It has been proven that increased nitrate content in water is instrumental in the decline of amphibians. The olm is particularly endangered since one of its main characteristics is neoteny, meaning it spends its entire life at the stage of a larva. Since it is constantly located in aqueous environment, this makes it all the more susceptible to negative influences from its environment. The latest findings indicate that safe concentrations for the existence of olm are under 10mg NO3/l. The legally permitted limit value of nitrates set from the viewpoint of drinking water protection amounts to no less than 50mg NO3/l, which is significantly too high in terms of olm protection.