What Is Copper Sulfate?

The National Pesticide Information Center says copper sulfate is an inorganic compound that combines sulfur with copper, that it can kill bacteria, algae, roots, plants, snails and fungi, and that it has been registered for use in pesticide products in the United States since 1956. The EPA says conventional copper products are registered for agricultural uses, primarily as bactericides and fungicides, as algaecides in rice production and aquaculture, and for non-agricultural uses including aquatic algaecides, herbicides and molluscicides, sewer root intrusion control and blight control on ornamental trees.

Swallowing it is dangerous. The National Pesticide Information Center says copper sulfate can cause severe eye irritation, and that eating large amounts can lead to nausea, vomiting and damage to body tissues, blood cells, the liver and kidneys, with shock and death possible in extreme exposures. ATSDR says blue copper sulfate crystals used to control algae in ponds have been accidentally swallowed by people who confused them for candy or toys. A 2022 case report in the Indian Journal of Nephrology describes copper sulfate as a potentially lethal poison and powerful oxidizing agent that causes corrosive injury to mucous membranes, with a clinical course of red blood cell destruction leading to anemia, jaundice and kidney failure.

In its 2018 interim registration review decision for copper compounds, the EPA says a final decision will occur only after an endocrine screening determination, an endangered species determination with any needed consultation, and an assessment of exposure to pollinators.