The diploma thesis deals with the detailed characteristics of wood, its composition, physico-chemical and fire-technical properties. It also discusses the issue of fire retardants – their distribution, functionality, effects, different types of application, as well as their possible impact on the environment. The aim of this diploma thesis is to evaluate the impact of fire retardant treated wood on the aquatic environment using ecotoxicological tests. Following preliminary tests were used for evaluation: Sinapis alba root growth inhibition test, Daphnia magna acute toxicity test, and Lemna minor growth inhibition test. Selected basic physico-chemical indicators were also determined: pH, conductivity, and chemical oxygen demand – potassium dichromate method. Fire retardants were applied to the tested wood by nano coating technologies using oxides (zinc oxide, titanium dioxide, silica). Positive test results show that substances used as fire retardants pose a risk to the aquatic environment. The worst results of the Daphnia magna acute toxicity test were present in the experimental samples treated with the H2O + 3 % ZnO fire retardant. This retardant immobilized up to 100 % of the Daphnia magna test organisms. Aqueous extraction from wood samples treated with H2O retarder + 3 % TiO2 caused the highest inhibition of Sinapis alba root growth. The results of the Lemna minor growth rate inhibition test were effective in all samples and the highest inhibition was recorded in the wood sample with the H2O + 3 % SiO2 fire retardant applied. It follows from the above that aqueous extracts of fire retardant treated wood have negative impact on the aquatic environment.