Cadmium

Cadmium is a soft, bluish white-metal that has similarities with transition metals. The average concentration of cadmium in the Earth's crust is between 0.1 and 0.5 parts per million (ppm). Cadmium is always associated with zinc. As a result, enough cadmium is obtained as a bi-product of zinc, lead and copper refining to furnish industrial needs. Approximately 14,000 tons of cadmium are produced each year.

Because pure cadmium is soft, easily formed into shapes, easily stretched, and resistant to corrosion it has a lot of uses. One of the best known uses is nickel-cadmium rechargeable batteries. Batteries account for about 75% of cadmium use. In addition to batteries, cadmium is used to make other electronic components. Cadmium makes an excellent protective layer for other metals. Another use of cadmium is electroplating to protect equipment parts, and the surfaces of ships, boats, and aircraft. Electroplating accounts for about 6% of the need for cadmium. Cadmium is used to help regulate nuclear fission. It is used as a stabilizer for plastics. Because of the many colors that can be formed by different kinds of cadmium containing compounds, it is widely used as pigments for art supplies. Another important source of cadmium emissions is the production and use of artificial phosphate fertilizers. In addition, people are exposed through the emissions produced by burning coal and petroleum products.

Common exposure thresholds

The minimum concentration level (MCL) for cadmium in drinking water is 0.005 milligrams per liter (mg/L).

Cadmium is difficult for the kidneys to excrete. Kidney damage may be present when levels of cadmium in the urine are above 10 micrograms per liter (μg/l).

The 4CSBC uses the National Health and Nutrition Examination Survey (NHANES) 95th percentile level as a screening threshold. Only five percent of the NHANES participants (representing the American population) have levels that exceed the 95th percentile level. Everyone else is below that level. Thus, that level is considered elevated. It may or may not be harmful. The 95th percentile screening threshold for cadmium is 1.1 μg/L

Whole blood levels at or greater than 5.0 μg/l are considered hazardous.

Health concerns

Most people are exposed to cadmium mainly through the consumption of foods. For example, liver, mushrooms, shellfish, cocoa powder, and dried seaweed, are all known to be sources of cadmium exposure. The use to tobacco is another significant source of cadmium exposure for some people. In addition, people who live near metal refining or cadmium using industries may be exposed to cadmium. Natural cadmium is not readily soluble in water. However, the use of some types of fertilizers can result in cadmium getting into water systems.

When cadmium enters the body it is first transported by blood to the liver. In the liver, cadmium binds to proteins to form complexes that are transported to the kidney. As cadmium accumulates in the kidneys, it damages the kidneys filtering mechanisms. This damage causes further kidney damage and can result in excretion of essential proteins and sugars from the body. When the kidneys are not working properly, other systems in the body can be harmed as well. One of the most sensitive systems is the central nervous system. Besides kidney damage, other health effects associated with cadmium poisoning include bone weakness and possible bone fractures; reproductive failure and infertility; weakened immunity; damage to cellular DNA maintenance; psychological and cognitive disorders developed from damage to the central nervous system.

Cadmium is classified as a known carcinogen (cancer causing agent) by the International Agency for Research on Cancer and the National Toxicology Program. Breathing cadmium fumes in the air as been associated with lung cancer. Cadmium exposure has been associated with cancers of the kidneys, pancreas, breast tissue, the prostate, and the urinary bladder.

Sources of additional information

Agency for Toxic Substances and Disease Registry (ATSDR)

Centers for Disease Control and Prevention (CDC)

U.S. Environmental Protection Agency (EPA)

International Agency for Research on Cancer (IARC)

Papers

Last Update: May 5, 2016