Postexercise proteinuria in childhood and adolescence.

Postexercise proteinuria has been observed in healthy adults but there was a need for information in young individuals. Boys and girls (n = 170) from 6 to 18 years of age were submitted to maximal exercise by the 20-meter shuttle run test. Urine collection was made prior to and 30 min after completion of the run. Total protein, albumin, beta 2-microglobulin (beta 2-m), retinol-binding protein (RBP) and creatinine were determined on each sample. Resting values for total protein, albumin, beta 2-m and RBP excretion rates were within the normal range for each component with a progressive increase for total protein and albumin. The effect of exercise increased with age. Between the 6 and 9 year olds there was a gender difference in postexercise proteinuria, boys enhanced the excretion of macromolecules while girls did not show any increase by maximal exercise. The excretion rates of all protein components were related to the absolute intensity of exercise expressed as maximal speed (R between 0.86 and 0.90, p < 0.001). High- and low-molecular weight protein excretion gave evidence of increasing disturbances from the age of 9 to 18 years in boys and girls. These data clearly demonstrate that 1) postexercise proteinuria is present at maximal exercise from childhood to adolescence; 2) the magnitude of protein excretion is strictly related to the absolute intensity of exercise; 3) the glomerulus permeability and the tubular reabsorption process are both different in pre- and postpubertal children and adolescents.

External quality assessment scheme in Belgium. Heavy metal analyses.

An external quality assessment scheme for heavy metal analyses has been implemented in Belgium (quality control in Belgium, QCB) by the Epidemiology Unit of the Institute of Hygiene and Epidemiology since 1993. Aims of the scheme are to improve laboratories performances by means of interlaboratory comparisons and to provide national authority with information about the dispersion of results for heavy metal analyses in Belgium. The analytes included in the QCB are lead, cadmium and selenium in blood. Control samples are in-house prepared from human blood, spiked with appropriate amounts of Pb, Cd and Se. Four exercises are performed every year and participants receive three samples to analyze. Target values are calculated for each element from the regression lines obtained by plotting the results of a reference laboratory against the added amounts. The QCB does not yet include acceptability criteria of the results and no measures are taken against poor performers at this stage, although advice is available by personal contacts with the organisers.

Influence of running different distances on renal glomerular and tubular impairment in humans.

Strenuous exercise has been claimed to modify renal glomerular and tubular function, the relative involvement of the two sites being unknown. These changes may be assessed by the determination of plasma high and low molecular mass proteins. A group of 13 man performed five runs (100, 400, 800, 1,500, 3,000 m) at maximal speed. The excretion rates and renal clearances of creatinine, albumin (Alb), beta 2-microglobulin (beta 2-m) and retinol-binding protein (RBP) were determined before and after each run. The glomerular filtration rate remained stable during the shorter runs and declined by about 40% during the longer runs. The excretion rate for Alb rose from 10-fold above the basal value (6 micrograms.min-1) for the 100 m to 49-fold for the 800 m and then declined for distances up to 3,000 m. The beta 2-m and RBP had a lesser initial increase, 3.5-(rest 55 ng.min-1) and 7.6-(rest 116 ng.min-1) fold, respectively, for the 100 m run and thereafter showed a higher excretion rate than Alb for the 400 m and 800 m runs. The renal clearances of these high (Alb) and low molecular mass (beta 2-m and RBP) proteins followed the changes observed for excretion rates. There was a linear relationship (r2 = 0.996) between plasma lactate concentration and total protein excretion in the postexercise period when taking all five runs into consideration. Glomerular permeability was primarily affected by the 100-m run while the longer runs modified both the glomerular and the tubular sites. To conclude, the present study demonstrated a differential response of the kidney to strenuous exercise with respect to the intensity and duration of the events.

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.

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.

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.

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.

Renal effects of cadmium body burden of the general population.

In a cross-sectional population study to assess whether environmental exposure to cadmium is associated with renal dysfunction, 1699 subjects aged 20-80 years were studied as a random sample of four areas of Belgium with varying degrees of cadmium pollution. After standardisation for several possible confounding factors, five variables (urinary excretion of retinol-binding protein, N-acetyl-beta-glucosaminidase, beta 2-microglobulin, aminoacids, and calcium) were significantly associated with the urinary excretion of cadmium (as a marker of cadmium body burden), suggesting the presence of tubular dysfunction. There was a 10% probability of values of these variables being abnormal when cadmium excretion exceeded 2-4 micrograms/24 h. Excretion reached this threshold in 10% of non-smokers. There was also evidence that diabetic patients may be more susceptible to the toxic effect of cadmium on the renal proximal tubule.

Health effects of environmental exposure to cadmium: objectives, design and organization of the Cadmibel Study: a cross-sectional morbidity study carried out in Belgium from 1985 to 1989.

Cadmium is a cumulative environmental pollutant. For the general population mainly exposed by the oral route and through tobacco smoke inhalation, the kidney is the critical organ. Belgium is the principal producer of cadmium in Europe, and certain areas of the country are polluted by cadmium mainly because of past emissions from nonferrous industries. Preliminary studies carried out in one polluted area have suggested that environmental pollution might lead to an increased uptake of cadmium by the human body and possibly to health effects. Thus, a large-scale morbidity study has been initiated to assess the validity of this hypothesis. The present paper describes the protocol of this study. Its main objectives are to determine to what extent environmental exposure to cadmium resulting from industrial emissions may lead to accumulation of the metal in the human organism; to establish whether or not environmental exposure may induce renal changes and/or influence blood pressure; and to assess the acceptable internal dose of cadmium for the general population. The study design takes advantage of the fact that biological indicators of exposure, body burden, and early nephrotoxic effects of cadmium are available, which increase the likelihood of detecting a cause-effect relationship.