In Poland, the first studies using mosses as indicators of the heavy metal air pollution level were carried out in national parks already in the 1970s. They were continued later in 10-year intervals. In 1990, when Poland join the European Heavy Metals Deposition Program, the entire area of the country was included in such research. Moss surveys were repeated at five-year intervals, to varying degrees. Pleurozium schreberi samples were collected from 150 (1990) to over 300 sites (1995 and 2015) throughout the country, either in selected regions diversified in terms of both the level of industrialization and urbanization (2001 and 2015), or only in national parks (2005). On a small scale, changes in the level of heavy metals were recorded in the period from 1975 to 2014 in the Niepolomice Forest located near Krakow. Concentrations of ten heavy metals were constantly monitored. Additionally, in some moss surveys, other elements or compounds, such as (137)cesium, PAHs and nitrogen were analyzed. During the 1990s, in all of Europe, there was a significant decrease in the level of heavy metals. In Poland, the spatial patterns of metal accumulation in mosses were similar throughout the entire study period: The southern part of the country, more industrialized and densely populated, is still the most polluted, and the northeastern part belongs to the cleanest regions. In the Niepolomice Forest, emissions from the big steel mill and from the Krakow agglomeration had the greatest impact on pollution from the 1970s to the 1990s, but lately the impact of local emission sources is more visible. Compared to other European countries, Poland and neighboring countries of Central Europe are at the forefront of the most polluted areas in Europe.
