Proteinuria of Workers Exposed to Cadmium Fume

[Anemia induced by cadmium intoxication]

Anemia is commonly induced by chronic cadmium (Cd) intoxication. Three main factors are involved in the development of Cd-induced anemia: hemolytic, iron-deficiency, and renal. Intravascular hemolysis can occur at the early stage of Cd exposure owing to the direct damaging effect on erythrocytes. In addition, Cd that accumulates in erythrocytes affects membrane cytoskeletons and decreases cell deformability, and these cells are then trapped and destroyed in the spleen. Iron deficiency can be detected in animals after an oral exposure to Cd, which competes with iron for absorption in the intestines, leading to anemia. However, an increase in body iron content along with anemia is often observed in cases of parenteral exposure or itai-itai disease. Therefore, it is estimated that Cd disrupts the efficient usage of iron in hemoglobin synthesis in the body. Renal anemia is observed during the very last phase of chronic, severe Cd intoxication, such as itai-itai disease, showing a decrease in the production of erythropoietin from renal tubular cells. Because the renal anemia is based on the same pathophysiology as Cd-induced osteomalacia, which is derived from the disturbance of mineral metabolism due to renal tubular dysfunction, it is reasonable to include renal anemia in the criteria for the diagnosis of itai-itai disease. Hemodilution could also contribute to the development of Cd-induced anemia. Bone marrow hypoplasia or the inhibition of heme synthesis might only be involved in Cd-induced anemia in severe cases of Cd intoxication.

Smell impairment in workers occupationally exposed to cadmium

ENT and olfactometric examinations were carried out on 73 workers at an electrochemical plant involved in the production of cadmium-nickel batteries, where cadmium fumes were emitted into the workplace. Exposure levels exceeded the maximum allowable concentrations by about 1-2 times. The controls included 43 non-exposed, age- and cigarette-smoking-matched people. The olfactometric tests were carried out by the blast injection method, using natural coffee, aniseed, lemon and mint oils; two threshold measurements were assessed: maximum perceptible odour (MPO) and minimum identifiable odour (MIO). In addition, blood chemistries and urinalysis were carried out. The study revealed the smell lesion in 45.2% of the exposed group vs 4.6% of the controls. A statistically significant correlation between olfactory dysfunction and cadmium concentrations in the blood and urine was found; however, no correlation with the duration of employment was observed. It seems most likely that cigarette smoking, which is a considerable source of cadmium, may intensify this dysfunction, hence heavy smokers should not work in conditions of cadmium exposure.

Effects of inhalation of cadmium on the rat olfactory system: behavior and morphology

To investigate the effects of cadmium on olfaction, two separate studies were conducted in which male adult rats were exposed to CdO, via inhalation, for 5 h per day, 5 days a week for 20 weeks. Target exposure values of 250 and 500 micrograms/m3 were measured at 200 and 325 micrograms/m3 for the low concentration in two experiments, and 550 and 660 micrograms/m3 for the high concentration. Prior to exposure, olfactory thresholds were obtained using a conditioned suppression technique. After 20 weeks of cadmium exposure, there was no evidence of anosmia in any of the rats nor were there any significant changes observed in olfactory thresholds. Although olfaction was not impaired, cadmium levels in the olfactory bulbs of exposed rats were significantly elevated compared to controls. Cardiac and respiratory histopathology were observed at all exposure levels, but there was no evidence of nasal pathology related to exposure to cadmium. Failure of cadmium to produce olfactory dysfunction may be due to the protective effects of metallothionein and/or to the highly resilient nature of the rodent olfactory system.

Association of cadmium exposure with rapidly progressive emphysema in a smoker

Rapidly progressive emphysema developed in a 59 year old smoker after exposure to cadmium fumes in a factory. Very high levels of cadmium in air sampled at the workplace and in the patient's blood, urine, and lung tissue confirmed massive exposure. These data strongly suggest an association between the patient's cadmium exposure and the development of emphysema.

A comparison of the concepts used to develop and apply occupational exposure limits for ionizing radiation and hazardous chemical substances

The rationales used by the American Conference of Governmental Industrial Hygienists (AC-GIH) to recommend exposure limits for 10 chemicals were reviewed. The 10 chemicals chosen were known to produce chronic disease after prolonged overexposure in the workplace. The chemicals were toluene diisocyanate, hydrogen fluoride, n-hexane, carbon disulfide, cadmium, inorganic mercury, cobalt, nitroglycerol, silica, and vinyl chloride. The rationales used by the International Commission on Radiological Protection (ICRP) to recommend limits for workplace exposure to ionizing radiation were reviewed. The rationales used in occupational health by ACGIH were then compared with those used by ICRP in health physics. The comparison revealed a significant divergence in the underlying concepts and philosophies of the two approaches. This divergence cannot be solely attributed to differences in scientific knowledge about toxicological and radiological effects. In areas of scientific uncertainty, exposure limits for ionizing radiation are based on worst case or conservative assumptions. This approach favors human safety. Parallel approaches could not be found for any of the 10 chemicals reviewed. Other factors such as the costs incurred by industry in meeting the proposed standards played a more significant role in establishing limits for workplace chemicals than for ionizing radiation.

Human health effects of exposure to cadmium

The health effects of human exposure to cadmium are discussed with emphases on intake, absorption, body burden, and excretion; osteomalacia in Japan; hypertension; and proteinuria, emphysema, osteomalacia, and cancer in workers. Elevated blood pressure has not been observed as a result of excessive exposures to cadmium in Japan or the workplace. Renal tubular dysfunction and consequent proteinuria is generally accepted as the main effect following long-term, low-level exposure to cadmium. Studies of workers show that proteinuria may develop after the first year of exposure or many years after the last exposure. Proteinuria and deterioration of renal function may continue even after cessation of exposure. The immediate health significance of low-level proteinuria is still under debate. However, there is evidence that long-term renal tubular dysfunction may lead to abnormalities of calcium metabolism and osteomalacia. The few autopsy and cross-sectional studies of workers do not permit conclusions to be drawn regarding the relationship between cadmium exposure and emphysema. Retrospective and historical-prospective studies are needed to settle this important question. No conclusive evidence has been published regarding cadmium-induced cancer in humans. However, there is sufficient evidence to regard cadmium as a suspect renal and prostate carcinogen. Because of equivocal results and the absence of dose-response relationships, the studies reviewed should be used with caution in making regulatory decisions and low-dose risk assessments.

Biochemical and hematological studies on perch, Perca fluviatilis, from the cadmium-contaminated river Emån

In a field investigation, biochemical and hematological parameters were measured in perch, Perca fluviatilis, living in the cadmium-contaminated river Emån in the southeast of Sweden. The number of lymphocytes was 45-100% higher in perch from the contaminated area than in the reference perch, indicating a stimulated immune defense. In addition, the cadmium-loaded fish suffered from a slight anemia and a disturbed carbohydrate metabolism and blood plasma ion composition. The observed effects suggest that cadmium affects fish in the environment similar to what has been observed in laboratory studied. However, the weaker response may imply that the perch in the field stimulation have been adapted and thus acquired an increased resistance to cadmium.

Human health effects of exposure to cadmium

The health effects of human exposure to cadmium are discussed with emphasis on intake, absorption, body burden, and excretion; osteomalacia in Japan; hypertension; and proteinuria, emphysema, osteomalacia, and cancer in workers. Elevated blood pressure has not been observed as a result of excessive exposures to cadmium in Japan or the workplace. Renal tubular dysfunction and consequent proteinuria is generally accepted as the main effect following long-term, low-level exposure to cadmium. Studies of workers show that proteinuria may develop after the first year of exposure or many years after the last exposure. Proteinuria and deterioration of renal function may continue even after cessation of exposure. The immediate health significance of low-level proteinuria is still under debate. However, there is evidence that long-term renal tubular dysfunction may lead to abnormalities of calcium metabolism and osteomalacia. The few autopsy and cross-sectional studies of workers do not permit conclusions to be drawn regarding the relationship between cadmium exposure and emphysema. Retrospective and historical-prospective studies are needed to settle this important question. No conclusive evidence has been published regarding cadmium-induced cancer in humans. However, there is sufficient evidence to regard cadmium as a suspect renal and prostate carcinogen. Because of equivocal results and the absence of dose-response relationships, the studies reviewed should be used with caution in making regulatory decisions and low-dose risk assessments.

Potentiation of Cd-induced pulmonary injury in alpha 1-antitrypsin suppressed rats

The interrelationship of alpha 1-antitrypsin (alpha 1-AT) or serum trypsin inhibitor capacity (TIC) level and cadmium exposure in the induction of pulmonary lesions was investigated. Sprague-Dawley rats were exposed to CdCl2, galactosamine, or galactosamine + CdCl2 for 24 hr. Biochemical study indicated a 20% reduction of serum TIC in animals exposed to galactosamine. A marked, 50%, reduction of serum TIC was induced in animals exposed to galactosamine + CdCl2. Histopathological study revealed no major morphological lesions in lungs of animals exposed to either CdCl2 or galactosamine. However, extensive lesions, including polymorphonuclear leukocyte (PMN) infiltration, distortion and distention of the alveolar spaces, and massive hemorrhages were observed in the lungs of animals exposed to galactosamine + CdCl2. It is believed that cadmium can induce rapid lesions in the pulmonary tissues when the alpha 1-AT is significantly suppressed. The present investigation has provided direct evidence on the importance and interrelationship of cadmium and alpha 1-AT in pulmonary lesion development.

Cadmium metabolism and toxicity in rats after long-term subcutaneous administration

Male Sprague-Dawley rats were given sc injections of Cd at 0.5 mg/kg body weight, 6 d/wk, for 22 wk. Concentrations in the liver, kidney, spleen, heart, testis, and blood were determined every week for 8 wk and at the end of 10, 12, 15, and 22 wk. Daily excretion of Cd and total protein in urine were determined every week in another series of rats given the same dose for up to 25 wk. Hepatic and renal Cd increased linearly for the first several weeks of Cd injection. The Cd concentration in the kidney leveled off at 156 microgram/g wet tissue after 7 wk, whereas hepatic Cd continued to increase for a few more weeks, reached its maximum level (330 microgram/g) at 10 wk, and then declined. Blood Cd showed a steady increase expressed by a logarithmic curve for the first several weeks and a rapid rise in response to the decline of hepatic Cd. Urinary excretion of Cd increased linearly but slightly for several weeks from the beginning of injections. In this period daily excretion of Cd remained less than 1% of the daily Cd dose. From 6 wk the Cd excretion increased rapidly and reached a plateau of about 10 microgram/d (several percent of the daily dose) with a simultaneous increase in urinary excretion of total protein. Urinary excretion of Cd showed a second sharp increase after 10 wk and reached a higher plateau level of 95 microgram/d (about 63% of the daily dose). From these findings the response of the exposed animals could be divided into three stages. The first stage was characterized by a steady increase in hepatic and renal Cd and low-level excretion in the urine. This stage was regarded as a latent period of Cd poisoning. The second stage, which developed between 5 and 7 wk, was characterized by leveling off of Cd accumulation in the kidney and increased excretion of Cd and total protein in the urine. This was an initial toxic stage represented by renal lesions. The third stage was characterized by the second sharp increase in urinary Cd excretion and an elevated level of blood Cd after 10 wk. These responses were related to a decrease in the hepatic capacity for Cd retention as a result of toxic effects of Cd on the liver.