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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Monday 9th June 2014 

I shall be keeping a watch for any new paper about ricin, the toxin found in the seeds of Ricinus communis, the castor oil plant. I’m not saying I expect to be fascinated by the subject of the paper because I can’t be certain of that. But, I do know that I will read the introduction very carefully.

I’ve written about the problem with the introductions of scientific papers before. This early blog entry 18/10/11 explains how the introduction to papers is often packed with references to previous work as a way of establishing the current state of knowledge. It also points out that these references have a tendency to be selective in order to make an argument that fits the researchers’ prejudices.

It is interesting to follow some of these introductions back because you find a form of ‘Chinese whispers’ is at work. Paper A says ‘ricin is said to be a potential bioterrorism weapon though there is no evidence of any incidents’. Paper B says ’ricin is said to be a potential bioterrorism weapon’ and cites paper A. Paper C says ‘ricin is a potential bioterrorism weapon’ citing paper B. Paper D drops the word ‘potential’ and cites paper C.

Ricinus communis, the castor oil plant

One of this year's plants starting to grow

As well as this process of what might be called ‘citation creep’, there is the better-known phenomenon of selection bias where the authors ignore items that contradict their direction of thought. That same October 2011 piece notes that, in 2009, long after it was public knowledge that no ricin had been found in east London in 2003, some introductions were still citing the ‘2003 ricin plot’ as a demonstration of ricin’s bioterrorism credentials.

What brings me back to the subject is four published items that call into question ricin’s position as one of the most feared natural substances. Three of these are recent while the fourth appeared last August but I missed it at the time.

The first two are scientific papers. At the time of writing I have only seen the abstracts and my attempts to contact the authors for copies of the papers have been unsuccessful. The abstracts, however, are adequate for my purposes. ‘NMR-based metabolomics approach to study the chronic toxicity of crude ricin from castor bean kernels on rats’1 reports on trials where rats were given ‘crude ricin (CR)’ i.e. castor bean residue after pressing to remove the oil. The key phrase in the abstract is ‘Long-term CR treatment produced…’. If ricin were the potent killer so often claimed, even in the form of crushed castor beans, then ‘long-term’ administration would be impossible.

The second paper, ‘Castor bean seed ingestions: A state-wide poison control system's experience’2 is not new research on the chemistry of ricin but is a review of calls to a poison control centre in Kansas, USA. Over a ten-year period, the centre dealt with 84 cases of castor bean ingestion. 50 cases were unintentional and 34 deliberate. Unsurprisingly, the median number of seeds ingested was much higher (10) for intentional consumption that for unintentional (1) though it is worth noting that the range for unintentional consumption included at least one case where 40 seeds were eaten.

Ricinus communis, the castor oil plant

The significant sentence in the abstract is ‘No delayed symptoms, serious outcomes, or deaths were reported’. So, even someone who ate 40 castor beans survived. Without the full paper, I can’t know if there were particular circumstances that aided that survival but it is clear that all those people who, when reporting another ‘ricin’ incident, inevitably write that one bean is fatal are repeating nonsense.

How journalists write about ricin brings me to the third piece that appeared on the Los Angeles Time website. I’ll start with full disclosure. When writing ‘How did Ricin become the poison of choice for incompetent schemers?’3 Deborah Blum contacted me and she has used quite a bit of what I told her in the piece. Her central point is that ricin has become the tool of the demented desperate to get attention from a world that, they believe, has done them wrong. Blum describes the notion that the authorities might be happy to see people chose an imperfect weapon to vent their anger at the world as ‘farfetched’ but I’m sure she’d agree that having such people chose automatic weapons to make their point is much more harmful.

And finally, brief mention of a piece on the Skeptical Scalpel blog ‘Why send letters containing ricin to public figures?’4 The central point is that anyone who thinks that the US president opens his own post is clearly a very long distance from reality. And, yet, large parts of the media will happily headline such stories as plots to kill rather than the sad manifestation of mental illness.

But back to my starting point. I’m waiting for the next paper on ricin to see if it cites the latest work showing that ricin, when ingested, is not the potent killer it is claimed or whether the latest publications will be ignored in favour of sticking to the ‘deadly bioterrorism’ line.

Of course, it’s not just ricin where people with an agenda ignore the latest work if it disagrees with their position. It happens all the time with ‘drugs’. But that’s a topic for another day. 


1.    ‘NMR-based metabolomics approach to study the chronic toxicity of crude ricin from castor bean kernels on rats’ Guo, Wang, Dong et al Molecular Biosystems published online 3rd June 2014
2.    ‘Castor bean seed ingestions: A state-wide poison control system's experience.’ Thornton, Darracq, Lo and Cantrell Clinical Toxicology April 2014
3.    ‘How did Ricin become the poison of choice for incompetent schemers?’ Deborah Blum Los Angeles Times 6th June 2014
4.    'Why send letters containing ricin to public figures?' Skeptical Scalpel 13th August 2013


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