Pollutants are substances that are dangerous to people and to the environment and they form pollution, which is just a build up of many types of pollutants. Pollution can affect the air, land and water. Some examples of air pollutants are: smoke from factories, dangerous gases from households and factories and car exhaust. Water pollution can be trash, oil, fertilizers and pesticides, and also waste that leaks from landfills, factories and sewage plants. Pollution on land includes fertilizers, pesticides and trash, and often this pollution will enter waterways as runoff. That means if someone changes the oil from their car and dumps it on the ground, it pollutes the ground and will eventually get into nearby rivers and lakes and cause water pollution.