with the explosion of population in the world, more and more poisonous waste is produced. as a resuit, a lot of rivers and lakes are polluted.

　　in some areas, the air also becomes dirty and harmful. consequently, animals and plants are endangered. and peopie's health is greatly affected.

　　fortunately, more and more people have realized the serious situation. many countries have passed laws to prevent the environment from being further polluted. people are working hard to find ways to keep the earth clean: they treat waste gases, protect water sources and purify waste water. definitely, controlling the increase of population is one of the most efficient ways.

　　however, in future more efforts will be needed to win the battle against pollution, the laws controlling pollution must be strictly enforced, and above all, attention should be paid to the education of the people so that everyone will show his concern about environmental protection.