Molybdenum is a chemical element with symbol Mo and atomic number 42.
The name is from Neo-Latin molybdaenum, from Ancient Greek
Μόλυβδος molybdos, meaning lead, since its ores were confused
with lead ores.
Molybdenum minerals have been known throughout
history, but the element was discovered (in the sense of
differentiating it as a new entity from the mineral salts of other
metals) in 1778 by Carl Wilhelm Scheele. The metal was first isolated
in 1781 by Peter Jacob Hjelm.
Molybdenum does not occur naturally as a free metal on Earth; it is
found only in various oxidation states in minerals. The free element,
a silvery metal with a gray cast, has the sixth-highest melting point
of any element. It readily forms hard, stable carbides in alloys, and
for this reason most of world production of the element (about 80%) is
used in steel alloys, including high-strength alloys and superalloys.
Most molybdenum compounds have low solubility in water, but when
molybdenum-bearing minerals contact oxygen and water, the resulting
molybdate ion MoO2−
4 is quite soluble. Industrially, molybdenum compounds (about 14% of
world production of the element) are used in high-pressure and
high-temperature applications as pigments and catalysts.
Molybdenum-bearing enzymes are by far the most common bacterial
catalysts for breaking the chemical bond in atmospheric molecular
nitrogen in the process of biological nitrogen fixation. At least 50
molybdenum enzymes are now known in bacteria, plants, and animals,
although only bacterial and cyanobacterial enzymes are involved in
nitrogen fixation. These nitrogenases contain molybdenum in a form
different from other molybdenum enzymes, which all contain fully
oxidized molybdenum in a molybdenum cofactor. These various molybdenum
cofactor enzymes are vital to the organisms, and molybdenum is an
essential element for life in all higher eukaryote organisms, though
not in all bacteria.
1.1 Physical properties
1.3 Compounds and chemistry
3 Occurrence and production
3.1 History of molybdenum mining
4.2 Other applications as a pure element
4.2.1 Compounds (14% of global use)
5 Biological role
Molybdenum cofactor enzymes
5.3 Human metabolism and deficiency
5.4 Related diseases
5.5 Copper-molybdenum antagonism
6 Dietary recommendations
7 Food sources
9 See also
11 External links
In its pure form, molybdenum is a silvery-grey metal with a Mohs
hardness of 5.5. It has a melting point of 2,623 °C
(4,753 °F); of the naturally occurring elements, only tantalum,
osmium, rhenium, tungsten, and carbon have higher melting points.
Weak oxidation of molybdenum starts at 300 °C (572 °F). It
has one of the lowest coefficients of thermal expansion among
commercially used metals. The tensile strength of molybdenum wires
increases about 3 times, from about 10 to 30 GPa, when their
diameter decreases from ~50–100 nm to 10 nm.
Isotopes of molybdenum
There are 35 known isotopes of molybdenum, ranging in atomic mass from
83 to 117, as well as four metastable nuclear isomers. Seven isotopes
occur naturally, with atomic masses of 92, 94, 95, 96, 97, 98, and
100. Of these naturally occurring isotopes, only molybdenum-100 is
Molybdenum-98 is the most abundant isotope, comprising 24.14% of all
molybdenum. Molybdenum-100 has a half-life of about 1019 y and
undergoes double beta decay into ruthenium-100.
with mass numbers from 111 to 117 all have half-lives of approximately
150 ns. All unstable isotopes of molybdenum decay into
isotopes of niobium, technetium, and ruthenium.
As also noted below, the most common isotopic molybdenum application
involves molybdenum-99, which is a fission product. It is a parent
radioisotope to the short-lived gamma-emitting daughter radioisotope
technetium-99m, a nuclear isomer used in various imaging applications
in medicine. In 2008, the
Delft University of Technology
Delft University of Technology applied
for a patent on the molybdenum-98-based production of
Compounds and chemistry
See also: Category:
Keggin structure of the phosphomolybdate anion (P[Mo12O40]3−), an
example of a polyoxometalate
Molybdenum is a transition metal with an electronegativity of 2.16 on
the Pauling scale and a standard atomic weight of
95.95 g/mol. It does not visibly react with oxygen or
water at room temperature, and the bulk oxidation occurs at
temperatures above 600 °C, resulting in molybdenum trioxide:
2 Mo + 3 O
2 → 2 MoO
The trioxide is volatile and sublimes at high temperatures. This
prevents formation of a continuous protective (passivating) oxide
layer, which would stop the bulk oxidation of metal. Molybdenum
has several oxidation states, the most stable being +4 and +6 (bolded
in the table at left). The chemistry and the compounds show more
similarity to tungsten than to chromium; the instability of
molybdenum(III) and tungsten(III) compounds, for example, contrasts
with the stability of the chromium(III) compounds. The highest
oxidation state is seen in molybdenum(VI) oxide (MoO3), while the
normal sulfur compound is molybdenum disulfide MoS2.
Molybdenum(VI) oxide is soluble in strong alkaline water, forming
molybdates (MoO42−). Molybdates are weaker oxidants than chromates,
but they show a similar tendency to form complex oxyanions by
condensation at lower pH values, such as [Mo7O24]6− and
[Mo8O26]4−. Polymolybdates can incorporate other ions, forming
polyoxometalates. The dark-blue phosphorus-containing
heteropolymolybdate P[Mo12O40]3− is used for the spectroscopic
detection of phosphorus. The broad range of oxidation states of
molybdenum is reflected in various molybdenum chlorides:
Molybdenum(II) chloride MoCl2 (yellow solid)
Molybdenum(III) chloride MoCl3 (dark red solid)
Molybdenum(IV) chloride MoCl4 (black solid)
Molybdenum(V) chloride MoCl5 (dark green solid)
Molybdenum(VI) chloride MoCl6 (brown solid)
The structure of the MoCl2 is clusters of Mo6Cl84+ and four chloride
ions compensating the charge.
Like chromium and some other transition metals, molybdenum forms
quadruple bonds, such as in Mo2(CH3COO)4. This compound can be
transformed into Mo2Cl84−, which also has a quadruple bond.
The oxidation state 0 is possible with carbon monoxide as ligand, such
as in molybdenum hexacarbonyl, Mo(CO)6.
Molybdenite—the principal ore from which molybdenum is now
extracted—was previously known as molybdena. Molybdena was confused
with and often utilized as though it were graphite. Like graphite,
molybdenite can be used to blacken a surface or as a solid
lubricant. Even when molybdena was distinguishable from graphite,
it was still confused with the common lead ore PbS (now called
galena); the name comes from
Ancient Greek Μόλυβδος molybdos,
meaning lead. (The Greek word itself has been proposed as a
loanword from Anatolian Luvian and Lydian languages).
Although (reportedly) molybdenum was deliberately alloyed with steel
in one 14th-century Japanese sword (mfd. ca. 1330), that art was never
employed widely and was later lost. In the West in 1754, Bengt
Andersson Qvist examined a sample of molybdenite and determined that
it did not contain lead and thus was not galena.
By 1778 Swedish chemist
Carl Wilhelm Scheele
Carl Wilhelm Scheele stated firmly that
molybdena was (indeed) neither galena nor graphite. Instead,
Scheele correctly proposed that molybdena was an ore of a distinct new
element, named molybdenum for the mineral in which it resided, and
from which it might be isolated.
Peter Jacob Hjelm successfully
isolated molybdenum using carbon and linseed oil in 1781.
For the next century, molybdenum had no industrial use. It was
relatively scarce, the pure metal was difficult to extract, and the
necessary techniques of metallurgy were immature. Early
molybdenum steel alloys showed great promise of increased hardness,
but efforts to manufacture the alloys on a large scale were hampered
with inconsistent results, a tendency toward brittleness, and
recrystallization. In 1906,
William D. Coolidge
William D. Coolidge filed a patent for
rendering molybdenum ductile, leading to applications as a heating
element for high-temperature furnaces and as a support for
tungsten-filament light bulbs; oxide formation and degradation require
that molybdenum be physically sealed or held in an inert gas. In
1913, Frank E. Elmore developed a froth flotation process to recover
molybdenite from ores; flotation remains the primary isolation
During World War I, demand for molybdenum spiked; it was used both in
armor plating and as a substitute for tungsten in high speed steels.
Some British tanks were protected by 75 mm (3 in) manganese
steel plating, but this proved to be ineffective. The manganese steel
plates were replaced with much lighter 25 mm (1.0 in)
molybdenum steel plates allowing for higher speed, greater
maneuverability, and better protection. The Germans also used
molybdenum-doped steel for heavy artillery, like in the super-heavy
howitzer Big Bertha, because traditional steel melts at the
temperatures produced by the propellant of the one ton shell.
After the war, demand plummeted until metallurgical advances allowed
extensive development of peacetime applications. In World War II,
molybdenum again saw strategic importance as a substitute for tungsten
in steel alloys.
Occurrence and production
Molybdenite on quartz
Molybdenum is the 54th most abundant element in the Earth's crust and
the 25th most abundant element in its oceans, with an average of
10 parts per billion; it is the 42nd most abundant element in the
Universe. The Russian
Luna 24 mission discovered a
molybdenum-bearing grain (1 × 0.6 µm) in a pyroxene fragment
Mare Crisium on the Moon. The comparative rarity of
molybdenum in the Earth's crust is offset by its concentration in a
number of water-insoluble ores, often combined with sulfur in the same
way as copper, with which it is often found. Though molybdenum is
found in such minerals as wulfenite (PbMoO4) and powellite (CaMoO4),
the main commercial source is molybdenite (MoS2).
Molybdenum is mined
as a principal ore and is also recovered as a byproduct of copper and
The world's production of molybdenum was 250,000 tonnes in 2011, the
largest producers being China (94,000 t), the United States
(64,000 t), Chile (38,000 t), Peru (18,000 t) and
Mexico (12,000 t). The total reserves are estimated at 10 million
tonnes, and are mostly concentrated in China (4.3 Mt), the US
(2.7 Mt) and Chile (1.2 Mt). By continent, 93% of world
molybdenum production is about evenly shared between North America,
South America (mainly in Chile), and China. Europe and the rest of
Asia (mostly Armenia, Russia, Iran and Mongolia) produce the
World production trend
In molybdenite processing, the ore is first roasted in air at a
temperature of 700 °C (1,292 °F). The process gives
gaseous sulfur dioxide and the molybdenum(VI) oxide:
2 MoS2 + 7 O2 → 2 MoO3 + 4 SO2
The oxidized ore is then usually extracted with aqueous ammonia to
give ammonium molybdate:
MoO3 + 2 NH3 + H2O → (NH4)2(MoO4)
Copper, an impurity in molybdenite, is less soluble in ammonia. To
completely remove it from the solution, it is precipitated with
hydrogen sulfide. Ammonium molybdate converts to ammonium
dimolybdate, which is isolated as a solid. Heating this solid gives
(NH4)2Mo2O7 → 2 MoO3 + 2 NH3 + H2O
Crude trioxide can be further purified by sublimation at
1,100 °C (2,010 °F).
Metallic molybdenum is produced by reduction of the oxide with
MoO3 + 3 H2 → Mo + 3 H2O
The molybdenum for steel production is reduced by the aluminothermic
reaction with addition of iron to produce ferromolybdenum. A common
form of ferromolybdenum contains 60% molybdenum.
Molybdenum had a value of approximately $30,000 per tonne as of August
2009. It maintained a price at or near $10,000 per tonne from 1997
through 2003, and reached a peak of $103,000 per tonne in June
2005. In 2008, the London
Metal Exchange announced that molybdenum
would be traded as a commodity.
History of molybdenum mining
Knaben mine in southern Norway, opened in 1885, was
the first dedicated molybdenum mine. It was closed in 1973 but was
reopened in 2007. and now produces 100,000 kilograms (98 long
tons; 110 short tons) of molybdenum disulfide per year. Large mines in
Colorado (such as the Henderson mine and the Climax mine) and in
British Columbia yield molybdenite as their primary product, while
many porphyry copper deposits such as the
Bingham Canyon Mine
Bingham Canyon Mine in Utah
Chuquicamata mine in northern Chile produce molybdenum as a
byproduct of copper mining.
A plate of molybdenum copper alloy
About 86% of molybdenum produced is used in metallurgy, with the rest
used in chemical applications. The estimated global use is structural
steel 35%, stainless steel 25%, chemicals 14%, tool & high-speed
steels 9%, cast iron 6%, molybdenum elemental metal 6%, and
Molybdenum can withstand extreme temperatures without significantly
expanding or softening, making it useful in environments of intense
heat, including military armor, aircraft parts, electrical contacts,
industrial motors, and filaments.
Most high-strength steel alloys (for example, 41xx steels) contain
0.25% to 8% molybdenum. Even in these small portions, more than
43,000 tonnes of molybdenum are used each year in stainless steels,
tool steels, cast irons, and high-temperature superalloys.
Molybdenum is also valued in steel alloys for its high corrosion
resistance and weldability.
Molybdenum contributes corrosion
resistance to type-300 stainless steels (specifically type-316) and
especially so in the so-called superaustenitic stainless steels (such
as alloy AL-6XN, 254SMO and 1925hMo).
Molybdenum increases lattice
strain, thus increasing the energy required to dissolve iron atoms
from the surface.[contradictory]
Molybdenum is also used to enhance
the corrosion resistance of ferritic (for example grade 444) and
martensitic (for example 1.4122 and 1.4418) stainless steels.[citation
Because of its lower density and more stable price, molybdenum is
sometimes used in place of tungsten. An example is the 'M' series
of high-speed steels such as M2, M4 and M42 as substitution for the
'T' steel series, which contain tungsten.
Molybdenum can also be used
as a flame-resistant coating for other metals. Although its melting
point is 2,623 °C (4,753 °F), molybdenum rapidly oxidizes
at temperatures above 760 °C (1,400 °F) making it
better-suited for use in vacuum environments.
TZM (Mo (~99%), Ti (~0.5%), Zr (~0.08%) and some C) is a
corrosion-resisting molybdenum superalloy that resists molten fluoride
salts at temperatures above 1,300 °C (2,370 °F). It has
about twice the strength of pure Mo, and is more ductile and more
weldable, yet in tests it resisted corrosion of a standard eutectic
salt (FLiBe) and salt vapors used in molten salt reactors for 1100
hours with so little corrosion that it was difficult to
Other molybdenum-based alloys that do not contain iron have only
limited applications. For example, because of its resistance to molten
zinc, both pure molybdenum and molybdenum-tungsten alloys (70%/30%)
are used for piping, stirrers and pump impellers that come into
contact with molten zinc.
Other applications as a pure element
Molybdenum powder is used as a fertilizer for some plants, such as
Elemental molybdenum is used in NO, NO2, NOx analyzers in power plants
for pollution controls. At 350 °C (662 °F), the element
acts as a catalyst for NO2/NOx to form NO molecules for detection by
Molybdenum anodes replace tungsten in certain low voltage X-ray
sources for specialized uses such as mammography
The radioactive isotope molybdenum-99 is used to generate
technetium-99m, used for medical imaging
Compounds (14% of global use)
Molybdenum disulfide (MoS2) is used as a solid lubricant and a
high-pressure high-temperature (HPHT) antiwear agent. It forms strong
films on metallic surfaces and is a common additive to HPHT greases
— in the event of a catastrophic grease failure, a thin layer of
molybdenum prevents contact of the lubricated parts. It also has
semiconducting properties with distinct advantages over traditional
silicon or graphene in electronics applications. MoS2 is also used
as a catalyst in hydrocracking of petroleum fractions containing
nitrogen, sulfur and oxygen.
Molybdenum disilicide (MoSi2) is an electrically conducting ceramic
with primary use in heating elements operating at temperatures above
1500 °C in air.
Molybdenum trioxide (MoO3) is used as an adhesive between enamels and
Lead molybdate (wulfenite) co-precipitated with lead
chromate and lead sulfate is a bright-orange pigment used with
ceramics and plastics.
The molybdenum-based mixed oxides are versatile catalysts in the
chemical industry. Some examples are the catalysts for the selective
oxidation of propylene to acrolein and acrylic acid, the ammoxidation
of propylene to acrylonitrile. Suitable catalysts and process
for the direct selective oxidation of propane to acrylic acid are
Ammonium heptamolybdate is used in biological staining.
Molybdenum coated soda lime glass is used in CIGS solar cells
Phosphomolybdic acid is a stain used in thin layer chromatography
Molybdenum-99 is a parent radioisotope of the daughter radioisotope
technetium-99m, used in many medical procedures. The isotope is
handled and stored as the molybdate.
The most important role of molybdenum in living organisms is as a
metal heteroatom at the active site in certain enzymes. In
bacterial nitrogen fixation, the nitrogenase enzyme involved in the
terminal step of reducing molecular nitrogen usually contains
molybdenum in the active site (though replacement of molybdenum with
iron or vanadium is also known). The structure of the catalytic center
of the enzyme is similar to that in iron-sulfur proteins: it
incorporates a Fe4S3 and multiple MoFe3S3 clusters. The oxidation
state of Mo in these clusters is less than in non-nitrogenase
molybdenum cofactor enzymes. The oxidation state of Mo in these
nitrogenases was formerly thought Mo(V), then Mo(IV), but more recent
evidence is for Mo(III).
The reaction that nitrogenase enzymes perform is:
displaystyle mathrm N_ 2 +8 H^ + +8 e^ - +16 ATP+16 H_ 2
Olongrightarrow 2 NH_ 3 +H_ 2 +16 ADP+16 P_ i
With protons and electrons from the electron transport chain, nitrogen
is reduced to ammonia and free hydrogen gas. This is an energy-using
process, requiring the splitting (hydrolysis) of ATP into ADP plus
free phosphate (Pi).
In 2008, evidence was reported that a scarcity of molybdenum in the
Earth's early oceans was a limiting factor for nearly two billion
years in the further evolution of eukaryotic life (which includes all
plants and animals). The chain of causation is as follows:
The relative lack of oxygen in the early ocean resulted in a scarcity
in dissolved molybdenum. Most molybdenum compounds have low solubility
in water, but the molybdate ion MoO42− is soluble and forms when
molybdenum-containing minerals are in contact with oxygen and water.
The lack of dissolved molybdenum limited the growth of prokaryotic
nitrogen-fixing bacteria, which require molybdenum-bearing enzymes for
The lack of prokaryotic nitrogen-fixing bacteria limited the growth of
ocean eukaryotes, which require oxidized nitrogen suitable for the
production of organic nitrogen compounds or the organics themselves
(like proteins) from prokaryotic bacteria. However, once
oxygen had been created in seawater by the limited eukaryotes, it
reacted with water and the molybdenum in minerals on the sea bottom to
produce soluble molybdate, making it available to nitrogen-fixing
bacteria. Those bacteria provided fixed usable nitrogen compounds for
higher forms of life.
Although oxygen once promoted nitrogen fixation by making molybdenum
available in water, it also directly poisons nitrogenase enzymes.
Thus, in Earth's ancient history, after oxygen arrived in large
quantities in Earth's air and water, organisms that continued to fix
nitrogen in aerobic conditions isolated and protected their
nitrogen-fixing enzymes from too much oxygen in heterocysts or
equivalent structures. This structural isolation of nitrogen fixation
reactions in most aerobic organisms continues to the present, but is
not quite universal. Trichodesmium (a cyanobacterial photosynthetic
diazotroph) perhaps the most important marine nitrogen fixing
organism is the only known diazotroph able to fix nitrogen in
daylight under aerobic conditions without the use of heterocysts.
The molybdenum cofactor (pictured) is composed of a molybdenum-free
organic complex called molybdopterin, which has bound an oxidized
molybdenum(VI) atom through adjacent sulfur (or occasionally selenium)
atoms. Except for the ancient nitrogenases, all known Mo-using enzymes
use this cofactor.
Molybdenum cofactor enzymes
Though molybdenum forms compounds with various organic molecules,
including carbohydrates and amino acids, it is transported throughout
the human body as fully oxidized MoO42−. At least 50
molybdenum-containing enzymes were known by 2002, mostly in bacteria,
and the number is increasing with every year; those enzymes
include aldehyde oxidase, sulfite oxidase and xanthine oxidase. In
some animals, and in humans, the oxidation of xanthine to uric acid, a
process of purine catabolism, is catalyzed by xanthine oxidase, a
molybdenum-containing enzyme. The activity of xanthine oxidase is
directly proportional to the amount of molybdenum in the body.
However, an extremely high concentration of molybdenum reverses the
trend and can act as an inhibitor in both purine catabolism and other
Molybdenum concentration also affects protein synthesis,
metabolism, and growth.
In animals and plants, a tricyclic compound called molybdopterin
(which, despite the name, contains no molybdenum) is reacted with
molybdate to form a complete molybdenum-containing cofactor called
molybdenum cofactor. Other than the phylogenetically-ancient
nitrogenases (discussed above) that fix nitrogen in some bacteria and
cyanobacteria, all molybdenum-using enzymes (so far identified) use
the molybdenum cofactor, where molybdenum is in the oxidation state of
VI, similar to molybdate.
Molybdenum enzymes in plants and animals
catalyze the oxidation and sometimes reduction of certain small
molecules in the process of regulating nitrogen, sulfur, and
Human metabolism and deficiency
Molybdenum is an essential trace dietary element. Four mammalian
Mo-dependent enzymes are known, all of them harboring a pterin-based
molybdenum cofactor (Moco) in their active site: sulfite oxidase,
xanthine oxidoreductase, aldehyde oxidase, and mitochondrial amidoxime
reductase. People severely deficient in molybdenum have poorly
functioning sulfite oxidase and are prone to toxic reactions to
sulfites in foods. The human body contains about 0.07 mg
of molybdenum per kilogram of body weight, with higher
concentrations in the liver and kidneys and in lower in the
Molybdenum is also present within human tooth enamel
and may help prevent its decay.
Acute toxicity has not been seen in humans, and the toxicity depends
strongly on the chemical state. Studies on rats show a median lethal
dose (LD50) as low as 180 mg/kg for some Mo compounds.
Although human toxicity data is unavailable, animal studies have shown
that chronic ingestion of more than 10 mg/day of molybdenum can
cause diarrhea, growth retardation, infertility, low birth weight, and
gout; it can also affect the lungs, kidneys, and liver. Sodium
tungstate is a competitive inhibitor of molybdenum. Dietary tungsten
reduces the concentration of molybdenum in tissues.
Low soil concentration of molybdenum in a geographical band from
northern China to Iran results in a general dietary molybdenum
deficiency, and is associated with increased rates of esophageal
cancer. Compared to the United States, which has a greater
supply of molybdenum in the soil, people living in those areas have
about 16 times greater risk for esophageal squamous cell
Molybdenum deficiency has also been reported as a consequence of
non-molybdenum supplemented total parenteral nutrition (complete
intravenous feeding) for long periods of time. It results in high
blood levels of sulfite and urate, in much the same way as molybdenum
cofactor deficiency. However (presumably since pure molybdenum
deficiency from this cause occurs primarily in adults), the
neurological consequences are not as marked as in cases of congenital
A congenital molybdenum cofactor deficiency disease, seen in infants,
is an inability to synthesize molybdenum cofactor, the heterocyclic
molecule discussed above that binds molybdenum at the active site in
all known human enzymes that use molybdenum. The resulting deficiency
results in high levels of sulfite and urate, and neurological
High levels of molybdenum can interfere with the body's uptake of
copper, producing copper deficiency.
Molybdenum prevents plasma
proteins from binding to copper, and it also increases the amount of
copper that is excreted in urine. Ruminants that consume high levels
of molybdenum suffer from diarrhea, stunted growth, anemia, and
achromotrichia (loss of fur pigment). These symptoms can be alleviated
by copper supplements, either dietary and injection. The effective
copper deficiency can be aggravated by excess sulfur.
Copper reduction or deficiency can also be deliberately induced for
therapeutic purposes by the compound ammonium tetrathiomolybdate, in
which the bright red anion tetrathiomolybdate is the copper-chelating
agent. Tetrathiomolybdate was first used therapeutically in the
treatment of copper toxicosis in animals. It was then introduced as a
treatment in Wilson's disease, a hereditary copper metabolism disorder
in humans; it acts both by competing with copper absorption in the
bowel and by increasing excretion. It has also been found to have an
inhibitory effect on angiogenesis, potentially by inhibiting the
membrane translocation process that is dependent on copper ions.
This is a promising avenue for investigation of treatments for cancer,
age-related macular degeneration, and other diseases that involve a
pathologic proliferation of blood vessels.
Institute of Medicine
Institute of Medicine (IOM) updated Estimated Average
Requirements (EARs) and Recommended Dietary Allowances (RDAs) for
molybdenum in 2000. If there is not sufficient information to
establish EARs and RDAs, an estimate designated
Adequate Intake (AI)
is used instead. The current EAR for molybdenum for people ages 19 and
up is 34 μg/day. The RDA is 45 μg/day. RDAs are higher than EARs so
as to identify amounts that will cover people with higher than average
requirements. RDA for pregnancy is 50 μg/day. RDA for lactation is 50
μg/day. For children ages 1–18 years the RDA increases with age
from 17 to 43 μg/day. As for safety, the IOM sets Tolerable upper
intake levels (ULs) for vitamins and minerals when evidence is
sufficient. In the case of molybdenum the UL is 2000 μg/day.
Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary
Reference Intakes (DRIs).
European Food Safety Authority
European Food Safety Authority (EFSA) refers to the collective set
of information as Dietary Reference Values, with Population Reference
Intake (PRI) instead of RDA, and Average Requirement instead of EAR.
AI and UL defined the same as in United States. For women and men ages
15 and older the AI is set at 65 μg/day. AI for pregnancy is 65
μg/day, for lactation also 65 μg/day. For children ages 1–14 years
the AIs increase with age from 15 to 45 μg/day. The adult AIs are
higher than the U.S. RDAs. The European Food Safety Authority
reviewed the same safety question and set its UL at 600 μg/day, which
is much lower than the U.S. value.
For U.S. food and dietary supplement labeling purposes the amount in a
serving is expressed as a percent of Daily Value (%DV). For molybdenum
labeling purposes 100% of the Daily Value was 75 μg, but as of May
27, 2016 it was revised to 45 μg. A table of the old and new
adult Daily Values is provided at Reference Daily Intake. The original
deadline to be in compliance was July 28, 2018, but on September 29,
2017 the FDA released a proposed rule that extended the deadline to
January 1, 2020 for large companies and January 1, 2021 for small
Average daily intake varies between 120 and 240 μg/day, which is
higher than dietary recommendations. Pork, lamb, and beef liver
each have approximately 1.5 parts per million of molybdenum. Other
significant dietary sources include green beans, eggs, sunflower
seeds, wheat flour, lentils, cucumbers and cereal grain.
Molybdenum dusts and fumes, generated by mining or metalworking, can
be toxic, especially if ingested (including dust trapped in the
sinuses and later swallowed). Low levels of prolonged exposure can
cause irritation to the eyes and skin. Direct inhalation or ingestion
of molybdenum and its oxides should be avoided. OSHA
regulations specify the maximum permissible molybdenum exposure in an
8-hour day as 5 mg/m3. Chronic exposure to 60 to
600 mg/m3 can cause symptoms including fatigue, headaches and
joint pains. At levels of 5000 mg/m3, molybdenum is
immediately dangerous to life and health.
List of molybdenum mines
Molybdenum mining in the United States
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