Protecting National Water Resources: A Call to Ban Copper Sulfate for Use in America’s Ponds and Lakes

Protecting National Water Resources

The purpose of this paper is to recommend a prohibition of the use of copper sulfate, a toxic and bioaccumulative chemical, in America’s waters.


Copper sulfate, a naturally occurring inorganic salt, is an algaecide, herbicide, germicide, and fungicide and is commonly used to maintain the aesthetic appearance of lakes, reservoirs, and ponds.  Being a trace element, its poisonous effects can be detected at levels as low as .33ppm, and its toxic potency is inversely related to the alkalinity and pH of water.[1] Copper sulfate is typically applied on a bi-weekly schedule, and what does not flow out of a water body into a receiving stream ends up binding to the underlying sediment. Here, this heavy metal accumulates indefinitely, serving as a reservoir of toxicity until the sediment is disturbed and conditions favor its release into the environment.

Because of its highly caustic nature, copper sulfate has been classified by the EPA as being in toxicity class I – highly toxic – and requires the signal words “DANGER – POISON” on its container.  Having the direct potential to disrupt photosynthesis, and because of its toxicity to downstream endangered species, its use requires a permit in certain jurisdictions and applications.[2]

Copper sulfate’s toxicity and propensity for accumulation is leading to a burgeoning problem at sites located throughout the US and the world.  Copper pollution is beginning to affect many coastal regions where river and storm water systems discharge; sites experiencing hazardously elevated levels of copper include: Delaware Bay, Chesapeake Bay, Naples Bay, North Miami, and Lake Pontchartrain.[3] In some cases, “[copper sulfate]…is the largest contributor to copper contamination.”[4]

As the effects of copper compounds and their persistence in coastal areas become better understood, some municipalities have included in their water resource management plans measures to reduce copper levels in stormwater discharge.  The application of copper sulfate as an algaecide has also been questioned in New York City, where authorities identified it as the primary cause of excessive copper levels in the City’s wastewaters and harbor.[5] However, in some cases, the specific regulatory approaches adopted have been criticized for their inefficiency.  San Francisco’s initiative to control copper contamination is estimated to have an end cost in excess of one billion dollars, primarily because of its inclusion of metallic copper, as well as all copper compounds, whatever their toxicity or fate.[6] Recent initiatives are taking a new direction, which is to improve upon water resources by targeting only volatile forms of copper, including copper sulfate.

Copper Sulfate: Detrimental to National Waters

Damaging Natural Habitats

The deleterious effects of copper sulfate on natural habitats have been widely documented. Long-term case studies have shown that, while algae is temporarily killed as intended, its decaying matter contributes heavily to dissolved oxygen depletion, fish kills, and the accelerated recycling of phosphorus which promotes algal blooms.[7] Eventually, the natural balance of the water body is upset: phytoplankton, the base of the food chain, are greatly reduced and no longer support small aquatic life; sediment-dwelling insects are killed by the accumulating poison; and plants, serving as both fish food and habitat, are killed by copper sulfate’s photosynthesis disruption.  After a local pond’s ecosystem has been become debilitated, the highly water-soluble residual algaecide is flushed downstream during a rain event, becoming a hazard for downstream organisms.

Catfish, one of the Fox River’s prime game fish, are visibly stressed by concentrations as low as 1.7ppm.  Enzyme activity in other fish increases due to stress at 2ppm, and the negative effects suffered were still observable after two weeks in clean water.[8] Furthermore, even at suggested application rates, the algaecide has been found to be lethal to salmonoids (e.g. salmon, trout, etc.).[9]

Animals that ingest copper sulfate by drinking from contaminated water bodies are also at risk as chronic exposures have lead to problems at levels as low as 20ppm per day—commonly leading to malfunction of the endocrine gland and testes.  After consumed, copper sulfate is strongly bioaccumulated, primarily in the heart, liver, brain, kidneys, and muscles of animals.[10]

Detrimental to Water Quality

As a treatment strategy, the use of copper sulfate as an algaecide addresses only the symptoms of the water body’s degraded condition, not the causes.[11] The underlying cause of the algal blooms is the urban runoff of fertilizers, detergents, and other phosphates.  The use of copper sulfate does nothing to minimize or manage these nutrients.  In fact, as a germicide, it destroys the beneficial bacteria that would naturally break down nutrients and, as an herbicide, kills plant life that would absorb them.

When this water is released into receiving streams, it brings with it the burden of excess nutrients and very low dissolved oxygen.  Considering that nutrient overabundance is already problematic for many  U.S. rivers and streams, any effort to lessen the problem should be taken.  This is especially important to downstream communities that already assume additional treatment costs to make water safe and potable for their residents.

Contributing to Pollution

Pollutants are defined as chemical constituents present at toxic levels and in bioavailable forms for a sufficient period that they adversely affect the beneficial uses of a water body.  Copper and its compounds are designated as pollutants, however it is the free form of the copper II ion that is biologically available and the most toxic form of this substance.  It is therefore important in creating a control approach to differentiate between sources such as metallic copper from brake pads and liners, and a wide array of ionic forms of copper of varying degrees of potential toxicity, the most problematic of which is copper sulfate.  Thus, environmental scientists continue to emphasize the importance of focusing “pollutant control on those chemical constituents that are significantly impairing…waterbody(s) within and downstream of the watershed.”[12]

Residents add copper sulfate to water bodies to satisfy an aesthetic desire, often without considering its potentially harmful effects.  This is especially true for storm detention ponds, which are increasingly seen as amenities and not as serving a specific, environmental function.  No longer should copper sulfate be permitted at the detriment of the local and downstream environments. An opportunity to remove an unnecessary, biologically available toxin from your local water bodies presents itself without significant drawbacks—and because of this, use of the copper sulfate pollutant should be forbidden.

On the Environmental Frontier

In considering a ban on copper sulfate, your community would not be unprecedented.  A number of jurisdictions are, or have, considered a ban on the use of copper sulfate.  Based on data revealing that copper “hot spots” coincide with storm water discharge points in the bay, the Naples City Council will consider a resolution in November 2008 that would prohibit the use of copper sulfate as an algaecide.  In early 2008, the City amended its budget, approving the installation of aerators in its stormwater retention ponds and lakes, in place of algaecide use to control algal blooms.13

Across the ocean from Naples, the European Union had scheduled a complete ban on all copper based algaecides because of the “effects of its use on the aquatic environment, impact on aquatic organisms, and soil accumulation.”[13] Reviewers found copper sulfate “not compatible with sustainable ecosystems and recommended against its use,” expressing concern about the impact it has when flushed into natural water bodies. [14] For these reasons, the review panel concluded that copper sulfate “should never be considered as a routine and convenient treatment to handle [algal] problems.”[15]

A Call to Action

As copper pollution becomes more widely recognized, more jurisdictions will move toward legislative and regulatory prohibitions targeting copper and its compounds.  Your local community has the opportunity to protect its ecosystems and preserve its vital water resources by preventing the intentional application of copper sulfate, a toxin and pollutant, to its waters.

By limiting this ban to copper sulfate as an algaecide, rather than more broadly to other copper species, smaller municipalities will be able to apply limited resources in the most beneficial and cost-effective manner.


1.  Iowa State University. Managing Iowa Fisheries: Use of Copper Compounds in Aquatic Systems.”

2.  Extension Toxicology Network. Pesticide Information Profiles: Copper Sulfate.

3.  Thomas O’Connor and Gunnar Lauenstein. “Status and trends of copper concentrations in mussels and oysters in the USA.” National Centers for Coastal Ocean Science in Marine Chemistry, no. 97 (2005) p 49-59.




7.  Mark Hanson and Heinz Stefan. “Side effects of 58 years of copper sulfate treatment on the Fairmont Lakes, Minnesota.” Journal of the American Water Resources Association. Vol 2:6, pp 889-900. June 2007.

8.  European Union Technical Advisory Panel. “Copper sulfate for use as an algicide and invertebrate pest control,” September 2001.

9.  ISU, Managing Iowa Fisheries

10.  Extension, Pesticide Profiles

11.  ISU, Managing Iowa Fisheries

12.  Lee, Aquatic Chemistry

13.  Personal Communication and Staats, Federal Study

14.  EU, Copper Sulfate for use

15.  Ibid.

16.  In light of these events, we have limited our recommendation to a ban on copper sulfate specifically for water applications.

Braden Galbreath-O’Leary is a pond management expert for Triplepoint Water Technologies, based outside of Chicago, IL. He and his colleagues are committed to providing efficient, sustainable, and environmental solutions to the water and waste wastewater industries.

For more information on the Pond Management, visit our home page and watch the video on Eco-Friendly Pond Aeration.

To read more about ponds, visit the Pond Blog.

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