Paraquat - an antiquated poison or necessary weapon in the fight against weeds?
New Zealanders are being asked by the Environmental Protection Authority to decide whether or not some paraquat-based products should be banned.
Sprayed to help fruit and vegetables flourish, paraquat is described by the Environmental Protection Authority as a "particularly harsh and hazardous chemical", and WorkSafe says it should only be used if there is no other alternative.
It is banned in the European Union and a number of other countries, but in New Zealand the amount used has risen five-fold since 2004 to 42 tonnes a year according to economic consultants Sapere. At least four people in New Zealand died using it intentionally between 2007 and 2015.
Paraquat has been used in New Zealand since the 1960s, mostly on clover seed and lucerne crops, but also on a wide range of foods for humans: brassicas, green beans, kumara, lettuce, onions, potatoes, spinach, strawberries, and sweet corn.
Sometimes it is sprayed before planting, sometimes as weed control throughout the year, but at other times for pre-harvest weed control and "pre-harvest dessication".
Now the EPA is reassessing its use, proposing to ban four paraquat-based products and place stricter controls on the use of others.
The ones it proposes to ban are known under the trade names of Gramoxone Inteon, Preeglone Inteon, Uniquat 250 and Parable 250 because they have "mutagenic, carcinogenic or reproductive toxicant classifications and pose unnecessary risk, regardless of controls".
The EPA says it is not paraquat itself that has these properties, but the ingredients added to it which make it so toxic.
Tougher controls are proposed over chemicals known in the trade by the names Preeglone, Kuatout, Speedy Herbicide, AGPRO Paraquat 200, Paraquat 200SL, PQ 200, Gramoxone 250, Flash Herbicide, and Parable.
They would be restricted to agriculture only, with downwind buffer zones, and restrictions on application rates, frequencies, and intervals.
In a submission to the EPA, WorkSafe sounded a strong note of caution over approving paraquat herbicides.
"As paraquat is one of the most hazardous herbicides approved for use in New Zealand the expectation is that it should only be used if there is no other alternative."
Besides causing skin irritation, eye injury or impaired sight, it has also been linked to Parkinson's disease and impaired lung function.
Safe Food campaign spokesman Meriel Watts said she was shocked that more was being used than ever, although that is disputed by the group representing the agricultural chemicals industry, Agcarm.
"I'm a bit shocked New Zealanders are using that much because 46 tonnes is a huge amount and. It's a really antiquated herbicide, people use it because it's cheap."
It was responsible for a significant number of deaths among workers in developing countries who did not use safety equipment, but even in developed countries it could kill people.
"In Australia a backpack malfunctioned, a pressure gauge failed and a worker got paraquat on his chest, and it killed him. It's so lethal," Watts said.
Potatoes NZ confirmed growers used paraquat, although the more favoured chemical was diquat. Both are designed to inhibit photosynthesis, with paraquat being sprayed before planting.
Growers who grow for the seed potato industry - customers include home gardeners - spray the green tops with diquat to make sure the tubers do not exceed the maximum certification size of 55mm.
But it is also sometimes used on potatoes that people eat, to limit tuber size and to remove the foliage to reduce the risk of diseases such as Liberibacter.
Watts suggested growers should look to alternatives such as steam or burning to control weeds and inhibit plant growth.
Federated Farmers arable chairwoman Karen Williams said it was "extremely rare" for pea seed growers to use paraquat.
The arable industry was always looking for ways to reduce dependence on certain chemicals, but was also concerned about the consequences of banning them. This included lower crop yields or having to use other chemicals.
"We're constantly battling new pests and diseases so the process needs to be really rigorous before outright banning something.
"We need to ask 'could it not be kept for a small number of instances where it is required with the right regulation and control'."
Regarding alternatives, Williams said they might be suitable for the home vege garden, but it was challenging to make them work at a large scale.
Agcarm chief executive Mark Ross said his members were reporting a decreased use of paraquat, which was "a safe and effective herbicide when used as directed".
Alternatives such as glyphosate (Roundup) killed the whole plant, whereas paraquat had a more limited impact. Weeds were becoming resistant to Roundup, but not to paraquat.
Ross said paraquat was rapidly absorbed in the soil, minimising the risk of it leaching into waterways, and also allowing for rapid replanting without adverse herbicidal effects on following crops.
The Australian Pesticides and Veterinary Medicines Authority had reviewed paraquat and concluded the continued approval of paraquat was unlikely to be harmful to people.
"Decisions by the EU to ban products are made according to their unique hazard-based regulatory system that is often misused for ideological or political purposes. It's important the EPA makes its decisions based on science and evidence rather than activist claims and precautionary principles," Ross said.
The public have until April12 to make submissions.
