An expanding world population is burning more fossil fuels, emitting more industrial chemicals and driving more automobiles. The number of automobiles is increasing three times faster than the rate of population growth. Following construction in 1968 of Egypt's Aswan High Dam and associated irrigation systems, prevalence of the Schistosoma mansoni organism in humans in the region increased from 5 percent to 77 percent. Cancer-related deaths in the United States increased from 331,000 in 1970 to 521,000 in 1992, with as estimated 30,000 deaths attributed to chemical exposure. In the United States, inadequate sanitation accounts for 940,000 diarrhea infections and about 900 deaths each year.
Respiratory disease is the leading cause of death in China.
However, mortality due to lung cancer is approximately equal in males and females. Although the use of lead in U.S. gasoline declined since 1985, other sources inject about 2 billion kilograms of lead into the atmosphere in this country each year. An estimated 1.7 million children in the United States have unacceptably high levels of lead in their blood. Production of another gasoline component, the carcinogen benzene that causes leukemia even at low dosages, rose from 0.5 billion kilograms in the United States in 1950 to current levels of about 7.5 kilograms per year. Most modern pesticides are more than 10 times as toxic to living organisms than those used in the 1950s.