Disturbance of equilibrium in forest ecosystems by high deposition of substances with acidifying action manifests itself in other environment components. The article deals with the effect of deposition on the forest ecosystem of selected substances which eventually affect the quality of the food chain and drinking water. The methods of study of affecting forest ecosystems start with determination of deposition of substances into the ecosystem and the contribution of treetop interception to the process as well as determination of the effect of chemical changes in soil on the quality of the soil solution and of the water flowing off the forest environment into water resources. The quality of that water is evaluated from the chemical composition in accord with the regulation of the Ministry of Agriculture No. 376/2000. The content of heavy metals in mushrooms as a part of the food chain is evaluated in relation to hygienic limits (regulation of the Ministry of Agriculture No. 298/1997).