Cadmium is a heavy metal which has numerous applications, primarily in the manufacture of rechargeable batteries and pigments. Substantial amounts of cadmium are released into the atmosphere from incinerators and factories, and if they are inhaled could lead to cadmium poisoning. Therefore, atmospheric cadmium levels are highest in industrial regions. Cadmium has also been found, albeit in small quantities, in fertilizers but the long-term application of the fertilizers can contaminate the soil. The metal has been established as a human carcinogen when ingested and inhaled. When inhaled, cadmium poisoning manifests itself in the form of muscle aches, chills, and fevers. Long-term exposure to cadmium fumes can lead to irreversible loss of smell and lung damage. The most profound effect of ingested cadmium is the weakening of the bones which lead to bone fractures. Kidney stones and renal failure has also been associated with cadmium poisoning.
Cadmium sulfide and cadmium sulfoselenide are the two primary cadmium-based compounds used in the manufacture of cadmium pigments. An estimated 2,000 tons of cadmium pigments are manufactured each year around the world, accounting for about half the annual cadmium production globally. Cadmium pigments are preferred on plastic surfaces which withstand temperatures of up to 3,000 degrees Celsius. While cadmium sulfide pigments are not highly toxic, the toxicity is highest in cadmium vapors which emanate from welding. The toxic effects of long-term cadmium exposure have made many of its traditional users to turn to other alternative pigments, one of which being azo pigments. Australia leads in the war against cadmium-based pigments and has banned the use of the pigments on plastics used to manufacture toys.
Cadmium is the main component in the manufacture of nickel-cadmium rechargeable batteries and makes up the battery’s negative electrode plate. Industrial nickel-cadmium batteries contain about 6% cadmium while the content of cadmium in commercial nickel-cadmium batteries is up to 18%. Workers in factories where nickel-cadmium batteries are manufactured are at the highest risk of cadmium poisoning from the batteries. The disposal of the batteries is a source of cadmium pollution and puts people at risk of cadmium poisoning. Many battery companies in the world have acknowledged the toxicity of cadmium and have phased out nickel-cadmium batteries, replacing them with lithium-ion batteries and nickel-metal hydride batteries. The European Union has banned the commercial use of nickel-cadmium batteries since 2016, while the batteries producers should do the disposal of industrial nickel-cadmium batteries.
The “Itai-Itai” Disease
The Itai-Itai disease is an ailment linked to cadmium poisoning and is most prevalent in Japan’s Toyama Prefecture which has a long history of the mining of heavy metals. The disease gets its name from its most common symptom, acute joint and spinal pains (“Itai-Itai” translates to “it hurts, it hurts”). Mining in the Toyama Prefecture dates back to the early 18th century, but large-scale mining of heavy metals began in the 20th century. Cadmium was among the by-products from the mining operations, and it released into the Jinzu River, which is the primary source of the water used in rice farming. The fish in the river were first affected by the cadmium, which was later absorbed by the rice. Eventually, people in the region started experiencing the severe joint and spinal pains characteristic of the cadmium disease.