Glyphosate is a common chemical used in commercial herbicide products such as Roundup, made by the Monsanto Company. The U.S. Environmental Protection Agency (EPA) has classified glyphosate as a Class II toxicity chemical, with Class I chemicals being more highly toxic. Glyphosate is good at killing plants when applied, but it can also cause environmental and human health problems.
Chemical Properties of Glyphosate
Glyphosate is a type of amino acid that interferes with other amino acids contained in plants, according to Iowa State University. Labels of herbicides that contain glyphosate state that their active ingredient is "Glyphosate, N-(phosphonomethyl)glycine, in the form of its isopropylamine salt." When this chemical disrupts plant enzymes, it causes death of most plants under most circumstances. Plants cannot metabolize glyphosate, so it spreads through the plant; this causes plant death that is more effective than other herbicides that quickly interfere with plant tissues.
Contamination of Water Supplies
When glyphosate enters ponds, streams and other bodies of water, it contaminates not only the water but also the plants and animals that dwell in those bodies, according to the EPA. The International Organization for Biological Control has reported that animals have died in aquatic areas where glyphosate is known to have spread from nearby fields or other areas where it was applied. Amphibians such as salamanders and frogs are especially at risk, according to a 2005 report that the University of Pittsburg published.
Human Health Risks
The organization Beyond Pesticides reported that incidents of human poisoning due to excessive exposure to glyphosate include sore or swollen eyes, diarrhea, headaches and symptoms resembling influenza. Other symptoms include a rise in blood pressure, chest pain, coughing and nausea. They also reported on the effects that glyphosate has caused in laboratory animals, such as tumors of the pancreas, thyroid gland and liver.
Persistence in Soil
Beyond Pesticides reports that glyphosate can remain active in soil where it has been applied for up to 47 days and adds that a study conducted by the Extension Toxicology Network in 1996 showed it can remain for as many as 174 days. When anaerobic soils are deficient in micronutrients, glyphosate can remain for many months. Its presence affects earthworms and other soil-dwelling creatures.
EPA Review of Toxicological Effects
The EPA determined in 1992 and again in 1994 that the main metabolite contained in glyphosate did not need regulation, although it shows "some toxicological effects." This metabolite is known as AMPA. The EPA decided that when glyphosate comes up for review of its registration it will conduct a reevaluation of AMPA to decide if its new risk assessment should include it.