Determinants of urinary thioethers, D-glucaric acid and mutagenicity after exposure to polycyclic aromatic hydrocarbons assessed by air monitoring and measurement of 1-hydroxypyrene in urine: a cross-sectional study in workers of coke and graphite-electrode-producing plants

A cross-sectional epidemiological study was performed on 286 workers from two coke oven and one graphite electrode plants. The aim was to evaluate the usefulness of monitoring 1-hydroxypyrene (1-HOP) in urine for assessing exposure to polycyclic aromatic hydrocarbons (PAHs), and that of the urinary excretion of thioethers and D-glucaric acid, and the mutagenic activity of urine as indicators or biological effects of PAHs. The results confirm that 1-HOP determination in urine probably reflects exposure to PAHs by all routes and is not significantly influenced by the smoking habit. In comparison with the total PAHs in the air and 1-hydroxypyrene in urine, taken as reference exposure parameters, the results indicate that urinary D-glucaric acid excretion is not positively influenced by PAHs exposure; thioethers determination in urine is of poor value, since the smoking habit is a strong confounding factor. The determination of urinary mutagenicity might contribute to the detection of groups of workers exposed to potentially genotoxic PAHs.

Urinary excretion of homovanillic acid in workers exposed to manganese

Homovanillic acid, an end product of dopamine catabolism, and manganese (Mn) were measured in the urine of 68 male workers exposed to Mn-containing dust in a dry alkaline battery plant or an Mn oxide and salt producing plant, and in 35 control male subjects. The geometric mean of the airborne concentration of inhalable (total) dust amounted to 0.95 and 1.37 mg/m3 in the dry alkaline battery plant and the Mn oxide and salt producing plant, respectively. In the latter, a higher prevalence of increased values of urinary homovanillic acid concentration was found. In the total population, there was a low but statistically significant positive correlation between the concentration of homovanillic acid and Mn in urine (r = 0.20, P = 0.04) but there was no significant correlation between the level of homovanillic acid in urine and Mn in airborne dust or duration of exposure. This observation might be compatible with the stimulation of dopamine turnover in the brain, which has been observed in the early phase of Mn intoxication in animals. However, the large variability in urinary homovanillic acid excretion in control subjects precludes the use of this biological indicator to detect early interference of Mn with the dopaminergic system.

Epidemiological survey of workers exposed to cobalt oxides, cobalt salts, and cobalt metal

Several organs (lung, skin, thyroid, heart, bone marrow) are potential targets of cobalt (Co). Whereas there is no doubt that inhalation of Co alone may cause bronchial asthma, its role in the occurrence of hard metal disease is still controversial because most cases were reported in workers exposed not only to Co but also to other substances such as tungsten carbide, titanium carbide, iron, silica and diamond. To assess whether exposure to pure Co dust (metal, oxides, or salts) may lead to adverse health effects a cross sectional study was carried out among 82 workers in a Co refinery. The results were compared with those in a sex and age matched control group. The Co group had been exposed for 8.0 years on average (range 0.3-39.4). The geometric mean time weighted average exposure assessed with personal samplers (n = 82) was about 125 micrograms/m3 and 25% of the values were higher than 500 micrograms/m3. The concentrations of Co in blood and in urine after the shift were significantly correlated with those in air. Concentration of Co in urine increased during the workweek. A slight interference with thyroid metabolism (decreased T3, T4, and increased TSH), a slight reduction of some erythropoietic variables (red blood cells, haemoglobin, packed cell volume) and increased white cell count were found in the exposed workers. The exposed workers complained more often of dyspnoea and wheezing and had significantly more skin lesions (eczema, erythema) than control workers. Within the exposed group a dose-effect relation was found between the reduction of the forced expiratory volume in one second/vital capacity and the intensity of current exposure to Co assessed by the measurement of Co in air or in urine. The prevalence of dyspnoea was related to the dustiness of the workplace as reflected by statistically significant logistic regression between this symptom and the current levels of Co in air and in urine. No difference between lung volumes, ventilatory performances, carbon monoxide diffusing capacity, and serum myocardial creatine kinase and procollagen III peptide was found between the Co and control groups and no lung abnormalities were detected on the chest radiographs in both groups. The results suggest that exposure to high airborne concentrations of Co alone is not sufficient to cause pulmonary fibrosis. This finding is compatible with experimental studies indicating that interaction of other airborne pollutants with Co particles play a part in the pathogenesis of parenchymal lung lesions.

Biological markers in PAH exposed workers and controls

Workers employed in a graphite electrode producing plant (n = 16) and a coke oven (n = 33) were compared with a control population of maintenance workers in a blast furnace (n = 54). The following parameters were analyzed: concentration of 13 different PAHs in the work environment measured by personal air samplers, concentration of hydroxypyrene in the urine, smoking habits (via urinary thiocyanate levels and a questionnaire) and cytogenetic aberrations in lymphocytes (SCE, HFC and MN). On the basis of PAH levels in the work environment and hydroxypyrene concentrations in the urine, the workers from the graphite electrode producing plant were the most exposed. However, statistically significant differences in SCE and HFC and positive correlations between the cytogenetic markers and airborne PAH levels on the one hand, and urinary hydroxypyrene concentrations on the other hand were only detectable in the workers from the coke oven with a lower exposure. No statistically significant effect of smoking was observed. As to the inter-comparison of the different cytogenetic markers, one may consider that SCE and HFC are more sensitive than MN frequencies for the biomonitoring of exposure to PAHs. Whether MN or SCE are the best biomarker for risk assessment of cancer and whether the presence of PAHs in the work environment is really responsible for the cytogenetic effects found in this study could not be ascertained.

Increased sister chromatid exchanges and tumor markers in workers exposed to elemental chromium-, cobalt- and nickel-containing dusts

Sister-chromatid exchange (SCE) in blood lymphocytes, serum tumors markers, carcinoembryonic antigen (CEA) and tissue polypeptide antigen (TPA), and urinary excretion of chromium, cobalt and nickel were determined in 26 male workers occupationally exposed to chromium, cobalt and nickel dust and in 25 controls matched for age and smoking habits. The differences in the urinary excretion of metals between exposed persons and controls were statistically significant. An analysis of variance on the SCE rank values revealed that both exposure status (exposed persons vs. controls) and smoking habits (smokers and former smokers vs. never smokers) had a statistically significant effect. For the tumor markers, the analysis of variance did not reveal a statistically significant difference between exposed persons and controls. However, CEA serum levels were significantly correlated not only with smoking habits but also with duration of exposure. As cobalt is only weakly mutagenic, these results suggest that the small amount of absorbed chromium and nickel may have been sufficient to induce SCE. The hypothesis that tumor markers may be increased in groups of subjects exposed to genotoxic substances deserves further study.

Markers of early renal changes induced by industrial pollutants. II. Application to workers exposed to lead

The present study has been carried out in the framework of a collaborative research project on the development of new markers of nephrotoxicity. A battery of more than 20 potential indicators of renal changes has been applied to 50 workers exposed to lead (Pb) and 50 control subjects. After application of selection criteria 41 exposed and 41 control workers were eventually retained for the final statistical analysis. The average blood Pb concentration of exposed workers was 480 micrograms/l and their mean duration of exposure was 14 years. The battery of tests included parameters capable of detecting functional deficits (for example, urinary proteins of low or high molecular weight), biochemical alterations (for example, urinary eicosanoids, glycosaminoglycans, sialic acid) or cell damage (for example, urinary tubular antigens or enzymes) at different sites of the nephron or the kidney. The most outstanding effect found in workers exposed to Pb was an interference with the renal synthesis of eicosanoids, resulting in lower urinary excretion of 6-keto-PGF1 alpha and an enhanced excretion of thromboxane (TXB2). The health significance of these biochemical alterations, detectable at low exposure to Pb is unknown. As they were not associated with any sign of renal dysfunction, they may represent reversible biochemical effects or only contribute to the degradation of the renal function from the onset of clinical Pb nephropathy. The urinary excretion of some tubular antigens was also positively associated with duration of exposure to Pb. Another effect of Pb that might deserve further study is a significant increase in urinary sialic acid concentration.

Markers of early renal changes induced by industrial pollutants. III. Application to workers exposed to cadmium

Cadmium (Cd) was the third heavy metal investigated in the European collaborative research project on the development and validation of new markers of nephrotoxicity. Fifty workers exposed to Cd and 50 control workers were examined. After application of selection criteria 37 workers (mean age 43) exposed to Cd for an average of 11.3 years; and 43 age matched referents were retained for final analysis. The average concentrations of Cd in blood (Cd-B) and urine (Cd-U) of exposed workers were 5.5 micrograms Cd/l and 5.4 micrograms Cd/g creatinine respectively. By contrast with lead and mercury, Cd had a broad spectrum of effects on the kidney, producing significant alterations in amounts of almost all potential indicators of nephrotoxicity that were measured in urine--namely, low and high molecular weight proteins, kidney derived antigens or enzymes, prostanoids, and various other biochemical indices such as glycosaminoglycans and sialic acid. An increase in beta 2-microglobulin and a decrease of sialic acid concentration were found in serum. Dose-effect/response relations could be established between most of these markers and Cd-U or Cd-B. The thresholds of Cd-U associated with a significantly higher probability of change in these indicators were estimated by logistic regression analysis. Three main groups of thresholds could be identified: one around 2 micrograms Cd/g creatinine mainly associated with biochemical alterations, a second around 4 micrograms Cd/g creatinine for high molecular weight proteins and some tubular antigens or enzymes, and a third one around 10 micrograms Cd/g creatinine for low molecular weight proteins and other indicators. The recent recommendation by the American Conference of Governmental Industrial Hygienists (ACGIH) of 5 micrograms Cd/g creatinine in urine as the biological exposure limit for occupational exposure to Cd appears thus justified, although for most of the effects occurring around this threshold the link with the subsequent development of overt Cd nephropathy is not established. In that respect, the very early interference with production of some prostanoids (threshold 2 micrograms Cd/g creatinine) deserves further investigation; although this effect might contribute to protect the filtration capacity of the kidneys, it might also play a part in the toxicity of Cd on bone.

Once-a-day administration of amikacin in neonates: assessment of nephrotoxicity and ototoxicity

Neonates, especially preterms, are known to have low glomerular filtration rates (GFR). This may result in elevated trough concentrations during multiple administration of aminoglycosides (AGs), potentially leading to nephro- and ototoxic reactions. The once-daily administration (q.d.) of AGs has been shown to be equally or better tolerated in adults and children than the conventional schedules (twice daily, b.i.d.; thrice daily, t.i.d.), while offering potential pharmacodynamic and nursing advantages. No data, however, are available for neonates. As a consequence, this pilot study was conducted in order to assess the tolerance of the once-a-day administration of amikacin in comparison with the twice daily dose regimen, in relation to the pharmacokinetics of the drug under these two schedules. 22 Male neonates (gestational age > or = 34 weeks; postnatal age < or = 2 days) were randomized to receive amikacin (AK) (15 mg/kg/day) q.d. (n = 10) or b.i.d. (n = 12) together with ampicillin (50 mg/kg/12 h). AK plasma levels were measured at days 1, 3, 5 and 7 of treatment just before the next dose (trough level) and 1 h after completion of infusion (peak level) and after 3 and 6 h only at day 1. Due to the small size of the samples, no difference in efficacy could be assessed and was not the aim per se. Glomerular dysfunction was assessed by creatinine clearance, and tubular injuries by the urinary excretion of proteins (retinol binding protein, beta 2-microglobulin, clara cell protein (P1) and microalbumin), enzymes (N-acetyl-beta-D-glucosaminidase, alkaline phosphatase, alanine aminopeptidase, and gamma-glutamyltransferase), and total phospholipids (TPL) in urine. Ototoxicity was assessed by brainstem auditory evoked potentials (BAEPs) at days 0, 3 and 9 of therapy. Eight healthy neonates served as controls. All patients showed a normal and similar increase of GFR during the first postnatal days. Proteinuria did not increase, but enzymuria and TPL increased significantly during the treatment in both AK groups without significant difference between groups. BAEPs at day 9 were not significantly different between treated and untreated patients. We conclude from this pilot study that, in the absence of more toxicity, the q.d. administration of AK in neonates of > or = 34 weeks of gestational age may be recommended over its bid schedule in view of its potential advantages.

Markers of early renal changes induced by industrial pollutants. I. Application to workers exposed to mercury vapour

Several markers of renal changes have been measured in a cohort of 50 workers exposed to elemental mercury (Hg) and in 50 control workers. After application of selection criteria 44 exposed and 49 control workers were retained for the final statistical analysis. Exposed workers excreted on average 22 micrograms Hg/g creatinine and their mean duration of exposure was 11 years. Three types of renal markers were studied--namely, functional markers (creatinine and beta 2-microglobulin in serum, urinary proteins of low or high molecular weight); cytotoxicity markers (tubular antigens and enzymes in urine), and biochemical markers (eicosanoids, thromboxane, fibronectin, kallikrein, sialic acid, glycosaminoglycans in urine, red blood cell membrane negative charges). Several bloodborne indicators of polyclonal activation were also measured to test the hypothesis that an immune mechanism might be involved in the renal toxicity of elemental Hg. The main renal changes associated with exposure to Hg were indicative of tubular cytotoxicity (increased leakage of tubular antigens and enzymes in urine) and biochemical alterations (decreased urinary excretion of some eicosanoids and glycosaminoglycans and lowering of urinary pH). The concentrations of anti-DNA antibodies and total immunoglobulin E in serum were also positively associated with the concentration of Hg in urine and in blood respectively. The renal effects were mainly found in workers excreting more than 50 micrograms Hg/g creatinine, which corroborates our previous estimate of the biological threshold of Hg in urine. As these effects, however, were unrelated to the duration of exposure and not accompanied by functional changes (for example, microproteinuria), they may not necessarily represent clinically significant alterations of renal function.

Determinants of serum zinc in a random population sample of four Belgian towns with different degrees of environmental exposure to cadmium

This report investigated the distribution of serum zinc and the factors determining serum zinc concentration in a large random population sample. The 1977 participants (959 men and 1018 women), 20-80 years old, constituted a stratified random sample of the population of four Belgian districts, representing two areas with low and two with high environmental exposure to cadmium. For each exposure level, a rural and an urban area were selected. The serum concentration of zinc, frequently used as an index for zinc status in human subjects, was higher in men (13.1 mumole/L, range 6.5-23.0 mumole/L) than in women (12.6 mumole/L, range 6.3-23.2 mumole/L). In men, 20% of the variance of serum zinc was explained by age (linear and squared term, R = 0.29), diurnal variation (r = 0.29), and total cholesterol (r = 0.16). After adjustment for these covariates, a negative relationship was observed between serum zinc and both blood (r = -0.10) and urinary cadmium (r = -0.14). In women, 11% of the variance could be explained by age (linear and squared term, R = 0.15), diurnal variation in serum zinc (r = 0.27), creatinine clearance (r = -0.11), log gamma-glutamyltranspeptidase (r = 0.08), cholesterol (r = 0.07), contraceptive pill intake (r = -0.07), and log serum ferritin (r = 0.06). Before and after adjustment for significant covariates, serum zinc was, on average, lowest in the two districts where the body burden of cadmium, as assessed by urinary cadmium excretion, was highest. These results were not altered when subjects exposed to heavy metals at work were excluded from analysis.

Evaluation of exposure to polycyclic aromatic hydrocarbons in a coke production and a graphite electrode manufacturing plant: assessment of urinary excretion of 1-hydroxypyrene as a biological indicator of exposure

OBJECTIVES

Characterisation of the airborne concentration of 13 polycyclic aromatic hydrocarbons (PAHs) at various workplaces in a graphite electrode and a coke production plant. Validation of the urinary excretion of 1-hydroxypyrene (hydroxypyrene) as a biological marker of exposure to PAH.

DESIGN

Cross sectional study of workers exposed to PAHs (106 in the graphite electrode producing plant and 16 in the coke works).

METHODS

Personal air sampling during at least six hours per workshift using a glass fibre filter and a Chromosorb 102 solid sorbent tube and analysis of PAHs by high performance liquid chromatography (HPLC) and spectrofluorometric detection (SFD). Collection of spot urine samples before and after the shift and analysis of 1-hydroxypyrene by HPLC and SFD.

RESULTS

The workers most exposed to PAHs were those occupied at the topside area of the coke oven plant and those working in the blending and impregnation areas of the graphite electrode producing plant (mean airborne concentration of total PAHs: 199 and 223 micrograms/m3 respectively). Except for naphthalene and perylene, the relative proportion of the different PAHs did not differ between the plants. Pyrene concentration in air was highly correlated with the total airborne PAH concentration (r = 0.83, p < 0.0001) and the correlation coefficients between hydroxypyrene concentration in postshift urine samples and pyrene or total PAHs in air were 0.67 (p < 0.0001) and 0.72 (p < 0.0001) respectively. Excretion of hydroxypyrene doubled when the exposure to pyrene in air increased 10-fold. The half life for the urinary excretion of hydroxypyrene was around 18 hours (95% confidence interval 16.1-19.8). Smoking habits only explained 2.3% of the variance in hydroxypyrene excretion compared with 45% for the pyrene concentration in air.

CONCLUSION

The determination of the urinary excretion of hydroxypyrene in postshift urine samples can be used as a suitable biomarker to assess individual exposure to PAHs in coke ovens and in graphite electrode manufacturing plants.

Impact of environmental cadmium pollution on cadmium exposure and body burden

The body burden of cadmium, as estimated from 24-h urine cadmium levels, was determined in 1,523 subjects who were not occupationally exposed and who lived in five areas of Belgium. Urinary cadmium levels differed significantly with place of residence. These differences persisted after standardization for the other significant determinants (i.e., age, body mass index, smoking habits, social class, alcohol consumption, and menopause). The highest 24-h urine cadmium levels were found in subjects who lived in areas that contained cadmium-polluted soils. The body burden overload has been attributed mainly to the consumption of locally grown vegetables and the use of contaminated well water for cooking and drinking. Blood cadmium levels were also dependent on place of residence. However, the geographical differences in blood cadmium did not parallel those of urine cadmium. Blood cadmium is more influenced by recent exposure; therefore, this latter observation might reflect the recent implementation of preventive measures in some areas.

Impairment of renal function with increasing blood lead concentrations in the general population. The Cadmibel Study Group

BACKGROUND

Nephropathy is known to occur in persons with heavy exposure to lead. Whether exposure to lead in the general population leads to impaired renal function is not known.

METHODS

We studied renal function and indexes of lead exposure in a random population sample of 965 men and 1016 women (age range, 20 to 88 years). In all the subjects we measured creatinine clearance and blood concentrations of lead and zinc protoporphyrin (an indirect measure of blood lead level).

RESULTS

The mean (+/- SD) creatinine clearance rate was 99 +/- 30 ml per minute in the men and 80 +/- 25 ml per minute in the women. In the men the geometric mean blood lead concentration was 114 micrograms per liter (0.55 mumol per liter) (range, 23 to 725 micrograms per liter [0.11 to 3.5 mumol per liter]), and in the women 75 micrograms per liter (0.36 mumol per liter) (range, 17 to 603 micrograms per liter [0.08 to 2.9 mumol per liter]); the zinc protoporphyrin values in blood averaged 1.0 and 1.1 micrograms per gram of hemoglobin, respectively. The creatinine clearance rate was inversely correlated with blood lead and zinc protoporphyrin values in the men and the women both before and after adjustments for age, bodymass index, and diuretic treatment. A 10-fold increase in blood lead concentration was associated with a reduction of 10 to 13 ml per minute in creatinine clearance. We also found a positive correlation between serum beta 2-microglobulin (which is inversely related to the glomerular filtration rate) and blood lead in men, between serum beta 2-microglobulin and zinc protoporphyrin in both sexes, and between serum creatinine and zinc protoporphyrin in men.

CONCLUSIONS

Exposure to lead may impair renal function in the general population. The alternative hypothesis that renal impairment may lead to an increase in the blood lead concentration cannot be excluded, however.

Fertility of male workers exposed to cadmium, lead, or manganese

The effect of exposure to cadmium, lead, or manganese on male reproductive function was examined in 1988-1989 in Belgian blue-collar workers. The workers were exposed to cadmium in two smelters (n = 83; geometric mean urinary cadmium level = 6.94 micrograms/g of creatinine; mean duration of exposure = 24 years), to lead in a battery factory (n = 74; mean blood lead level = 46.3 micrograms/dl; mean duration of exposure = 10.7 years), or to manganese (manganese dioxide) in a dry alkaline battery plant (n = 70; median atmospheric concentration of total manganese dust = 0.71 mg/m3; mean duration of exposure = 6.2 years). Fertility in these workers and in an unexposed population (n = 138) was assessed by examining the birth experiences of their wives through a logistic regression model. The probability of a live birth was not different between the unexposed workers and the cadmium- or manganese-exposed workers before or after the onset of exposure. While the fertility of the lead-exposed workers was somewhat greater than that of the unexposed before the onset of exposure, a significant decrease in fertility was observed during the period of exposure to the metal (odds ratio = 0.65, 95% confidence interval 0.43-0.98).

Relation between airborne arsenic trioxide and urinary excretion of inorganic arsenic and its methylated metabolites

The relation between exposure to As2O3 fumes and dust, and the urinary excretion of inorganic arsenic metabolites (monomethylarsonic acid, dimethylarsinic acid, unchanged inorganic arsenic) has been studied in 18 workers from a sulphuric acid producing plant. The concentration of arsenic in the breathing zone of each worker was measured during five consecutive days and urine samples were obtained after one shift and before the next. The collection efficiency of the air sampling system exceeded 95%. The time weighted average exposure (TWA) concentrations of As2O3 ranged from 6 to 502 micrograms As/m3 and were log normally distributed. Although exposure probably occurred by ingestion as well as inhalation, statistically significant correlations (log scales) were found between airborne TWA of As2O3 and the inorganic arsenic metabolites in urine collected immediately after the shift, or just before the next shift. For a TWA of 50 micrograms As/m3, the mean concentration of the sum of the three inorganic arsenic metabolites in a postshift urine sample amounted to about 55 micrograms arsenic/g creatinine (95% confidence interval (95% CI) 47-62). Higher estimates of urinary arsenic reported by other authors are probably due either to the influence of dietary organoarsenicals when total arsenic is measured in urine or to a low retention efficiency of the air sampling system for As2O3 in the vapour phase.

Assessment of the permissible exposure level to manganese in workers exposed to manganese dioxide dust

The prevalence of neuropsychological and respiratory symptoms, lung ventilatory parameters, neurofunctional performances (visual reaction time, eye-hand coordination, hand steadiness, audioverbal short term memory), and several biological parameters (calcium, iron, luteinising hormone (LH), follicle stimulating hormone (FSH), and prolactin concentrations in serum, blood counts, manganese (Mn) concentration in blood and in urine) were examined in a group of workers (n = 92) exposed to MnO2 dust in a dry alkaline battery factory and a matched control group (n = 101). In the battery plant, the current exposure of the workers to airborne Mn was measured with personal samplers and amounted on average (geometric mean) to 215 and 948 micrograms Mn/m3 for respirable and total dust respectively. For each worker, the lifetime integrated exposure to respirable and total airborne Mn dust was also assessed. The geometric means of the Mn concentrations in blood (MnB) and in urine (MnU) were significantly higher in the Mn exposed group than in the control group (MnB 0.81 v 0.68 microgram/100 ml; MnU 0.84 v 0.09 microgram/g creatinine). On an individual basis, MnU and MnB were not related to various external exposure parameters (duration of exposure, current exposure, or lifetime integrated exposure to airborne Mn). On a group basis, a statistically significant association was found between MnU and current Mn concentrations in air. No appreciable difference between the exposed and the control workers was found with regard to the other biological measurements (calcium, LH, FSH, and prolactin in serum). Although the erythropoietic parameters and serum iron concentration were in the normal range for both groups, there was a statistically significant trend towards lower values in the Mn exposed workers. The prevalences of reported neuropsychological and respiratory symptoms, the lung function parameters, and the audioverbal short term memory scores did not differ between the control and exposed groups. The Mn workers, however, performed the other neurofunctional tests (visual reaction time, eye-hand coordination, hand steadiness) less satisfactorily than the control workers. For these tests, the prevalences of abnormal results were related to the lifetime integrated exposure to total and respirable Mn dust. On the basis of logistic regression analysis it may be inferred that an increased risk of peripheral tremor exists when the lifetime integrated exposure to Mn dust exceeds 3575 or 730 micrograms Mn/m3 x year for total and respirable dust respectively. The results clearly support a previous proposal by the authors to decrease the current time weighted average exposure to Mn dust.

Effects of exposure to cadmium on calcium metabolism: a population study

The objective was to investigate the hypothesis that environmental exposure to cadmium may affect calcium metabolism in the population at large. The 1987 participants (965 men and 1022 women), from 20 to 80 years old, constituted a random sample of the population of four Belgian districts. The urinary excretion of cadmium, a measure of lifetime exposure, averaged 9.3 nmol/24 h in men (range 0.4-324 nmol/24 h) and 7.1 nmol/24 h (range 0.1-71 nmol/24 h) in women. Serum alkaline phosphatase activity and the urinary excretion of calcium correlated significantly and positively with urinary cadmium excretion in both men and women, and serum total calcium concentration negatively with urinary cadmium excretion in men only. The regression coefficients obtained after adjustment for significant covariates indicated that when urinary cadmium excretion increased twofold, serum alkaline phosphatase activity and urinary calcium excretion rose by 3-4% and 0.25 mmol/24 h respectively, whereas in men serum total calcium concentration fell by 6 mumol/l. After adjustment for significant covariates the relation between serum total calcium concentration and urinary cadmium excretion was not significant in women. The findings suggest that even at environmental exposure levels calcium metabolism is gradually affected, as cadmium accumulates in the body. The morbidity associated with this phenomenon in industrialised countries remains presently unknown and requires further investigation.

Potentiation of diabetic glomerulopathy in uninephrectomized rats subchronically exposed to cadmium

The renal effects of diabetes mellitus and cadmium (Cd), separately or in combination, were investigated in unilaterally nephrectomized female Sprague-Dawley rats. Diabetes was induced by injection of streptozotocin and Cd was administered in drinking water at a concentration of 100 p.p.m. for 2.5 months. Cd did not affect the reduction in glomerular filtration rate or the rise in beta 2-microglobulinuria caused by diabetes. By contrast, the effect of diabetes on the urinary excretion of albumin, transferrin or IgG was greatly enhanced by concomitant exposure to Cd. This interaction occurred at Cd levels in the renal cortex which are very similar to those found in the general population of industrialized countries. These observations, in agreement with the results of a recent epidemiological study, suggest that Cd polluting the environment might potentiate the development of diabetic nephropathy.

Blood pressure, the prevalence of cardiovascular diseases, and exposure to cadmium: a population study

In a population study conducted from 1985 to 1989 in Belgium, the authors investigated whether exposure to cadmium is associated with blood pressure elevation and with an increased prevalence of cardiovascular diseases. The participants, aged 20-88 years, constituted a random sample of the households living in two low exposure areas (n = 803) and two high exposure areas (n = 1,283). For each exposure level, a rural and an urban district were selected. The cadmium levels in blood (8.5 vs. 11.0 nmol/liter) and urine (7.2 vs. 8.7 nmol/24 hours) were significantly (p less than 0.001) raised in the two high exposure areas compared with the two low exposure areas (p less than 0.001). Systolic pressure was similar in both rural areas, but in the urban area with high exposure systolic pressure was 5 mmHg (p less than 0.001) higher than in the control town. Diastolic pressure was similar in the four districts and the same was true for the prevalence of hypertension and of other cardiovascular diseases. Adjustment of systolic pressure for blood and urinary cadmium did not remove the difference in systolic pressure between both urban areas, suggesting that it was not related to the cadmium burden on the environment. Further analyses in individual subjects showed that neither blood pressure nor the presence of cardiovascular diseases were significantly and positively correlated with blood and urinary cadmium. Thus, the present population study did not confirm the hypothesis that increased exposure of the population to cadmium is associated with blood pressure elevation and with a higher prevalence of cardiovascular diseases.

Assessment of the filtration reserve capacity of the kidney in workers exposed to cadmium

It has been assessed whether an internal dose of cadmium (Cd), as reflected by a Cd concentration in urine not yet sufficient to induce a significantly increased urinary excretion of various plasma proteins (microproteinuria defined as beta 2-microglobulin in urine greater than 300 micrograms/g creatinine, or retinol-binding protein in urine greater than 300 micrograms/g creatinine, or albumin in urine greater than 15 mg/g creatinine, or a combination of these), may affect the filtration reserve capacity of the kidney. The last was determined by measuring the difference between the baseline creatinine clearance and the maximal creatinine clearance after an acute oral load of protein (400 g of cooked red meat). In total 215 men were examined of whom eventually 87 Cd exposed workers (concentration of Cd in urine greater than 2 micrograms/g creatinine) from zinc/cadmium smelters and 92 control workers (concentration of Cd in urine less than 2 micrograms/g creatinine, absence of microproteinuria, normal fasting serum creatinine) were retained for data analysis performed separately for workers aged less or more than 50 years. Microproteinuria was present in 20 Cd workers, all older than 50. This study confirmed the previous observation that the age related decline of the baseline glomerular filtration rate (GFR) is accelerated in male workers with Cd induced microproteinuria; the same observation was made for the maximal GFR. It was found, however, that a renal Cd burden that had not yet caused microproteinuria did not impair the filtration reserve capacity of the kidney. This study therefore validates the previous estimate of the threshold effect concentration of Cd in urine (10 micrograms/g creatinine) that is intended to prevent the occurrence of microproteinuria in male Cd workers. It should be kept in mind, however, that because of the likely interference of the healthy worker effect, this conclusion may not be directly extrapolated to the general population.

Experimental and human studies on antimony metabolism: their relevance for the biological monitoring of workers exposed to inorganic antimony

Unlike inorganic arsenic, inorganic trivalent antimony (Sb) is not methylated in vivo. It is excreted in the bile after conjugation with glutathione and also in urine. A significant proportion of that excreted in bile undergoes an enterohepatic circulation. In workers exposed to pentavalent Sb, the urinary Sb excretion is related to the intensity of exposure. It has been estimated that after eight hours exposure to 500 micrograms Sb/m3, the increase of urinary Sb concentration at the end of the shift amounts on average to 35 micrograms/g creatinine.

Does environmental exposure to cadmium represent a health risk? Conclusions from the Cadmibel study

Cadmium is a very dispersive pollutant which has progressively accumulated in the environment mainly in the areas where nonferrous smelters have been in operation. An important toxicological feature of cadmium is its exceptionally long biological half-life in the human body. For the general population mainly exposed to cadmium by the diet and smoking, the kidney is the main target organ. Some studies have also suggested that cadmium might play a role in the pathogenesis of hypertension. A cross-sectional study (called Cadmibel) was undertaken to assess whether environmental pollution by cadmium in Belgium might represent a health risk. This paper does not present the detailed results of this study which are published elsewhere but simply report its main conclusions. A total number of 2327 subjects (stratified according to age and sex) was randomly sampled in two urban (Liège and Charleroi) and two rural (Hechtel-Eksel and Noorderkempen) areas, with different environmental pollution by cadmium. After allowing for the various factors known to influence cadmium accumulation, it was estimated that the cadmium body burden of the residents of the most polluted district (Noorderkempen) was 50 to 85% higher than in the less polluted areas. No statistical association was found between environmental exposure to cadmium and blood pressure elevation or the prevalence of cardiovascular diseases. However, the study has shown that the environmental exposure of the general population to cadmium may induce slight renal tubular dysfunction and may probably also affect cadmium homeostasis. The probability of tubular dysfunction (as assessed by sensitive tests) is about 10% when cadmium in urine reaches 2 micrograms/day. The morbidity associated with the changes in the renal proximal tubule and the calcium metabolism observed when the body burden of cadmium exceeds this value remains to be assessed.