污染（pollution）是指自然环境中混入了对人类或其他生物有害的物质，其数量或程度达到或超出环境承载力，从而改变环境正常状态的现象。
environmental problem are becoming more and more eriou all overthe world. for example, car have made the air unhealthy for people to breatheand poionou ga i given off by factorie. tree on the hill have been cutdown and wate water i being poured continuouly into river.furthermore,wherever we go today, we can find rubbih carelely dipoed. pollution i, infact, threatening our exitence.
the earth i our home and we have the duty to take care of it forourelve and for our later generation. fortunately, more and more people haverealized thee problem. meaure have been taken to cope with thee problemby the government. law have been paed to top pollution. i hope the problemwill be olved in the near future and our home will become better and better.