Dioxins in Pork

dioxin-pigDioxins Before Swine – Irish pork is off the menu, according to the BBC.

The UK’s Food Standards Agency is monitoring pork products in the Irish Republic because of fears of contamination with dioxins. “Tests showed some pork products contained up to 200 times more dioxins than the recognised safety limit.” Interestingly, dioxin levels in soil have been declining in recent years, according to another BBC report from 2007. The alert over dioxins followed an alert after PCBs (polychlorinated biphenyls) were reported to have been found in Irish pork on 1st December after samples were taken 19th November.

There is some hint that machine lubricating oils contaminated with PCBs (stable polychlorinated biphenyls) may have degraded to release dioxins which somehow found their way into the pig feed. But, more likely is that non-feed grade oil is being used at some point in the cycle to dry biscuit meal (out of date biscuits and bakery goods from the food industry). Such non-feed oils obviously do not have the same quality controls as extra virgin olive oil and so could very easily have higher than food-safe levels of contaminants, including PCBs and dioxins. This suggestion hints once again, as did the ongoing melamine scandal, at how easy it seems to be for unscrupulous sectors of the food industry to use non-food materials in their products, allegedly.

So, what are dioxins and should we be worried about them?

DioxinDioxins are organic compounds formed when a huge range of materials, particularly chlorinated polymers (PVC plastics) burn and in some industrial processes. They are ubiquitous in the environment and became the focus of environmental activism because of their reputation for being among the most toxic compounds known. Colloquially “dioxin” is talked of as if it were a single compound rather than a class of compounds, but the most usual reference is to the chlorine-containing compound 2,3,6,7-t​etrachlor​odibenzod​ioxin. Dioxins should not be confused with the compound 1,2-dioxin and 1,4-dioxin, which are heterocyclic, organic, antiaromatic compounds.

2,3,6,7-T​etrachlor​odibenzod​ioxin can have some nasty effects such as irritation to the eyes, allergic dermatitis, chloracne, porphyria; gastrointestinal disturbance, possible reproductive, teratogenic effects, liver, kidney damage, haemorrhage, and occupational carcinogenicity. But, does that long list of problems mean anyone eating any of the food products from Ireland – bacon, ham, sausages, white pudding and pizzas with ham toppings – were or are in any danger. “The UK’s Food Standards Agency said it did not believe at this stage that UK consumers faced any ‘significant risk’,” reports the BBC. Seems like fair comment, only serious chronic exposure to low levels of dioxins or acute high level exposure are of real concern.

No member of the public has ever died from dioxin poisoning, despite the fact that for several decades industry has been inadvertently releasing these materials into the environment as impurities in hundreds of products and that countless burning materials release the same supposedly deadly compounds across the globe continuously. Occupational exposure has led to probably at most four deaths from industrial accidents involving release of dioxins, according to John Emsley writing in The Consumer’s Good Chemical Guide.

Don’t forget to grab the Sciencebase email newsletter or newsfeed for a more complete update on the porcine dioxin story soon. And watch out for any porkies (pork pies, lies).

16 thoughts on “Dioxins in Pork”

  1. that Guardian story is in error (so no change there then!). Why would anyone (not even the Irish!) want to make ‘green diesel’ into ‘red diesel’.??? And I can’t see why removing the red dye would add dioxins, especially as the latter is formed from other substances (which are seldom mentioned), or that dioxins are formed in any processes that may be used, where does the chlorine come from?

    If Dioxins are found, they are as a small component of their parent compounds, pcb’s, for example. For me, the most likely origin of the dioxin (found in Irish pork/beef and who knows what else?) is from transformer oil, which contains large quantites of pcb’s. The chemical properties of pcb’s and dioxins (PCDD + PCDF) are very similar, so if dioxins are present, and their origin is pcb’s, these must be present as well.

    The plot thickens, maybe not everything is being reported by the Irish police (wonder why!). Interesting that the Irish (and British) food agencies are saying dioxins are not a cause for concern here.

  2. Detectives on both sides of the Irish border were yesterday investigating claims that smuggled fuel may have contaminated the animal feed behind the Irish pork crisis, which last night prompted the Food Standards Agency to order the withdrawal of all Irish pork products from supermarket shelves in Britain.

  3. Effects of dioxins on human health
    Short-term exposure of humans to high levels of dioxins may result in skin lesions, such as chloracne and patchy darkening of the skin, and altered liver function. Long-term exposure is linked to impairment of the immune system, the developing nervous system, the endocrine system and reproductive functions. Chronic exposure of animals to dioxins has resulted in several types of cancer. TCDD was evaluated by the WHO’s International Agency for Research on Cancer (IARC) in 1997. Based on animal data and on human epidemiology data, TCDD was classified by IARC as a “known human carcinogen”. However, TCDD does not affect genetic material and there is a level of exposure below which cancer risk would be negligible.

  4. Ah, righto, thanks Bryan. It *has* been found in Irish beef, see my earlier addendum. PCBs were the start of this they were apparently discovered in pig feed in September:



    I think basically, the food industry is using mineral oil instead of vegetable oil as a drying agent and the mineral oil is contaminated with PCBs which break down to dioxins…

  5. David,
    I was really commenting on the ‘media’s’ view of all this, rather than your very lucid remarks. I can’t remember having seeen or heard any news about ‘other’ compounds being found, which have to be there, if not, the only conclusion is that dioxins were added deliberately.

    Also, I cannot see why Irish beef is not contaminated as well, if using similar feed.

    It all seems that we are only being fed certain information, so no change there!

    There does not seem to be a distiction between mineral oil and vegetable oils in the Irish incident, the former I can see a contamination route, the latter is not so clear!

  6. Bryan, the sources I tracked for this post pointed out that PCBs were found in pork products previously and as I actually say in the post, they could be degradation products formed during excessive heating of non-feed oils used at some point in the production process. I don’t think I suggested anywhere in my post that other compounds were not present with dioxins. I was merely stating that “pure” dioxin has a certain level of toxicity, it can, after all, be produced relatively pure and tested regardless of whether that happens naturally or not.

  7. it should be made aware that dioxins occur as a byproduct or metabolite, they (dioxins) are not useful, and therefore not produced (deliberately) by industry, so they must have been produced from other substaces, like pcb’s, chlorophenols, hexachlorophene, 245T, etc. I don’t remember seeing any of these mentioned in connection with the Irish pork problem, surely dioxin cannot be the only thing in the contaminted oil (if it is this).

    As dioxin is not produced alone, i.e. other substances (in much greater amounts) are always present, it is very unscientific to suggest that dioxin (alone) in solely responsible for symptoms of acute/chronic exposure.

  8. It has just been confirmed by PA what I alluded to in the post – “Unlicensed oil was used at a food recycling plant at the centre of the pork contamination crisis which has crippled the country’s pig industry, it has been confirmed.” Apparently pig and beef farms across Ireland and Northern Ireland have received the dioxin-contaminated feed.

  9. Yes, Seveso was a tragedy, but that was massive acute exposure, not the kind of tiny concentrations they’re worried about in the Irish pork. As to Yushchenko, I’d just mentioned him to my wife as your comment popped up. There was some doubt at the time about whether it was chloracne caused by dioxin ingestion, but I remember wondering at the time what else it could’ve been, and the tests proved that it was indeed that.

  10. Bryan, yes, something does stink. I strongly suspect that TCDD and PCBs are present as a contaminant in some kind of filler, or bulking agent, that feed producers have been fobbing off to pig farmers, in much the same way that the dairy supply chain was deliberately contaminated with melamine in China earlier this year. Although that was being added to spoof protein levels, the suspect filler is presumably just adding to total mass at lower cost than actual feed.

  11. Has anyone seen the levels of ‘dioxin’ found in Irish pork? Has there been any mention of the levels of pcb’s found (surely much higher than the dioxins?). Has anyone mentioned that dioxins/pcb’s are industrial chemicals/contaminants, so what were they doing on premises handling animal feed?
    Something stinks?

Comments are closed.