[spr33]

Could you help me out?
The question is as follows:

Conder the following information:
i. The layer of dead sking on our bodies is sufficient to protect us from most alpha particle radiation
ii. Plutonium is an alpha particle producer
iii. the chemistry of Pu4+ is similar to that of Fe3+
iv. Pu oxidizes readily to Pu4+

Why is plutonium on of the most toxic substances known?


I know why it is dangerous, but do you have idea why it is that involves all of these facts about plutonium? Much appreciated

[Mitch]

Plutonium is not a very toxic substance at all! The AP has this completely wrong.

[constant thinker]

Alpha particles aren't dangerous on the outside of our bodies, but what about inside of our bodies...

[Donaldson Tan]

A lot of Alpha Particles = Helium Gas.

Helium is a Noble Gas. How reactive is it chemically?

[Yggdrasil]

Helium = Alpha Particle - velocity (and w/o electrons)

It's like saying bullets aren't dangerous because without a gun to shoot them, they can't hurt you.  But when you fire a bullet out of a gun and give it velocity, then it becomes dangerous.  Same deal with alpha particles.  Helium nuclei are relatively innocuous until they get ejected from radioactive nuclei at high speeds.

[g_maxi]

i'm going to have shot in the dark with this one....

i know that Nd (Neodymium 3+) has the v. similar ionic radii to Ca (Calcium 2+), and that in vitro the Nd ions can replace Ca ions in enzymes, causing them to stop functioning. i'm going to assume that maybe that case here, where there are many enzymes like p450s that used Fe ions (2/3+) and replacing them with Pu 4+, would disable them.
and about the alpha particle points, assuming the Pu replaces the Fe in the heam, it would be transported around the body and exposing alpha particles throughout the body. the alpha pratical penetration depth is irrelevant in such a case.

oh and a google'ed ref to the Nd and Ca ion thingi

http://www.regional.org.au/au/gcirc/2/399.htm

[jacobcolbert]

I don't know anything about this, but when i see Iron and biology, I think hemoglobin. Maybe it incorportates itself into hemoglobin in preference to iron? But that would'nt really make sense because Fe³⁺ is already oxidized so then it wouldn't be able to pick up oxygen. I don't know.

[enahs]

http://en.wikipedia.org/wiki/Plutonium#Toxicity

[aranciolightning]

Pu4+ is an alpha emitter.
If ingested, it replaces Fe3+ in the body and results in the inhibition of the production of red blood cells.

(Chemical Principles by Loretta Jones and Peter Arkins, 2009)

[sjb]

(Chemical Principles by Loretta Jones and Peter Arkins, 2009)

Peter Atkins

[pcm81]

If you want to know just how toxic Pu is (or not), google search IPPU.

Its a heavy metal, its bad for you like lead. It's an alpha emitter, so ingested it will kill cells if ingested in high enough concentration.

[Arkcon]

If you want to know just how toxic Pu is (or not), google search IPPU.

Its a heavy metal, its bad for you like lead. It's an alpha emitter, so ingested it will kill cells if ingested in high enough concentration.

That specific Google choice doesn't really lead anywhere useful.  But otherwise, that's good conjecture, from you and others in this thread.

Its funny that this decade old question is still worth debating, all the more odd since it was on the AP Chemistry test.  I'm betting its gone by now.

At any rate, the horrifying toxicity of plutonium was a meme, before there were memes.  Or at least before we called them memes.  The Guinness Book of World Records listed plutonium as so toxic that only a few atoms, inside a person's lungs was lethal.  Problem is, no one can manipulate a few atoms of an element outside of an atomic force microscope, so amounts that small will never get into the lungs.  It was just a superlative for superlatives sake, the Guinness Book was full of those back before there was an internet.  By applying random mish-mashes of its oxidative state, similarity to other elements, and its radioactivity, we can declare anything, but that's not proof.

[pcm81]

I messed up. It was supposed to be UPPU. mistype. I now realize that actually doing google search for IPPU by itself does not produce meaningful results. I was not trying to be literal with this instruction, but rather let people search for a piece of historic data and a great story with it.

Long story short, scientists that worked with Pu during WWII were heavily exposed to it. So much so, that even 25 years later plutonium could be detected in their urine. Hence those individuals became knows as "UPPU club"

https://www.youtube.com/watch?v=89UNPdNtOoE

[Enthalpy]

[Plutonium is] an alpha emitter, so ingested it will kill cells if ingested in high enough concentration.

The ²⁴⁰Pu fraction emits also gammas that have a longer range than alphas. And for cancer, there is no minimum amount nor concentration: the scientific consensus is that the risk decreases linearly with the amount. Inhalation is worse than ingestion.

[pcm81]

[Plutonium is] an alpha emitter, so ingested it will kill cells if ingested in high enough concentration.

The ²⁴⁰Pu fraction emits also gammas that have a longer range than alphas. And for cancer, there is no minimum amount nor concentration: the scientific consensus is that the risk decreases linearly with the amount. Inhalation is worse than ingestion.

That is only haft the story. Long time ago i actually majored in nuclear engineering and here is what i remember (note: product usually means integral, since quantities may have dependence on energy):

Damage is the time integral of volume integral of energy integral of the product of the response function and radiation flux.

Here is what it all means:
Radiation has some number density per unit area per second, this is called flux.  More scientifically accurate is to say Flux = N*v. Where v is direction vector for velocity and N is number density.  Since for our purposes direction does not matter we can integrate over v to get some value for flux F.
F is still a function on energy and varies with energy. A particle (alpha, beta, gamma) has some probability to interact with matter. This probability is called cross section and depends on type of particle, energy of the particle and material that we are considering. Since human body has about fixed composition of hydrogen, oxygen, carbon and other elements we can calculate the average cross section for that composition.
An interaction of a given particle of given energy with human body will cause given amount of damage.  So we can define a quantity, which is a function of energy and is the product of damage and cross section. We call this quantity response function. So, now we have flux times response function equal damage. Of course this quantity needs to be integrated over the volume we are considering (lets say volume of the liver) as well as energy spectrum of the radiation flux causing the damage.

Here is a link explaining the same thing in different terms: http://web.utk.edu/~rpevey/NE406/lesson16.htm

The Flux part is what differentiates the damage done by radiation coming from outside of the body vs damage coming from inside the body. Skin can shield from big heavy, high energy types of radiation like alpha particles and it can somewhat shield from other types of radiation. Re result is that damage done to the body by radioactive source located inside the body is much greater than by radiation source located outside the body. The things that do the most damage are also the things that are easiest to shield for, like alpha particles. Meanwhile a weakly interacting type of radiation like neutrons is harder to shield for because it has lower cross section, but it will also do less damage. Not saying that you cant die from neutron radiation, but an alpha particle source located inside the body will do much more damage that the same alpha particle source located outside the body and significantly more damage than neutron or gamma ray source of the same intensity located inside or outside the body.Neutron or gamma ray sources located inside the body will do about the same amount of damage as those same sources (of equal intensity hitting the body) located just outside the body. Equal intensity hitting the body here is necessary to account for the fact that a body will present 4Pi solid body angle to a source located inside of it and about 2PI to a source just outside the body, since half of radiation would fly away from the body.