What is the main problem in the world today?

The environment is everything around us, both natural and made by man. A major problem in the world today is the destruction of the natural environment.

This is a complicated problem. We burn fuel, and this causes air pollution. We throw away lastic bags, containing toys and other objects. These stay in the environment, they are not like paper or wood that slowly disappear. We have made thousands of new chemicals. Factories that make or use chemicals always have chemical wastes. These are often poisonous, and they also stay in the environment.

Since 1945 several countries have been testing nuclear bombs in the air and underground. The explosions in the air cause nuclear fallout. The fallout causes cancer and kills animals and people. Nuclear power plants that make electricity also produce dangerous wastes and have accidents that can be very disastrous.
1. What is the main problem in the world today?
2. What does burning fuel cause? 
3. Do factories make or use chemicals always have chemical waste?