Glyphosate herbicides get absorbed in the gut or through the skin. 30% of glyphosate is absorbed in most test animals after ingestion. Most of the absorption is excreted in the urine. The acute toxicity of glyphosate itself is classified in Toxicity Category III –which is “slightly toxic and slightly irritating”.
In spite of tests showing low toxicity to animals, poisoning caused by both intentional and accidental introduction to glyphosate have been recorded in humans and laboratory animals. Physicians in Japan first exposed the threats of surfactants in glyphosate herbicides in a study of 56 cases of Roundup poisoning. These cases mostly resulted from suicides or attempted suicides, which included nine deaths. They found that the fatalities happened after ingesting about 200 ml of glyphosate. A range of symptoms has been noted from glyphosate poisoning.
Workplace Exposure
Exposure to small amounts of glyphosate herbicides in the workplace has been shown to cause serious poisoning symptoms. A study requested by the USDA Forest Service found that the use of Roundup with hand applicators or tractor sprayers resulted in exposure to glyphosate despite using special protective clothing. Reports of poisoning incidents are frequent. An assortment of symptoms has been disclosed from various incidents. Including eye and skin irritation, contact dermatitis, eczema, cardiac and respiratory issues, and allergic reactions.
Animal Exposure
Monsanto (RoundUp) claims that glyphosate herbicides do not cause reproductive complications. However, tests with rabbits have determined adverse effects on semen and sperm quality. Other studies at high dosages have reported problems such as decreased litter size and reduced sperm counts in rats.
Some articles suggest that glyphosate herbicides can cause chronic health effects in laboratory animals. Lifetime glyphosate feeding studies have exposed reduced weight gain, liver and kidney effects, and deterioration of the eye lens. These effects were found in the higher doses tested. At lower doses inflammation of the stomach’s mucous membrane was shown.
Glysophate Studies
The EPA classifies glyphosate in ‘Group E’- non-carcinogenic for humans. They base this conclusion on three studies conducted between 1967 and 1990 of laboratory animals fed fluctuating doses of glyphosate. Observations include testicular tumors in males, thyroid cancers in females, kidney tumors in male mice, and pancreatic and liver tumors in male rats. For an assortment of reasons all of the effects were discounted.
However, a Swedish study found that increased rates of non-Hodgkin’s lymphoma were connected with exposure to Roundup. The scientists stated that “glyphosate deserves further epidemiologic studies”. Another recent study tested the genotoxicity of glyphosate and recorded cytogenetic damage in mouse bone marrow which was more noticeable for Roundup. DNA-damaging activity was also observed in the mice’s liver and kidneys.
Glyphosate Herbicides in Food
The use of glyphosate may result in exposure in crops and animal tissue or water destined for human consumption. The World Health Organization found that pre-harvest use of glyphosate results in leftovers in the grain and plant material. The WHO also found that glyphosate residues in animal feed arising from pre-harvest glyphosate treatment of cereals may result in low glyphosate levels in meat, milk and eggs. In storage, glyphosate herbicides are stable for one year in plant material and two years in animal products. Monitoring Glyphosate residues in food is complex and costly. Likewise, the measurement of glyphosate exposure in the general population through diet has not been conducted.
Grains
Research by Monsanto showed the existence of glyphosate in samples of all grains harvested from treated plots. The metabolite AMPA was detected at low levels. Studies showing the outcome of glyphosate residues in wheat found that levels in white flour were 20% of the levels in wheat. The bran residues were 2 to 4 times higher. However, the residues were not lost during baking. Levels of glyphosate in the final bread product depend on how much glyphosate-contaminated flour is diluted with uncontaminated flour.
In a 2 year study in Canada, residues of glyphosate in wheat after pre-harvest treatment increased with the rate of application and decreased with seed moisture. When the maximum application rate was sprayed at seed moisture of 40% or less, glyphosate was found. Glyphosate residues in beer made from barley were 4% of the original level in the barley. Levels of glyphosate in processed oats were found to be 50% of the levels in the pre-harvest treated oats.
Animals fed a diet of 100mg of glyphosate resulted in significant residues in liver and kidney. Levels of glyphosate in milk, eggs and meat were low.
Berries
Field studies of glyphosate on wild berries found that residues in the fruit after spraying remained above the maximum permissible level throughout the 61 days of study period. The berries absorbed the glyphosate at different rates. These fruits are typically sprayed in late summer when the fruit is ripe. Contaminated fruit may be eaten by wildlife or picked for human consumption. Glyphosate has been found in strawberries, lettuce, carrots, and barley after they were sprayed. Glyphosate was found in some of these food items a year after glyphosate was applied.
Drinking-Water
Monsanto advertises that glyphosate is not a threat to drinking water since it is constrained by soil and is biodegraded quickly. However, glyphosate has the potential to contaminate surface water if it is carried by soil particles suspended in a run-off. Glyphosate has also, on rare occasions, been detected in groundwater. Once in water, glyphosate is not readily broken down by water or sunlight. Dispersion from water is usually due to absorption to sediment or uptake by plants.
Generally, glyphosate residues in water are not monitored because they are extremely difficult to isolate and many authorities do not consider glyphosate to be a major concern as a contaminant. In the US, routine monitoring for glyphosate in groundwater is infrequent. Glyphosate has been found in seven US wells: 1 in Texas and 6 in Virginia.
Aquatic Life
Very little research has been done on the effects of glyphosate on aquatic microorganisms or invertebrates however here is what we have learned:
- A study to determine the effects of glyphosate on carp found that toxic effects included changes in enzyme activity in serum, liver and kidneys and morphological changes in gills.
- A study in Louisiana tested the effect of glyphosate on an snail species, Pseudosuccinea columella. They found that low levels of glyphosate adversely affect snail reproduction. It also found that glyphosate can stimulate growth and increase the number of eggs laid containing more than one embryo.
- A study examined the DNA damage caused by 5 pesticides, including Roundup on bullfrog tadpoles. Significant DNA damage was observed for 2 out of 3 concentrations tested. There was a strong linear correlation between DNA damage and dose. The study concluded that Roundup is clastogenic (causes DNA damage) in tadpoles.
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