Since 1950, various plants with a strong ability to bioaccumulate have been used for continuous monitoring of the land contamination or water areas by the main categories of pollutants. These plants, containing certain chelating components, have the property of accumulation in large amounts of certain halogens, such as chlorine and fluorine. Heavy metals, like lead and cesium, are also retained. These pollution bioaccumulators can detect pollution difficult to be demonstrated by direct analysis of the water, soil or air.In the case of atmospheric contamination, the lichens are the most suitable bioindicators. They constitute powerful bioaccumulators because of their ability to collect contaminants in the air as they entirely depend on their mineral nutrition from the extraction of nutrients from the atmosphere. Lichens have been used as biological indicators of contamination by toxic or radioactive metals. The purpose of this work is to determine the level of pollution in the Bizerte region by atomic absorption spectrometry and by emission spectrometry with plasma torch.