What is all the fuss about?
The use of the poison 1080 has been under the microscope because of widespread concerns about the toll it is taking on wildlife and the environment.
The Department of Conservation says it is the most suitable poison for aerial drops to kill possums which are destroying native bush.
The New Zealand possum population is estimated at more than 70 million and chomps its way through seven million tonnes of vegetation a year.
Destroying possums limits the spread of tuberculosis from the pests to livestock on farms. Left unchecked, it is estimated TB could could cost the deer, beef and dairy industries industries up to $5 billion over 10 years.
But opponents say the poison kills not only pests, but also native birds and wildlife such as kiwi. Further, they say, it is a cruel method of pest control and may contaminate the ground and waterways.
Hunters oppose 1080 because it kills deer and recreationists say it makes a mockery of New Zealand's claim to be clean, pure and green.
This year on the West Coast, 1080 opponents stole 100kg of poison pellets from a pest control company and threatened to kill pets to demonstrate the pain it causes.
What is 1080?
Sodium monofluoroacetate, commonly known as 1080, is a fine white powder. It has a slight odour and taste and is said to dissolve easily in water.
While manufactured 1080 is a highly lethal poison to many species, the active ingredient, fluoroacetate, is identical to a substance that occurs naturally in many poisonous plants.
These plants are found in Brazil, Africa, and Australia.
1080 comes in several forms, usually in small dyed green pellets, but also sprayed with carrot baits, pastes and gels.
How long has it been used here?
1080 has been used in New Zealand for pest control since the mid-1950s and is the only poison registered for aerial drops. It is also used in Australia, USA, Mexico and Israel. However, New Zealand uses about 80 per cent of the world's production of manufactured 1080.
How does it work?
Whether laid on the ground, or dropped from the sky in large remote areas, the 1080 is eaten by the animal.
If enough is ingested, the poison disrupts the process of breaking down food to provide energy for cells to function. Once the animal has run out of energy, it dies from heart or respiratory failure.
Herbivores like possums become lethargic and usually die within 6-18 hours from cardiac failure. Carnivores experience problems with their central nervous systems and may suffer convulsions before dying.
What are the risks?
1080 is extremely toxic to many animals, and dogs are particularly sensitive to it.
In June, West Coast man Ryan Fitzmaurice lost his pet labrador, Tigger, which died after eating a possum that had 1080 in its system.
The possum had been poisoned by a drop near his home.
Mr Fitzmaurice was offered undisclosed compensation by the pest control company. Humans are also at risk if they ingest 1080.
What measures are taken to keep the public and their animals safe?
DoC must meet strict Ministry of Health conditions before getting a permit for a 1080 operation.
DoC must also talk to communities where 1080 operations are planned, let the public know an operation is going ahead and put up signs to show areas where poisoning has taken place.
* Sources: Department of Conservation, NZ Herald