Cadmium in kidney cortex of inhabitants of North-West Germany: its relationship to age, sex, smoking and environmental pollution by cadmium

Associations of urinary cadmium with age and urinary proteins: further evidence of physiological variations unrelated to metal accumulation and toxicity

BACKGROUND

The current risk assessment for environmental cadmium (Cd) largely relies on the assumption that urinary Cd (U-Cd) is a reliable biomarker of the Cd body burden. Recent studies have questioned the validity of this assumption.

OBJECTIVES

We studied the lifetime trend of U-Cd as a function of diuresis, gender, smoking status, and protein tubular reabsorption. We also analyzed the associations between U-Cd and urinary proteins.

METHODS

Cd, retinol-binding protein, and albumin were measured in the urine of six cohorts of the general population of Belgium, with a mean age ranging from 5.7 to 88.1 years (n = 1,567). Variations of U-Cd with age were modeled using natural cubic splines.

RESULTS

In both genders, U-Cd decreased to a minimum (~ 0.20 μg/L) at the end of adolescence, then increased until 60-70 years of age (~ 0.60 μg/L in never-smokers) before leveling off or decreasing. When U-Cd was expressed in micrograms per gram of creatinine, these variations were amplified (minimum, 0.15 µg/g creatinine; maximum, 0.70 µg/g creatinine) and much higher U-Cd values were observed in women. We observed no difference in U-Cd levels between never-smokers and former smokers, and the difference with current smokers did not increase over time. Lifetime curves of U-Cd were higher with increasing urinary retinol-binding protein or albumin, a consequence of the coexcretion of Cd with proteins.

CONCLUSIONS

At low Cd exposure levels, U-Cd and age are associated through nonlinear and nonmonotonic relationships that appear to be driven mainly by recent Cd intake and physiological variations in the excretion of creatinine and proteins.

Cadmium, mercury, and lead in kidney cortex of living kidney donors: Impact of different exposure sources

BACKGROUND

Most current knowledge on kidney concentrations of nephrotoxic metals like cadmium (Cd), mercury (Hg), or lead (Pb) comes from autopsy studies. Assessment of metal concentrations in kidney biopsies from living subjects can be combined with information about exposure sources like smoking, diet, and occupation supplied by the biopsied subjects themselves.

OBJECTIVES

To determine kidney concentrations of Cd, Hg, and Pb in living kidney donors, and assess associations with common exposure sources and background factors.

METHODS

Metal concentrations were determined in 109 living kidney donors aged 24-70 years (median 51), using inductively coupled plasma-mass spectrometry (Cd and Pb) and cold vapor atomic fluorescence spectrometry (Hg). Smoking habits, occupation, dental amalgam, fish consumption, and iron stores were evaluated.

RESULTS

The median kidney concentrations were 12.9microg/g (wet weight) for cadmium, 0.21microg/g for mercury, and 0.08microg/g for lead. Kidney Cd increased by 3.9microg/g for a 10 year increase in age, and by 3.7microg/g for an extra 10 pack-years of smoking. Levels in non-smokers were similar to those found in the 1970s. Low iron stores (low serum ferritin) in women increased kidney Cd by 4.5microg/g. Kidney Hg increased by 6% for every additional amalgam surface, but was not associated with fish consumption. Lead was unaffected by the background factors surveyed.

CONCLUSIONS

In Sweden, kidney Cd levels have decreased due to less smoking, while the impact of diet seems unchanged. Dental amalgam is the main determinant of kidney Hg. Kidney Pb levels are very low due to decreased exposure.

Cadmium and lead levels in human liver and kidney samples obtained from Bursa Province

Autopsy samples of liver and kidney from 43 Turk cadavers obtained from the Department of Forensic Medicine of Bursa City were analysed for cadmium and lead. All subjects were born between 1918 and 1982. The means of cadmium residue levels were found to be 0.63235 - 0.06345 ppm in the liver and 0.8507 - 0.077 ppm in the kidney. The means of lead residue levels were measured as 0.44675 - 0.0591 ppm in the liver and 0.42905 - 0.0528 ppm in the kidney. In addition, the cadavers were grouped according to sex, age and place of dwelling, city or village. Although samples contained both of the metals in their normal levels, it was concluded that these results do not indicate whether both of the metals will be a serious threat to public health in the future

The German Environmental Survey 1990/92 (GerES II): primary predictors of blood cadmium levels in adults

As part of the representative Environmental Survey in Germany in 1990-1992, investigators determined cadmium levels in blood provided by 3,965 subjects aged 25-69 yr. The investigators considered approximately 150 variables (i.e., demographics, household and occupational characteristics, environmental exposures, smoking habits, frequency of food consumption, and additional life-style features) as potential predictors in multivariate regression analysis. On the basis of the results of multivariate regression analysis, the authors derived 2 slightly different models for the prediction of blood cadmium levels in populations from West and East Germany. Both models included 3 primary predictors of blood cadmium levels. The 2 models explained 51.3% and 61.2% of the observed variance in blood cadmium levels in West and East Germany, respectively. The most important predictor was a specific indicator for smoking habits, which was determined from a separate mathematical model. In this model, the effect of smoking was considered, and the model accounted for the biological half-life of cadmium in blood.

Selection and evaluation of air pollution exposure indicators based on geographic areas

Geographic exposure indicators (GEIs) use point estimates of ambient air pollutant concentrations to characterize the exposure of populations residing within a specified area. Both zone- and proximity-type GEIs have been widely employed in epidemiological studies and other applications to identify regions or populations at high risk. Their use requires a number of assumptions, for example, pollutant concentrations should be homogeneous within the area, and concentrations should differ between areas in a predictable manner. These assumptions have not been rigorously examined. This paper evaluates the most common types of GEIs as surrogate measures of ambient air pollutant exposures. Statistical measures proposed to evaluate GEIs include accuracy, homogeneity, misclassification and statistical power. GEIs and statistical measures are evaluated in two case studies that use different air pollution sources and an air quality dispersion model. The case studies show that pollutant levels may vary substantially within a small area, and significant errors and exposure misclassification may result if the GEI represents a large geographic area. GEIs based on residential proximity to a pollution source should not be used for elevated emission sources, and the use of proximity measures is discouraged for ground level sources. A systematic evaluation is suggested to evaluate and improve the accuracy of the GEIs used in epidemiological and other applications.

Kinetics of DNA alkylation, depurination and hydrolysis of anti diol epoxide of benzo(a)pyrene and the effect of cadmium on DNA alkylation

Anti benzo[a]pyrene diol epoxide (BPDE) alkylates guanines of DNA at N7 in the major groove and at the exocyclic amino group in the minor groove. In this report we investigated the rates of BPDE hydrolysis, DNA alkylation and subsequent depurination of BPDE-adducted pBR322 DNA fragment using polyacrylamide gel electrophoresis. Preincubation studies showed that it hydrolyzed completely in triethanolamine buffer in <2 min. The depurination kinetics showed that a fraction of the N7 alkylated guanine depurinated rapidly; however a significant amount of N7 guanine alkylation remained stable to spontaneous depurination over a 4-h period. Similar results were obtained for the hydrolysis and alkylation rates of syn isomer but it required nearly 500 times more concentration to induce similar levels of N7 guanine alkylation. Cadmium ion strongly inhibited the N7 guanine alkylation of both isomers. But the minor groove alkylation was not affected as demonstrated by postlabeling assay which confirmed the presence of heat-and cadmium-stable minor groove adducts in BPDE-treated calf thymus DNA. Based on these and our earlier findings, we propose a mechanism for the synergistic effect of cadmium in chemically induced carcinogenesis.

Cadmium inhibits BPDE alkylation of DNA in the major groove but not in the minor groove

Cadmium, a constituent of tobacco, has the potential to act in synergy with other carcinogens in tobacco smoke. Working on the hypothesis that cadmium interactions with DNA enhances the mutagenic lesions induced by tobacco carcinogens, we investigated the site and sequence selectivity of DNA binding by cadmium using DNA reactive chemical probes. Our results show that this divalent cation binds to N7 guanines with a great preference for those occurring in runs of G's. Further, cadmium considerably diminishes N7 guanine alkylation by the tobacco carcinogen metabolite BPDE; however, the biologically relevant guanine alkylation in the minor groove by BPDE was not affected. The relevance of our findings to cadmium's role in the tobacco carcinogenesis is discussed.

Age dependent accumulation of cadmium in the human ovary

Cadmium (Cd) was determined by atomic absorption spectrophotometry in small pieces (< 1 g) of healthy human ovaries excised for histologic examination. Cd levels in the ovary increased linearly between 30 and 65 years of age. Below 30 years, there was no age dependent increase and over 65 a tendency was observed for ovarian Cd levels to decrease. There was no difference in the Cd content of fresh luteal and nonluteal tissue taken from regularly cycling ovaries. In smokers, the amount of Cd in the ovaries was elevated compared to nonsmokers. In multiparous women (more than 3 children) a tendency of decreased Cd ovarian levels was observed. There was no difference between ovarian Cd content of physical and mental workers. It can be proposed that Cd may be a risk factor for conception and pregnancy in women in their forties.

Cadmium, zinc, copper and metallothionein levels in the kidney and liver of humans from central Poland

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±28.6 µg Cd/g, 52.0±16.7 µg Zn/g, 2.4±1.0 µg Cu/g, 0.79±0.40 µmol Hg/g, and 3.5±1.8 µg Cd/g, 66.7±30.5 µg Zn/g, 4.9±2.1 µg Cu/g, 0.50±0.38 µmol Hg/g wet tissue in renal cortex and liver, respectively, with mean age 54.0±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 33.4±17.3 mg. Smoking increases it twofold from 22.0 mg in non-smokers to 41.8 mg in smokers.

The relationship between placental cadmium, zinc, and copper

A number of interactions between the essential metals zinc (Zn) and copper (Cu), and the toxic metal cadmium (Cd), have been described in animal, but not in human tissues. The purpose of this study was to determine whether Cd levels are directly related to Zn or Cu levels in the human placenta at term, and whether this relationship is affected by parity or smoking. Atomic absorption spectroscopy was used to determine Cd, Zn and Cu in perfused placental cotyledons from 292 low-risk parturients. Plasma thiocyanate levels were used to determine smoking status. Linear regression and repeated measures analysis of variance (ANOVA) were used to examine relationships between the elements and the effects of parity and smoking status. Results show significant correlations between placental Cd and both Zn (r-0.41; p < 0.01) and Cu (r-0.35; p < 0.01), but only in multiparous patients. These relationships were not altered by smoking. These results suggest that Cd-Zn and Cd-Cu interactions occur in the placenta at "normal" levels of Cd exposure and over a very short time period.

Cadmium, zinc, copper, and metallothionein levels in the kidney and liver of inhabitants of upper Silesia (Poland)

The levels of Cd, Zn, Cu and metallothionein (MT) were determined in renal cortex and liver of 75 subjects decreased in the period 1986-1989 in the area of Upper Silesia (Katowice). The mean age of the population studied was 53.6 +/- 14.6 years. The determined levels (mean +/- SD) were: 43.1 +/- 23.5 micrograms Cd/g; 52.5 +/- 17.4 micrograms Zn/g; 2.2 +/- 0.7 microgram Cu/g; 0.80 +/- 0.36 mumol Hg/g in renal cortex and 3.5 +/- 2.5 micrograms Cd/g; 82.8 +/- 34.3 micrograms Zn/g; 4.5 +/- 2.6 micrograms Cu/g; 0.69 +/- 0.44 mumol Hg/g in the liver. The level of Cd in renal cortex was 40% higher in smokers compared to nonsmokers and was independent of the gender. Whole-body retention of Cd was 34.1 +/- 18.5 mg; smoking elevated the value from 27.1 to 38.2 mg. Compared with a similar study made in central Poland (Lódź), a significant difference was found only regarding the level of Zn and MT in the liver, pointing to the possibility that exposure to this element in the region of Upper Silesia may be higher.

Cadmium in human lung tissue

In 101 unselected autopsies, cadmium (Cd) in lung tissue was analyzed by means of flameless atomic absorption spectrometry (AAS). The subjects originated from Bochum (BO), Dortmund (DO), and neighbouring cities in the Ruhr District (BO/DO) as well as from Muenster (MS) and vicinity. The sample included eight persons who had died from bronchial carcinoma. The Cd concentration in lung tissue (CdL) did not show a significant age-dependency. There was only a slight increase of CdL in the age around 50. For males, the median CdL value was found to be 1.32 micrograms/g dry wt in the age group from 20-45, 1.48 micrograms/g dry wt from 45-65, and 0.64 micrograms/g dry wt greater than 65 (the corresponding means and standard deviations were 1.48 +/- 1.22, 1.73 +/- 1.42, and 1.18 +/- 1.27 micrograms/g dry wt). CdL in men was twice that in women. There were no differences between the two regions (BO/DO:MS) examined. CdL of the bronchial carcinoma cases were mostly clearly above the expected level, often similar to the Cr and Ni concentration of the same specimens. Besides the amount of inhaled metal aerosols, insufficient lung clearance may play a leading role for their retention in lung parenchyma. However, with regard to the determination of causality between uptake and disease the data are difficult to interpret, in our study due to a lack of enough consistent and reliable data on occupation, environment, and smoking habits, and in general due to a lot of variables which, until now, cannot be sufficiently quantified.

In vivo measurements of cadmium and lead in occupationally-exposed workers and an urban population

This paper reports the preliminary findings of a survey of lead and cadmium body burdens in a nonoccupationally exposed population in Swansea, Wales, using the techniques of in vivo neutron activation and X-ray fluorescence analysis. Some measurements on an occupationally cadmium-exposed group are also included. The results confirm the association between cadmium and smoking and bone lead and age. The in vivo measurements demonstrate a degree of comparability with other data, which supports the further detailed analysis of the relationships between body burden and exposure, on the one hand, and possible health effects on the other.

Variables influencing cadmium concentrations in hair of pre-school children living in different areas of the Federal Republic of Germany

The influence of several factors on cadmium (Cd) concentrations in the hair of 474 pre-school children was examined. The study was performed in an industrial (Duisburg) and rural area (Westfalen) of the (FRG). Season, sex, hair color, and place of residence were found to be the main factors influencing Cd levels in hair. Concentrations of Cd in samples obtained during summer were on the average nearly twice as high as those sampled during winter (geometric means: 116.1 vs. 63.7 ng/g). Boys had more Cd in their hair than girls (111.5 vs. 74.0 ng/g). Cd levels in hair decreased from red to blond, to brown, and black hair. Children living in Duisburg had more Cd in their hair than those from rural areas (103.9 vs. 77.0 ng/g). Cd content in hair was inversely related to age.

Exposure to lead and cadmium of children living in different areas of north-west Germany: results of biological monitoring studies 1982-1986

Between 1982 and 1986 several surveys were carried out to determine the levels of lead and cadmium in blood, urine, and shed deciduous teeth (incisors only) of children living in rural, suburban, urban, and industrial areas of North-West Germany. Blood lead (PbB) and blood cadmium (CdB) were measured in about 4000 children. In rural, suburban and urban areas the median PbB levels vary between 5.5 and 7 micrograms/dl, with 98th percentiles varying between 10 and 13 micrograms/dl. The median CdB levels are between 0.1 and 0.2 microgram/dl, with 95th percentiles between 0.3 and 0.4 microgram/l. Children from urban areas have significantly higher PbB levels than children from rural and suburban areas. Regarding CdB no differences could be detected. Children living in areas around lead and zinc smelters, particularly those living very close to the smelters, have substantially increased PbB and CdB levels. Children from lead worker families also have substantially increased PbB and CdB levels. The lead levels in shed milk teeth (PbT) were determined in about 3000 children. In rural, suburban and urban areas the median PbT levels are between 2 and 3 micrograms/g, with 95th percentiles between 4 and 7 micrograms/g. Children from urban areas have significantly higher PbT levels than children from rural and suburban areas. The highest PbT levels (on a group basis) are in children from nonferrous smelter areas. The median levels of lead in urine (PbU) are between 6 and 10 micrograms/g creatinine, with 95th percentiles between 20 and 30 micrograms/g creatinine. Children from polluted areas have higher PbU levels than children from less polluted areas. The median levels of cadmium in urine (CdU) are in the order of 0.1 microgram/g creatinine, with 95th percentiles being in the range of 0.5 and 1.0 microgram/g creatinine. Girls have higher CdU levels than boys. There are no differences between groups of children from different areas. Children from lead worker families have higher PbU and CdU levels than otherwise comparable children. The results of the present studies indicate a further decrease of PbB in children from North-West Germany since the CEC blood lead campaigns carried out in 1979 and 1981. The decrease of lead exposure also seems to be reflected by a decrease of tooth lead levels.