Cadmium long-term exposure

Like many technological innovations, nickel-cadmium batteries carry risks as well as benefits. After being discharged repeatedly, they eventually wear out. In theory, worn-out nicad batteries should be recycled. In practice, however, many end up in garbage dumps. Over time, discarded nicad batteries release toxic cadmium. The toxicity of this substance makes it hazardous to the environment, as cadmium can enter the food chain. Long-term exposure to low levels of cadmium can have serious medical effects on humans, such as high blood pressure and heart disease. 

Cadmium is a cumulative toxicant with a biologic half-life of up to 30 years in humans. More than 70% of the cadmium in the blood is bound to red blood cells accumulation occurs mainly in the kidney and the liver, where cadmium is bound to metallothionein. In humans the critical target organ after long-term exposure to cadmium is the kidney, with the first detectable symptom of kidney toxicity being an increased excretion of specific proteins. 

Chronic effects are of particular concern because cadmium is very slowly excreted from the body, with a half-life of about 30 years. Thus low levels of exposure can result in considerable accumulation of cadmium. The main organ of damage following long-term exposure is the kidney, with the proximal tubules being the primary site of... 

The results of studies on animals show that cadmium is an extremely toxic metal. Cadmium is poorly excreted by the human body and although only 5-10% of that ingested is absorbed, it does accumulate in the body over time with renal damage being caused by long-term exposure.14 One sign of this damage is proteinuria (the appearance of increased levels of unaltered proteins in the... 

Toxicokinetics Toxic effects of cadmium Acute toxicity Long-term exposure Reproductive toxicity Carcinogenicity Nephrotoxicity ... 

Since the kidneys are the main depot for cadmium, they are of greatest concern for cadmium toxicity. Cadmium interferes with the proximal tubule s reabsorption function. This leads to abnormal actions of uric acid, calcium, and phosphorus. Amino aciduria (amino acids in the urine) and glucosuria (glucose in the urine) result in later stages, proteinuria (protein in the urine) results. When this happens, it is assumed that there is a marked decrease in glomerular filtration. Long-term exposure to cadmium leads to anemia, which may result from cadmium interfering with iron absorption. 

Lauwerys RR, Bernard A, Rods H, et al. 1992. Health risk assessment of long term exposure to chemicals Application to cadmium and manganese. Arch Toxicol Suppl 15 97-102. 

The toxic effects of long-term exposure to cadmium differ somewhat with the route of exposure. 

Short and long term exposure to cadmium and detoxifying capabilities of C. brunneus... 

Human exposure to high concentrations of cadmium are rare and current concern centers around the chronic toxicity caused by long-term exposure to low levels of the metal. Bone disorders are one manifestation of chronic cadmium exposure. Cadmium is present in all tissues of adults, with the most significant amounts found in the liver and kidney, and the concentrations tend to increase with age. The WHO regards a tolerable daily intake of cadmium to be 70pgd for an adult of 70 kg. 

Fig. I V.3. Adhesion of zirconium particles to cadmium sulfide surface (1) in the dark (2) with brief exposure to light (3) with steady, long-term exposure to light.

Long-term (chronic) exposure. Repeated or long-term exposure to cadmium, even at relatively low concentrations, may result in kidney damage and an increased risk of cancer of the lung and of the prostate. 

In addition to acute lung effects and chronic renal effects, long term exposure to cadmium may cause other severe effects on the respiratory system. Reduced pulmonary function and chronic lung disease indicative of emphysema have been observed in workers who have had prolonged exposure to cadmium dust or fumes (Exs. 4-29, 4-22, 4-42, 4-50, 4-63). In a Study of workers conducted by Kazantzis et a ., a statistically significant excess of worker deaths due to chronic bronchitis was found, which in his opinion was directly related to high cadmium exposures of 1 mg/m or more (Tr. 6/8/90, pp. 156-157). 

For preventing kidney dysfunction following long-term exposure to Cd, one must define the critical dose of cadmium, that is the dose which under chronic exposure conditions may lead to the appearance of adverse functional changes in the kidney. Attempts have been made to evaluate the critical internal dose of cadmium, i.e. the amount of cadmium absorbed which gives rise to renal disturbances in a certain percentage of the exposed population. Since we have sufficient information on the metabolism of cadmium in man, it is then possible to estimate the external critical dose (air, food, water). 

Adamsson E, Piscator M, Nogawa K (1979) Pulmonary and gastrointestinal exposure to cadmium oxide dust in a battery factory. Environ. Health Perspect. 28 219-222 Al-Haddad IK, Chettle DR, Fletcher JG, Fremlin JH (1981) A transportable system for measurement of kidney cadmium in vivo. Int. J. Appl. Radiat. Isot. 32 109-112 Bernard A, Buchet JP, Roels H, Masson PL, Lauwerys R (1979) Renal excretion of proteins and enzymes in workers exposed to cadmium. Eur. J. Clin. Invest. 9 11-22 Bernard A, Goret A, Buchet JP, Roels H, Lauwerys R (1980) Significance of cadmium levels in blood and urine during long-term exposure of rats to cadmium. J. Toxicol. Environ. Health 16 31-41... 

The lack of epidemiological studies evaluating the effects of cadmium on the immune system make it difficult to assess its effects in humans. Reports of cadmium immunotoxicity in rodents after long-term exposure would argue for the need for human clinical studies (for reviews, see Roller 1980 Descotes 1992). Mice chronically exposed to cadmium exhibit an immunosuppressive effect on the humoral immune response, i.e., a decreased antibody response (Roller et al. 1975) however, conflicting results demonstrate an elevated antibody response or no response. An immunosuppressive effect of cadmium on cell-mediated immunity, i.e., a decrease in delayed-type hypersensitivity, has also been reported in mice (Muller et al. 1979). Cadmium has been shown to decrease phagocytosis in peritoneal macro-... 

A recently pubhshed study has shown that exposure to cadmium and elevated temperature can also have an evolutionary effect. When Daphnia magm (a freshwater flea commonly used for testing ecotoxicity) were exposed to a combination of higher temperature and cadmium, microevolutionary effects (several fitness traits) were observed [64]. This research suggests that long-term exposures to thermal stress, coupled with toxic exposure, may have unanticipated evolutionary effects. 

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