Glyphosate toxicity – impacts on the environment and non-target species

A few important facts not readily found in information from Monsanto-funded and lobbied government agencies and conservation programs, and subsequently not common knowledge amongst bush regenerators, farmers and gardeners. Sale of Roundup and glyphosate herbicides for controlling “invasive alien non-native species” is a multi-million dollar business, but what are the hidden costs and implications of this popular biocide?

We take a look at some research revelations about Roundup and its constituents, Glyphosate and sufactants, and their impacts on soil, non-target plants, animals, humans and aquatic organisms.


Glyphosate when it comes into contact with soil is adsorbed onto soil particles, binding to soil in a similar way to phosphates, remaining residual for many years . Adsorption of glyphosate is higher in soils containing clay and organic matter than in sandy loam soils. (4)

Glyphosate bound to soil particles can remain active and may be released from soil and taken up by plants. The US-EPA has also stated that many endangered plants may be at risk from glyphosate use in conservation areas.

Glyphosate in soil takes 140 days to break down to half it’s toxicity and will continue to be taken up by plants from the soil for 2 years and longer.

Some soil invertebrates including springtails, mites and isopods are also adversely affected by glyphosate. Of nine herbicides tested for their toxicity to soil microorganisms, glyphosate was found to be the second most toxic to a range of bacteria, fungi, actinomycetes and yeasts” (1)

Glyphosate is hazardous to earthworms, Tests using New Zealand’s most common earthworm showed that glyphosate, in amounts as low as 1/20 of standard application rates, reduced its growth and slowed its development.

Roundup inhibits mycorrhizal fungi. Canadian studies have shown that as little as 1 part per million of Roundup can reduce the growth or colonization of mycorrhizal fungi. Mycorrhizal fungi are essential for tree health, collecting nutrients and water to feed their host plant and protecting tree roots from harmful fungi and root rot diseases.

Glyphosate reduces nitrogen fixation. Amounts as small as 2 parts per million have had significant effects, and effects have been measured up to 120 days after spraying.

Ground spraying of Glyphosate can drift up to 400m in still conditions (i.e. no wind)


Glyphosate, N-(phosphonomethyl) glycine, is the most extensively used herbicide in the history of agriculture.  However, this relatively simple, broad-spectrum, systemic herbicide can have extensive unintended effects on nutrient efficiency and disease severity, thereby threatening sustainability. A significant increase in disease severity associated with the wide spread application of the glyphosate herbicide can be the result of direct glyphosate-induced weakening of plant defenses and increased pathogen population and virulence. Indirect effects of glyphosate on disease predisposition result from immobilization of specific micronutrients involved in disease resistance, reduced growth and vigor of the plant from accumulation of glyphosate in meristematic root, shoot, and reproductive tissues, altered physiological efficiency, or modification of the soil micro?ora affecting the availability of nutrients involved in physiological disease resistance” (8)

Findings of research at Hohenheim University  concluded that: “There is a common understanding that the widely used herbicide glyphosate is easily degraded and adsorbed in soils and thus, harmless for use in agriculture. We can demonstrate, however, that this conclusion is wrong and dangerous for farmers because in former risk assessments the behaviour of glyphosate in the rhizosphere was not properly considered.

In nutrient solution, rhizobox and pot experiments we can show that foliar applied glyphosate to target plants is released into the rhizosphere after a fast translocation from shoots to roots. In the rhizosphere glyphosate can obviously be stabilized long enough to achieve negative effects on non-target plants. Such a negative side-effect is for example inhibited acquisition of micronutrients such as Mn, but also Zn, Fe and B, which are involved in plants own disease resistance mechanisms.

From this glyphosate transfer from target to non-target plants (from weeds to trees) we predict an increase in disease problems, particularly on soils with low micronutrient availability as already reported in the USA. In view of plant and soil health, we urgently call for a re-assessment of glyphosate as herbicide.” (9)

Roundup can increase the spread and severity of plant diseases. Over 40 major plant diseases have been found to increase following use of glyphosate including nine different species of root rot (e.g. Fusarium spp, Phytophthora spp, Monosporascus spp), as well as Anthracnose, wilts and rust diseases.

Glyphosate reduces resilience (e.g. cold hardiness, drought tolerance) in trees and their resistance to fungal disease. Damage to non-target trees in woodlands sprayed with Roundup for weed control is greatest 2 years following spray application.

Glyphosate used to control weeds under trees inhibits the trees uptake of essential nutrients including Manganese, Zinc, Iron and Boron, which plants need to fight disease.

Studies in Germany have established a “relationship between glyphosate application and negative effects reported for various non-target organisms in agro-ecosystems. These observations comprise: (1) increased sensitivity to plant diseases, associated with a low Mn-, and Fe- nutritional status, (2) increased nematode infections, (3) inhibition of root growth, possibly induced by glyphosate interactions with the calcium metabolism, (4) reduced honey production due to limited synthesis of flavonoids as flower pigments, and (5) reduced biological nitrogen fixation” (HUBER and MCCAY-BUYS, 1993; KING et al. 2001; KREMER et al. 2001). (9)



Roundup kills beneficial insects. Tests conducted by The International Organization for Biological Control showed that Roundup caused mortality of live beneficial species including  Thrichgramma, predatory mites, lacewings, ladybugs, and predatory beetles.

Glyphosate has shown a wide spectrum of chronic toxicity in laboratory tests. The National Toxicology Program found that chronic feeding of glyphosate caused salivary gland lesions, reduced sperm counts, and a lengthened estrous cycle (how often an individual comes into heat). Other chronic effects found in laboratory tests include an increase in the frequency of lethal mutations in fruit flies, an increase in frequency of pancreas and liver tumors in male rats along with an increase in the frequency of thyroid tumors in females, and cataracts.” (3)


In Australia most formulations of glyphosate have been banned from use in or near water because of their toxic effects on tadpoles and to a lesser extent on adult frogs. There is also concern about non-lethal effects of the herbicide on frogs.

It has been shown that aquatic wetland communities can be dramatically impacted by low concentrations of pesticides (from run-off) including glyphosate (both separate and combined) and these results offer important insights for the conservation of wetland species and communities. (5)

“Fish and aquatic invertebrates are more sensitive to glyphosate and its formulations. Its toxicity is increased with higher water temperatures and pH. (1)

Primary producers (algae and macrophytes) are amongst the most sensitive test species for glyphosate acid, the IPA salt and Roundup. The most sensitive species reported for glyphosate acid are the beneficial diatoms and green algae, and aquatic plants (macrophytes) (6)  This can impact up the aquatic foodchain.

Glyphosate causes DNA damage to tadpoles (7)

Roundup can also cause substantial mortality in juvenile terrestrial frogs and toads. Many frogs that breed in water also routinely use non-aquatic areas and could easily be exposed to glyphosate formulations that contain harmful surfactants through direct application and incidental drift.

Glyphosate toxicity in water has a half-life of 2-12 weeks, but remains residual for much longer periods in sediment where it binds with clay and organic matter.


Studies on human cells showed toxicity and hormone disruption at sub agricultural levels with effects within 24 hours caused by concentrations as low as 0.5 parts per million. And DNA damage at  5 parts per million.  The impact of glyphosate-based herbicides residues in food, feed or in the environment now has thus to be considered real. PMID: 19539684

The exposure of children to glyphosate should be avoided as recent animal studies have shown that commercial formulation of glyphosate is a potent endocrine (hormone) disruptor, causing disturbances in reproductive development when the exposure was during the puberty period (5)

Pregnant women are also at risk as others have found that glyphosate exposure from commercial preparations can affect human reproduction and fetal development in case of contamination. Chemical mixtures in formulations appear to be underestimated regarding their toxic or hormonal impact. PMID: 17486286 (5)

A study carried out by Swedish oncologists in 2001 showed that glyphosate may induce cancer of the lymphatic system and is considered a risk factor for non-Hodgkin lymphoma (NHL) (5)

Roundup has been found to inhibit the production of steroid hormones and this may result in loss of fertility in men (7)

Exposure of farm workers to smaller amounts of Roundup, for example by rubbing in an eye, is reported to have caused swelling of the eye and lid, rapid heartbeat and elevated blood pressure, or swelling of the face, due to residues transferred from the hands after touching leaky equipment, while accidental drenching caused eczema of the hands and arms which lasted two months (7)

acute toxic pneumonitis after inhalation of vapors and air-borne droplets containing glyphosate has been diagnosed, based on clinical evidence (7)


Surfactants in Roundup

ethylated amines. POEA (polyoxy-ethyleneamine), used to improve solubility of glyphosate and penetration into plants. Surfactants have now been found to amplify the effects of glyphosate in living organisms

significantly more toxic than glyphosate, surfactants causes serious irritation of eyes, the respiratory tract and skin, and have been found to contain carcinogenic dioxane (not dioxin) contaminants

At concentrations of less than 2% of recommended agricultural usage, all common surfactants have been found to kill cells, damaging cell membranes, mitochrondria and fragmenting DNA in cell nucleus.  Impact of these are greater in combination with glyphosate than when trialed individually. (2)

In the UK, glyphosate is the most frequent cause of complaints and poisoning incidents recorded by the Health and Safety Executive’s Pesticides Incidents Appraisal Panel (PIAP). Between 1990 and 1995, 33 complaints were received and 34 poisonings recorded including a single death by suicide in 1990(12,13). In California, glyphosate is one of the most commonly reported causes of illness or injury to workers from pesticides. The most common complaints are eye and skin irritation(14). The US authorities have recommended a no re-entry period of 12 hours where glyphosate is used in agricultural or industrial situations. No such recommendation exists in the UK.”

A US EPA report says: “Effects on pregnant mothers and foetuses included diarrhoea, decreased weight gain, nasal discharge and death of mothers and kidney and digestive disorders in rat pups””




(2) Death by Multiple Poisoning, Glyphosate and Roundup: Scientists pinpoint how very low concentrations of the herbicide and other chemicals in Roundup formulations kill human cells, strengthening the case for phasing them out

(3) from NCAP Journal of Pesticide Reform

(4)  NTP Technical Report on Toxicity Studies of Glyphosate, US Dept of Health and Human Services

(5) notes from published medical science papers indexed by the US National Library of Congress.

(6) Aquatic ecotoxicity of glyphosate and formulated products containing glyphosate


(8) European Journal of Agronomy: Glyphosate effects on diseases of plants, G.S. Johal ? , D.M. Huber 1

(9) Relevance of glyphosate transfer to non-target plants via the rhizosphere. Hohenheim University, Stuttgart, Germany