The impact of the nitrogen fertilizer plant in Puławy involved profound, destructive alterations to the broad-sense natural environment which comprised not only the soil, water and air but also plants and animals. Initially, at the end of 1960's and at the beginning of 1970's the changes were very acute only to become of chronic character later on. The results of the studies were used as bio-indicators to measure both the extent of damage to the environment and to assess the validity of the methods developed to reclaim the degraded environment. Tested and calibrated as a synthetic bio-indicator of air pollution in the Puławy area, lichens were used as a tool to evaluate the extent of air contamination with different kinds of emission. Those measurements can also be used in monitoring large areas, a very important practical consideration with respect to assessing environment pollution status.