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Last updated on Tuesday, June 16, 2015

August 3, 2013;

Here are the 27 elements that compose the human body taken from The Periodic Table in order of descending body weight (our cosmic recipe derived from star dust) [1,2]. For interest, elements that are toxic have been added in the next section.

Essential Elements:

Atom Percent by Weight Full Name
1. O 65.0 oxygen
2. C 18.5 carbon
3. H 9.5 hydrogen
4. N 3.3 nitrogen
5. Ca 1.5 calcium (in bone)
6. P 1.0 phosphorus (in phosphates)
7. K 0.4 potassium
8. S 0.3 sulfur
9. Cl 0.2 chlorine (in salt)
10. Na 0.2 sodium (in salt)
11. Mg 0.1 magnesium
12. I * iodine (in thyroxin T3, T4)
13. Fe * iron (in hemoglobin)
14. Zn * zinc (in carbonic anhydrase)
15. Co * cobalt (in Vitamin B12)
16. Mn * manganese (in SOD)
17. Cr * chromium (in picolinate)
18. B * boron
19. Ni * nickel
20. V * vanadium
21. Sn * tin
22. Si * silicon
23. Mo * molybdenum
24. Cu * copper
25. F * fluorine (fluoride placed in municipal water supplies to strengthen tooth enamel)
26. Li * lithium (contaminates some water wells in the form of lithium carbonate and is now used for Rx: Bipolar Disorder)
27. Se * selenium (only at low doses; see Toxic Table)
* Only trace amounts (< 0.1 percent); some mineral elements are essential while the value of others (or their dosages) in human nutrition has not been established. Conversely, too much of some of these minerals - - like manganese, chromium, or selenium - - can also be toxic or even fatal.

Toxic Elements:

Here are 42 toxic elementts and/or isotopes. Many toxic elements are fatal if inhaled or ingested, but even a compound as simple as Carbon Monoxide (CO) [an odorless, colorless gas] becomes fatal when inhaled inadvertently. Many heavy elements are toxic due to their weight. Many of these have isotopes that are toxic due to their radioactivity...

Atom Full Name
1. Pu plutonium (the most toxic element known to man) [6]
2. U uranium [U 239 in pitchblend] (the next most toxic element known to man) [6]
3 . Ra radium (carcinogen; from [1910-1927] US Radium, Inc. of New Jersey sold paints containing radium to help women manufacture watch dials that glowed in the dark. :-( )
4. Po polonium (once used in a political assassination in London by the Soviet KGB)
5. As arsenic (a favorite poison from the Renaissance but still used today as a rat poison)
6. Au gold
7. Ag silver
8. Pt platinum
9. Pb lead (neurotoxic in paints)
10. Al aluminum
11. W tungsten
12. Rn radon (as a gas commonly in the soil)
13. Hg mercury (neurotoxic; Alice in Wonderland's mad hatter was actually a problem in London at one time)
14. Ga gallium
15. Ge germanium
16. Cd cadmium
17. Se selenium (toxic only at high doses)
18. Th thorium
19. Be beryllium
20. Tm thullium
21. Sb antimony
22. Rb rubidium
23. Br bromine
24. Sr strontium [strontium-90]
25. Ce cerium
26. Ba barium
27. Cs cesium (caesium)
28. Ti titanium (application in hip or knee replacement orthopedic surgery)
29. H-3 tritium [hydrogen-3]
30. Tc-99m technesium [medical isotope]
31. I-123 iodine-123 [medical isotope]
32. TI-201 thallium-201 [medical isotope]
33. Ru-106 ruthenium-106 [medical isotype]
34. Ir-192 iridium-192 [medical isotope]
35. Co-60 cobalt-60 [medical isotope]
36. Cs-137 caesium-137 [medical isotope]
37. Y-90 yttrium-90 [medical isotope]
38. Pd-106 palladium-106 [medical isotope]
39. Rb-82 rubidium-82 [medical isotope]
40. F-18 fluorine-18 [medical isotope]
41. Ga-67 gallium-67 [medical isotope]
42. Kr-81 krypton-81 [medical isotope]

Note: Plutonium and uranium are both heavy metals, and thus are toxic due to chemical effects, but not more so than all other heavy metals. However, if we consider only chemical effects, radon doesn't belong on the list, since it is an inert noble gas, and thus is harmful only because it's radioactive. (Also, radium and polonium, which are mentioned, are harmful mostly because of their radioactivity.) If it is meant to include the effect of radioactivity, there are elements whose common isotopes are far worse than plutonium or uranium (in some cases by several orders of magnitude). Some of these are also more radioactive than radium, polonium, or radon, which in turn are more radioactive than plutonium and uranium. - - Donald Gennery, Biostatistics, JPL; Pasadena, CA (August 7, 2013)

Compounds: Both fiber glass and asbestos insulation are highly toxic (and complex) compounds when inhaled due to the physical dimensions of the fibers when they get lodged in the lungs. Poisonous mushrooms, belladonna (deadly nightshade, atropine), and extremely minute amounts of LSD when swallowed have caused many deaths. But so has alcohol (wood alcohol [methanol] as well as pure ethanol, as in wine, beer, and liquor) and nicotine (in tobacco). Even too much water can lead to water intoxication. Castor beans (Ricin) and Anthrax, likewise. Poison gas (phosgene) was used in chemical warfare heavily in WW-1.


1. Discover Magazine, p. 11 (September 2013).
2. Biology (Campbell and Reece, 8th Edition).

The third most common atom in the human body, hydrogen, was created shortly after the time of the "Big Bang" and was not synthesized and blown out in supernovas as so-called "star dust" for the heavy elements. If there are question marks (?) in the Wikipedia Tables referenced below [3-5], this indicates that nobody knows, not that Wikipedia doesn't know.
3. Abundance of elements in the human body
4. Composition of elements in the human body
5. Minerals
6. Plutonium is less toxic than arsenic in terms of being a metallic poison, so breathing plutonium dust will not normally deliver a toxic dose, but of course it's not the metal that will do most damage; it's the radiation. A large dose of a uranium salt will cause vomiting and diarrhea but again it's not as dangerous as consuming arsenic. I assume breathing uranium dust would again not deliver a fatal dose, but you never know with the lungs because there are some metals which breathed-in cause chronic illnesses such as beryllium and manganese.
-- John Emsley. ( August 9, 2013