Talk:Polonium-210/Archive 1

Archive 1

How toxic is Po-210?

I had a look at the inconsistencies in the figures given for a "lethal dose" of Po-210

In Death by Polonium-210 by Robin B. McFee, & Jerrold B. Leikin (https://www.researchgate.net/publication/24206298_Death_by_polonium-210_Lessons_learned_from_the_murder_of_former_Soviet_spy_Alexander_Litvinenko/link/58188c4b08aee7cdc685a640/download) they say:

"Estimates suggest one gram of 210-Po could kill 50 million individuals and sicken another 50 million, and less than a microgram of Polonium could have caused Litvinenko’s death."

McFee and Leikin quote Kaplan K, Maugh TH: “A restless killer radiates intrigue.” The Los Angeles Times. Jan. 1, 2007. http://www.mjwcorp.com/rad_dose_ assessments_poloniumarticle.php https://www.latimes.com/archives/la-xpm-2007-jan-01-sci-polonium1-story.html

"Pound for pound, polonium-210 is at least a million times more toxic than hydrogen cyanide, the poison used to execute prisoners in gas chambers, according to medical toxicology books. Radiation safety experts calculate that a single gram of polonium could kill 50 million people and sicken another 50 million."

Two things; why are McFee and Leikin quoting Kaplan and Maugh in the LA Times and not a better source? And the microgram dose for Litvinenko is not in the LA Times article.

Anyhow, if 1 g is capable of killing 50 million; that implies that 0.02 ug would kill one person. I guess you could say that is "less than a microgram" but that is an odd way to describe 0.02 ug. Like saying 2 cents is "less than a dollar".

There is another inconsistency. The LA Times says "polonium-210 is at least a million times more toxic than hydrogen cyanide" (HCN) but then it is reported as 250 000 times more toxic than HCN. That latter figure comes from Ahmed et al:

International Journal of Environmental Research and Public Health Health Risk of Polonium 210 Ingestion via Drinking Water: An Experience of Malaysia Minhaz Farid Ahmed, Lubna Alam, Che Abd Rahim Mohamed, Mazlin Bin Mokhtar and Goh Choo Ta Int. J. Environ. Res. Public Health 2018, 15, 2056; doi:10.3390/ijerph15102056 www.mdpi.com/journal/ijerph

"Alam and Mohamed [5] also reported Po-210 is about 250,000 times more toxic than hydrogen cyanide" who quote Alam, L.; Mohamed, C.A.R. Polonium. Radionuclides in the Environment; Atwood, D.A., Ed.; John Wiley & Sons Ltd.: Chichester, UK, 2010; pp. 149–154, which I can't access.

According to https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+165 the lethal does for HCN is 50 mg.

• 50 mg / 250 000 = 0.2 ug (Ahmed et al, quoting Alam and Mohamed)
• 50 mg / 1 000 000 = 0.05 ug (Kaplan and Maugh, and this is an upper figure as they say Po is "at least a million times more toxic")

Maybe 50 mg is not the only figure for HCN lethal dose, and the two sources use different figures.

• From Kaplan and Maugh, 0.02 ug would allow 1 g to kill 50 million
• Only McFee and Leikin quote "less than a microgram"

All a bit confusing! Ewen (talk) 11:21, 30 July 2019 (UTC)

More digging:

According to this site: http://www.3rd1000.com/elements/Polonium.htm#Overview

"the oral LD50 for 210Po is about 50 ng compared to about 250 mg for Hydrogen Cyanide" which means it is "around 5 million times more toxic than Hydrogen Cyanide, HCN". This would be 1 million times if the HCN figure were 50 mg

The https://en.wikipedia.org/wiki/Poisoning_of_Alexander_Litvinenko#210Po_content_in_the_body_of_Litvinenko article quotes the Lancet as

"post-mortem samples were used to estimate intake as 4.4 GBq"

I calculate:

4.4 GBq x half life * molar mass / (Avogadro's number x ln(2)) 4.4 GBq x 138.37 days x 24 x 60 x 60 * 209.98 / (6.022 x 10^23 x 0.693) = 26 ug (1 GBq of Po-210 is 6 ug)

Updated list of figures for a "lethal dose" of Po-210:

• 0.05 ug (50 ng) (www.3rd1000.com)
• 1.0 or 0.2 ug (using 250 mg or 50 mg figures for HCN) (Ahmed et al, quoting Alam and Mohamed)
• 0.25 or 0.05 ug (Kaplan and Maugh, and this is an upper figure as they say Po is "at least a million times more toxic")
• From Kaplan and Maugh, 0.02 ug would allow 1 g to kill 50 million
• Only McFee and Leikin quote "less than a microgram" and actually it was about 26 micrograms that murdered Litvinenko (35 ug of PoCl2 if that's what was used).

Ewen (talk) 12:06, 30 July 2019 (UTC)

@Ewen: I see; though I only realize it now, no one seems to agree even on the LD50 for hydrogen cyanide, much less the LD50 of ²¹⁰Po. I did, though, find another source for 250,000 times more toxic ([1]), as well as some for 1 million. It also is important to note that some sources compare ²¹⁰Po to hydrocyanic acid (HCN dissolved in water). Perhaps the text can be amended to incorporate these sources, or say something along the lines of "at least 250,000 times more toxic..." - what do you think of this? ComplexRational (talk) 15:32, 30 July 2019 (UTC)

@ComplexRational: Thanks for helping with the digging! Yes, that's another one for "250,000 times" and an LD50 of 1 ug for Po-210 (by implication, putting the LD50 of HCN at 250 mg). I wonder if Alam & Mohamed are singing from the same source? I couldn't get their full text.

So, we have two (250 mg and 50 mg) figures for HCN and anywhere from 1.0 ug to 0.02 ug for Po-210. Dividing one substance's LD50 by the other's gives a range of 50,000 to 12,500,000. I guess the 250,000 and 1 million times figures are in the right range, but it's quite a range!

Ewen (talk) 16:19, 30 July 2019 (UTC)

@Ewen: Glad to help - though unfortunately I also cannot access the full text of Alam, 2010. Nevertheless, it is indeed quite a wide range given that these are reliable sources. Additionally, I also saw a few mentions of 250 billion, which is well outside this range and is inconsistent with all of the LD50 figures. One was in reference to hydrocyanic acid, so I can't assume its equitable with the rest. As I said, though, I feel a mention of this variation (at least 250,000 to a million) is needed if we're sure these sources are accurate. ComplexRational (talk) 17:19, 30 July 2019 (UTC)