E X T O X N E T
Extension Toxicology Network
A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Michigan State University, Oregon State University, and University of California at Davis. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.
INTRODUCTION
Copper sulfate is a fungicide used to control bacterial and fungal diseases of fruit, vegetable, nut and field crops. Some of the diseases that are controlled by this fungicide include mildew, leaf spots, blights and apple scab. It is used in combination with lime and water as a protective fungicide, referred to as Bordeaux mixture, for leaf application and seed treatment. It is also used as an algaecide, an herbicide in irrigation and municipal water treatment systems, and as a molluscicide, a material used to repel and kill slugs and snails. Copper sulfate is a naturally-occurring inorganic salt and copper is an essential trace element in plant and animal nutrition. It is available in the following formulations: dusts, wettable powders, and fluid concentrates.
TOXICOLOGICAL EFFECTS
ACUTE TOXICITY
Copper is one of 26 essential trace elements occurring naturally in plant and animal tissue. The usual routes by which humans receive toxic exposure to copper sulfate are through skin or eye contact, as well as by inhalation of powders and dusts. Copper sulfate is a strong irritant.
Copper sulfate is only moderately toxic upon acute oral exposure. There have been reports of human suicide resulting from the ingestion of gram quantities of this material. The lowest dose of copper sulfate that has been toxic when ingested by humans is 11 mg/kg. Ingestion of copper sulfate is often not toxic because vomiting is automatically triggered by its irritating effect on the gastrointestinal tract. Symptoms are severe, however, if copper sulfate is retained in the stomach, as in the unconscious victim. Some of the signs of poisoning which occurred after 1-12 grams of copper sulfate was swallowed include a metallic taste in the mouth, burning pain in the chest and abdomen, intense nausea, vomiting, diarrhea, headache, sweating, shock, discontinued urination leading to yellowing of the skin. Injury to the brain, liver, kidneys and stomach and intestinal linings may also occur in copper sulfate poisoning.
Copper sulfate can be corrosive to the skin and eyes. It is readily absorbed through the skin and can produce a burning pain, along with the same severe symptoms of poisoning from ingestion. Skin contact may result in itching or eczema. It is considered a skin sensitizer and can cause allergic reactions in some individuals. Eye contact with this material can cause: conjunctivitis, inflammation of the eyelid lining, excess fluid buildup in the eyelid; cornea tissue deterioration due to breaks, or ulceration, in the eye's mucous membrane; and clouding of the cornea.
The amount of copper sulfate that is lethal to one-half (50%) of experimental animals fed the material is referred to as its acute oral lethal dose fifty, or LD50. The LD50 for copper sulfate is 30 mg/kg in rats. Ingestion by animals of three ounces of a 1% solution of copper sulfate will produce extreme inflammation of the gastrointestinal tract, with symptoms of abdominal pain, vomiting, and diarrhea. When copper sulfate is given intravenously, or injected into the vein, as little as 2 mg/kg copper sulfate is lethal to guinea pigs; and 4 mg/kg is lethal to rabbits.
CHRONIC EFFECTS
Vineyard sprayers experienced liver disease after 3 to 15 years of exposure to copper sulfate solution in Bordeaux mixture. Long-term effects are more likely in individuals with Wilson's disease, a condition which causes excessive absorption and storage of copper. Chronic exposure to low levels of copper can lead to anemia. The biological or chemical manner by which excessive doses of copper sulfate work is not well understood.
The growth of rats was retarded when 25 mg/kg of copper sulfate was included in their diets. 200 mg/kg caused starvation and death. Sheep with access to salt licks that contained five to nine percent copper sulfate showed signs of absence of appetite (anorexia), anemia, and degenerative changes, followed by death within one or two days of exposure. This material caused a significant increase in the death rates in mice that were exposed to an air level equivalent to human inhalation exposures.
The EPA limit for copper sulfate in drinking water is 1 ppm. This limit has been set to prevent a disagreeable taste from copper in drinking water, as well as to provide adequate protection from toxicity.
Reproductive Effects
Developing embryos were resorbed in pregnant hamsters given copper salts intravenously on the eighth day of gestation. Testicular atrophy increased in birds as they were fed larger amounts of copper sulfate. Reproduction and fertility was affected in pregnant rats given this material on the third day of pregnancy.
Teratogenic Effects
Heart disease occurred in the surviving offspring of pregnant hamsters given intravenous copper salts on the eighth day of gestation. EPA does not require data on the teratogenic effects of copper sulfate.
Mutagenic Effects
At 400 and 1,000 ppm, copper sulfate caused mutations in two types of microorganisms. Data on the potential mutagenic effects of this material is not required by the EPA.
Carcinogenic Effects
Ten mg/kg of copper sulfate caused endocrine tumors in chickens given the material parenterally, that is, outside of the gastrointestinal tract through an intravenous or intramuscular injection. EPA does not require this data for copper sulfate.
Organ Toxicity
Examinations of copper sulfate-poisoned animals showed signs of acute toxicity in the spleen, liver and kidneys. Injury may also occur to the brain, liver, kidneys and gastrointestinal tract in response to overexposure to this material.
Fate in Humans and Animals
Absorption of copper sulfate into the blood occurs primarily under the acidic conditions of the stomach; the mucous membrane lining of the intestines acts to some extent as a barrier to absorption of ingested copper. After ingestion, more than 99% of copper is excreted in the feces. Copper is an essential trace element that is strongly bioaccumulated. It is stored primarily in the liver, brain, heart, kidney and muscles. About one-third of all the copper in the body is contained in the liver and brain. Another third is contained in the muscles. The remaining third is dispersed in other tissues.
ECOLOGICAL EFFECTS
Effects on Birds
Copper sulfate poses less of a threat to birds than to other animals. The lowest lethal dose (LDLo) for this material in pigeons and ducks is 1,000 mg/kg and 600 mg/kg, respectively. The oral LD50 for Bordeaux mixture in young mallards is 2,000 mg/kg.
Effects on Aquatic Organisms
Copper sulfate is very toxic to fish. Its toxicity to fish varies with the species and the physical and chemical characteristics of the water. Even at recommended rates of application, this material may be poisonous to trout and other fish, especially in soft or acid waters. Its toxicity to fish generally decreases as water hardness increases. Fish eggs are more resistant than young fish fry to the toxic effects of copper sulfate. Very small amounts of this material can have damaging effects on fish. Permits are being required in some situations for application of copper sulfate to water bodies. Further field studies have been required by the EPA. Direct application of copper sulfate to water may cause a significant decrease in populations of aquatic invertebrates, plants and fish.
Effects on Other Animals (Nontarget Species)
Copper sulfate and similar fungicides have been poisonous to sheep and chickens on farms at normal application rates. Most animal life in soil, including large earthworms, have been eliminated by the extensive use of copper-containing fungicides in orchards. Frogs died after being given intravenous doses of 25 mg/kg of copper sulfate. The lethal concentration fifty, or LC50, is that concentration of a chemical in air or water that kills half of the experimental animals exposed to it for a set time period. The 96-hour LC50 of copper sulfate to pond snails is 0.39 mg/l, at 20 degrees C. Higher concentrations of the material caused some behavioral changes, such as secretion of mucous, and discharge of eggs and embryos.
ENVIRONMENTAL FATE
Copper is strongly bioaccumulated. Biological activity is a major factor in determining the occurrence and distribution of copper in the ecosystem.
Breakdown of Chemical in Soil and Groundwater
Copper is considered to be among the more mobile of the heavy metals in surface environments. Copper is bound, or adsorbed, to organic materials, and to clay and mineral surfaces. The degree of copper adsorption to soils depends on the level of acidity or alkalinity of the soil. The distance that it can travel in soil is limited by its strong adsorption to many types of surfaces. All applied copper will become a part of the soil copper content. Although copper sulfate is highly water soluble-that is, it dissolves very easily in water-the copper ions are strongly adsorbed or precipitated to soil particles when it is applied to soil. The leaching potential of this material is low in all but sandy soils.
When applied to irrigation water, copper sulfate does not accumulate in the surrounding soils. 60% of applied copper was deposited in the sediments at the bottom of the irrigation ditch, where it became adsorbed to clay, mineral and organic particles. Copper compounds, or precipitates, also settle out of solution, in a process called precipitation. This occurs less often than adsorption. Usually, precipitates are biologically inactive, meaning that they do not undergo further biological changes.
Breakdown of Chemical in Water
Due to its high water solubility, excessive amounts of copper sulfate should be kept out of lakes, streams and ponds. Water can be contaminated by inappropriate cleaning of application equipment, or disposal of waste associated with this material. High concentrations of this type of copper are toxic to aquatic organisms and may cause a significant decrease in populations of aquatic invertebrates, plants, and fish. A state Fish and Game Agency should be consulted before copper sulfate application to public waters, as permits may be required for such treatment.
Copper sulfate products should not be used to treat more than half of a lake or pond at one time, in order to avoid depletion of oxygen caused by decaying vegetation. One to two weeks should be allowed between copper sulfate treatments to allow water oxygen levels to recover.
The effectiveness of copper sulfate decreases as water hardness increases. As a naturally-occurring substance, copper can persist indefinitely. No evidence has been found to show that this material gets removed from water through volatilization.
Breakdown of Chemical in Vegetation
One of the limiting factors in the use of copper compounds is their serious potential for phytotoxicity, or poisonous activity in plants. Copper sulfate can kill plants by disrupting photosynthesis. 200 ppm of copper was found in grass five months after it was sprayed with copper sulfate to control liver fluke.
PHYSICAL PROPERTIES AND GUIDELINES
Boots, protective gloves, and goggles should be worn by anyone handling this material. Skin should be washed immediately if contaminated, and work clothing should be changed daily if it is reasonably likely that it is contaminated with copper sulfate.
Copper sulfate is blue and odorless. It gives off moisture when exposed to air. Copper sulfate is classified for shipping purposes as a hazardous substance or hazardous waste. It may pose unreasonable risk to health, safety, or property, when transported. Copper sulfate is highly corrosive to plain steel, iron and galvanized pipes. All metal in contact with solutions of this material should be 304 stainless steel, monel or plastic. It should not be stored in metal containers. Copper sulfate is also incompatible with acetylene gas and with magnesium metal. Containers of this material should be kept tightly sealed. It is indefinitely stable when kept dry and is stable to heat, cold, or light. However, there is slight decomposition of copper sulfate at temperatures above 200 degrees C. Above 400 degrees C, it decomposes, giving off sulfur dioxide gas.
Burning copper sulfate may produce irritating or poisonous gases, and pollution may be caused by runoff from fire control or dilution water.
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