Influence of polymeric derivatives of guanidine on hydrobionts
Keywords: polyhexamethylene guanidine, aquatic ecosystems, hydrobionts, toxicity, histological studies
AbstractIt is known that polymeric derivatives of guanidine are actively used in many countries of the world as disinfectants and antiseptics. Polyhexamethylene guanidine (PHMG) and polyhexamethylene biguanidine (PHMB) are typical representatives of this class of compounds. They show a bacteriostatic effect in concentrations from 1 mg/l (or 10–4%) or above, and a bactericidal effect from 10 mg/l (10–3%) and above. It is considered that PHMG and PHMB are not very toxic to higher organisms. This is explained by the different mechanism of drugs action on prokaryotic and eukaryotic cells. However, their safety for the fauna of freshwater hydrocenoses has not been sufficiently studied. The toxic effect of the salts of PHMG on the representatives of various types and classes of hydrobionts was studied in the experiments. It has been established that the safe concentration of PHMG in water with a one-time action on selected test objects is 0.1 mg/l (10–5%). The histological analysis of a one-year-old carp that lived in an aquarium with a constant concentration of PHMG at 0.5 mg/l for 12 days showed that concentrations of an order of magnitude smaller – 0.01 mg/l (10–6%) is absolutely safe to consider. Chronic intoxication of fish caused by sublethal doses of PHMG leads to the development of numerous disorders in the liver, kidneys, and spleen, and to the inflammation of the pancreatic islets. A comparative analysis of the toxicity of PHMG for microand macroorganisms does not allow us to state that the latter are less sensitive to this xenobiotic. So far, there are not enough convincing reasons to believe that the mechanisms of action of PHMG on pro and eukaryotic cells are fundamentally different. At the same time, the binding of PHMG molecules to suspended particles in water, organic and inorganic impurities, flocculation, and biodegradation by microorganisms leads to a rapid decrease of free active molecules of this biocide in aquatic ecosystems.