Chemical reactions of SO 2 create acids. Precipitation can transport these acids into the soil and trigger indirect damages, such as lack of nutrients and acid stress. Value limits for direct damaging effects on plants are clearly lower than for animals and humans. High sulfur dioxide concentrations lead to air pollution damages on coniferous trees, including non-specific chloroses, necroses, growth inhibition, and impairment of reproduction. Lead is a heavy metal and has special environmental relevance because it is toxic.
Leaded gasoline is still the main source.
Most lead particles remain on the surface of leaves. Only a small amount becomes physiologically active and damages plants. This process can lead to accumulation in the food chain. Toxic effects for grazing animals or humans cannot be ruled out. Fluorine is released from various industrial processes, waste burning, and by fossil fuel energy production.