y, pollution was not a major problem. Most people lived in uncrowded rural areas and the pollutants (waste products) they produced were widely scattered. People had no pollution-causing machines or motor vehicles. The development of crowded industrial cities in the 1700 «s and 1800» s made pollution a major problem. People and factories in these cities put huge amounts of pollutants into small areas. During the 1900s, urban areas continued to develop, and automobiles and other new inventions made pollution steadily worse. By the mid - 1900s, pollution had affected the water in every major lake and river and the air over every major city in the United States and other industrial countries. Since the late 1960s, millions of people have become alarmed by the dangers of pollution, and scientific studies have improved our understanding of the problem. Large numbers of people are now working to reduce environmental pollution.
