL level is 3.5+1.8 #g/g and is close to that observed in polluted areas in Belgium (0.9-3.3 #g/g [7]) and in the FRG (3 #g/g [11]). Much higher CdL concentrations, amounting to ca. 10 #g/g in nonpolluted areas and ca. 60 #g/g in polluted areas, have been observed only in Japan [10]. As can be seen from the data in Table III no growth of CdL could be observed with age. The CdL were correlated with those of CdK (Table IV). Similarly to the kidney, no difference between men and women could be found (Tables I and II). Unlike to the kidney cortex the elevated CdL levels in smokers were not statistically different from non-smokers. In our opinion monitoring value of CdL levels is of little use in the case of low and moderate cadmium exposure.
10
EWA M. BEM ET AL.
Cadmium in human liver is bound to MT which in this organ is Zn-thionein [48,49]. In our material this is clearly reflected in the presence of a marked correlation between ZnL and MTL, and the lack of correlation between CdL and MTL. However, we have observed a correlation between MT levels in the renal cortex and the liver (Table IV). The mean ZnL concentration 66.7-+-30.5 #g/g is close to the levels found in Japan [50,51] and Canada [9], and does not depend on sex and smoking habits (Table I). A correlation exists between Zn levels in the liver and in the renal cortex (Table IV). Mean copper levels in the renal cortex and the liver are 2.4+1.0 #g/g and 4.9-t-2.1 #g/g, respectively (not included in the tables). These levels are not correlated with other parameters studied (sex, smoking), except for the decreasing tendency with age seen in the liver (Table IV). The cadmium body burden was calculated by means of two methods: (1) assuming that the kidney and the liver contain 50% of the total cadmium in the organism: and (2) assuming that the kidney contains 1/3 of the total cadmium in the organism. In both cases the 1.25 coefficient was applied, reflecting the ratio of concentration in the cortex to the concentration in the whole kidney [19]. A very high correlation (r : 0.95) between body burden calculated with both the methods has been observed. Mean body burden (K+L) is 33.4+17.3 mgCd (GM 28.5 mg, GSD 1.9). Smoking doubles the mean body burden (from 22.0 mg to 41.8 mg). The main reason for the higher body burden in men (36.2 mg) than in women (28.1 mg) seems to be smoking, since there were 28 smokers in the 45 person group of men, and only 7 smokers in the 25 person group of women. The mean body burden of cadmium in Poland is much higher than in Southem Bavaria (21.9 mg [14]) and even in Japan (21 mg [52]). The comparison of body burden in non-smokers (22.0 mg) with the same levels in Bavaria (13.5 mg) [14] allows us to suppose that dietary cadmium intake is not comparable in both countries. The markedly higher body burden in Polish smokers (41.8 mg), compared with the Bavarian figure of 33.2 mg [14], makes it possible to conclude that, apart from food, smoking is the main reason for high cadmium levels in the population investigated.
Acknowledgements The authors wish to express their gratitude to Dr. Cz. Dmuchowski (Department of Pathology, Medical University, Lodz) for making available the proper autopsy material, Mrs. M. Skrzypifiska-Gawrysiak, M.Sc., for interlaboratory quality control, and Mr. A. D~bicki for his assistance in the determinations.
References 1.
Piotrowski, J.K. and Coleman, D.D.: 1980, 'Environmental Hazards of Heavy Metals: Summary
CADMIUMIN HUMANKIDNEY AND LIVER
2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24.
11
Evaluation of Lead, Cadmium and Mercury', MARC Report, No. 20. Lantzy, R.J. and MacKenzie, F.T.: 1979, 'Atmospheric Trace Metals: Global Cycles and Assessment of Men's Impact', Geochim. Cosmochim. Acta 43, 511-525. Drasch, G.A.: 1983, 'An Increase of Cadmium Body Burden for This Century- An Investigation on Human Tissues', Sci. Total Environ. 26, 111-119. Friberg, L., Piscator, M., Nordberg, G.F., and Kjellstr6m, T.: 1974, Cadmium in the Environment, 2nd edn. CRC Press Inc. Cleveland. Vahter, M.: 1982, Assessment of Human Exposure to Lead and Cadmium through Biological Monitoring, National Swedish Institute of Environmental Medicine, Stockholm. Ellis~ K.J., Yuen, K., Yasumura, S., andCohn, S.H.: 1984, 'DoseResponseAnalysisofCadmium in Man: Body Burden vs Kidney Disfunction', Environ. Res. 33, 216-226. Lauwerys, R., Hardy, R., Job, M., Buchet, J-P., Roels, H., Bruaux, P., and Rondia, D.: 1984, 'Environmental Pollution by Cadmium and Cadmium Body Burden: An Autopsy Study', Toxicol. Lett. 23, 287-289. Roels, H., Lauwerys, R., and Dardenne, A.N.: 1983, 'The Critical Level of Cadmium in Human Renal Cortex: A Reevaluation', Toxicol. Lett. 15, 357-360. Chung, J., Nartey, N.O., and Cherian, M.G.: 1986, 'Metallothionein Levels in Liver and Kidney of Canadians - A Potential Indicator of Environmental Exposure to Cadmium', Arch. Environ. Health 41, 319-323. Nogawa, K., Honda, R., Yamada, Y., Kido, T., Tsuritani, I., Ishizaki, M., and Yamaya, H.: 1986, 'Critical Concentration in Kidney Cortex of Humans Exposed to Environmental Cadmium', Environ. Res. 40, 251-260. Thtirauf, J., Schaller, K.H., Valentin, H., Welte, D., Grote, K., and Schellmann, B.: 1986, 'Cadmium Concentrations in Autopsy Material from Differently Polluted Areas of West Germany (FRG)', Zbl. Bakt. Hyg. B 182, 337-347. Honda, R. and Nogawa, K.: 1987, 'Cadmium, Zinc and Copper Relationships in Kidney and Liver of Humans Exposed to Environmental Cadmium', Arch. Toxicol. 59, 437-442. Summer, K.M., Drasch, G.A., and Heilmaler, H.E.: 1986, 'Metallothionein and Cadmium in Human Kidney Cortex: Influence of Smoking', Human Toxicol. 5, 27-33. Drasch, G.A., Kauert, G., and Mayer, L.: 1985, 'Cadmium Body Burden of an Occupationally Non-Burdened Population in Southern Bavaria (FRG)', Int. Arch. Occup. Health 55, 141-148. Elinder, C.G., Piscator, M., and Linnman, L.: 1984, 'Cadmium and Zinc Relationship in Kidney Cortex, Liver and Pancreas', Environ. Res. 33, 216-226. Blanusa, M., Kralj, Z., and Bunarevic, A.: 1985, 'Interaction of Cadmium Zinc and Copper in Relation to Smoking Habit, Age and Histopathological Findings in Human Kidney Cortex', Arch. Toxicol. 58, 115-117. Pandya, C.B., Parikh, D.J., Patel, T.S., Kulkarni, P.K., Sathawara, N.G., Shah, G.M., and Chatterjee, B.B.: 1985, 'Accumulation and Interrelationship of Cadmium and Zinc in Human Kidney Cortex', Environ. Res. 36, 81-88. Scott, R., Anghey, E., Fell, G.S., and Quinn, M.J.: 1987, 'Cadmium Concentration in Human Kidneys from the UK', Human. Toxicol. 6, 111-119. Svatengren, M., Elinder, C.G., Friberg, L., and Lind, B.: 1986, 'Distibution and Concentration of Cadmium in Human Kidney', Environ. Res. 39, 1-7. Hahn, R.,Ewers, U.,Jerman, E.,Freier, I.,Brockhaus, A.,andSchlipkter, H.W.: 1987,'Cadmium in Kidney Cortex of Irdaabitants of North-West Germany: Its Relationship to Age, Sex, Smoking and Environmental Pollution by Cadmium', Int. Arch. Occup. Environ. Health 59, 165-176. Kido, T., Tsuritani, I., Honda, R., Yamaya, H., Ishizaki, M., Yamada, Y., and Nogawa, K.: 1988, 'Selenium, Zinc, Copper and Cadmium Concentration in Livers and Kidneys of People Exposed to Environmental Cadmium', J. Trace Elem. Electrolytes Health Dis. 2, 101-14. Von Grukl, H. and Gilek, U.: 1988, 'Untersuchungen zur Cadmiumbelastung der Bev01kerung irn Raum Augsburg (Sfiddeutschland)', J. Clin. Chem. Clin. Biochem. 26, 627-633. Piotrowski, J.K., Zelazowski, A., Pasek, W., and L~giewski, A.: 1978, 'Cadmium Binding in Human Kidney', Bromat. Chem. Toksykol. XI, 323-328. Slotwifiska-Palugniok, E., and Sybirska, H.: 1984, 'Zinc, Cadmiujm and Lead Levels in Human Kidney and Liver', II Conference of the Polish Toxicological Society, L6d~.
12 25. 26. 27. 28. 29. 30. 31. 32. 33.
34. 35. 36. 37.
38. 39. 40. 41. 42. 43. 44. 45.
EWA M. BEM ET AL. Slotwifiska-Palugniok, E. and Sybirska, H.: 1987, 'Exposure to Cadmium, Lead and Zinc in the Inhabitants of Upper Silesia Based on the Metal Levels in Selected Autopsy Samples', III Conference of the Polish Toxicological Society, Kozubnik. Bern, E.M., Piotrowski, LK., Sobczak-Kozlowska, M., and Dmuchowski, Cz.: 1988, 'Cadmium, Zinc, Copper and Metallothionein Levels in Human Liver', Int. Arch. Occup. Environ. Health 60, 413-417. Jaworowski, Z., Bilikiewicz, J., Pietrzak-Flis, Z., and Suplifiska, M.: 1988, 'Influence of Industry on Contamination of Polish Population with Natural Radionuclides and Heavy Metals', Arch. Ochr. ~rod. 1, 101-112. Bem, E.M., Piotrowski, J.K., and Koziara, H.: 1989, 'Cadmium and Metallothionein Levels in the Liver of Humans Exposed to Environmental Cadmium in Upper Silesia, Poland', ToxicoI. Left. 45, 35-39. Jakubowski, M., Trojanowska, B., Ra£niewska, G., Halatek, T., Trzcinka-Ochocka, M. and Szymczak, W.: 1990, 'Environmental Exposure to Cadmium: Impact on Renal Function', Toxicol. Environ. Chem. 27, 17-29. Kulka, E., Sokolowska, D., and Dutldewicz, T.: 1990, 'Toxic Metals (Cd,Pb) in Blood of Children from Bieszczady Area', IV Conference of the Polish Toxicological Society, Jastrz~bia G6ra. Just, J. and Kelus, J.: 1971, 'Cadmium in Atmospheric Air of 10 Selected Towns in Poland', Rocz. PZH XII, 249-256. Jakubowski, M., Ra~niewska, G., Trzcinka-Ochocka, M., Trojanowska, B.: 1991, 'Lead and Cadmium Levels among Inhabitants of Three Regions in Poland', In press. Bem, E.M., Tegegnework, H., and Piotrowski, J.K.: 1986, 'The Choice of the Optimal Mineralization Method of Biological Samples for Zinc and Copper Determination', Bromat. Chem. Toksykol. XIX, 37-41. Zelazowski, A.J. and Piotrowski, J.K.: 1987, 'A Modified Procedure for Determination of Metallothionein-like Proteins in Animal Tissue', Acta Biochim. Pol. 24, 325-333. Bronisz, H., Szost' T., Lipska, M., and Zawada, M.: 1983, 'Cadmium Content in Cigarettes', Bromat. Chem. Toksykol. XVI, 121-127. Zawadzka, T., Bruli6ska-Ostrowska, E., Wojciechowska-Mazurek, M., Cwiek, K., and Starska, K.: 1989, 'Determination of Cadmium and Lead Content in Polish and Foreign Cigarettes', Rocz. PZH XL, 145-151. Buchet, J.P., Lauwerys, R., Roels, H., Bernard, A., Bruaux, P., Claeys, F., Ducoffre, G., de Plaen, P., Staessen, J., Amery, A., Lijnen, P., Thijs, L., Rondia, D., Sartor, F., Saint-Remy, A., and Nick, L.: 1990, 'Renal Effects of Cadmium Body Burden of the General Population', Lancet 336, 699-702. Lindqvist' B., Nystr6m, K., Stegmayr, B., Wirell, M., and Eriksson, A.: 1989, 'Cadmium Concentration in Human Kidney Biopsies', Scand. J. Urol. Nephrol. 23, 213-217. Chmielnicka, J. and Cherian, M.G.: 1986, 'Environmental Exposure to Cadmium and Factors Affecting Trace-Element Metabolism and Metal Toxicity', Biol. Trace Element Res. 10, 243261. Nabrzyski, M. and Gajewska, R.: 1982, 'Mercury, Cadmium and Lead in Daily Food', Roczn. PZH XXXIII, 19-26. Buchet, J.P., Lanwerys, R., Vandevoorde, A., and Pycke, J.M.: 1983, 'Oral Daily Intake of Cadmium, Lead, Manganese, Copper, Chromium, Mercury, Calcium, Zinc and Arsenic in Belgium: A Duplicate Meal Study', Fd. Chem. Toxic. 21, 19-24. Syversen, L.M.: 1975, 'Cadmium-Binding in Human Liver and Kidney', Arch. Environ. Health 30, 158-164. Drasch, G.A., Kretschmer, E., Neidlinger, P., and Summer, K.H.: 1988, 'Metallothionein in Human Liver and Kidney: Relationship to Age, Sex, Diseases and Tobacco and Alcohol Use', J. Trace Elem. Electrolytes Health Dis. 2, 233-237. Piotrowski, LK., Orlowski, Cz., and Kaszper, B.W.: 1989, 'Postmortem alterations in Tissue Binding of Cadmium in Rat', Bromat. Chem. Toxicol. XXII, 15-18. Oh, S.H., Deagen, J.T., Whanger, P.D., and Weswig, P.H.: 1978, 'Biological Function of Metallothionein. V. Its Induction in Rats by Various Stresses', Amer. J. Physiol. 234, E282-E285.
CADMIUM IN HUMANKIDNEY AND LIVER 46.
13
Dieter, H.H., Miiller, L., Abel, J., and Summer, K.H.: 1986, 'Determination of Cd-Thionein in Biological Materials: Comparative Standard Recovery by Five Current Methods Using Protein Nitrogen for Standard Calibration', Toxicol. Appl. Pharma~ol. 85, 380-388. 47. Adamska-Dyniewska, H. and Trojanowska, B.: 1981, 'The Relationship Between Cadmium Concentration in Liver Biopsy Material and in Venous Blood', Acta Med. Pol. 22, 319-323. 48. Btichler, R.H.O. and K~igi, J.H.R.: 1974, 'Human Hepatic Metallothionein', FEBS Lett. 39, 229-234. 49. Hunziker, RE. and K~igi, J.H.R.: 1985, 'Isolation and Characterization of Six Human Hepatic Metallothioneins', Biochem. J. 231, 375-382. 50. Sumino, K., Hayakawa, K., Shibata, T., and Kitamura, S.: 1975, 'Heavy Metals in Normal Japanese Tissues', Arch. Environ. Health 30, 487-494. 51. Onosaka, S., Min, K.-S., Fukuhara, C., Tanaka, K., Tashiro, S-I., Shimizu, I., Furata, M., Yasutomi, T., Kobashi, K., and Yamamoto, K.-I.: 1986, 'Concentrations of Metallothionein and Metals in Malignant and Non-Malignant Tissues in Human Liver', Toxicology 38, 261-268. 52. Kjellstr6m, T.: 1979, 'Exposure and Accumulation of Cadmium in Populations from Japan, the United State, and Sweden', Environ. Health Persp. 28, 169-197.
Department of Toxicological Chemistry, Institute of Environmental Research and Bioanalysis, Medical University, 90-151 Lodz, Muszyhskiego 1, Poland. (Received: August 1991)
Abstract. Cd, Zn, Cu, and metallothionein (MT) levels have been determined in the renal cortex and liver of 70 persons who died in Lodz and its surroundings in the years 1985-1989. The mean concentrations were: 44.9-4-28.6 #g Cd/g, 52.04-16.7/zg Zn/g, 2.44-1.0 #g Cu/g, 0.794-0.40 #mol Hg/g, and 3.54-1.8 #g Cd/g, 66.74-30.5/zg Zn/g, 4.94-2.1 #g Cu/g, 0.504-0.38/zmol Hg/g wet tissue in renal cortex and liver, respectively, with mean age 54.04-13.8. Smokers showed 2.4 times higher levels of Cd in the renal cortex than non-smokers. The mean body burden of Cd was 33.44-17.3 mg. Smoking increases it twofold from 22.0 mg in non-smokers to 41.8 mg in smokers.
1. Introduction
Cadmium is a toxic metal of great concern. In the environment cadmium can be found everywhere: in the soil, water, air, as well as in food and cigarettes. Cadmium production, which started only in the nineteenth century, had, by the seventies of the present century, amounted to 15 000-18 000 tons y-1 [1]. Therefore anthropogenic sources of atmospheric cadmium emissions are almost 20-fold higher than the emissions from natural sources [2]. This has caused an almot 5-fold increase in cadmium body burden in humans [3]. The biological half-life of cadmium is about 20 y and the element accumulates mainly in the renal cortex and the liver, which jointly contain 50% of the total amount of cadmium in the organism (the kidney alone contains one third [4]). The kidney is the critical organ in long-term, low-level (environmental) exposure, and cadmium concentration in the renal cortex (CdK) grows with age, reaching its maximum at c a . 50 years of age [4]. From the fact that cadmium accumulation in humans may result from a variety of sources it follows that the best way of cadmium exposure evaluation and risk assessment is biological monitoring. CdK is a source of information on cadmium accumulation during a lifetime and the most certain source for cadmium exposure evaluation for the general population. Monitoring investigations of CdK levels have been carried out in Belgium, China, India, Israel, Sweden, the USA, and Yugoslavia as part of a UNEP/WHO programme started in 1978. The results were published in 1982 [5]. The project drew the attention of many investigators to the problem of environmental cadmium This work was supported by the grant CPBR 11.12(C-56/86) from the Institute of Rural Medicine, Lublin, Poland. Deceased.
Environmental Monitoring and Assessment 25: 1-13, 1993. (~) 1993 Kluwer Academic Publishers. Printed in the Netherlands.
2
EWA M. BEM ET AL.
exposure of general populations in many countries. Many papers on that subject have followed [6-22]. Data conceming environmental exposure to cadmium in Poland are only flagmentary [23-30]. The aim of the present paper was to collect monitoring data conceming environmental cadmium exposure of central Poland's general population.
2. Materials and methods 2.1. SUBJECTS The investigations were carried out on people who died in the years 1985-1989, as inhabitants of Lodz or its close surroundings. The autopsy was performed at the Department of Pathology, Medical University, Lodz, 384-13.6 hours after death, on average. Renal cortex and liver samples were collected from persons with no occupational exposure to cadmium and with no history of liver or kidney diseases. No macroscopic lesions were found in these organs at autopsy. Information about the patient (taken from the case history) was included in a questionnaire concerning the sex, age, body weight, the mass of the kidney and the liver, profession, dwelling place, and smoking history. Unfortunately, full information was not always available. The samples were obtained from 70 persons (25 women, 7 of them smokers and 9 non-smokers, and 45 men - 28 smokers and 4 non-smokers), mean age 544-13.8. Data for subjects (13 men and 9 women) whose smoking habits could not be identified were not included in the analysis of smokers/non-smokers. 2.2. AREA Lodz (population 800 000) is the second largest city in Poland and is a centre of the textile industry, but with no heavy industry. Mean cadmium concentrations in the air have changed during the last decade from 0.005 #g/m 3 in 1971 [31] to 1-10 #g/m 3 in 1980 [32]. Mean cadmium concentrations in the blood of the inhabitants of this region were: 3.01 #g Cd/1; in non-smokers 1.93 #g/1 and in smokers 4.63 #g/1 [32]. Urine Cd concentrations were 1.12 #g/l; in non-smokers 0.72 #g/1 and in smokers 1.73 #g/1 [32]. 2.3. SAMPLE PREPARATION
Samples (ca. 20 g) of tissues were collected from the lower left pole of the kidney after separating the cortex from the medulla, and from the upper part of the left lobe of the liver, and then placed in acid washed (10% HNO3 - 48 h) polyethylene containers, which were then closed tightly and frozen at -20°C, and thus stored until analysis.
CADMIUM IN HUMAN KIDNEY AND LIVER
3
2.4. ANALYTICAL METHODS
Metals (Cd, Zn, Cu) were measured by flame AAS (Pye-Unicam SP-192) with deuterium background correction after tissue digestion with a mixture of acids (HNO3, HCIO4, H2SO4, Merck, Suprapure) as described in [33]. Three samples were always prepared from each tissue. The detection limits were: 0.02 #g Cd/ml, 0.01 #g Zn/ml, and 0.04 #g Cu/ml. The relative standard deviation for 10 determinations at 0.2 #g/ml was 5%, 2% and 5 % for Cd, Zn and Cu, respectively. Metallothionein (MT) was determined in full homogenates using the 2°3Hg method [34] giving a relative standard deviation of 5%. Levels of MT were expressed in #molHg/g wet tissue to enable easy comparison with MT levels determined by different methods. 2.5. ANALYTICAL QUALITY ASSURANCE
All the analyses were performed under strictly defined conditions alongside samples of internal laboratory control based on a CL- 1 standard (lyophilized cabbage leaves) supplied by AGH (Poland) with certified metal levels. To further assure the accuracy of our determinations we participated in the interlaboratory analytical quality control program conducted by the Institute of Veterinary Science (Poland) with the cooperation of experts from the EC and the United States Department of Agriculture. In three received samples our results were: 0.991, 0.989 and 0.983 #g Cd/g. The correct values were: 0.9974-0.0610, 0.9764-0.0854, and 1.014-t-0.0589 #g Cd/g, respectively. 2.6. STATISTICAL ANALYSIS
All the determined values revealed log-normal distributions. All the parameters for each distribution are given in Table I along with the arithmetic mean and standard deviation for easier comparison with the results of other authors. Student t-tests were used to evaluate statistical differences between groups. 3. Results and discussion The concentrations of cadmium, zinc, and metallothionein in the renal cortex (CdK, ZnK, and MTK) and in the liver (CdL, ZnL, and MTL) for the whole investigated population, as well as Cd levels in relation to smoking and gender are given in Tables I and II. The dependence of CdK on age is shown in Figure 1. A very wide range of concentrations (4.0-133.0 #g/g) was observed, with levels increasing up to about 50 years of age and decreasing thereafter (Table III), which is in agreement with previous observations of other authors [4,5,7,9,10,13,17,18,20]. CdK levels found in this study for individuals who had had no occupational exposure (GM 35.5 #g/g) are among the highest in Europe (Belgium 30.5 #g/g, Sweden 13.1 #g/g, Jugoslavia 24.2 #g/g [5], FRG 12 and 19 #g/g [11], 25.7 #g/g [ 13], 17.1 #g/g [20], CSFR 18.7 #g/g [20]). Higher levels were only found in Japan
4
EWA M. BEM ET AL.
TAB LE I Statistic characterization of the population investigated and monitoring parameters determined.
Age
Kidney Cortex Cd Zn MT /zg/g /zg/g #mol Hg/g
Cd /zg/g
Liver Zn MT #g/g /zmol Hg/g
Total
n x SD GM GSD Median 90-percentile
70 54.0 13.8 52.0 1.3 49.2 71.9
70 44.9 28.6 35.5 2.1 31.6 82.0
70 52.0 16.7 49.6 1.4 49.2 73.7
63 0.79 0.40 0.68 1.78 0.63 1.31
70 3.5 1.8 3.0 1.8 2.9 5.9
70 66.7 30.5 61.6 1.5 65.0 106.4
63 0.50 0.38 0.40 1.86 0.44 0.99
Smoker
n x SD GM GSD Median
35 51.9 9.2 51.1 1.2 50.4
35 62.5, 26.1 57.5 1.5 57.1
35 55.5 15.2 53.4 1.3 54.0
29 1.01. 0.39 0.92 1.6 0.87
35 4.2 1.7 3.8 1.6 3.6
35 72.7 34.6 66.8 1.5 67.3
29 0.59 0.47 0.46 2.00 0.47
90-percentile
63.9
96.4
75.3
1.52
6.3
117.6
1.21
Nonsmoker
n x SD GM GSD Median 90-percentile
13 47.9 16.7 44.5 1.6 45.9 69.7
13 26.2* 17.4 20.2 2.3 19.8 48.9
13 49.1 18.0 46.1 1.5 45.5 72.5
12 0.49* 0.26 0.42 1.85 0.42 0.83
13 2.9 2.4 2.3 2.1 2.3 6.0
13 62.0 17.7 59.6 1.4 59.3 85.0
12 0.41 0.16 0.38 1.50 0.40 0.62
Females
n x SD GM GSD Median 90-percentile
25 51.8 15.5 49.4 1.4 48.4 71.9
25 39.5 28.2 30.3 2.2 29.9 76.1
25 52.6 18.1 49.9 1.4 49.2 76.2
22 0.72 0.43 0.60 1.95 0.57 1.28
25 3.7 2.1 3.1 1.9 3.0 6.4
25 61.2 19.4 58.7 1.3 58.8 86.4
22 0.44 0.34 0.37 1.78 0.36 0.88
45 69.8 35.1 63.3 1.5 65.6 115.3
41 0.53 0.40 0.43 1.90 0.46 1.05
n 45 45 45 41 45 x 55.2 47.9 51.7 0.82 3.4 SD 12.7 28.6 16.0 0.39 1.7 GM 53.6 38.7 49.4 0.73 3.0 GSD 1.3 2.1 1.4 1.70 1.8 Median 51.7 35.7 49.3 0.70 19.4 90-percentile 71.8 85.2 72.5 1.30 5.7 x = mean, SD = standard deviation, G M = geometric mean, GSD = geometric standard deviation; • = p < 0.001.
Males
CADMIUM IN HUMAN KIDNEY AND LIVER
5
TABLE II Cadmium levels (/zg/g wet weight) in kidney cortex and liver in relation to smoking and gender. Total
Females
Males
70 54.04-13.8 44.94-28.6
Kidney Cortex 25 51.84-15.5 39.54-28.2
45 55.24-12.7 47.94-28.6
35
7
28
Age x4- SD
51.94-9.2 62.54-26.1.
44.9-4- 9.8 62.44-31.6. * *
53.74- 8.3 62.54-25.2**
Nonsmoker
n Age a:4- SD
13 47.94-16.7 26.24-17.4.
9 50.74-14.5 29.24-18.4. * *
4 41.84-22.0 19.54-14.9.*
Total
rz Age x4- SD
70 54.04-13.8 3.54- 1.8
Liver 25 51.84-15.5 3.74- 2.1
45 55.24-12.7 3.44- 1.7
Smoker
n Age z4- SD
35 51.94- 9.2 4.24- 1.7
7 44.94- 9.8 4.64- 1.4
28 53.74- 8.3 4.04- 1.7
Nonsmoker
n Age z4- SD
13 47.9-4-16.7 2.94- 2.4
9 50.74-14.5 3.34- 2.7
4 41.84-22.0 2.24- 1.3
Total
Smoker
n Age x4- SD n
* = p < 0.001; ** = p < 0 . 0 0 5 ; * * * = p < 0.02.
(56.2 #g/g [5], 90.1 #g/g [10], 91.37 #g/g [21] and 93.4 #g/g [12]). It is known that smoking markedly affects the cadmium levels in the organism [4,5]. The information concerning smoking was available for part of the population only. It has been found that smokers (62.5 #g/g) show c a . 2.4 times (Tables I and II) higher CdK than non-smokers (26.2/,g/g), with only a slight age difference between both groups (51.9 and 47.9 years, Tables I and II). Considering all age groups the CdK ratio for smokers and non-smokers is c a . 2 for women and c a . 3 for men (Table II). Similar values for heavy smokers have been given [6,13,16] while the other data [5,1 l, 18,20] point only to several dozen per cent growth. The high mean CdK level (44.94-28.6/,g/g) is the result of the smoking habits of a large part of the population investigated. Tobacco produced in Poland, like that of the GDR and Switzerland, contains high amounts of cadmium: 1.3-3.20 #g Cd/cigarette [35,36].
6
EWA M. BEM ET A L
TABLE Ill Cadmium, zinc and metallothionein concentrations* in kidney c o ~ x and liver in relation to age and smoking. 20-40 yr Total
n Age Cd Zn MT
11 36.14- 3.4 52.04-38.6 60.14-19.2 0.894-0.50
41-60 yr > 61 yr Kidney Cortex 34 23 52.04- 5.9 68.74- 5.6 53.4±26.2 31.9-t-21.0 52.54-14.4 48.64-18.0 0.864-0.41 0.694-0.34
Smoker
n Age Cd Zn MT
5 37.04- 2.6 81.14-33.5 65.54-18.2 1.14-0.54
24 52.04- 5.9 60.44-25.1 53.74-15.1 0.97+0.41
Nonsmoker
n Age Cd Zn MT
2 35.8 17.4 64.0 0.56
6 3 52.34- 5.3 66.74- 3.5 3 8 . 8 - 4 - 1 5 . 8 17.24-11.5 55.04-11.2 34.74-11.2 0.634-0.27 0.374-0.23
Total
n Age Cd Zn MT
11 36.14- 3.4 3.84- 1.8 66.74-27.6 0.444-0.46
Liver 34 52.04- 5.9 3.74- 1.7 68.14-28.3 0.544-0.35
23 68.74- 5.6 3.44- 2.0 65.74-36.7 0.494-0.40
Smo~r
n Age Cd Zn MT
5 37.04- 2.6 4.94- 0.8 79.84-35.6 0.584-0.74
24 52.04- 5.9 4.0+ 1.6 70.24-31.7 0.594-0.41
6 64.04- 3.1 4.14- 2.3 76.64-48.9 0.624-0.56
6 64.04- 3.1 55.6+20.4 55.9+12.0 1.14-0,16
n 2 6 3 Age 35.8 52.34- 5.3 66.7q- 3.5 Cd 2.3 2.8-t- 1.9 4.7-4- 3.9 Zn 57.7 70.54-14.0 52.04-26.5 MT 0.33 0.484-0.14 0.374-0.26 * Metals (Cd,Zn) are expressed as #g/g wet weight (mean-4-SD), MT is expressed as/zmol Hg/g wet weight (mean+SD).
Nonsmoker
7
CADMIUM IN HUMAN KIDNEY AND LIVER
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'
AGE(YEARS) Fig. 1. Cadmium in kidney cortexin relation to age in deceasedpersons from central Poland.
These amounts are higher than the cadmium levels in imported cigarettes sold on the Polish market. These amounts are: 1.18-1.73, 0.91-1.96, 0.5-1.10 and 0.850.91 #g/cigarette for FRG, American, Finnish and Cuban cigarettes, respectively [36]. However, for economic reasons, smokers prefer Polish cigarettes. No effect of sex on CdK level has been found (Tables I and II), and small differences are statistically insignificant. The average mean CdK found in this study is lower than the generally accepted (on the basis of data from occupational exposure) critical concentration of 200 #g/g [4]. However, CdK corresponding to 90% is already 82 #g/g, which for a part of the investigated population is responsible for a safety factor of only 2 (for nonsmokers 90% makes up 48.9 #g/g and the safety factor is 4). The results of recent investigations [37] on renal effects caused by cadmium in the general population in Belgium led to the conclusion that renal risk can be observed after renal excretion has exceeded 2 #g Cd/24 h. This occurred in 10% of the population. Such excretion corresponds to a CdK concentration of c a . 50 #g/g [37]. Furthermore, Lindqvist [38] claims that the critical CdK concentration should be much lower than that accepted at present, and suggests the value of 30 #g/g. It is worth noticing that CdK for non-smokers in the age range 41-60 years is 38.8 #g/g (Table III). Thus, even in non-smokers for whom the only source of Cd is food, the safety margin is not great, even with the now commonly assumed critical value of 200 #g/g. CdK levels for non-smokers in general (26.2 #g/g) are close to comparable values in Belgium [5]. The levels should reflect daily cadmium intake with food.
8
EWA M. BEM ET AL.
TABLE IV Correlation coefficients in kidney cortex and liver of the subjects studied. N
/g
Regression equation
Kidney Cortex Cd - Zn
70
0.40,
Zn(#g/g) = 0.23
C d - MT
63
0.82,
MT(/zmol Hg/g) = 1.32
Cd(#g/g) + 41.6
Zn - MT Zn - Cu
63 70
0.52* 0.40*
MT(/zmol Hg/g) = 0.85 Zn(/zmol/g) + 0.12 Cu(/zg/g) = 0.024 Zn(#g/g) + 1.17
Z n - MT
63
0.79,
MT(#mol Hg/g) = 0.618
Cu - age
70
-0.29, • •
C d K - CdL ZnK-ZnL
70 70
0.58* 0.61,
M T K - MTL
63
0.38**
Cd(#me!/F) ~ 0.2 '~
Liver Cu(#g/g)=-0.044
Z n ( # m o l / g ) - 0.135
Age (years) + 7.32
Kidney/Liver CdL(#g/g) = 0.037 CdK(#g/g) + 1.84 ZnL(#g/g) = 1.11 ZnK(#g/g) + 8.88 MTL(#mol Hg/g) = 0.352
MTK(/zmol Hg/g) + 0.222
* = p < 0.001; ** = p < 0.005; * * * = p < 0.02.
Such data for Poland are available, but quite divergent e.g. 20 #g [39] and 65/,g [40], and only partially reveal a violation of the ADI. In Belgium the daily cadmium intake is 15 #g [41]. However, CdK levels in non-smokers are not always a simple reflection of the daily cadmium intake. For instance, in the FRG intakes are 30-55 #g Cd/day [39], while CdK levels in non-smokers are markedly lower than those observed in our study and amount to 13.3 #g/g [20], c a . 16.5 #g/g [13], and 11.7 #g/g [11]. Similarly low levels (13.9/,g/g) have been found in non-smokers in England [18] with daily intakes in the range 8.6-35 #g [39]. It is known that cadmium in the human kidney is bound mainly to metallothionein [42], a protein induced by heavy metals, whose level has been suggested as a marker of exposure to these metals [9]. MTK levels found in this study are in the range 0.1-2.01 #molHg/g. The dependence of MTK on age is similar to cadmium - the levels grow up to about 55 years and then decrease (results partly shown in Table III), which is in agreement with the results of refs. [9,43]. The mean MTK level was 0.79-t-0.40 #mol Hg/g and is almost three times higher than that in Canada [9], similar to the CdK mean. No statistically significant differences in MTK levels between men and women have been found (Table I). In accordance with the fact that MT in humans is a Cd,Zn protein [42], high correlations in the renal cortex between MT and Cd levels and between MT and Zn levels have been observed (Table IV). Similarly to the CdK findings, smoking increases the MTK level by a factor of two (Table I). MT levels are not easy to compare directly for several reasons. It has been
CADMIUM IN HUMAN KIDNEY AND LIVER
9
found recently [44] that due to postmortem changes in tissue cadmium binding at room temperature, MT decomposition follows, with further cadmium release. The cadmium is then bound to high molecular weight proteins. The process is not observed, however, even after seven days, if the tissues are stored at - 9 ° C (refrigerator freezer) or - 4 0 ° C (dry ice). Therefore the time between death and autopsy is an important factor affecting MT levels in humans. It is known that alcohol consumption increases MTK in humans [43]. Stress may be also expected to affect the levels, as has been found in rats [45]. An additional factor complicating the comparison of MT levels obtained in various laboratories is the nonspecificity of the different analytical methods used [46]. That is why we think that only trends conceming the MT levels and not their absolute values can be compared, and therefore MTK levels are of limited monitoring value. Similarly to CdK levels, zinc levels in the renal cortex (ZnK) show great scatter of individual values (26.5-106.0 #g/g) (Tables I and III). Although zinc in the renal cortex is only partly bound by Zn,Cd-MT, similar changes of cadmium and zinc levels with age are revealed in the clear correlation between them (Table IV). No effect of smoking on ZnK has been found (Table I) as opposed to the results of Blanusa et al. [16] who observed a ca. 40% ZnK increase in smokers. The mean ZnK level 52.0+16.7 #/g is slightly higher than that observed in Canada (40.1+3.2 #g/g [9]) and India (36.044-9.22 #g/g [17]). The Cd]Zn weight ratio reaches the maximum value (1.02) in the 41-60 age group (Table III), which confirms the results of other authors [9,17]. Values of the Cd/Zn ratio found in these studies are low, which is connected with lower levels of cadmium. Though it is known that the kidney is a critical organ in the case of long-term cadmium exposure, when CdK exceeds 200 #g/g the concentration of cadmium in the kidney decreases, despite the further growth of exposure. The value of 200 #g/g in a normal kidney corresponds to 30 #g/g in the liver [8]. Roels et al. [8] suggest that cadmium levels in the liver grow with exposure, even after exceeding the critical value. The results of Honda and Nogawa [12] confirm this hypothesis, and thus CdL levels have become interesting for monitoring purposes. CdL, ZnL and MTL concentrations observed in the population investigated are shown in Table I. All the data are in accordance with our preliminary data published earlier [26] as well as with other data for that region [32,47]. The mean CdL level is 3.5+1.8 #g/g and is close to that observed in polluted areas in Belgium (0.9-3.3 #g/g [7]) and in the FRG (3 #g/g [11]). Much higher CdL concentrations, amounting to ca. 10 #g/g in nonpolluted areas and ca. 60 #g/g in polluted areas, have been observed only in Japan [10]. As can be seen from the data in Table III no growth of CdL could be observed with age. The CdL were correlated with those of CdK (Table IV). Similarly to the kidney, no difference between men and women could be found (Tables I and II). Unlike to the kidney cortex the elevated CdL levels in smokers were not statistically different from non-smokers. In our opinion monitoring value of CdL levels is of little use in the case of low and moderate cadmium exposure.
10
EWA M. BEM ET AL.
Cadmium in human liver is bound to MT which in this organ is Zn-thionein [48,49]. In our material this is clearly reflected in the presence of a marked correlation between ZnL and MTL, and the lack of correlation between CdL and MTL. However, we have observed a correlation between MT levels in the renal cortex and the liver (Table IV). The mean ZnL concentration 66.7-+-30.5 #g/g is close to the levels found in Japan [50,51] and Canada [9], and does not depend on sex and smoking habits (Table I). A correlation exists between Zn levels in the liver and in the renal cortex (Table IV). Mean copper levels in the renal cortex and the liver are 2.4+1.0 #g/g and 4.9-t-2.1 #g/g, respectively (not included in the tables). These levels are not correlated with other parameters studied (sex, smoking), except for the decreasing tendency with age seen in the liver (Table IV). The cadmium body burden was calculated by means of two methods: (1) assuming that the kidney and the liver contain 50% of the total cadmium in the organism: and (2) assuming that the kidney contains 1/3 of the total cadmium in the organism. In both cases the 1.25 coefficient was applied, reflecting the ratio of concentration in the cortex to the concentration in the whole kidney [19]. A very high correlation (r : 0.95) between body burden calculated with both the methods has been observed. Mean body burden (K+L) is 33.4+17.3 mgCd (GM 28.5 mg, GSD 1.9). Smoking doubles the mean body burden (from 22.0 mg to 41.8 mg). The main reason for the higher body burden in men (36.2 mg) than in women (28.1 mg) seems to be smoking, since there were 28 smokers in the 45 person group of men, and only 7 smokers in the 25 person group of women. The mean body burden of cadmium in Poland is much higher than in Southem Bavaria (21.9 mg [14]) and even in Japan (21 mg [52]). The comparison of body burden in non-smokers (22.0 mg) with the same levels in Bavaria (13.5 mg) [14] allows us to suppose that dietary cadmium intake is not comparable in both countries. The markedly higher body burden in Polish smokers (41.8 mg), compared with the Bavarian figure of 33.2 mg [14], makes it possible to conclude that, apart from food, smoking is the main reason for high cadmium levels in the population investigated.
Acknowledgements The authors wish to express their gratitude to Dr. Cz. Dmuchowski (Department of Pathology, Medical University, Lodz) for making available the proper autopsy material, Mrs. M. Skrzypifiska-Gawrysiak, M.Sc., for interlaboratory quality control, and Mr. A. D~bicki for his assistance in the determinations.
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