• Blog Stats

    • 79,937 hits
  • Archives

  • Enter your email address to subscribe to this blog and receive notifications of new posts by email.

    Join 157 other followers

  • Copyright notice

    This blog entry and all other text on this blog is copyrighted, you are free to read it, discuss it with friends, co-workers and anyone else who will pay attention.

    If you want to cite this blog article or quote from it in a not for profit website or blog then please feel free to do so as long as you provide a link back to this blog article.

    If as a school teacher or university teacher you wish to use content from my blog for the education of students then you may do so as long as the teaching materials produced from my blogged writings are not distributed for profit to others. Also at University level I ask that you provide a link to my blog to the students.

    If you want to quote from this blog in an academic paper published in an academic journal then please contact me before you submit your paper to enable us to discuss the matter.

    If you wish to reuse my text in a way where you will be making a profit (however small) please contact me before you do so, and we can discuss the licensing of the content.

    If you want to contact me then please do so by e-mailing me at Chalmers University of Technology, I am quite easy to find there as I am the only person with the surname “foreman” working at Chalmers. An alternative method of contacting me is to leave a comment on a blog article. If you do not know which one to comment on then just pick one at random, please include your email in the comment so I can contact you.

Cherry picking and a challenge to “everyone knows”

OK everyone knows xyz abc blagh blagh blagh, you must have heard it before.

If you are a person who does not want to blindly follow like a sheep by now it must be grating on your nerves just like a person dragging their nails over a blackboard. I want to address this problem of the fallacy and also at the same time consider cherry picking of the literature and data.

I am sure that many people hold the view that plutonium is the most dangerous substance known by man; some might even view it as a blasphemous horror element. It is often thought of by many people as a corruptor of goodness and a destroyer of all that is wholesome and good. It is often thought of as a substance which will extinguish all life forms. I guess by now that you understand what I am writing about.

It is widely assumed that it is a super toxic substance, but when you look at the evidence things are not quite what everyone thinks it they will be. While the fact that internal contamination with plutonium is not healthy, a great debate exists over how unhealthy is it to be contaminated with plutonium and the other actinides.

Some years ago I heard a talk by Mary Neu who works in the USA on plutonium chemistry, she is responsible for a rare study in which the chemical toxicity of plutonium is compared with other (more mundane) metals. What her group did was to grow bacteria with or without toxic metals present in the growth medium. For the paper see C.E. Ruggiero, H. Boukhalfa, J.H. Forsythe, J.G. Lack, L.E. Heresman and M.P. Neu, Environmental Microbiology, 2005, 7(1), 88-97.

She found firstly that the effect of plutonium on soil bacteria was independent of the radioactivity level but dependant on the chemical concentration of the plutonium. She did this by using different isotopes of plutonium. She used a short-lived (238Pu), “normal” (239Pu) and a very long lived plutonium isotope (242Pu). So this suggests that to the bacteria that the plutonium is a chemical poison to the soil bacteria and not a radioactive poison to the bacteria. This was quite a surprise to me.

Next she compared a series of metals; in her test she worked out how high a concentration is needed to stop 70 % of the growth of the germs. I find it interesting that for the two types of bacteria which Mary used that copper and zinc appear to be more toxic than plutonium.

Bar chart of toxicity data for bacteria (Pseudoomonas Putida) for some elements a range of toxicity has been estimated, bars are shown for the upper and lower estimates.

Now the work of Mary Neu is interesting in several ways, firstly it challenges the idea that plutonium is the supreme and universal poison which many people think it is. It also offers an insight into the problem of cherry picking. It is noteworthy that one of the two bacteria which Mary did use is one (Deinococcus radiodurans) which is very radiation resistant.

Secondly, if you were to use Mary Neu’s paper as your only information source on plutonium and living things then you would assume that plutonium is close to harmless. This is clearly wrong; this would be an example of cherry picking. It is far better to use a large and diverse range of serious sources on the subject.

I am aware that a range of different people try to cherry pick data and the literature to suit a political end.

By the way Mary’s biological work is good it would be interesting if as the next step someone was to extend it to a human cell line and the Salmonella strain used for the Ames test.

Advertisements

Go on, Have your say !

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: