Water pollution involves contaminating bodies of water with any number of pollutants. Water pollution can occur in most bodies of water, from surface water such as rivers and oceans to aquifers below the ground, and contaminants can range from natural to synthetic compounds.

While waste dumping and oil spills contribute to water pollution, atmospheric deposition and nutrient over-enrichment do as well.

According to the Natural Resources Defense Council, dirty water provides the world's No. 1 health risk. It is by far one of the most globally prominent environmental issues, especially considering that water is essential to sustaining life on Earth. (Photo: Shutterstock)