Bio-chemical and Toxic Effects of Cadmium

Cadmium as distinct was discovered by Stromeyer of Germany in 1817, Cadmium is highly toxic element.

Occurrence: Cd occurs in nature and is found in sulfide deposits. The natural sources of Cadmium are

1. Volcanic activity
2. Spray from occans and forest fires
3. Soil contains at about 4.5 ppm of Cd because of its biogenic enrichment in humid materials.

Industrial Uses:

• Cadmium is widely used in various alloy formulations electroplating, paint-pigments, plastics and sliver cadmium batteries.
• Cadmium stearates are used as stabilizers in the manufacture of PVC.
• Cadmium acetate is employed for producing iridescent effects on porcelain and potteries.
• Cadmium bromide and iodide are used in photography, process engraving and lithography.
• Cadmium oxide is used in glass manufacture, in ceramic glazes, in electroplating and in the manufacture of ceramic alloys.
• Cadmium selenite is used in photoelectric cells, photoconductors, rectifiers and in phosphors.
• Cadmium sulphide is used in colouring glass, soaps, textiles, paper, rubber, printing inks, ceramic glazes and fireworks.

Pollution Sources:

• About 52% of total cadmium pollution comes from the incineration or disposal of cadmium-bearing products such as automobile tires, motor oils, fungicides, plastics, and coal.
• Human’s activity adds more cadmium to the atmosphere than natural sources, coal mining, non-ferrous metal mining, refineries, coal combustion, burning of iron and steel industries and phosphate fertilizers are main sources of cadmium.

Biochemical effects of Cadmium:

• Cadmium acts as an inhibitor of sulphydryl enzymes.
• It has also got the affinity for other ligands in cells, such as hydroxyl, carboxyl, phosphatidyl, cysteinyl and histidyl sidechains of proteins, purines, and porphyrin.
• It can disrupt pathways of oxidative phosphorylation.
• Cadmium interacts or competes with others metals such as Cu, Fe, and Zn and induces the deficiency symptoms of these essential metals.

Metabolism of Cadmium

The major portion of Cd ingested into our body is trapped in kidneys and eliminated. A small fraction is bound most effectively by the body proteins, metallothionein, present in the kidneys, while the rest is stored in the body and gradually accumulates with age. When excessive amounts of Cd²⁺ are ingested, it replaces Zn²⁺ at key enzymatic sites, causing metabolic disorders.

Toxic effects of Cadmium:

Cadmium is highly toxic because of the absence of homeostatic control for this metal in the human body. The general population is exposed to cadmium via ingestion or inhalation. The workers in mining and smelting industries may be occupationally exposed to higher levels of Cd in the body by steady accumulation over a long period.

The symptoms of cadmium toxicity produced by enzymatic inhibition include hypertension, respiratory disorders, damage to kidney and liver, aminoaciduria, hypercalciuria, glucosuria, proteinuria, osteoporosis, the formation of kidney stones etc. Carcinogenic and teratogenic effects have also been observed in epidemiological studies on animals.

Itai-Itai disease

A disease specifically associated with Cadmium poisoning was recognized in Japan. People were consuming the rice which was contaminated with Cadmium and they were ingesting 100 to 1000 mg of Cd every day. The pollution was due to a nearby mining complex and by the end of 1965, about 100 deaths were reported the victims accumulated about 500 to 600 mg of Cd in their body over several years of consuming the contaminated rice as their staple food and finally fell fatal due to the so-called Itai- Itai disease.

The disease was characterized by kidney malfunction; drop in the phosphate level of the blood serum, loss severe osteoporosis.

Treatment of Cadmium poisoning:

There is no specific antidote for acute cadmium poisoning. The mainstay of management for most inhalation exposure victims’ in supportive treatment including.

• Fluid replacement
• Supplemental oxygen and
• Mechanical ventilation

In case of ingestion, gastric decontamination by emesis or gastric lavage can be helpful just after being exposed .The most effective treatments for actuate cadmium poisoning by ingestion are:

• Standard chelation therapy by using calcium disodium ethylenediamine tetra acetic acid.
• Standard chelation therapy using dimercaprol.

Written by

Farhana Afrin
M.Sc. Student
Dept. of Chemistry
RU

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