Glyphosate, The World’s Favourite Herbicide

Glyphosate-based herbicides are global pollutants of groundwater, rivers and surface water. More recently it has been detected in rain. Now the International Agency for Research on Cancer (IARC), the World Health Organisation’s cancer agency, says glyphosate made by agrobusiness company Monsanto, was “classified as probably carcinogenic to humans”.

I wrote this piece last year for The Organic Gardener magazine in response to an enquiry from a gardener who’s partner likes spraying glyphosate, the world’s favourite herbicide.

Glyphosate is the active ingredient in a range of proprietary herbicides. There are a variety of formulas, additives, strengths and trade names. All products containing glyphosate are prohibited from use in organic gardens.

Thanks to over reliance on this herbicide, weeds across the world have developed resistance. A super-strength formula is now sold. You can buy glyphosate with 680 grammes per litre of glyphosate instead of the 360 g/L strength…great for those hard to kill weeds says the advert.

One off use

I admit that in certain circumstances and where specific weeds cannot be manually removed, then glyphosate is an option for one off control.

For example, at the Royal Botanic Gardens, Sydney, a systemic herbicide was essential to stop repeated regrowth of African olive trees. These trees were growing thickly in the steeply sloping, rocky sides of Woolloomooloo Bay. As part of the Woolloomooloo Bay revegetation project, staff abseiled down the slopes, injecting the olive trunks with herbicide.

It took years for these olive trees to decay, and during that time their dead roots stabilised the soil and their dead branches made great perches for seabirds.

Another example where a systemic herbicide may be necessary is where running bamboo is invading the banks of a creek. By painting the stumps after removing the culms, a systemic herbicide reduces the risk of bank erosion while the bamboo dies, rots and is succeeded by native vegetation.

In both instances – a steep, rocky, harbour-side slope, and a fragile riparian habitat – complete excavation is impractical. In such cases, one off weed control to facilitate bush regeneration is an acceptable, non-organic control.

Routine use

The risk to human, animal and environmental health stems from the routine, widespread use of glyphosate in an ever increasingly concentrated form.

So much has been written on this chemical, I’m drawing from the website of The Soil Association (a campaigning British charity that created the first organic standards) which seems to have the simplest and shortest of explanations.

Robert Kremer is a microbiologist with the US Department of Agriculture’s Agricultural Research Service, and an adjunct professor in the Division of Plant Sciences at the University of Missouri. His and other scientists’ research has found that glyphosate:

1 Increases fungal root diseases in crops;

2 Locks away manganese, an essential micronutrient (trace element) plants require for healthy growth;

3 Can be toxic to rhizobia, a bacterium that converts atmospheric nitrogen into nitrates on certain plant roots. This renders the cultivation of legumes, which would normally add nitrogen to the soil, useless for that purpose.

Glyphosate-based herbicides are now major global pollutants of groundwater, rivers and surface waters. More recently it has been detected in rain in Canada and the USA. Glyphosate was first detected in the rain in Belgium in 2004. This is likely to be more widespread if more countries complete testing. I’m glad I decided to filter my rainwater using four methods in 2003.

Paul Capel, head of the agricultural chemicals team at the US Geological Survey, and co-author of a study into glyphosate, published evidence of glyphosate in rain in the USA2, 3. “The real significance of this study is the documentation that it is present in the streams year round in warm areas where it is used on crops from spring to fall…“It is also present most of the time in the air and rain most of the time”…“glyphosate was found in every stream sample examined in Mississippi over a two year period and in most air samples taken”.

Glyphosate applied on plants and soil can bind with colloids – loam and clay soils being the most colloid-rich soil types. Contaminated colloids then pollute surface water indirectly as sediment in runoff, entering waterways and, by wind erosion,  the atmosphere. Glyphosate is routinely sprayed on aquatic weeds.

glyphosate

breakdown products of a glyphosate molecule

Glyphosate contributes to toxic algal blooms. The chemical compound we call glyphosate breaks down. As this happens, it releases a burst of phosphorous, a plant nutrient. Phosphorous pollution is most significant where sediment is deposited as silt, and silt accumulates in estuaries, sea grass meadows, coral reefs and lakes.

Contrary to advertising, glyphosate persists in soils longer than manufacturers will admit. Studies have found that its degradation in soil is slow, especially when it is applied in autumn. Cool conditions extend this chemical’s life.

Leaching enables glyphosate to contaminate soil down to one metre below ground level, another surprise the manufacturers left for independent research to discover.

Safe?

It is very important that gardeners – whether organic or not – understand that when a chemical is registered as being ‘safe’ for use, registration only covers the active ingredient. When glyphosate was registered for use, no equivalent research was done for any of the additives, like ‘spreaders’ (detergents) or ‘adjuvants’ (enhancers) mixed in to create the chemical cocktail sold simply as ‘glyphosate’.

Few gardeners realise that sometimes these additives can be more hazardous than the active ingredient. In the 1990’s, when I managed the horticultural estate of the Royal Botanic Gardens, Sydney, there was a panic replacement of standard formula glyphosate with a ‘biactive’ formula. Retailers took back the original and swapped it, free of charge.

The ‘biactive’ formula contains a different spreading agent. The reason for this burst of activity was scientific proof that, contrary to advertising, the original formula was lethal to amphibians at all stages of their lifecycle, even for short periods of exposure, and at low doses.

Glyphosate is still used in Australia to spray floating aquatic weeds, like water hyacinth, Eichhornia crassipes. The Queensland Government sprays sources of drinking water, such as the Brisbane River, with glyphosate to control water hyacinth.

The US Environmental Protection Agency considers glyphosate to be relatively low in toxicity 4, and without carcinogenic effects, while the California Environmental Protection Agency’s Pesticides Illness Surveillance programme indicates glyphosate-related incidents are one of the highest reported of all pesticides5.

Independent scientific research provides increasing evidence of toxicity over the past twenty years. Now the world’s most frequently used weedkiller, glyphosate has been linked with spontaneous abortions, non-Hodgkin’s lymphoma, and multiple myeloma in humans.

Glyphosate has been found to kill human placental cells at concentrations below rates approved for agricultural use.

Research has also detected residues in crops of lettuce, carrot and barley planted one year after glyphosate was applied at approved rates. If you eat non-organic bread, it is being made from contaminated flour.

In Australia there is one regulatory body that assesses and approves all formulas of glyphosate, how they can be used, and their respective rates of application. This is the Australian Pesticides and Veterinary Medicines Authority.

The APVMA receives a significant proportion of the funds it needs to function from the licensing of pesticides for sale in Australia.

References:
1
Grappling with Roundup, by Lynda Brown, published 4.5.2011, W: http://www.soilassociation.org
2 Roundup (glyphosate) found year round in air, water and rain, by Town & Country Gardening, published 2.9.2011, W: survivalfarm.wordpress.com/2011/09/02/roundup-glyphosate-found-year-round-in-air-water-and-rain/
3 Widely Used Herbicide Commonly Found in Rain and Streams in the Mississippi River Basin, released: 29.8.2011, US Department of the Interior, US Geological Survey Office of Communications and Publishing, 12201 Sunrise Valley Dr, MS 119, Reston, VA 20192. Contact: Paul Capel, Phone: (USA) 612 625 3082, or Kara Capelli, Phone: (USA) 571 420 9408
4, 5 Glyphosate, Wikipedia: en.wikipedia.org/wiki/Glyphosate

Jerry Coleby-Williams
20th February 2012
Reviewed 11th September 2016