What explains the absence of lichens near major freeways and industrial sites?

Lichens receive minerals mainly from dust in the air and from drops of rainwater. Therefore, they have a high sensitivity to air cleanliness, since together with minerals they absorb harmful toxic substances. This is due to the lack of organs in lichens to extract fluid and absorb it with all the thallus (lichen body). The main reason for the death of many lichens is the high content of sulfur dioxide in the air.

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