Copper pollution from waste streams may enter the air through waste and fossil fuels combustion. Copper pollution from waste streams may enter the air through burning waste and fossil fuels. These two sentences are grammatically correct and would have the same meaning, though the first is more formal. However, I don't really understand the sentence...how does burning waste and fossil fuels make water pollution (from streams) enter the air? Perhaps there's something in the context I'm not seeing, but if not you might want to rewrite the sentence to make it a little clearer.

Copper pollution from waste streams may enter the air through waste and fossil fuels combustion.>This itself is totally incorrect . I cant understand what you are trying to say. Copper pollution X Waste stream X through waste and fossil fuels combustion >X