I have to admit to a few doubts.

In a recent press release about the planned 1080 drop in the Hunua Ranges I ended with the statement, "I would be happy to drink the water from the reservoirs downstream of the 1080 operation."

I pressed send and then panicked. Would I really? If someone handed me a glass and said "drink this" would I? As a scientist, I was advising people that this water is safe to drink, for families, pets, children. If it was my family on the line does my answer really stay the same?

It should be no surprise that I turned first to the science.

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I reread a lot of the published literature about sodium monofluoroacetate (1080) and water.

My first finding was that there is a lot of evidence and scientific research about 1080. What it does under what conditions, how much is toxic, when, how, for what species and why.

As a toxicologist, my work sometimes involves looking at new chemical entities, new chemicals that are going through approval for use as medicines, agrichemicals or even household cleaning products.

Companies submit a dossier detailing all the studies they have done on how toxic the chemical is, and under what conditions.

Compared with 1080 we approve many other chemicals for use in our homes and workplaces using dramatically less data and evidence than we now have available for 1080.

This is not a failure of the international regulatory systems but a contrast to highlight just how much we understand about 1080 as a chemical.

Through the work of dozens of scientists over dozens of years we have a very comprehensive picture of how the chemical acts, how it breaks down and what happens to it in the environment.

Because of early failures better mechanisms of delivery and pellet formulation have been developed. These have drastically reduced the chances that birds and other native species will eat the 1080 bait. By-kill rates have plummeted.

We know that 1080 is water soluble. This is a good thing. Our bodies, and the bodies of plants and animals, are designed to metabolise and excrete water soluble chemicals. They don't stay in our body and they don't stay the same, we breakdown chemical structures to deactivate and remove chemicals from our system.

This happens with the food we eat, the medications we take and all the chemicals we are exposed to. For 1080, the main detoxification action is to remove the fluoride ion breaking 1080 down to glycolic acid and fluorine which are harmless and excreted.

Micro-organisms (eg. bacteria) in the water and soil have the enzyme for this reaction, as do many plants and animals.

When 1080 is dropped on soil or in water the micro-organisms and plants immediately start breaking it apart into non-toxic components.

Multiple studies have shown that within four hours a substantial amount of the original 1080 has been degraded and after 24 hours it is unusual to detect 1080 in water. Dilution is part of the reason for the low levels, but the breakdown into non-toxic compounds is also important.

The rate of breakdown varies depending on previous rain fall, current rain fall, air temperature, soil temperature and many other factors, but water testing consistently shows that 1080 does not persist in waterways.

At this point the rational part of my brain reassured me that if someone offered me a glass of water to drink that could contain 1080, albeit at very low doses, that I could drink it. But still I hesitated. I found this rational argument wasn't enough.

Years of conditioning has instilled in us that drinking poisoned water is not a good idea. So, I turned to the Ministry of Health guidelines which state that 1080 levels must be under 2 parts per billion (ppb) in drinking water.

I calculated that I would need to drink around 70,000 litres in one sitting to reach the minimum toxic level (lethal dose in humans is 2mg/kg of 1080). Published case studies report that drinking 8 litres of pure water in one sitting is toxic (reported toxicity 90ml/kg), so at 2 ppb the water is essentially more toxic than the 1080.

Additionally, in the case of the Hunua ranges all water would be tested prior to release into the drinking water systems (this is standard practice for managed, urban, water supplies).

So, should we use 1080 in our forests? I think the data is compelling but I'm not a conservationist, an ecologist, a zoologist, a farmer, a hunter or an activist so I'm not going to make a judgment on the overall costs vs benefits of using 1080 in our forests.

But I am a toxicologist, and as a toxicologist I can say – yes, I would drink the water.

* Dr Belinda Cridge is a toxicologist and lecturer at the University of Otago