By Syndi Nettles Anderson, guest writer for the Independence Institute Energy Policy Center
Earlier this week Todd Shepherd of Complete Colorado reported that before thin-filmed cadmium-telluride solar panel manufacturer Abound Solar declared bankruptcy it was the subject of a Colorado Department of Public Health and Environment (CDPHE) investigation after an anonymous tip raised concerns about cadmium contamination.
Shepherd provided documents showing that the now abandoned Weld County plant produced monthly 630 pounds of highly toxic cadmium waste that was shipped to Deer Trail in Arapahoe County for storage.
Because of the recent interest in cadmium, below is a primer on the rare earth element used in so many products besides solar panels.
Cadmium, one of the 17 rare earth elements (REE), is a soft silver-grey metal, commonly found in ores containing zinc. Products that use significant cadmium include rechargeable batteries, solar cells and protective steel coatings. Recently cadmium has been priced about a dollar per pound.
Cadmium is a byproduct when zinc is refined from zinc ore, or recycled from nickel-cadmium rechargeable batteries. The largest producers of cadmium are China, South Korea, Japan and North America. The concentration of cadmium in the earth’s crust is between 0.1 and 0.5 parts per million (ppm). This is about one hundred times more common than gold.
Cadmium is very useful in rechargeable batteries and solar cells. In the U.S., about 27 percent of cadmium-nickel batteries are recycled, which requires batteries to be taken apart.
However, cadmium is also very poisonous. Exposure is most dangerous when breathing in dust or vapors containing cadmium. Other methods of exposure are also dangerous, as cadmium can be absorbed through the skin or by ingestion.
People can absorb cadmium through inhalation, absorption or by eating it. The cadmium is transported through the body by blood cells and plasma. Cadmium goes into the kidneys, resulting in kidney failure. Before toxic levels are reached, kidney function will start to deteriorate. Generally a third to half of the cadmium that is in a body will be found in the kidneys. Cadmium will also move to the liver and muscles. In the liver, the half-life of the cadmium is 5-15 years, in the muscles-30 years and in the kidneys 10-30 years.
During ore smelting processes, cadmium is released into the air. It may also be released into the atmosphere by burning cadmium-containing garbage. Cadmium exposure can cause throat and lung irritation. Lower levels of exposure also cause shortness of breath, and with prolonged exposure resulting in bronchiolitis and emphysema with lung damage, bloody coughing, and accumulation of fluids in the body. One highly concentrated exposure can cause lifetime damage to lungs. 
Metal fume fever can be caused by inhaling cadmium during the welding and metal heating processes of older silver solder. Metal fume fever can cause flu like symptoms with fainting, sore throats, coughs, and headaches. Working with cadmium requires extremely well ventilated areas, respirators, and extreme care. Regular blood and urine checks are required to monitor the amount of cadmium that can get into the body. 
Phosphate fertilizers, sewage sludge and contaminated water can deposit cadmium into food sources. Growing rice and wheat can absorb Cadmium. Large ocean fish can also take up a lot of cadmium. Smokers also intake cadmium into their bodies and have about double the cadmium levels that non-smokers have. Cadmium is associated with breast cancer, lung cancer, prostate cancer, heart disease, and kidney dysfunction. 
As a result of the increased awareness of the danger of cadmium to humans, the EPA released a new report December 3, 2012, expanding the regulations and proposing new regulations regarding cadmium.
This final rule requires manufacturers (including importers) of cadmium or cadmium compounds, including as part of an article, that have been, or are reasonably likely to be, incorporated into consumer products to report certain unpublished health and safety studies to EPA. 
Occupational Safety Health Association (OSHA) also highly regulates workers contact with cadmium stating,
Cadmium and its compounds are highly toxic and exposure to this metal is known to cause cancer and targets the body’s cardiovascular, renal, gastrointestinal, neurological, reproductive, and respiratory systems.
Requirements to protect workers from cadmium exposure are addressed in specific OSHA cadmium standards covering general industry (1910.1027), shipyards (1915.1027), construction (1926.1127) and agriculture (1928.1027).
In conclusion, Cadmium is critical to the solar cell and rechargeable battery industry but extreme care must be taken to prevent cadmium from getting into the air, water or plant life. Cancer, lung damage and kidney failure are real risks for cadmium exposure.
 Wilburn, D.R., 2007, Flow of cadmium from rechargeable batteries in the United States, 1996-2007: U.S. Geological Survey Scientific Investigations Report 2007–5198, 26 p., available at http://pubs.usgs.gov/sir/2007/5198/.
 Common environmental contaminant, cadmium, linked to rapid breast cancer cell growth. ScienceDaily. Retrieved February 14, 2013, from http://www.sciencedaily.com /releases/2012/04/120423184203.htm
American Association for Cancer Research (AACR) (2012, March 15). Dietary cadmium may be linked with breast cancer risk. ScienceDaily. Retrieved February 14, 2013, from http://www.sciencedaily.com /releases/2012/03/120315094506.htm
Cell Press (2012, September 12). Studies shed light on how to reduce the amount of toxins in plant-derived foods. ScienceDaily. Retrieved February 14, 2013, from http://www.sciencedaily.com /releases/2012/09/120912125517.htm