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What Is a One Part Per Million Solution?

Author(s): Nancy P. Moreno, PhD, Barbara Z. Tharp, MS, and Judith Dresden, MS.

The Science of Water Pollution and Health

All the water on Earth is part of a single, immense system. Oceans, wetlands, streams, lakes, and underground water supplies all are linked through drainage patterns in watersheds and through the endless cycling of water on our planet. Because water sources are connected, pollutants are transferred from one part of the system to another. Over time, contaminants can reach and impact ecosystems and human/plant/animal populations very far from their points of origin. Water pollutants can be divided into several major categories, all of which impact human health and well-being.

  • Nutrients can come from chemical sources (fertilizers or detergents) or can be biological in origin (sewage or manure). They usually are carried into water sources by rainwater. Nutrients cause excessive growth of water plants and algae, which can clog navigable waterways and consume oxygen needed by other organisms, such as fish. The introduction of excess nutrients can damage lakes and wetlands, and can affect drinking water quality as well. Fertilizers also can impact groundwater and make water from wells unsafe to drink.
  • Soil and sand from plowed fields, construction zones, logging sites and strip mines can fill up lakes, wetlands and streams, thereby making these waterways more shallow, which limits their use for transportation and damages wildlife habitats. Topsoil lost to erosion also can be a source of excess nutrients.
  • Disease causing organisms, such as bacteria, viruses and single-celled parasites, can enter water supplies from inadequately treated sewage, storm water drainage, septic systems, livestock pens, and boats that dump human wastes. These organisms cause diseases such as dysentery and typhoid, as well as skin and respiratory illnesses.
  • Metals (such as mercury and lead) and toxic chemicals (such as those found in pesticides, herbicides, cleaning solvents, plastics and petroleum derivatives) can be poisonous to humans, plants and wildlife. Metals and many manufactured chemicals persist in the environment. Metals and manufactured chemicals can remain in the environment for many years. They build up in the bodies of fish and other animals, making them unsafe to eat. These toxins also can pollute groundwater, making it unhealthy to drink.
  • Heat. Warm water discharged from power plants (which use water for cooling) can drastically alter aquatic ecosystems. Changes in water temperature can alter the amount of oxygen in the water and make some organisms more susceptive to disease, parasites and toxic chemicals.

Most cases of water pollution are spread over large areas. Water from rain and irrigation collects pollutants as it washes over the land or filters into the soil. Because this type of pollution is not attributable to a single location, it generally is known as “non-point source” pollution. It is much more difficult to monitor and to control than is point source pollution, which is discharged from a single place (such as from a factory, waste treatment plant or chemical spill).


Funded by the following grant(s)

National Institute of Environmental Health Sciences, NIH

National Institute of Environmental Health Sciences, NIH

The Environment as a Context for Opportunities in Schools
Grant Numbers: 5R25ES010698, R25ES06932


Houston Endowment Inc.

Houston Endowment Inc.

Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education