Background

 Among all bioindicators, lichens have been identified as the most useful to monitor the level of pollution in the environment (Ferry et al 1973). Lichens can be found in different areas starting from warm, tropical regions to cold, polar regions and even extreme conditions, which might be deemed as too harsh for other living organisms (Weerakoon 2015). The symbiotic relationship between an algae and fungus gives rise to a lichen. The association involves the alga producing the nutrients since it has the chlorophyll to photosynthesize and the fungus provides water to the alga (Hale 1969, 1993). There are three bodies for lichens: crustose, foliose and fruticose (Brodo et al 2001). They can be used in two ways to monitor air pollution: 1) grouping the species of lichens present in a specific area 2) measuring the morphological changes or the accumulation of pollutants in the lichens (Richardson, 1991; Seaward, 1993; Gries, 1996).