Herbicide Myths

Public Spaces and Herbicide Use

A large proportion of herbicide use occurs in public spaces; National Parks and State Forests, sports fields, parks and gardens, play grounds, road sides, drains, school yards and rail lines which increases the risks of exposure to the general public.

Up to 50% of the herbicide used in urban areas falls onto hard surfaces such as bitumen and concrete and washes into drains and enters our rivers and creeks as runoff where it can remain in sediments and impact aquatic ecosystems (1).

Lawn and garden weeds are rarely a threat to human health, public safety, or the environment and the use is generally for cosmetic purposes, that is, they are used to improve the appearance and keep vegetation ‘tidy’. In response to growing global concern about the risks of pesticide exposures, many local and regional authorities (see ‘Case Studies – Public Spaces’) are moving to ban the cosmetic or non-essential use of potentially cancer-causing pesticides on gardens, green spaces and around homes to protect human health.

Are herbicides safe?

Many people believe that because herbicides are designed to kill plants they can’t harm people. In the same way insecticides are designed to kill insect pests but can also impact humans and other animals, so too can herbicides. Herbicides, insecticides, fungicides etc. are all called pesticides.

One concern is the possible connection between herbicide exposures and cancer. According to the Canadian Cancer Society,

“The pesticide issue is very complex. The extensive number of ingredients, the innumerable volume of chemical combinations in the thousands of available products in addition to the many uses and exposure routes of pesticides (as well as other factors), makes establishing causation between specific chemicals and certain cancers virtually impossible within the ethical restrictions of scientific research.

“According to the precautionary principle, this absence of conclusiveness does not justify inaction. Given the current body of research and the seriousness of the associated health risks, The Society strongly recommends eliminating exposure to pesticides wherever possible.” (2)

The Society says there is increasing evidence that

“A growing body of human, population – based or epidemiological evidence implicate pesticide exposure in the occurrence of several types of cancers including non-Hodgkin lymphoma, multiple myeloma, prostate, and kidney and lung cancer, among others. Increasingly convincing evidence comes from research on children exposed to residential pesticides and increased cancer incidence.

“Our review is regularly updated to take into account new research findings as well as new evaluations of evidence from respected, international, scientific bodies such as the WHO’s International Agency for Research on Cancer, the US National Toxicology Program and the US Environmental Protection Agency”(2).

Pesticide exposure and health risks

In addition to cancer, pesticide exposures have also been linked to many other health risks including:

  • Neuro-developmental and neurodegenerative effects such as Parkinson’s disease
  • Adverse reproductive outcomes including limb reductions, urogenital anomalies (urinary tract and genital), central nervous system defects, orofacial clefts (mouth and face), heart defects, eye anomalies
  • Decreased fertility
  • Altered growth including low birth weight and prematurity, and foetal death
  • Learning disabilities
  • Asthma
  • Death caused by acute poisonings.

The most commonly used herbicide globally is glyphosate (particularly as Roundup) and it has been well marketed by Monsanto, its original manufacturer, as both safe for human health and the environment and readily broken down in soils. Independent review finds that neither of these claims is valid. The Australian Pesticide and Veterinary Medicine Authority (APVMA) has also accepted the manufacturer’s evidence that there are no unacceptable risks to human health associated with glyphosate.

Misleading advertising regarding the biodegradability of Roundup has been successfully challenged in court (e.g. New York State 1996, France 2009). While three quarters of a cup of Roundup is an average fatal dose the frequent exposure at lower levels has longer term health consequences. Glyphosate has been found in several scientific studies (3) to be linked to Parkinsons Disease, Non-Hodgkinson’s Lymphoma, endocrine disruption, DNA damage, birth defects, and infertility.

Emphasising the lack of adequate and transparent research in registering pesticides, in 2015 the IARC World Health Organisation determined that glyphosate was “probably carcinogenic to humans” (4). Glyphosate is the key ingredient in Monsanto’s Roundup herbicide and other similar products and brands. In addition, they found that 2,4D – also very widely used – ‘possibly’ causes cancer in humans. These findings of ‘possibly’ and ‘probably’ were unable to be definitive due to the lack of research on humans and are based on strong evidence of carcinogenicity to other animals. There was an immediate response from manufacturers like Dow Chemicals and Monsanto to downplay the listing.

In general, pesticides are registered on the basis of their ‘active’ ingredients but they also contain many adjuvants which boost herbicidal activity (and without which the product would be far less effective). These so-called ‘inerts’ are usually kept confidential by manufacturers. A 2014 study published in Biomedical Research International by Mesnage et al. on whole formulations indicated that almost all were up to one thousand times more toxic than their ‘active’ principals.  “Despite its relatively benign reputation, Roundup was among the most toxic of herbicides and insecticides tested.” It was 125 times more toxic than its active ingredient studied in isolation. (5)

Protecting the Vulnerable

“In view of the many young people and pregnant mothers with toddlers who often use these recreational areas, why are we continuing to put at risk public health?” (Canadian Cancer Society)

The dangers to human health and the environment of pesticide (including herbicide) use are well-recognised internationally though not yet so clearly acknowledged in Australia. The unique vulnerability of children has also been well documented (6,7,8). The American Academy of Pediatrics goes further, in providing recommendations to paediatricians and to Government to increase diagnostic knowledge and reduce exposures.

Children are particularly vulnerable to the dangers of pesticides because of:

  • their smaller bodies and therefore larger amounts of pesticide contacted per kilogram of body weight
  • their rapidly dividing cells and growing bodies
  • their developing immune systems
  • their larger skin area in relation to body weight.
  • their habit of putting fingers and objects into their mouths

Children are also at greater risk of exposure to pesticides because they are more likely than adults to spend time on the ground, crawling or playing on grass and other areas where pesticides have been used directly or on floors where residues may persist. Pesticides are also known to cross the placental barrier and therefore children are also at risk before birth.

But by what means do they affect humans and other animals? The idea is strongly entrenched that they mainly affect plants. For example, Glyphosate, the most commonly used herbicide, has been marketed as not harmful to humans or to any mammals because the shikimate pathway, by which it works in plants, is absent in all animal cells. However, this metabolic pathway IS used by bacteria and fungi including those which live in our gut microbiome (9). While they have been shown to affect animal cell lines (5), their chief effect is through damage to our gut microbiome.

“Soil microbes degrade glyphosate to aminomethylphosphoric acid (AMPA). Blood AMPA detection after poisonings suggests intestinal microbial metabolism in humans. Glyphosate and glyphosate formulations induced DNA and chromosomal damage in mammals, and in human and animal cells in vitro.” (10)

These organisms in our guts play a critical role in digestion and other metabolic processes, including our immune systems, and brain functioning. Samsel and Seneff (11)“show how interference with CYP enzymes acts synergistically with disruption of the biosynthesis of aromatic amino acids by gut bacteria, as well as impairment in serum sulfate transport. Consequences are most of the diseases and conditions associated with a Western diet, which include gastrointestinal disorders, obesity, diabetes, heart disease, depression, autism, infertility, cancer and Alzheimer’s disease.”

Protecting the Environment

Pesticides cannot be confined to a single location but move through the environment in the air, land, and water, and will impact on non-targeted organisms and plants.

We often see herbicides used around drains and waterways but even when used away from them, they are readily washed in with storm water. Some herbicides bind with soil particles, which may also be mobilised by water. Whether washed down a paddock or down a street gutter, herbicide-laden run-off will eventually drain into a waterway. The surfactants in pesticides are particularly damaging to aquatic species but the toxicity data provided by authorities is generally not for the whole formulation so gives little indication of the real effects.

In the Orge watershed in France, a study of glyphosate and its breakdown product (aminomethyl phosphonic acid or AMPA) showed them to be the most frequently detected molecules in the rivers
“and usually exceeded the European quality standard concentrations of 0.1microg L(-1) for drinking water. The annual glyphosate estimated load was 1.9 kg year (-1) upstream (agricultural zone) and 179.5 kg year (-1) at the catchment outlet (urban zone). This result suggests that the contamination of this basin by glyphosate is essentially from urban origin (road and railway applications)’ and ‘reached surface water prevalently through storm sewer during rainfall events” (12).

The determination by WHO’s International Agency on Research into Cancer of 2A (probable) carcinogenicity for Glyphosate and 2B (possible) for 2,4-D was based on convincing evidence of carcinogenicity in animals. (4) Nevertheless the effects on native animals has not been considered or researched despite their widespread use, even in conservation areas. Yet we know that, as for humans, they will be affected through their gut microbiome.

Eastern Grey Kangaroos have been observed fitting after grazing in recently Roundup sprayed areas and National Toxics Network has been notified of effects on dogs and frogs. In our coastal national parks, hundreds of kilometres have been regularly sprayed in the narrowly-defined Bitou Threat Abatement Program which fails to take a ‘whole of environment’ approach and has little scientific research into the effect on non-target species.

We are becoming increasingly aware of the importance of a healthy soil microbiome and these chemicals, in affecting soil micro-organisms and in remaining active in the soil for some time will affect the direction of restoration. Research indicates that herbicides may significantly reduce mycorrhizal fungi spore viability and thus root mycorrhization. (13, 14)

In some cases, where a dense weed cover is sprayed, native plants which are hidden below the canopy may be affected and some herbicides like Metsulfuron are particularly ‘effective on weeds that include bulbs or tubers’ (15). This bodes poorly for ground orchids, lilies etc.

Research on honey bees by Sol Balbuena et al. (16) showed that Glyphosate impairs the cognitive capacities needed to retrieve and integrate spatial information for a successful return to the hive. This potentially has long-term negative consequences for colony foraging success.

The overuse of herbicides in non-agricultural situations, particularly glyphosate, is contributing to the development of herbicide-resistant weeds which require ever greater applications of herbicide; Glyphosate resistance in weeds has caused an increase in glyphosate use and a switch to other, possibly more toxic, chemicals. Herbicides such as atrazine, dicamba, Fusilade, and 2,4-D are acknowledged as even more toxic than glyphosate products.

But aren’t we protected by legislation?

What we have now

The most commonly used herbicide globally is glyphosate (particularly as Roundup) and it has been well marketed by Monsanto as both safe for human health and the environment and readily broken down in soils. Our regulatory authority, the Australian Pesticides and Veterinary Medicine Authority (APVMA), has, to date, accepted the manufacturers position but since it receives much of its funding from the industry that it is supposed to regulate, it therefore cannot be considered independent (17). However, since determination of the International Agency for Research into Cancer the APVMA is to examine IARC’s detailed research findings with a view to regulatory action around glyphosates.

In 2015, the World Health Organisation determined that the most widely used herbicide globally – glyphosate – was “probably carcinogenic to humans”. In addition, they found that 2,4D ‘possibly’ causes cancer in humans. These findings of ‘possibly’ and ‘probably’ were unable to be definitive due to the lack of research on humans.

This illustrates a number of things:

  • That there is inadequate independent research before chemicals are released onto the market – sometimes this is simply through computer simulation modelling, regulators often relying on out dated and poorly conducted work by manufacturers which generally determines ‘no risk’ and not on that of health effects researchers—endocrinologists, developmental biologists and epidemiologists
  • The revolving door between regulators and industry and the establishment of industry facilities masquerading as independent research which skews the outcome and interpretation of ‘research’

Both these issues are well discussed in an article by Valerie Brown and Elizabeth Grossman “Why the United States Leaves Deadly Chemicals on the Market” (18). The situation is the same for Australia. Dr Jonathon Lathum discusses the inadequacy of the regulation of agrochemical and pharmaceutical products here. He says “A few authors have argued that the history of chemical regulation, from the point of view of protecting public health and ecological health, is better described as a long line of failure brought on unavoidably by the fact that such a myriad of endpoints greatly exceeds the practical and financial limitations of science“.

In Australia, the APVMA has produced a booklet ‘Understanding Pesticide Chemical Labelling’ which includes such items as brand name, active constituent, what the chemical is registered to do, directions for use and restraints on use, resistance group (to prevent the target building up resistance due to constant use of the same type of pesticide), basic first aid, storage and disposal as well as manufacturer’s contact information.

It does not give clear information for understanding and preventing chronic toxicity. It does not specify the pesticide class. It does not provide information on ‘other’/’inert’ ingredients which may have significant toxicity or may act synergistically to increase toxicity. So-called inert ingredients may, in fact, be the majority of the product. Labels are in English and in technical language not accessible by all those who use the products. There is limited monitoring of off-label use.

The American Academy of Pediatrics outlines similar problems in the USA and point out that “Beyond acute poisoning, the influences of low-level exposures on child health are of increasing concern.” (8)

In 2015, Statecover, compensation insurers of NSW Local Government organisations, sent a fact sheet to all local councils which recommends that they take a cautious approach and investigate their use of glyphosate. The process suggested involves councils undertaking a risk assessment of current weed control chemicals, and to consider a range of control measures to reduce risk (19). Similarly, Workcover, NSW workers compensation insurance, also provides a fact sheet for glyphosate, malathion, diazionon, tetrachlorvinphos and parathion (20). The fact that insurers are concerned should be a wake-up call to users.

What we should have in regulation of pesticides

Pesticides have a myriad of known and suspected health impacts and even more unknown health and environmental impacts. Our authorities should acknowledge that we have little knowledge of the effects of long-term exposures and of the synergistic effects of various pesticides. National Toxics Network believes that in both the agricultural sphere and the public sphere, there are demonstrated alternatives to using toxic herbicides.

Given that profligate use of pesticides is likely to continue for some time, recommendations based on those from the Cancer Council Canada (21) and the American Academy of Pediatrics (8) which should be considered by the APVMA include:

  1. Reliance should not be based on evidence provided by pesticide manufacturers. This poses a conflict of interest. The APVMA should investigate all third party, peer-reviewed research and identify research gaps before a pesticide is accepted.
  2. Epidemiological research should be carried out on populations to assess the real-world effects of pesticide exposure taking into account daily exposure, persistent exposure, dosage etc.
  3. Evaluation should be of the whole product and not of individual ‘active’ ingredients.
  4. Long-term, low-level exposures and the combined effects of multiple pesticides, while extremely complex should be scientifically researched. The Canadian Cancer Society looks at persistent exposure on the job or in the home.
  5. Chronic toxicity information should be assessed.
  6. We frequently see breeches of pesticide usage, particularly in terms of protective equipment and use near waterways. It is not adequate to cover for insurance purposes that recommendations for application and approved use are provided. Risk assessment should also include an assessment of hazards of real-life exposure.
  7. Labelling should include all product constituents, including inert ingredients, carriers, and solvents either on the label and/or the manufacturer’s Web site.
  8. The American Academy of Pediatrics believe the label should include a section specific to “Risks to children,” which informs users whether there is evidence that the active or inert ingredients have any known chronic or developmental health concerns for children.
  9. Reporting: there should be a central database which reports all pesticide-related suspected poisonings to optimize national surveillance.
  10. Safety: right-to-know procedures when pesticide spraying occurs in public areas should be developed and standardised nationally.
  11. Require the development of diagnostic tests to assist providers with diagnosing (and ruling out) pesticide poisoning. Human biomarker, such as a urinary or blood measure, should be developed that can be used to identify exposure and/or early health implications with new pesticide chemical registration or reregistration of existing products.
  12. Developmental toxicity, including endocrine disruption, should be a priority when evaluating new chemicals for licensing or reregistration of existing products.
  13. Least toxic pesticide alternatives should be prioritised.
  14. Health provider education and support: support educational efforts to increase the capacity of pediatric health care providers to diagnose and manage acute pesticide poisoning and reduce pesticide exposure and potential chronic pesticide effects in children.


  1. Weedsteamers website
  2. Canadian Cancer Society (PDF)
  3. Watts, Meriel, nd. Glyphosate, PANAP (PDF). See also Dr Meriel Watts, Glyphosate: Addendum 2012, PANAP (PDF).
  4. International Agency for Research into Cancer, 2015. Glyphosate monograph (PDF). World Health Organisation.
  5. Mesnage, R., Defarge, N., de Vendômois, J.S., and Séralini, G., 2014. Major Pesticides Are More Toxic to Human Cells Than Their Declared Active Principles. Biomedical Research International.
  6. American Academy of Pediatrics Recommendations
  7. Watts, Dr Meriel, 2013. Poisoning our future: children and pesticides. PANAP (PDF)
  8. Roberts, J.R., Karr, C,J., 2012. Technical Report: Pesticide Exposure in Children. Pediatrics, Vol 130 Issue 6. American Academy of Pediatrics.(PDF)
  9. Whiteman, H., 2015. The gut microbiome how does it affect our health. Medical News Today. (More information at Gut Microbiota for Health )
  10. Kathryn Z Guyton, Dana Loomis, Yann Grosse, Fatiha El Ghissassi, Lamia Benbrahim-Tallaa, Neela Guha, Chiara Scoccianti, Heidi Mattock, Kurt Straif,2015 Carcinogenicity of tetrachlorvinphos, parathion, malathion, diazinon, and glyphosate on behalf of the International Agency for Research on Cancer Monograph Working Group. International Agency for Research on Cancer, Lyon, France (PDF)
  11. Samsel, A., and Seneff, S., 2013. Glyphosate’s Suppression of Cytochrome P450 Enzymes and Amino Acid Biosynthesis by the Gut Microbiome: Pathways to Modern Diseases. Entropy, 15(4), 1416-1463
  12. Botta F., Lavison G., Couturier G., Alliot F., Moreau-Guigon E., Fauchon N., Guery B., Chevreuil M., Blanchoud H., 2009. Transfer of glyphosate and its degradate AMPA to surface waters through urban sewerage systems. Chemosphere, 77(1):133-9.
  13. Druille, M., Cabello, M.N., Marina Omacini, M., Golluscio, R.A., 2013. Glyphosate reduces spore viability and root colonization of arbuscular mycorrhizal fungi. Applied Soil Ecology, Volume 64, February 2013, pp. 99–103.
  14. Zaller, J.G., Heigl, F., Ruess, L., Grabmaier, A., 2014. Glyphosate herbicide affects: Below-ground interactions between earthworms and symbiotic mycorrhizal fungi in a model ecosystem. Scientific Reports, 4: 5634
  15. AGVET Chemicals Information Sheet, Tasmania (PDF)
  16. Sol Balbuena M., Tison L., Hahn M.L., Greggers U., Menzel R., Farina W.M., 2015. Effects of sub-lethal doses of glyphosate on honeybee navigation. Journal of Experimental Biology, Jul 10.
  17. APVMA funding
  18. Brown, V., and Grossman, E., 2015. Why the United States Leaves Deadly Chemicals on the Market. In These Times, November 2.
  19. Statecover 2015. Fact Sheet: Use of Roundup. (PDF)
  20. Workcover Fact Sheet : Be aware: Glyphosate and organophosphates – fact sheet.(PDF)
  21. Cancer Council Canada, 2013. Cosmetic Pesticides: Information Brief.(PDF)

Comments are closed.