Lichens as biomonitors for organic air pollutants

• Lichens are suitable biomonitors for semi-volatile organic air pollutants.
• Soxhlet and ultrasound-assisted extraction extract organic pollutants from lichens.
• Reported total concentrations of polyaromatic hydrocarbons (PAHs) vary in lichens.
• Phenanthrene, fluoranthene, naphthalene and pyrene dominate PAH profiles.
• Reproducible sensitive analysis is needed for organic analytes in lichens.

Lichens are useful biomonitors for semi-volatile organic air pollutants, particularly polyaromatic hydrocarbons (PAHs), as a result of their ability to respond to air pollutants at different levels, their slow growth rate, their longevity and their ability to indicate the presence and the concentrations of these pollutants. Consequently, there has been a recent global trend in environmental analytical research to utilize lichens in this way, with Soxhlet and ultrasound-assisted extractions being the most common analyte extraction techniques. A wide range of total PAH concentrations has been determined in lichens from different environments, although phenanthrene, fluoranthene, naphthalene and pyrene tend to dominate the PAH profiles, with higher 2-ring and 3-ring PAH concentrations than 6-ring. In order to facilitate inter-study comparison, there is a need to develop a reproducible, sensitive analytical method for organic pollutants in lichens.