1. The Environment

4.  Harmful chemicals released into the air by cars and factories can mix with water in the air to make smog.  When air pollution mixes with rain, acid rain can form.  Air pollution has caused a hole in the ozone layer.

7.  Heavy rains wash fertilizers, pesticides, and road materials from the land into rivers, lakes, and oceans.  Waste products from factories and mines also flow into the waters.  About 40 percent of American lakes and rivers are too polluted for fishing or swimming.  In poorer countries, garbage left on the streets has polluted rivers and caused millions of deaths.

9.  Deforestation means cutting down all of the trees in one area.  Trees take in carbon dioxide from the air and produce oxygen, which people need to breathe.  Fewer trees means that there is less oxugen and more carbon dioxide in the air.  Increased carbon dioxide might contribute to global warming.

11.  Canada, the United States, and other nations have passed laws to clean up the air and water.  Automobile makers make engines that burn fuel more cleanly.  Nations are working together to address environmental problems.  Individuals are practicing conservation and recycling.