If the system were opened to change a filter drier, for example, and pollen were to inadvertently enter the lines, the debris in the system could lead to severe damage to the compressor if not trapped by the filter drier. However, this is probably not the biggest concern with pollen and the proper operation of the compressor.
The role of the compressor in the HAC/R system is to move the refrigerant through the system. When the system is operating properly, the refrigerant absorbs heat from the air in areas where we don't want it and moves this heat to areas where it may not be objectionable. The heat is then rejected from the refrigerant.
The evaporator coil aids the refrigerant in the absorption of heat present in the ambient air while the condenser coil helps with the removal of this heat from the refrigerant. In addition, blowers and fans assist in this process by moving air over, through and around the evaporator and condenser coils. This improves the efficiency and effectiveness of the absorption and rejection of heat in the system. If the coils have a layer of pollen, dirt, dust, grass clippings, leaves, or other debris on them, it restricts airflow through the coil. That restriction of airflow impedes the heat transfer through the coils, which will result in operating temperatures and pressures that the system is not designed for. When operating at elevated temperatures and pressures, the compressor will be damaged, resulting in a shortened operating life.