Kadmium - Förekomst, exponering och hälsorisker

Sammanfattning: This bachelor thesis mainly focuses on the cadmium in the environment, how we are exposed to cadmium and it´s human toxicity. Cadmium (Cd) is a heavy metal that occurs naturally in the earth's crust (0,08 -0,05 μg Cd/g). Pure cadmium minerals are rare and cadmium is often found associated with zinc minerals, such as sphalerite (ZnS) with a Cd-concentration usually lower than 0,5 percent. The link between cadmium and sphalerite was also examined in a field study near Lund at Hardeberga and Dalby quarries. Cadmium spreads in the environment through natural processes (e.g. weathering and volcanic eruptions) and through anthropogenic emissions. Mobility in the soil (bioavailability) is mainly controlled by pH, clay content, amount of organic matter and the amount of competing ions (e.g. zinc). High levels of cadmium can accumulate in lake sediments, but the content is typically low in ground- and surface water and oceans. Plants can accumulate considerable amounts of cadmium and crops are the largest source of human exposure. That large amounts of cadmium are harmful has been known for a long time, but new data suggest that health effects can occur even at low levels (urine-Cd level of 0,5-3 µg/g creatinine), near the normal daily intake. WHO/FAO has a provisional tolerable weekly intake (PTWI) of 7μg/kg body weight. EFSA has with reference to new studies lowered the limit and set a tolerable weekly intake (TWI) to 2.5 µg/kg body weight. Cadmium has a long residence time in the body and accumulates primarily in the kidneys, which is the critical organ. In addition to renal damage, skeletal disorders and cancer are also associated with cadmium exposure. Low zinc, calcium and iron values increase the uptake of cadmium and therefore women of childbearing age are a particularly vulnerable group. Other exposed groups are people living close to point sources of cadmium, smelt workers, smokers, vegetarians and children.