Paraquat or not?

• 

Paraquat - widely used in South African forestry to prepare tracer belts before burning firebreaks - is facing world-wide bans, forcing foresters to reach for the old-fashioned hoe. GAYNOR LAWSON reports.

It sounds so benign: “A non-selective herbicide - an aqueous solution contact herbicide for the control of annual grasses and annual broadleaf weeds in crops as listed and as a sugarcane desiccant. Inactivated on contact with the soil.” But this listed herbicide that contains Paraquat, “could have killed 2000 people” when maliciously used by a disgruntled employee to poison a tank of milk in the Cape in 2017, according to a News24 article. It is highly toxic.

Locally, Paraquat is extensively used to create tracer-belts as part of a fire management programme to prevent fires running out of control during the burning of firebreaks. The herbicide creates a boundary area devoid of vegetation before burning takes place. It is considered cost-effective, efficient and useful as it only desiccates the above-ground part of the vegetation (it leaves the root stock below ground unharmed), allowing for regeneration with the rainy season and thus preventing erosion or invasion by alien plants.

First produced for commercial purposes in 1961, Paraquat remains one of the world’s most commonly used herbicides, despite its potentially lethal impact on humans, either through deliberate poisoning or simply by working irresponsibly with it. It may be airborne when applied as a fine spray and can be spread through contact with clothing so it requires special training to ensure safe handling by users.

China reportedly experiences 5,000 deaths from Paraquat poisoning annually, although whether this is through accidental or deliberate poisoning is unconfirmed - Paraquat is known to be used in suicide attempts. It reputedly doubles the risk of Parkinson’s disease in those who come into contact with it, and the Michael J Fox Foundation issued an anti-Paraquat appeal on its website in October last year (the popular actor’s much-publicised battle with Parkinson’s has brought about heightened awareness of the disease): “Take action today to ban Paraquat. Your support can help protect people from environmental exposure to a known pesticide that increases the risk of Parkinson’s disease. We need your help to educate your Senators and Representatives…”

• 

The appeal was posted in response to the reapproval by the Environmental Protection Agency (EPA) of several pesticides (including Paraquat) for use in the United States. The EPA reviews all herbicides and pesticides every 15 years to confirm they are safe for use, based on “assessments of human and environmental impact”. Despite its “well-documented harms”, the use of Paraquat in the United States “is at an all-time high, and it is one of only two pesticides still used in the United States that is either banned or being phased out in the European Union, China and Brazil”, according to the website.

Measures have indeed been put in place to control its availability. It cannot be bought or used in the UK (although, ironically, it is legally manufactured there), Thailand, Vietnam, Malaysia and the European Union (where it has been banned since 2007). It has been banned in Switzerland since 1989 because it is deemed too dangerous for use even when wearing protective clothing and equipment. In the USA, only commercially licensed users have access to it.

A complete international ban is apparently blocked by the US and developing nations whenever this is proposed. According to an article, “Poison on a plate”, which appeared in The Daily Maverick on 26 January this year, “It’s a shocking display of global north hypocrisy, allowing dangerous agrochemical companies to flood low- and middle-income countries for the financial gain and profit of European nations.”

The situation in South Africa
In South Africa, plantations certified under the Forest Stewardship Council (FSC) may not use Paraquat in any formulation that is available on the market. Gerrit Marais of the FSC Southern Africa Office, says: “Paraquat has been on the FSC Highly Hazardous list since the first pesticide policy was published way back in 2006. The figure below provides information on the reasons why this is done i.e., acute toxicity. Use of the product is thus not limited but prohibited unless it is approved, via a formal FSC process, for temporary emergency use. The South African forestry industry used to have a special derogation (exemption) for the use of this active ingredient and product, but this expired in 2020…Traditionally, the only alternative (to Paraquat) was to hoe the tracers by hand. This is, however, not ideal from an environmental perspective as hoeing often leads to erosion and thus this option – especially on steep slopes - is most undesirable. Some certificate holders have used other systemic herbicides (such as Glyphosate), but here too, the entire plant is killed and the risk of erosion is increased. The South African forestry industry is looking at other options…”

The stance of the Sustainable African Forest Assurance Scheme (SAFAS) – which has been endorsed by the other global certification body, PEFC - is that Paraquat can be used for tracer belt preparation, providing strict control/mitigation measures are in place. Steven Germishuizen, SAFAS general manager, says: “SAFAS supports the use of Paraquat from an environmental perspective because it is the best solution for fire management in grasslands. However, we acknowledge that it is highly toxic, so in accordance with our risk-based approach, we insist on strict precautions as far as training, use of PPE and application methods go.”

Craig Norris, NCT Forest Technology Manager, adds: “In addition to what Steve has said, we encourage an integrated approach to chemical use. In other words, the use of agrochemicals is the last choice of action and must be defendable. Agrochemicals can be detrimental to human and environmental health and will only be used after due consideration is given to other options/mitigation measures:
• Chemical control must be used in combination with above methods to minimise quantities used.
• Strategy for reduction of chemical use must be implemented.
• Chemical label specifications must be followed.
• Recommended safety, training, application procedures must be adhered to.

Steven comments: “We also encourage the use of technology, such as drones, to keep people away from the chemical. We strongly encourage exploration into environmentally suitable alternatives that are less toxic.” There is some experimentation with drone spraying currently underway in an attempt to cut humans out of the Paraquat-handling process almost completely.

• 

What is the history behind Paraquat use in SA?
According to Dr John Scotcher of ForestLore Consulting in a report written for the FSC in 2014: “Burning green grass is not possible and, in any event, adversely affects biodiversity. In order to improve the safety aspects of burning firebreaks, a system of fire tracer lines was introduced which entailed the hoeing or ploughing of two parallel strips of vegetation approximately one metre wide (the fire tracer line) and 30 metres apart during the late summer to early autumn. These tracer lines are now devoid of vegetation and are used as lines from which to burn the intervening 30 metres (the firebreak) during winter when the grass is dry.”

The report continues: “Approximately 30 years ago, the use of chemicals was introduced as an approach that could be used where mechanical methods such as hoeing, ploughing or use of a brush-cutter was impractical and dangerous to use … normally on steep and mountainous terrain. Paraquat was first used in South Africa in 1982 by the nature conservation agencies responsible for the management of high-altitude grasslands in the uKhahlamba-Drakensberg Park, which is a registered World Heritage Site. The use of Paraquat in this mountainous region enabled the elimination of the historic use of hoed or ploughed tracer lines that resulted in soil loss and scars across the landscape, which even after 100 years are still visible to this day. Paraquat was soon adopted by the agriculture and forestry industry. Paraquat was ideal for use in conservation areas and later in no-till systems such as forestry and grazing lands since it only affects the foliage part of the sprayed plants, thus promoting intact root systems and preventing soil erosion. It also does not leach into groundwater since it is absorbed into clay particles and neutralised when it comes into contact with the soil … In the forestry industry, the use of Paraquat was seen as a best management practice because there was no need to continue with the damaging practice of hoeing or ploughing.”

The Forestry South Africa Environmental Guidelines for Commercial Plantations in South Africa (Version 4 2020, chapter 4) proposes the following approach to the preparation of firebreaks:

1. Mowing
2. Slashing
3. Burning
4. Desiccant chemicals (Paraquat) – on slopes greater than 20 per cent
5. Manual hoeing – now discontinued
6. Mechanical methods (ploughing) – now discontinued

The Wildland Fire Management Handbook for sub-Saharan Africa provides detailed advice on fire protection and advocates the use of ‘chemical surface sprays’ for the preparation of tracer lines i.e. Paraquat.

Paraquat may still be used by the man in the street, although a global shortage because of it being discontinued in many countries has sent prices rocketing. Is there an alternative?

Roger Poole, chairman of the Timber Industry Pesticide Working Group or TIPWG, says: “The forestry industry in collaboration with Professor Keith Little of Nelson Mandela University (NMU) has been researching and testing alternatives for the past nine years since the FSC first indicated that Paraquat would be prohibited. One alternative, pelargonic acid, has shown results similar to Paraquat as a desiccant and was heading for registration under Act 36 of 1947. Unfortunately, the manufacturer was involved with a company buy-out and the new owners changed the formulation of the original product that had been tested. Bridging trials were done to compare the new formulation to the original pelargonic acid; sadly the new formulation did not show favourable results and could not be registered. Glufosinate-ammonium is an active ingredient that is used in agriculture, classed as a partly systemic contact herbicide that is an alternative for tracer preparation - but supervision is imperative as over-application could result in it being more systemic than contact and grass root systems could be severely damaged. TIPWG has stated that Glyphosate formulations should not be used for tracer preparation as this active ingredient could result in a complete kill and thus erosion will occur, especially on steep terrain.”

Dr Scotcher adds in another factor - the human element of the spraying process: “When terrain is steep, the person spraying naturally slows down to navigate safely up or down the hillside, resulting in a higher application rate per unit area.”

Dr Gerhard Verdoorn, Operations and Stewardship Manager for CropLife SA, comments: “There is currently no herbicide with the properties of Paraquat apart from diquat which is also a bipyridinium compound with high toxicity. It is not registered for the purposes of industrial vegetation management like Paraquat is. A possibility is pelargonic acid but the dosage rates required to desiccate plants is much higher than what was originally anticipated and that makes it a very costly option. Furthermore, it is not registered in South Africa. Attempts with many other herbicides have all failed to emulate the effects of Paraquat. Glyphosate is registered for such purposes as making firebreaks but due to its systemicity, it kills plants completely which leads to terrible erosion.”

When asked about the slower progress of workers on steep slopes leading to over-application, he disagrees, saying: “Glyphosate is super-systemic and even with a low dosage (lower than label directions) it will kill plants completely, especially broad-leaved plants. Some of the tough monocotyledons like Cynodon will survive but most of the softer grass species are wiped out completely. Another issue is the problem of resistance development when sub-optimal dosages of Glyphosate are used for chemical mowing; although it is on labels of some Glyphosate-containing herbicides, it is the best catalyst for resistance development I have ever heard of and the crop sector is currently battling with Glyphosate resistance (Amaranthus palmeri, Amaranthus hybridus, Conyza bonariensis, etc).”

• 

Is a total ban an over-reaction?
“People are very quick to point fingers at the use of pesticides but are sadly ignorant of potentially toxic products they use daily at home and, which, if used incorrectly, can be fatal,” says Roger Poole. “Everyone loves coffee, but do they know that the caffeine in coffee's LD50 is 150-200 mg/kg?” {LD50 is the amount of a substance, given all at once, that causes the death of 50% of a group of test subjects; it is a way of determining the short-term poisoning potential or acute toxicity of a substance}.

“So why has no one died from coffee? Simply put, the risk of consuming lethal quantities in your morning cup of java is not possible so the risk of poisoning is reduced. Consider household cleaning detergents, has anyone ever read the label or safety data sheet of the detergents they have in their home? Are these locked away so the uninformed cannot access them? Are certain products kept separately so that they cannot react with each other? Bleach is one of the most commonly used products found in households throughout South Africa, but did you know that if bleach and vinegar come into contact with each other their reaction can cause chlorine gas? Whatever product you are using at home or in the workplace, be it a pesticide or a detergent, they can all be toxic if used or applied incorrectly.” His message is loud and clear - use Paraquat correctly to minimise potential risks!

Is a total ban on Paraquat likely in the near future?
The Rotterdam Convention is scheduled to take place this year, although with the global COVID-19 pandemic, whether it goes ahead is uncertain. Poole says: “Paraquat is one of the many listed active ingredients for consideration to be banned worldwide and has been listed numerous times but never seems to be banned due to pressure from the large world economies. We wait in anticipation for the outcome, as we've done in the past.”

A year later on…
It’s a year since an article entitled 'Weaning the forestry industry from its paraquat reliance' by Jacqui Meyer appeared in SA Forestry magazine. According to the article, “the next step is applying for an Emergency Registration under Act 36 of 1947, which Dr Gerhard Verdoorn of CropLife SA is currently assisting TIPWG with. With CropLife’s support and the information obtained from the bridging trials, we hope to have pelargonic acid available for the 2021 summer rainfall area fire season.”

Well, that was in March 2020, and in April 2021, Dr Verdoorn was doubtful about the predictions - for this fire season at least. “I am not sure this is going to materialise… if we are able to get our hands on pelargonic acid. It is quite expensive … and I wonder if it will make the grade for the timber industry.”

In the meantime, creating tracer belts using mechanical methods such as brush-cutters and tractor-operated grass-slashers is the norm, with some landowners and companies using Glufosinate-ammonium. “It’s been very difficult, with manual clearing and a return to traditional hoeing on flat terrain,” says Simon Thomas, Operations Manager for KZN FPA. So, what will the situation be by next year’s fire season? Is a total switch to drone-spraying a feasible option? Only time will tell.

•