Today, one of the greatest dangers to life on earth is the wholesale pollution of the environment. This can create serious health problems for people. Most city residents must breathe foul air. Industrial waste and fumes pour into the air. Rivers and lakes are being filled with waste products which endanger all forms of life. Testing of nuclear weapons has spread much contamination. Plutonium is difficult to dispose of. Overcrowded living quarters add to the problem. Too many people in a small area create tremendous amounts of waste and trash.