31 January 2013

Zimbabwe: A Herbicide's Silent Rage

A week before Christmas last year I visited my rural home in Mhondoro communal lands. And having last visited in April, it was only natural for me to go round the village meeting old friends and kinsfolk to catch up and exchange a few pleasantries.

My nephew accompanied me. One of the homesteads we visited belonged to my uncle - brother to my father. He was said to have gone to the shops to nurse a hangover from the previous day's imbibing.

His son, Tendai welcomed us.

"You are very lucky. You could have missed me for I was about to leave for the field. Weeds are choking my tobacco crop so I have a lot to do this morning if the rains do not disturb me," he said.

My nephew, who had been quiet since we left home, at this point joined in saying he also was facing serious problems with weeds in his tobacco field and was planning to engage a few casual hands to help him. Another villager who had been following the conversation from his adjacent field came over to greet me and naturally joined the discussion on weeds.

He revealed that he had no such problem as he had used a herbicide called paraquat to control the weeds before planting his tobacco. The three farmers then discussed the benefits of using herbicides over the manual route and each promised to use them next season. And before I left for the city my nephew begged me to buy him some paraquat for next season.

I had heard about the herbicide many times but had never bothered to get information on how it is used or where it could be obtained. My search landed me where I had not imagined - the discovery that the herbicide was, in fact, very toxic and therefore unsuitable for use and was consequently being phased out.

I learnt that several years ago, Chinese researcher Sun Jing and some members of the Pesticide Eco-Alternatives Centre in China discovered that farmers were mysteriously falling ill and dying. They suspected this had something to do with paraquat that farmers were using. The farmers had no idea what a deadly chemical they were handling everyday.

There was little research and no warning label. Paraquat is an acutely toxic weed killer. It destroys green plant tissue on contact and is also toxic to animals; direct contact on the skin causes death. Long-term exposure can result in Parkinson's disease and skin cancer. China is the world's largest producer of paraquat, manufacturing 100 000 tonnes per year.

Sun Jing and her colleagues took action. They researched the chemical. They talked to farmers. They established relationships with officials in the Ministry of Agriculture, shared their research, and advocated for change. Global Greengrants Fund supported their work from the beginning and sustained it over several years. In April 2012, their efforts bore fruit. The Chinese government announced that they would halt all production and use of liquid paraquat by 2016. Sun Jing pointed out that this would not only protect farmers in China, but also in countries such as Laos, Vietnam, and the United States that purchase paraquat from China.

"This is meaningful to the health and life of millions of people. Protection and conservation are critical tools for preserving biodiversity and pristine ecosystems," Sun Jing said then.

Global Greengrants Fund supports local protection and conservation efforts that are led by the people who steward the land. Their grantees protect forests, wetlands, marine ecosystems, water supplies, animals and people.

These findings on paraquat left me baffled especially as I knew that many of my people back in Mhondoro were using the herbicide and did not have the slightest idea of the danger that was stalking them every time they opened the container to mix the chemical with water before spraying.

I decided to visit the Department of Research and Specialist Services where my first port of call was the head of agronomy, Mr Brian Neurashe's office. He professed ignorance on the impending ban on paraquat and referred me to the acting director, Crop Division, Mr Victor Chingwara. Mr Chingwara likewise said he was not aware of the ban and referred me to the DRSS principal director, Mrs Danisile Hikwa. She too was not aware of the impending ban on paraquat use.

"If there is information like that coming from China, it will soon be shared so that we look for alternative chemicals to use in weed control without endangering the lives of the farmers, biodiversity and other plants. Paraquat is not a selective herbicide and kills everything in its path on contact.

"We will have to look for alternatives. There are conventions guiding the use of chemicals and Zimbabwe has ratified some of them so we have to conform. The Rotterdam Convention, for instance, which regulates the trade of chemicals and the Stockholm Convention that is concerned with the disposal of chemicals are some of the conventions to which Zimbabwe is a signatory," said Mrs Hikwa.

She said it was now the prerogative of different countries either to stop the use of the chemical at once or to phase it out gradually.

"There are stocks of the chemical in the custody of farmers out there and it will take time for all of them to be exhausted so we shall see how it goes before we can even think of setting a deadline for the total ban of the chemical," she said.

Mrs Hikwa added that paraquat was part of the chemicals that bear the purple label and were dangerous and traditionally not allowed to be handled by smallholder farmers without supervision from trained personnel. She confessed that her department tended to focus more on research involving crops, soils and the benefits derived from using chemicals and had not looked at the health side of things or the impact chemicals like paraquat were having on the environment.

This finding exposed gross shortcomings in our specialist and research services and the Government in particular that did not invest in such vital research. This is leaving millions of people at risk from getting affected by agro-chemicals either directly or indirectly.

Paraquat is widely used for broadleaf weed control, and some common trade names of the product include Crisquat, Dextrone, Herba-xone, and Spot Killer. Its effects take place quickly upon contact and are non-selective, meaning that the compound can affect a wide range of weed plants rather than a particular few. It may also be used as an aquatic herbicide and the United States and Mexico once used it to kill marijuana plants.

However, this particular application proved fatal when a number of deaths were observed when marijuana contaminated with this chemical was inhaled.

Paraquat is a toxic chemical that is widely used as an herbicide (plant killer), primarily for weed and grass control. In the USA it is classified as "restricted use", which means that it can be used only by people who are licensed applicators. It was first produced for commercial purposes in 1961 and is still one of the most commonly used herbicides globally.

The most likely route of exposure to paraquat that would lead to poisoning is ingestion (swallowing). It can be easily mixed with food, water, or other beverages. Paraquat poisoning is also possible after skin exposure. Poisoning is more likely to occur if the skin exposure lasts for a long time, involves a concentrated version of paraquat, or occurs through skin that is not intact (skin that has sores, cuts, or a severe rash). If it is inhaled, paraquat could cause poisoning leading to lung damage.

Licensed applicators of paraquat are the people most at risk for exposure. After a person ingests a large amount of paraquat, he or she is likely to immediately have pain and swelling of the mouth and throat. The next signs of illness following ingestion are gastrointestinal (digestive tract) symptoms, such as nausea, vomiting, abdominal pain, and diarrhoea (which may become bloody).

Severe gastrointestinal symptoms may result in dehydration (not enough fluids in the body), electrolyte abnormalities (not enough sodium and potassium in the body), and low blood pressure.

Ingestion of large amounts of paraquat leads to pulmonary oedema (fluid in the lungs), lung scarring (evolves more quickly than when small to medium amounts have been ingested), liver failure, kidney failure, confusion, coma, seizures, injury to the heart, fast heart rate, muscle weakness and respiratory (breathing) failure, possibly leading to death within a few hours to a few days.

People with high-dose exposure to paraquat are not likely to survive. Applicators must quickly take off clothing that has liquid paraquat on it. Any clothing that has to be pulled over the head should be cut off the body instead of pulled over the head. Those helping other people remove their clothing must try to avoid touching any contaminated areas and remove the clothing as quickly as possible.

Although paraquat is acutely toxic to mammals through all routes of exposure, it is at its most lethal via the ingestion pathway. Dermal exposure to paraquat has been shown to induce dry and fissured hands, the loss of fingernails, ulceration, and diarrhoea.

In general, paraquat rapidly and strongly absorbs to soil particles, especially those of clay. In soil, the compound can have a half-life of greater than 1 000 days. Because it binds so strongly to soil, during rainstorms paraquat may also run off into water bodies, which makes it a potential ground water contaminant.

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