Balneology in Estonia: importance of the geochemical backgound information of the Estonian curative mud

In Estonia, natural remedies were commonly used during the first half of the 19th century. Thanks to its specific geological and geomorphological characteristics, Estonia has several significant deposits of lacustrine and marine curative (or therapeutic) mud, which has public health and commercial benefits. Many Estonian spas have traditionally incorporated a combination of natural remedies with a range of physical therapies, including gentle exercise, massage and heat and water therapies. Yet, the mud research in Estonia has been stagnating since the 1990s, and therefore one of the main limiting factor for the redevelopment of the public and commercial use is a lack of up-to-date scientific understanding about the sediment composition and deposit characteristics.

There is a long-term tradition in using fine-grained sediments (mud) for cosmetic and medical purposes but more precise information about the characteristics of such sediments is lacking. Since there are no specific standards regarding the bio-geo-chemical composition of curative mud, only the different geochemical and bioactive compound groups could be identified.

We reviewed the regional history of curative mud and the existing scientific rationale for the public and commercial applications of mud for healing purposes. We mapped spatial distribution organic and mineral matter, heavy metals in the surface sediments Estonian deposits of curative mud. Polycyclic aromatic hydrocarbons (PAHs) were controlled for the Haapsalu curative mud. Importantly, the geochemical characterisation is used to provide insights into all of the mud deposits and the broader ecosystem services of muds. The presence of heavy metals in mud is not always dangerous because many factors can affect their toxicity, including pH, and the oxygen, mineral and organic content. Muds can be used in assessing environmental quality, since the pollutants contained in them reflect the conditions of the water-body they were deposited in. The mechanisms of action of the curative mud are not fully elucidated; the net benefit is probably the result of a combination of mechanical, thermal and chemical effects. Additional studies are necessary to clarify the mechanisms of action of balneology.