The chemicals in these that are not biodegradable can remain dangerous for a long time. .
When an animal eats a plant that's been treated with certain non-degradable chemicals, the chemicals are absorbed into the tissues or the organs of the animals. When other animals feed on a contaminated animal, the chemicals are passed up to them. As it goes up through the food chain, the chemical becomes more harmful, so animals at the top of the food chains may suffer cancers, reproductive problems, and death. .
More than 14 million Americans drink water contaminated by pesticides, and the EPA estimates that ten percent of wells contain pesticides. Nitrates can cause a lethal form of anemia called blue baby syndrome in infants. .
Heavy Metals - heavy metals, such as copper, lead, mercury, and selenium, get into the water from industries, automovile exhaust, mines, and natural soil. Heavy metals also become more harmful as they follow the food chain. When they reach high levels in the body, they can be immediately poisonous, or can result in long-term health problems. They can sometimes cause diarrhea and, over time, liver and kidney damage. Children exposed to lead in water can suffer mental retardation. .
Hazardous Wastes - chemical wastes that are either toxic, reactive, corrosive, or ignitable. If not treated or stored properly, they can pollute water supplies. They can reach toxic levels when animals eat one another. .
Excess Organic Matter - fertilizers and other nutrients used to promote plant growth on farms and in gardens may fine their way into water. At first the nutrients will help the plants and algae in the water grow, but when they die and settle underwater, microorganisms decompose them, while decomposing them the microorganisms take in oxygen that is dissolved in the water. The oxygen levels in the water may drop so low that fish and other oxygen-dependent animals in the water suffocate, and die.
