The mechanism of action of peloids (medicinal muds) applied in spa therapy has been mostly unknown, especially in aspect of chemical features. Recently, several organic compounds have been detected from spa waters using gas chromatographic methods, without exact knowledge on biological activity. They may have important roles in therapy, but may possess carcinogenic and other toxic properties, as well. This aim requires severe methodological developments in this field.

In the present paper two peloid samples from Hévíz (West-Hungary) and Kolop (East-Hungary) were tested. We performed two types of experiments on peloids, at first without any pre-treatment (in toto), and in the second set of experiment aqueous, hydrochloric acidic, methanol and toluene extracts of peloids were prepared for mutagenicity testing. The solvent extraction study was repeated twice. The objective of this study was to detect complex genotoxic effects of peloids, the risk assessment and protection of the exposed population.

In the in toto experiment there was no statistically significant mutagenicity. The solvent extraction studies represented statistically significant mutagenicity in several fractions. Mutagenicity in samples was fluctuating. In the first study more mutagenic fractions were found. In the repeated experiment the mutagenic pattern was almost completely different, only minimal overlapping occurred.