The main objective of this seminar is to present and discuss the results of the studies on calcium and magnesium in groundwater and their importance for the human's health. Therefore the seminar is directed to hydrogeologists and hydrochemist as well as to physicians.

Calcium and magnesium are essential to human health. Inadequate intake of either nutrient can impair health. Recommended daily intakes of each element should be set at national and international levels, but no numerical guidelines for most of the countries drinking water quality exist for calcium or magnesium.
Calcium and magnesium in drinking water may have many beneficial effects, but at very high levels can have some negative health effect:

• Calcium may block the absorption of heavy metals in the body and is thought to increase bone mass and prevent certain types of cancer. Very high concentrations of calcium may adversely affect the absorption of other essential minerals in the body.
• Magnesium is an essential element in cardiac and vascular functions, but in drinking water may have a laxative effect, particularly with magnesium sulphate concentrations above 700 mg/L. However, the human body tends to adapt to this laxative effect with time.