Glyphosate-based herbicides are global pollutants of groundwater, rivers and surface water. More recently it has been detected in rain.

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, a herbicide.

Glyphosate is the active ingredient in a range of 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.

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.

Glyphosate applied on plants and soil can bind with soil particles. These can then contaminate surface water indirectly when that soil is washed into rivers. This sort of pollution is most significant where silt is deposited and accumulates in estuaries or lakes.

Contrary to advertising, glyphosate persists in soils. Studies have found that its degradation in soil is slow, especially when applied in autumn, and contamination can leach down to one metre below ground level.

Paul Capel, head of the agricultural chemicals team at the US Geological Survey, and co-author of a study into glyphosate, has confirmed that this chemical can now even be detected 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”.

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 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 a year after glyphosate was applied at approved rates.

In Australia the regulatory body that assesses and approves all formulas of glyphosate, their uses and their respective rates of application, is the Australian Pesticides and Veterinary Products Authority.

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