Cadmium (Cd) is a soft, silver-white or blue, lustrous metal typically found in mineral deposits with lead, zinc and copper. Cadmium is normally found in the forms of cadmium oxide, cadmium chloride, or cadmium sulfate/sulfide. Cadmium most frequently occurs in zinc deposits as cadmium sulfide and is a by- product of zinc concentrates, making its production dependent on the demand for zinc.
Cadmium and its compounds have been classified by IARC as Group 1, carcinogenic to humans, on the basis of sufficient evidence of carcinogenicity in humans and animals. A recent review of Class 1 carcinogens reaffirmed the classification for cadmium and its compounds. Epidemiological studies reviewed by IARC showed consistent evidence that cadmium workers were at increased risk of lung cancer. Other studies have suggested elevated risks of prostate, kidney and bladder cancers.[3,18]
Acute inhalation of cadmium at high concentrations affects the lungs, causing severe damage and possibly death. Chronic inhalation at low concentrations affects the kidneys, resulting in cadmium accumulation and possible kidney disease. Chronic ingestion of cadmium at low levels can result in kidney damage and bone effects.
Schedule 1, paragraphs A and C for ‘inorganic cadmium’
The most common use of cadmium is in battery production, specifically as cadmium hydroxide, one of two electrode materials used in rechargeable nickel-cadmium (Ni-Cd) batteries. Global use of cadmium in 2005 was distributed as follows: batteries, 81%; pigments, 10%; coatings, 6%; stabilizers, 2% and alloys and minor uses, 1%.
Cadmium sulphide is used as a pigment in plastics, ceramics, glasses, enamels and artists colours (yellows and reds). Cadmium salts are used as stabilizers in polyvinyl chloride (PVC) plastics, and also in coatings for electronics, steel and aluminum for corrosion resistance. Other minor uses for cadmium include alloys, solar cells and semiconductors. Other than for batteries, production and use of cadmium has decreased significantly over the past 50 years.
Approximately 10-15% of cadmium produced in the western world is from recycled products. There are 9 recycling facilities in the US, Japan and Europe capable of recycling industrial and commercial Ni-Cd batteries and manufacturing scrap.
Production and Trade
In 2006, Canada was the fifth largest producer of cadmium, producing 2,094 tonnes of refined cadmium - an increase of 21% from the previous year.
Cadmium is mined as a by-product in New Brunswick, Quebec and Ontario and refined at all four Canadian zinc smelters (located in Valleyfield, Quebec; Trail, BC; Timmins, Ontario; and Flin Flon, Manitoba). The majority of Canada’s exports are sent to Belgium, Japan, China, and the Netherlands.
Export: Mainly to Belgium, China
1673 t of ‘cadmium and articles thereof’
Import: Mainly from Brazil, US
89 t of 'cadmium and articles thereof'
Inhalation and ingestions are main routes of occupational exposure to cadmium. Occupations with high potential of exposure include those involved in zinc, lead and steel production and processing, cadmium coating and plating, machining and welding cadmium-coated steel, and manufacturing of cadmium-nickel batteries.
Forest fires and volcanic eruptions contribute to the amount of cadmium in the environment; however the mort important natural source is erosion or weathering of cadmium-containing rocks.
Cadmium particles can be dispersed very long distances before settling. Some particles are soluble in water, while others bind tightly to soil.
Environmental exposure to cadmium can occur through consumption of contaminated food and drinking water; incidental ingestion of contaminated soil and dust; and/or inhalation of cadmium-containing particles in air or cigarette smoke.
Food is the major source of cadmium exposure to the general population in Canada (nearly 100% of daily exposure for non-smokers).
Cigarette smoking increases the daily intake of cadmium by about 25% (for those smoking 1 pack/day).
Spills and leaks at hazardous waste sites are sources of soil and groundwater contamination.
Cadmium occurs naturally in phosphates; therefore manufacturing and application of phosphate fertilizers contributes to environmental contamination.
Cadmium is one of the substances selected for the Canadian Health Measures Survey (CHMS), a joint project of Statistics Canada and Health Canada to establish the current level of exposure to environmental contaminants. The first cycle, which includes a biomonitoring component, is being conducted from 2007-2009.
Preliminary biomonitoring data from the CHMS, released in November 2008 on approximately 2,500 Canadians, found detectable levels of cadmium in 98% of respondents, with a geometric mean concentration of 0.35 µg/L in blood.
NPRI and US Household Products Database
Search term: ‘cadmium and its compounds’
Released into Environment
Mining, smelters, pulp and paper, power generation, water treatment and oil refineries. (357 companies)