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Can Nutrients in Water Cause Harm?

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

Let's Talk About It

In general, water pollution in the United States is caused by one of two sources. Point sources introduce pollutants into waterways at a single place. Factories, sewage treatment plants, abandoned mines and oil tankers are examples of point sources of water pollution. Although this type of pollution is not always significant in terms of volume, it is the primary point of entry for toxic chemicals into water supplies. In most cases, point sources of pollution can be identified and monitored by government agencies.

Non-point sources of pollution include large areas of land that drain into underground and surface water sources. With non-point source pollution, water collects pollutants as it travels over land and through layers of soil. Major contributors to non-point source pollution include agricultural operations (which can add chemical fertilizers, pesticides, manure and soil to water), logging and other industries that leave the soil surface bare (thereby allowing soil to be washed into waterways), urban and suburban activities (where lawn chemicals, household chemicals, motor oil and gasoline can be washed into water supplies), and septic systems (which can contaminate underground water supplies with disease-causing bacteria). Non-point sources of water pollution are difficult to monitor and control because they can be spread over many square miles.


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 Number: 5R25ES010698


Houston Endowment Inc.

Houston Endowment Inc.

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