Lichens are widely recognized as bioindicators of air quality, particularly sensitive to atmospheric pollutants. They can be used to assess the presence and concentration of major elements and other pollutants in the environment.

Here’s how lichens act as pollution indicators:

• Accumulation of Elements: Lichens absorb nutrients and water from the atmosphere rather than through roots from the soil. As a result, they accumulate elements from the air, including pollutants. This accumulation reflects the levels of pollutants in their environment.
• Sensitivity to Pollutants: Lichens are particularly sensitive to air pollutants such as sulfur dioxide (SO2), nitrogen oxides (NOx), heavy metals, and other major elements. High levels of these pollutants can damage or kill lichens.
• Species Distribution: The presence, absence, or abundance of specific lichen species can indicate the level of pollution. Some species are tolerant to pollution, while others are highly sensitive. The diversity and health of lichen communities can therefore serve as a bioindicator of air quality.
• Elemental Analysis: Scientists can analyze the elemental composition of lichen tissues to determine the concentration of various elements, including major pollutants. This provides quantitative data on the levels of pollution in a given area.

Major elements that lichens can indicate include:

• Sulfur: High sulfur content in lichens often indicates SO2 pollution, commonly associated with industrial activities.
• Nitrogen: Elevated nitrogen levels can suggest pollution from NOx, often emitted by vehicles and industrial processes.
• Heavy Metals: Lichens can accumulate heavy metals like lead (Pb), cadmium (Cd), mercury (Hg), and arsenic (As), indicating industrial or vehicular pollution.

Several studies and monitoring programs use lichens to assess air quality and pollution levels:

• Monitoring Programs: Environmental agencies often use lichens in long-term monitoring programs to track changes in air quality over time.
• Research Studies: Numerous scientific studies have documented the effectiveness of lichens as bioindicators of air pollution.