A handbook of environmental toxicology: human disorders and ecotoxicology.

Chapter 26 (Page no: 384)

Cadmium I. Exposure and human health effects: an overview.

Cadmium is a metal that has been extensively used for a wide variety of industrial applications in the past, but more recently the growing awareness of the adverse health effects has led to restrictions and ban of use in several applications. Cadmium is emitted into the environment via both natural and anthropogenic activities, leading to a wide dispersion in the environment and contamination of soil, including arable land, in many areas of the world. This is of concern, as cadmium is easily taken up by vegetable crops (e.g. rice, wheat, vegetables and potatoes) as well as tobacco leaves. Accordingly, today food is considered to be the major source of cadmium exposure for the majority of the world's population, while smokers are additionally exposed. In populations with high rice consumption, this is usually the main source of cadmium, while in other populations the main dietary sources are usually cereals, vegetables and root vegetables. Fortunately, only a small percentage of the cadmium intake is absorbed in the gastrointestinal tract, but it is increased at low iron stores. In blood, cadmium is mainly incorporated into erythrocytes and a smaller fraction is bound to metallothionein in plasma. Because of the small size of the cadmium-metallothionein complex, it is filtered through the glomeruli, making urine the primary route of excretion. However, it is also readily reabsorbed in the proximal tubular cells, leading to accumulation in the renal cortex where it has a biological half-life of 10-45 years. The cadmium concentration in urine is a marker of long-term exposure, whereas the concentration in blood is a better reflection of more recent exposure. The current risk assessments of cadmium have considered tubular damage as the critical effect. Besides the renal effect, cadmium exposure has also been associated with cardiovascular disease, osteoporosis, impaired fetal and child development, cancer and mortality, which are reviewed in this and the subsequent chapter.

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