pollution: a social problem
when we read newspapers, we often come across the word pollution. this word was not familiar to the people some decades ago. but now, it is a serious threat to us because. it means the poisoning of the air, seas, rivers and lands, which would do harm to our health.
there are many factories that bring pollution to us. we can not have fresh air in the morning. this is mainly because of the poisonous smoke coming from factories, especially chemical ones. in rivers, seas and oceans, there are industrial wastes. some factories just throw their wastes into seas or let them flow into rivers. when people drink the water from such rivers, they get poisoned. besides, there is rubbish from ships and when sometimes an accident occurs in an ocean, oil flows out from tankers.
on land, the accumulation of rubbish in the streets may dirty the city and ruin our health. this is mainly due to the improper disp