Lead Week, 10 #Pbweekmia

This is Lead Week on this blog.

Pb shot grouse 1

OK – so these are the data.

Remember, all the shot were removed from these samples, by a combination of searching by hand and eye and then X-raying the samples.  These lead levels refer to the lead left in the meat after the lead shot is removed – caused by tiny shards and fragments of lead coming off the pellets (see Lead Week, 3)

What proportion of Red Grouse bought from Iceland Foods, when tested for lead levels, would have been illegal had they been beef, lamb, chicken etc? Answer 31 out of 40 (78%). 31 out of 40 samples are above the dashed line (a few are superimposed on each other – but count them and you’ll get a good idea).  If this meat were beef, pork, chicken etc all the points would have to be below the dotted line. Why is there no MRL (maximum residue level) set for game meat which, after all, has lead shot into it?

What proportion of lead levels in Red Grouse meat bought for human consumption from Iceland Foods  were at least ten times the maximum residue level (MRL) for beef, pork, chicken lamb etc? They are easier to see, count the points above ‘1’ on the Y-axis – 15 out of 40. That’s more than a third of samples (37.5%) have ten times the maximum allowable level for lead in non-game meat.

And as you can see, there is one sample that had over 100 times the legal maximum lead level (but less than 1000 times) for non-game meat – 168 times, actually.

And that single sample up in the top right corner? That’s above 1000 times the legal maximum lead level for beef, pork, chicken, lamb etc – in fact it is at 3699 times the maximum level (though because it is game meat there is no maximum lead level set – rather strangely).  That is a lot of lead to find in a meat sample.

I’ll let you digest that for a while.







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13 Replies to “Lead Week, 10 #Pbweekmia”

  1. Interesting that the second highest sample is in the no shot found column which many diners might think of as being the 'safest' to eat.
    What is the mean quantity of lead found per bird, excluding the outlier?
    Lidl were selling braces of the similar sized red-legged partridge before Christmas, I didn't see any warnings on the pack other than the standard 'may contain lead shot' which was on the back of the pack. http://www.lidl.co.uk/en/10708.htm?action=showDetail&id=28277

  2. David - thank you for your comment. If one excludes the highest two (almost true of three) lead levels the average lead levels are still ten times the maximum allowable levels for non-game meat.

    I now want to discuss those high values and your use of the term outlier. They are high values but they aren't really outliers. If we were looking at heights of men, then somebody seven foot tall would be an outlier because human heights work that way - they are clumped around a mean according, more or less, to a 'nomal' distribution. Lead levels aren't like that.

    Lead levels in meat always (to the best of my knowledge) have lots of high values, some very high values and some very very high values. That's what life is like. So they are high values but calling them outliers could give the wrong impression.

    The mean values are influenced by the high values - but so they should be!

    I could go on, but I'm sitting in a motorway service station writing this on my phone.

    Thank you for your comment again

    1. Mark - no need to go on. If you have enough data you can do what the European Food Standard Agency (EFSA) did when they looked at lead levels in a wide range foods in 2012. They applied Turkey's method (1977) which identifies as outlier a value greater than the 75th percentile plus 1.5 times the interquartile distance, or less than 25th percentile minus 1.5 times the inter-quartile distance, and then review for plausibility. The EFSA chose to delete 129 results as outliers (meat having the highest number of outliers). Happy to help. Drive safely. Andrew

      1. Andrew - go on? Go on? Me?

        I'm happy to stay here, it is you who wishes to move on.

        You still haven't told me when to pop round to see you eat your thyme and sea salt meal. Tell you what, I'Lloyd bring some cherries with me - I know you like them.

        And Green and Pain? You keep ignoring it. UK diet and impact of eating game meat on lead levels?

        That paper is clearer, domestic and more recent than the EFSA report.

        But I see you phoned a friend this time - very wise. Trying to blind us with science? What point were you trying to make that cannot be answered by Green and Pain?

        You'd better get on the phone again.

        Still raining - now in a layby in Devon. May not be able to stop too many more times.

        Cherries anyone?

        1. 1977 - back in the delightful dark ages when Virginia Wade won Wimbledon, soon be celebrating four decades & you want mark to use a sell by date?

          Quite rightly real science looks to use most recent works most relevant to the issue IF it is sufficiently robust and not straight out of a 'Boys Own'!

          Maybe I've mis-read but Mark appears to have offered every caveat going & yet still, there is overwhelming evidence that there is serious cause for concern? I think I'm being a tad too lenient but why the deafening silence to his questions and others?

      2. Lies, damned lies and auto-correct.
        Anyone can use copy-and-paste but only auto-correct can make a Turkey out of a Tukey.

  3. Is the sample taken of the meat around the wound (as this where most lead shot is likely to be found) or a randomised sample of the edible parts of the bird post-homogenisation? Was the geographical origin of the birds analysed? Many grouse moors, especially in the UK, are coincident with areas rich in hydrothermal mineralisation which has resulted in high background levels of lead in the soil, vegetation & water. A concurrent analysis of zinc would provide a potential assessment of this. Finally, lead shot often contains impurities in the form of antimony & arsenic; I would have expected to see data on those too. Statistical analysis hasn't been used, to my knowledge, so I assume this is raw, verified (but uncorrected for bias) data.

    Background - Geo-Environmental Engineer specialising in contamination & toxicology.

    1. Daniel - see blog 2 in this series for more detail. All the meat is homogenised and then a sample taken (standard practice).

      Grouse come from a Scottish firm but that's all we know.

      Your 'uncorrected for bias' comment makes no sense to me.

      If you'd like to pay for further analysis, and explain the point, then it could be done.


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