Air is an important element of our environment. a, clean air is essential for our life. b, air is polluted in many ways. c, one thing that pollutes air is smoke. Smoke is produced from different sources. d, we make fire to cook food and it creates smoke. e buses and trucks plying in the roads emit smoke. f, the burning of coal in the railway engine also produces smoke. g, the mills and factories also produce a huge amount of smoke. h we melt tar for road constructions which produces black smoke. i, all these smokes mix with the air and pollute it. j, smoke from different sources is causing serious harm to our environment.