Copper Sulfate Pesticides Used In Organic Farming Can Kill You

I learned something kind of horrifying yesterday. It all started when I shared a photo of one of the minerals in my collection, Chalcanthite, which is a type of copper sulfate and one of the most toxic minerals on the planet. I was doing a fun, 'name that stone,' tweet which opened up a horrifying dialogue about the use of copper sulfate as a pesticide in organic farming.





In July of 2020, the Genetic Literacy Project (GLP) published an article detailing just how deadly copper sulfate and other copper products used in agriculture can endanger your life. First, I'll quickly explain what copper sulfate is. Copper sulfate is an inorganic compound with the chemical formula CuSO₄ₓ, in which case the x can range from 0 to 5.

My specimen has the 5. Its most common form is pentahydrate and it's easily identifiable by its beautiful blue color. I mean, that's primarily why I bought my piece--while not knowing it was toxic. It's also water-soluble and this is why I have mine in a sealed, plastic container--the humidity (even when the air conditioner is running) could make it melt.

How It's Used In Agriculture.

Dear God, I can't believe I'm writing this. Actually, I'm pretty shocked that this toxic stuff is used in farming and agriculture. The reason why copper sulfate is used in organic farming as a fungicide is because it's made from 'natural' sources. It's used by both organic and conventional farmers but it has its own toxicity. The article by GPL shared a comparison of the toxicity of copper sulfate with other synthetic and natural chemicals. GLP noted that several anti-GMO activists have raised awareness about the highly toxic organic 2,4-D as dangerous to people, animals, and our environment. This is what The Environmental Working Group had to say about that particular chemical:
"Researchers have linked 2,4-D to hypothyroidism, suppressed immune function, Parkinson’s disease, cancer and other serious disorders. Farmworkers could inhale 2,4-D and get it on their skin while spraying it. The chemical could drift from sprayed fields into nearby neighborhoods. People would track it into their homes. The damage can reach beyond the farmers who live close to sprayed areas."

  Christie Wilcox, a scientist, and a science journalist wrote this about copper sulfate for Scientific American:

"T]here are a lot of myths out there about organic foods and a lot of propaganda supporting methods that are rarely understood. … Organic farming, just like other forms of agriculture, still uses pesticides and fungicides to prevent critters from destroying their crops. … It has been assumed for years that pesticides that occur naturally (in certain plants, for example) are somehow better for us and the environment than those that have been created by man. As more research is done into their toxicity, however, this simply isn’t true, either. Many natural pesticides have been found to be potential – or serious – health risks."


Copper sulfate is one of the many pesticides approved under the USDA National Organic Program yet several studies have proven it to be highly toxic to humans, animals, insects, and the environment. In fact, the USDA says this about copper sulfate:

"Copper sulfate is listed as allowed for use in crop systems in 7CFR 205 for plant disease control, with a restriction that it be used in a manner that minimizes copper accumulation in the soil. It is also listed for use as a micronutrient with a testing requirement for documented deficiency. The petition is for use as an algicide and to control invertebrates, specifically tadpole shrimp in rice production. This material has been historically widely used for organic crop disease control in the US and internationally, but the EU has proposed a complete ban on all copper use scheduled to take effect in May 2002."
Although copper is one of the nutrients our body needs, in high doses, it is extremely toxic. This is why I caution any of my customers when they purchase copper-bearing jewelry pieces from me--especially bracelets and rings. Some minerals turn the water toxic if you leave the jewelry on when washing your hands. Malachite is one such mineral.

How Copper Sulfate Can Be Harmful To The Environment

Texas A&M Agrilife Extension shared how using copper sulfate to bathe the feet or heels of dairy cows contributes to the environmental toxicity of copper. The chemical is added to footbath mixtures to prevent the spread of footrot in dairy cows.

The article noted that once the footbath solutions are disposed of in the milking center waste, this raises the concentration of copper in the slurry, which leads to raising the levels of copper in the soil over long periods of time. This poses a threat to soil, crop, and livestock health.

And let's not forget if it gets into the groundwater, there's another issue to deal with. It also stated that copper is acutely toxic to all aquatic organisms especially on soft or acidic water.

"The negative effects of copper in ecosystems persist for long periods after exposure. The EPA drinking water standard is 1.33 milligrams per liter (mg/L), and levels that stress fish and kill algae are only slightly higher than the freshwater standard of 2.6 micrograms per liter (μg/L)."
The article also dives into copper toxicity in soil and noted that even low levels of copper can significantly damage crops.
"The potential for soil toxicity is high where copper-rich manure or wastewater has been applied long-term. Although copper is an essential micronutrient, high concentrations in the soil can be toxic to plants. The degree of copper toxicity varies by plant species.
As for copper toxicity in livestock, most swine and poultry are often fed high levels of copper to promote growth. Sheep, however, are so sensitive that they could die within hours of ingesting feed containing only 10 ppm.