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Paracelsus' poison

Bute for Brutes

The discovery that certain overseas processed meat products contained, Quelle Horreur, meat that was not exactly the promised beef has generated a fair degree of shock and outrage.

There’s a number of elements in this story, from the damage to the trust in our regulators and markets, to the ick factor of eating an animal many consider to be an intelligent friend to the reports that the meat may be contaminated with pharmaceuticals.

It doesn’t help when you have newspaper accounts breathlessly reporting that the meaty treats in question have “cancer causing chemicals” in them. So, what is going on?

The chemicals in question are phenylbutazone, also known as bute) and its breakdown products (mostly oxyphenylbutazone).

Phenylbutazone is a Non-Steroidal Anti-inflammatory, one of a large class of structurally diverse compounds that reduce inflammation and are, well, not steroids. Other compounds in this class are things like aspirin, indomethacin and ibuprofen. They all work by inhibiting the enzyme that makes the signalling molecules that result in inflammation (steroids, such as prednisone, switch off the gene that makes this enzyme).

Phenylbutazone was a reasonably effective anti-inflammatory, which was often used in Ankylosing spondylitis when other anti-inflammatories failed. Unfortunately, it had a high rate of side effects. The most important were aplastic anaemia and agranulocytosis, where the patients bone marrow failed.

The blood disorders side effect was rare, about 14-22 people contracting them per million prescriptions, but considering this side effects severity the drug was pulled from the human market.

However, phenylbutazone is a very effective veterinary anti-inflammatory, especially in horses (I can find no reports of aplastic anaemia in horses, although it occurs in dogs). When phenylbutazone was banned, it was banned not only from human use but also from being present in all food producing animals, which created a bit of a problem with horses.

In the UK and Ireland, horses are not seen as a food animal, whereas in many parts of Europe they are seen as food animals. Faced with the possible loss of an effective anti-inflammatory agent, veterinarians negotiated a system in the European Union where animals (usually racehorses) that were treated with phenylbutazone were issued with certification (a “passport”) that they would not enter the human food chain.

This would all be well if all the traders adhered to this certification, but it’s is now clear that the meat trading system is not as accountable as one would wish.

It is not yet clear that any of the horse meat in the suspect meat products actually comes from animals treated with phenylbutazone. While some animals sent for slaughter have had traces of phenylbutazone, it has not been found in any meat products yet.

While Woolworths has announced it will conduct DNA tests on its home-brand meals, what is the risk from potential contamination with horse meat?

Not much. Phenylbutazone is relatively rapidly removed from a horses system, if your meals were made 100% from horses that had been injected with phenylbutazone just before slaughter, you would need to eat about a kilo of that meat a day every day for over a week to get the kinds of concentrations needed to see serious side effects.

That is not going to happen, any realistic level of phenylbutazone will be much, much lower than the scenario I outlined above, and the overall risks are minute.

But the low risks are beside the point, the fact is that the surveillance and tracing systems failed big time. Good food policy needs reasoned debate, which can’t happen when people are hyperventilating about a minimal risk.

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