Adverse health effects in workers exposed to cadmium

Urinary cadmium levels in the U S working population, 1988-1994

Few studies have estimated the prevalence and mean urinary cadmium levels in U.S. workers and the factors associated with high cadmium exposure. In this study, urinary cadmium measurements were obtained on 11228 U.S. workers aged 18 to 64 years who participated in the Third National Health and Nutrition Examination Survey (NHANES III, 1988-1994). Urinary cadmium levels ranged from 0.01 to 15.57 microg/L, with a geometric mean of 0.30 microg/L (0.28 microg/g creatinine) for all U.S. workers. The prevalence of urinary cadmium levels >or=5 microg/L was 0.42% (551000) for U.S. workers aged 18 to 64 years. Among U.S. workers in the metal industry (two-digit Standard Industrial Classification or SIC codes 33 and 34), the geometric mean urinary cadmium level was 0.48 microg/L (0.39 microg/g creatinine), and 0.45% of these workers had urinary cadmium levels >or=10 microg/L. The prevalence of urinary cadmium levels >or=15 microg/L was 0.0028% (3907). The agriculture industry (two-digit SIC codes 01, 02, and 07-09) was associated with low urinary cadmium levels, compared with repair services industries (two-digit SIC codes 75 and 76). Results from ordinary least squares regression analyses indicated that smokers had significantly higher urinary cadmium levels than nonsmokers (p <or= 0.0001). The results also showed that there were high urinary cadmium levels among workers in selected occupations and industries.

Changes in the structure and function of the kidney of rats chronically exposed to cadmium. I. Biochemical and histopathological studies

The aim of this study was to assess the effects of chronic exposure to cadmium (Cd) on the structure and function of kidneys, as well as to establish the body burden of Cd at which the changes occur. For this purpose we have created an experimental model using rats intoxicated with Cd administered in drinking water at the concentration of 5 or 50 mg Cd/l for 6, 12 and 24 weeks. The degree of kidney damage was evaluated biochemically and histopathologically. Sensitive biomarkers of Cd-induced proximal tubular injury such as urinary total N-acetyl-beta- d-glucosaminidase (NAG-T) and its isoenzyme B (NAG-B), and alkaline phosphatase (ALP) were used. Cd content in the kidney increased with the level and duration of exposure leading to dose- and time-dependent structural and functional renal failure. In rats exposed to 5 mg Cd/l, first symptoms of injury of the main tubules of long and short nephrons (structural damage to epithelial cells, increased urinary activities of NAG-T and NAG-B) were noted after 12 weeks of the experiment. The damage occurred at a low kidney Cd concentration amounting to 4.08+/-0.33 micro g/g wet weight (mean +/-SE) and a urinary concentration of 4.31+/-0.28 micro g/g creatinine. On exposure to 50 mg Cd/l, damage to the main tubules (blurred structure of tubular epithelium, atrophy of brush border, partial fragmentation of cells with release of nuclei into tubular lumen as well as increased urinary activities of NAG-T, NAG-B and ALP) was already evident after 6 weeks with the kidney Cd concentration of 24.09+/-1.72 micro g/g wet weight. In rats exposed to 50 mg Cd/l, a lack of regular contour of glomeruli was noted after 12 weeks, whereas after 24 weeks thickening of capillary vessels and widening of filtering space were evident. After 24 weeks of exposure to Cd, increased urea concentration in the serum with simultaneous decrease in its level in the urine, indicating decreased clearance of urea, and increased excretion of total protein were observed, but endogenous creatinine clearance remained unaffected. At the lower exposure, symptoms of structural, but not functional, damage to the glomeruli were also evident after 24 weeks of the experiment. Our results provide evidence that chronic exposure to Cd dose-dependently damages (structurally and functionally) the whole kidney. The injury affects the main resorptive part (proximal convoluted tubules and straight tubules) and the filtering part (glomeruli) of the nephron. But the target site for Cd action is the main tubule. We hypothesize that the threshold for Cd effects on the kidney is less than 4.08+/-0.33 micro g/g wet kidney weight and greater than 2.40+/-0.15 micro g/g (at this Cd concentration no symptoms of kidney damage were noted), and it may be close to the latter value. A very important finding of this study is that Cd acts on the whole kidney, especially on the main tubules, even at relatively low accumulation in this organ. It confirms the hypothesis that humans environmentally exposed to Cd, especially smokers, are at risk of tubular dysfunction.

Influence of cadmium speciation for the evaluation of in vitro cadmium toxicity on LLC-PK(1) cells

The main objective of the present work was to assess the potentiality of in vitro models to improve our understanding of cadmium-induced toxicity, especially on epithelial renal cells. Indeed cadmium, a potent toxic metal, poses a serious environmental threat and the mechanisms of its renal toxicity need to be clarified. Cytotoxicity studies presented here were performed in a tubular proximal original established porcine kidney cell line (LLC-PK(1)). We have compared cytotoxicity induced by different chemical cadmium forms in LLC-PK(1) cells as a function of media cell culture pH and protein content. Cadmium stock solutions were prepared either by dissolving cadmium chloride or cadmium sulphate with increasing protein concentrations in the media cell culture. Its pH was monitored during experiments. Cytotoxicity was measured by neutral red uptake after 24 h of exposure. Dose-dependent cytotoxicity curves, calculated with REGTOX, were systematically correlated with pH and protein content. Experiments in vitro revealed that cadmium was dose-dependently toxic for LLC-PK(1) for concentrations ranging from 10(-4) to 10(-6) M. We have noticed a lack of influence of the media cell culture pH on the cadmium cytotoxicity. REGTOX determines closely the EC(50) values but EC(50)CdCl(2)>EC(50)CdSO(4) and cadmium have been assayed with an inductively coupled atomic emission spectrometer (ICP/AES) directly in the media cell culture and the cellular pellet.