Air Pollution

There was one thought that air pollution affected only the areas immediately around large cities with factories and heavy automobile traffic. ____1____

On several occasions over the past decade, a heavy cloud of air pollution has covered the east of the United States and brought health warnings in rural areas away from any major concentration of manufacturing and automobile traffic. In fact, the very climate of the entire earth may be infected by air pollution

Some scientists consider that the increasing concentration of carbon dioxide((二氧化碳) in the air resulting from the burning of coal and oil is creating a"greenhouse effect". It conserves heat reflected from the earth and raised the world’s average temperature. ___2___ Thus much of the polar ice cap will melt and cities such as New York, Boston, Miami, and New Orleans will be in water.

___3___ This is a result that would be equally disastrous. A drop of just a few degrees could create something close be to a new ice age, and would make agriculture difficult or impossible in many of our top farming areas.

Today we do not know for sure that either of these conditions will happen. ___4___ Driven by economic profit, people neglect by the damage on our environment caused by the"advanced civilization".___5___ But is it really worthwhile?