How toxic is 1080? Toxicologist explains

SECURITY MEASURES: Warnings and safety measures were put in place to counter the 1080 threat.

SECURITY MEASURES: Warnings and safety measures were put in place to counter the 1080 threat.

Professor Ian Shaw explores why and how 1080 is so toxic and asks what is the risk of a child dying from contaminated formula.

New Zealand is one of a very few countries where four numbers in a specific order - 1080 - leads to vehement debate, outright disagreement and intellectual fisticuffs. This is because our green and pleasant land uses 1080 regularly; other countries have either banned or severely restricted its use because of its non-discriminatory and extreme toxicity.

1080, of course, is used to control animal pests (in particular possums) that are threatening our delicate, unique flora. As a result, there is a significant amount of pure, white crystalline 1080 imported for incorporation into baits designed to appeal to our marauding furry invaders.

Whether we should or should not use 1080 is a debate that has rumbled on for a long time, but is not for consideration here. The vehemence of the debate has led to extreme factions, one of which sent an anonymous letter to the CEO of Fonterra in November threatening to poison milk powder used in infant formula with 1080; and, to prove the point, sent a sample of 1080-laced milk powder with the letter.

So, what is 1080 and why is it so toxic? It is the sodium salt of fluoroacetic acid and is converted to fluorocitric acid in mammalian (including human) cells - this stops cell metabolism dead.

This interesting quirk of biochemistry is the key to 1080's extreme toxicity because citric acid is important in the generation of energy in cells. To initiate the energy generation process, citric acid is converted by an enzyme to a slightly different molecule (aconitic acid) that is converted to something else which is converted to something else and so on, eventually leading back to citric acid.

As this cycle turns, energy-rich molecules spin off which drive cellular processes. Without them the cell would die. The fluorocitric acid produced from 1080 stops the enzyme that converts aconitic acid in the cycle dead in its tracks. This stops energy generation and kills the cell.

This process is called lethal synthesis and is a very devious mechanism of toxicity.

1080 could spell death to any cell it enters. It does not discriminate between cells or target animal. Providing the cell has the citric acid cycle it is doomed. So, if anyone tells you that 1080 can discriminate between pests and native animals they are talking complete and utter rubbish.

The only way to target the effect is to use baits that a particular pest prefers (eg, carrots for possums), but even then if another animal eats the 1080-laced bait it will die, as might animals that eat poisoned carcases.

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This biochemical jiggery-pokery explains how 1080 so effectively kills cells, but to understand the risk associated with the eco-terrorist threat we are currently facing we need to know how much would kill a child.

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Surprisingly few reliable data are available to base this on. Perhaps the best are studies in dogs carried out many years ago. This introduces an important discussion - do all species respond similarly to 1080? The answer is almost certainly no; it is likely, but not proved that humans are less susceptible and so need a higher dose to give the same effect as in, for example, dogs.

However, based on dog studies about 0.4 mg taken by mouth would kill a 5kg infant. This is a very low dose - enough to just about see. Studies in rats, on the other hand, suggest that 0.4mg would harm, but not kill a child. I have introduced this toxicological conjecture to illustrate that we don't know how much 1080 is needed to kill or harm a child, but that the dose is likely to be very low.

All of this means that very sensitive analytical methods are needed to test milk powder to decide whether it is safe. Such methods are reported to have been developed and applied to tens of thousands of milk powder samples. The negative findings should assure us that the supply chain is clean. And inspecting infant formula containers for evidence of tampering would identify any product that has been individually adulterated.

So, where does all this take us? On the negative side, we have a deranged individual who has written a letter threatening to add a highly toxic chemical to infant formula, and the amount of 1080 that might be added could easily kill a child.

On the positive side, we have a supreme surveillance scheme that has so far shown no adulteration; combined with vigilance in retail outlets to minimise the risk of someone tampering with individual containers of formula, and mums and dads checking that the containers of formula they purchase have not been tampered with. The risk of contaminated formula ending up in a baby's bottle is surely very low.

But this whole incident has heightened our awareness to what an evil person can do to make a point that they are passionate about.

Professor Ian Shaw is professor of toxicology at the University of Canterbury and author of Is it Safe to Eat? (Springer, 2005) and Food Safety - the Science of Keeping Food Safe (Wiley-Blackwell, 2013).

 - The Press

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