13 August 2019

Glyphosate issues have been discussed in previous News articles from November 2015, June 2016 and May 2017.


Glyphosate is the active substance in broad-spectrum herbicides, which were introduced in 1974, and since have become the most commonly and intensively used herbicides worldwide, and they are used in increasing rate.

Also in Denmark, glyphosate was the most sold active substance in pesticides in 2017 with 1241 tons or 48 % of the total amount of active substances in pesticides.

Glyphosate is used in form of various salts, for example the isopropyl amine salt, which is mixed with water and other chemicals known as “inert ingredients” to constitute glyphosate based herbicides, which include the popular Roundup® product, that are used in agricultural fields and home gardens to fight weeds.

The widespread application of glyphosate to crops has spurred the spread of tolerant and resistant weeds in the US, and worldwide, which in turn has created the need for more frequent applications at higher concentrations. Recent findings suggest glyphosate and its metabolites may also spread by wind and water erosion and found in dust within non-agricultural homes.

Therefore, it is not surprising, that Individuals increasingly may be exposed to glyphosate in occupational and environmental settings through various routes, such as dusts, food and drinking water.

A US FDA review of glyphosate levels in food in the United States found that over 60% of corn and soybean samples analyzed had detectable glyphosate residues, which would contaminate foods and feeds.

A recent paper (Gillezeau et al. 2019) has reviewed 19 research studies of occupational or/and public exposures to glyphosate. Glyphosate levels in human beings can be quantified by measuring levels of glyphosate in urine, and glyphosate has regularly been detected in human urine in the general population of the US and Europe at concentrations of 1–10 μg/L, and occupational exposures at about 10 times higher concentrations.

A recent study (Connolly et al. 2019) has estimated the biological half-life of glyphosate in human urine as 5-10 hours.

In an older study of 30 cows from 8 Danish farms (Krüger et al. 2013) the glyphosate concentrations in the urine were 20-100 μg/L and higher than in humans.

Pet animals, particularly dogs and cats, have often been used as sentinels of human exposure to emerging environmental chemicals. Widespread occurrences of glyphosate in urine from 60 pet dogs and cats have been determined in New York State, USA (Karthikraj and Kannan, 2019). The mean urinary concentration of the sum of glyphosate and its metabolites (AMPA and N-methyl glyphosate) in cats averaged 34 μg/L, which was 2-fold higher than that in dogs, where the average concentration was 17 μg/L.

The main reason for these higher levels than in humans was the residues of glyphosate in feedstuff.


Many laboratory studies have recently underlined that glyphosate, may not be as harmless, as the authorities have claimed based by its low acute toxicity to mammals. Especially, the potential effects on male and female reproduction have increasingly become in focus. Observations suggest that generational toxicology needs to be incorporated into the risk assessment of glyphosate and all other potential toxicants. The ability of glyphosate and other environmental toxicants to impact our future generations needs to be considered, and is potentially as important as the direct exposure toxicology mostly done today for risk assessment.

The exposure of a gestating female directly exposes the F0 generation female, the F1 generation offspring, and the germline within the F1 generation offspring that will generate the F2 generation grand-offspring. The direct exposure mechanisms of action in the F0, F1 and F2 generations are distinct from the trans-generational germline mediated actions. Therefore, the first trans-generational generation is the F3 generation great-grand-offspring not having any direct exposure. Although the F2 generations grand-offspring can have a mixture of direct exposure and generational actions, the lack of any direct exposure is first observed in the trans-generational F3 generation.

A recent study (Milesi et al. 2018) suggested that perinatal exposure to low doses of a glyphosate-based herbicide impaired female reproductive outcomes by inducing fetal growth retardation and structural congenital anomalies in F2 offspring in the offspring of exposed Wistar rats.

In another recent study (Kubsad et al. 2019) female Wistar rats (F0 generation) were daily exposed to 25 mg glyphosate/kg bw during day 8-14 of gestation.  In the study glyphosate induced epigenetic trans-generational inheritance of disease and pathology through germline (i.e. sperm) epimutations in the rats. Negligible pathology was observed in the F0 and F1 generations, while a significant increase in pathology and disease was observed in the F2 generation grand-offspring and F3 generation great-grand-offspring.

Therefore, glyphosate appeared in this study to have a low or negligible toxic risk for direct exposure, but promoted generational toxicology in future generations. The authors recommended that the authorization of pesticides takes into account generational toxicology being potentially as important as the direct exposure toxicology used today.

Note! In the introduction to the paper the authors refer to the IARC evaluation from 2015, when glyphosate was classified as a group 2A carcinogen. However, in addition the authors mentioned with reference to a large published review paper, that the IARC evaluation was retracted in 2016. However, this is a placed mistake based on industry sponsored spin; IARC has never retracted its cancer evaluation of glyphosate! Uncritical accept of that fake news down-rates the quality of the scientific paper by Kubsad et al. 2019.

Another recent study (Pham et al. 2019) showed that perinatal exposure to glyphosate and a glyphosate-based herbicide affect spermatogenesis in mice. Pregnant mice were treated from 10.5 to 20 days postpartum by adding glyphosate or a Roundup product to their drinking water at 0.5 (the acceptable daily intake, ADI), 5 and 50 mg/kg/day. Male offspring derived from treated mice were sacrificed at 5, 20, and 35 days old (d.o.) and 8 months old (m.o.) for analysis. Their data demonstrated that glyphosate and Roundup could cause endocrine-disrupting effects on male reproduction at low doses, even at the ADI level.

Thus, the claim by the industry and the European authorities, that glyphosate is safe to use, is wrong, based on both data about carcinogenicity and reproduction toxicity!

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