Water pollution can affect the quality of life for people and other living things around the globe. By affecting the water in the ocean, in land-based water sources like rivers, and in the groundwater, water contamination becomes a worldwide threat to human health.
Much human activity can pollute nearby water. For example, industrial waste dumped into rivers is a direct source of pollution. National Geographic reports that 70 percent of industrial waste dumped into the water in developing countries is not treated or cleaned. Fertilizers also pollute water. They contain harmful phosphorus and nitrogen, and according to National Geographic people use nearly 100 million pounds of fertilizer each year.
The ocean is vulnerable to pollution. Plastic and other trash can accumulate in large clumps around the world, such as the Pacific trash vortex in the northern Pacific Ocean. Other pollutants can sink into the ocean, where fish eat it. If humans eat the fish, those pollutants enter their bodies. Pollution can also affect the beaches and coasts of the world.
Groundwater is water that seeps into cracks in the soil and rocks that make up the Earth's surface. As this water moves, fertilizers, sediments and other pollutants in the soil become dissolved in the water. This water can carry the contamination to freshwater sources like rivers, or underground to the water table, where trees draw water up through their roots. Groundwater pollution is strongest in areas of the world with heavy unregulated agriculture, and groundwater makes up 97 percent of the world's fresh water.
The effects of this pollution are wide-ranging, but they can damage life in the ocean and freshwater, which continues up the global food chain as animals that feed on fish and other aquatic life take in pollution. Examples include mercury pollution, which comes from human industrial activity and puts toxic mercury in the ocean, where fish eat it. When humans then eat the fish, they are at risk for mercury poisoning.