【参考译文】Clean air is vital to good health. If the air contains impurities, they may be absorbed by our bodies and make us ill. We need clean air, but unfortunately, air pollution is generally present, especially in cities. There are many food factories, garment factories and factories for making other products in cities. Every day these factories discharge million tons of smoke and soot into the air. Things made in factories wear out after a while and then are thrown away as trash. We burn a lot of trash, which produces more smoke and soot. And factory cars, once out of the factory on the street, will suck in air, emit toxic gases, and add to the air soot.
No area in the world can completely be free of air pollution. We must take measures to control it. Now more and more people are realizing the importance of clean air. Schools offers courses on pollution. Industries begin to help clean up, by installing equipment to clean up their smoke. Scientists and inventors are making efforts to develop cleaner automobiles and the engine of train.
Perhaps the day when people are able to breathe fresh air in cities will come at last.