WATER HARDNESS IN BULGARIA – SPATIAL DISTRIBUTION AND POTENTIAL IMPACT ON HUMAN HEALTH

Abstract

The article examines water hardness in Bulgaria by analyzing variations in calcium (Ca²⁺) and magnesium (Mg²⁺) levels across different regions of the country. Water hardness is measured in German degrees and is classified as very soft (0–4 °dH), soft (5–8 °dH), moderately hard (9–12 °dH), hard (13–18 °dH), and very hard (above 18 °dH). The undesirable effects of using hard water in everyday household activities and its potential impact on human health are also discussed. The aim of the publication is to identify regions in Bulgaria with varying water hardness levels and to assess the potential influence of calcium and magnesium on human health. Materials and Methods: A descriptive, comparative, and documentary methods were used. The analysis is based on published data from water supply companies, scientific publications on the topic, health documents, and reports. The geographical distribution is visualized through maps of regions in Bulgaria with different levels of water hardness. The results show significant regional differences depending on geological structure and water sources (groundwater, rivers, reservoirs, mountain springs, etc.). In Sofia, the water is soft with very low hardness (< 2.49 °dH). Along the Black Sea coast, water hardness varies in different parts of cities or regions, ranging from softer (8.4–9.4 °dH) to hard (17.4–19.1 °dH) and very hard (19.9–21.3 °dH). In Northwestern Bulgaria, drinking water hardness is moderate to hard (approximately 8–18 °dH). In Southwestern Bulgaria, the water is soft, although in some smaller settlements there may be local cases of higher hardness. In Plovdiv (11.1–13.8 °dH) and Asenovgrad (12.3–13.4 °dH), the water is hard, while in smaller settlements such as Sopot (3.1–3.4 °dH) and Karlovo (2.2–4.1 °dH), soft to moderately hard water is observed. Mountainous areas and parts of Southern Bulgaria also have soft water. From a health perspective, hard water is not considered harmful under normal consumption. Calcium and magnesium in water are beneficial to health; however, since the conducted studies do not include control groups to establish a direct relationship between human health and water hardness, the effects are classified as potential. Negative effects are observed in household settings—limescale buildup on appliances and reduced efficiency of cleaning and laundry detergents. Conclusion: Water hardness in Bulgaria is a factor with regional differences, affecting both everyday life and mineral intake, with the predominant effect on human health being positive. There is no convincing evidence that hard water causes kidney stone disease in healthy individuals. Numerous population-level scientific studies demonstrate that water hardness is not a factor in disease prevalence in specific regions.