Biological Elements/Trace Elements

[questar]

I'm trying to determine the elements that are present in the human body. Online I'm finding inconsistent determinations. I'm reading that some lanthanoids are present, then on another site, none are present, though I see no reason that all lanthanoids would be present to some miniscule degree. The same with the actinoids, platinum group metals as well as the other extremely rare elements, Technetium, Rhenium, Astatine and Francium.

My question is, is it technically accurate to say that all elements, with the exception of the noble gases and the synthetics, are present in the human body? In other words, all elements that we are naturally exposed to (i.e. present in nature), are, to some limited extent, present in our bodies. This appears most accurate to me, what say you?

 

[phyzguy]

I'm trying to determine the elements that are present in the human body. Online I'm finding inconsistent determinations. I'm reading that some lanthanoids are present, then on another site, none are present, though I see no reason that all lanthanoids would be present to some miniscule degree. The same with the actinoids, platinum group metals as well as the other extremely rare elements, Technetium, Rhenium, Astatine and Francium.

My question is, is it technically accurate to say that all elements, with the exception of the noble gases and the synthetics, are present in the human body? In other words, all elements that we are naturally exposed to (i.e. present in nature), are, to some limited extent, present in our bodies. This appears most accurate to me, what say you?

I agree with you, only I would not exclude the noble gases and synthetic elements. I would say that there are atoms of every element in your body. Your body has on the order of 10^27 atoms in it, so even exceedingly rare atoms will be present at some level. The only exception would be elements with very short half lives. I'm sure even man-made elements like Neptunium and Plutonium are present in your body at some low level.

 

[Yanick]

Something to keep in mind when thinking about rare elements/compounds and small quantities is that of the nature of measurement in determining these quantities. You can assume whatever you want but the fact is that measurements have limits to their sensitivity as well as error bars. There may very well be some small amount of something present but the methods applied may not have been sensitive enough to detect it or the contamination from the laboratory environment may have led to a greater amount of the substance than the actual sample. You are likely finding mixed results about rare elements because the quantities are so small that signal:noise makes a judgment hard to make, especially if the work was performed in varying environments, conditions, methodologies etc.

 

[questar]

I agree with you, only I would not exclude the noble gases and synthetic elements... I'm sure even man-made elements like Neptunium and Plutonium are present in your body at some low level.

It's my understanding that all elements/atomic numbers 1-98 are naturally occurring, albeit some only in minute amounts. Therefore it seems reasonable to me that all these elements, including as you pointed out, the noble gases, could be found in "metaminute" amounts within the human body. However, synthetic elements are not naturally occurring- so I'm at a loss as to how they could be found in the environment, let alone the body.

Just to note that when I say natural, I mean terrestrial... perhaps there is an atmosphere composed entirely of ununoctium in the Andromeda galaxy, but we seem to be far removed from its physical presence.

 

[mfb]

However, synthetic elements are not naturally occurring- so I'm at a loss as to how they could be found in the environment, let alone the body.

Nuclear explosions released elements beyond plutonium in the multi-kilogram-range. If you distribute 1kg evenly in the biosphere, your body will have some atoms. This even distribution is not real, of course, but a few atoms are really reasonable.

Just to note that when I say natural, I mean terrestrial... perhaps there is an atmosphere composed entirely of ununoctium in the Andromeda galaxy, but we seem to be far removed from its physical presence.

Spectroscopy shows other stars and other objects have chemical compositions similar to our solar system.

 

[phyzguy]

Nuclear explosions released elements beyond plutonium in the multi-kilogram-range. If you distribute 1kg evenly in the biosphere, your body will have some atoms. This even distribution is not real, of course, but a few atoms are really reasonable.

Right. This Wikipedia page shows that there have been over 2000 documented nuclear explosions on the Earth. As mfb points out the products of these explosions have been scattered through the biosphere. Short half-life nuclei will have decayed, but long half-life elements, including elements like Neptunium, Plutonium, Californium, etc. will still be around.

 

[questar]

...Short half-life nuclei will have decayed, but long half-life elements, including elements like Neptunium, Plutonium, Californium, etc. will still be around.

So basically all of the elements that can be found in the body are the same as those that can be found in the environment that the body inhabits. The synthetic elements are unlikely to be found in the body for the same reason that they are unlikely to be found in the environment- and that reason is that they have decayed.

Hydrogen...Californium=likely present in the human body

Einsteinium...Ununoctium= not likely present in the human body
(though if any atoms remain it would be the result of nuclear testing)

 

[questar]

In regards to biological benefits, I believe this outline is fairly accurate. It begins with the elements of greatest mass, then the lesser essentials, then on to those that are suspected of being lesser essentials, and finally those with unknown benefits in what remains of the indigenous and the 20 synthetic elements.

I'm obviously new at this, but I find it interesting that most all of the confirmed biologically beneficial elements are those with an atomic number ranging from 1-30 with very few exceptions- the three noble gases... and Beryllium alone. They say Hydrogen is the individualistic element, but it seems from an biological standpoint, Beryllium is the odd man out.

I. ELEMENTS [118]
1. Essential [19]
a. Greater [5]
8 Oxygen O
6 Carbon C
1 Hydrogen H
7 Nitrogen N
20 Calcium Ca
b. Lesser (Traces) [14]
15 Phosphorous P
19 Potassium K
16 Sulfur S
11 Sodium Na
17 Chlorine Cl
12 Magnesium Mg
26 Iron Fe
9 Fluorine F
30 Zinc Zn
29 Copper Cu
34 Selenium Se
25 Manganese Mn
53 Iodine I
27 Cobalt Co
2. Potential Essential [18]
a. Lesser (Traces) [18]
3 Lithium Li
5 Boron B
13 Aluminum Al
14 Silicon Si
21 Scandium Sc
22 Titanium Ti
23 Vanadium V
24 Chromium Cr
28 Nickel Ni
31 Gallium Ga
32 Germanium Ge
33 Arsenic As
35 Bromine Br
37 Rubidium Rb
38 Strontium Sr
42 Molybdenum Mo
48 Cadmium Cd
50 Tin Sn
3. Unknown Potential [81]
a. Indigenous [61]
b. Synthetic [20]

 

[phyzguy]

I think the point you need to consider is the abundance of the different elements. Look at the abundance graph at this Wikipedia page. Beryllium is more than a million times rarer than elements like carbon, oxygen, or nitrogen. Given this, I would not expect life to evolve a dependency on beryllium. Life that was dependent on such a rare substance would be at a real disadvantage compared to life that was only dependent on more common elements.

 

[questar]

...Beryllium is more than a million times rarer than elements like carbon, oxygen, or nitrogen. Given this, I would not expect life to evolve a dependency on beryllium. Life that was dependent on such a rare substance would be at a real disadvantage compared to life that was only dependent on more common elements.

It is true that beryllium is much less abundant than carbon, oxygen and nitrogen... but what about the essential trace elements? Beryllium is just as abundant as cobalt and copper, and more abundant than both iodine and selenium. All four are considered essential elements, all four are more rare than beryllium, yet human life evolved a dependancy on all four of them. There are also other elements that are suspected of being necessary- many of which are also less abundant than beryllium.

 

[mfb]

The distribution and the chemical properties also matter. Something that accumulates in very few places, with chemically inert molecules and without an unreplaceable role in some molecule won't become an essential element.