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UNITED STATES ATOMIC ENERGY COMMISSION
TOXICITY OF CERTAIN HEAVY METAL CARBONYLS-Ni(CO)4, Mo(CO),, W(CO),, Cr(CO),
University of Rochester
This document consists of 3 pages.
Date of Manuscript: March 20, 1945
Date Declassified: June 16, 1947
This document is for official use.
Its issuance does not constitute authority
for declassification of classified cornes
of the same or similar content and title
and by the same authorss.
Technical Information Division, Oak Ridge Directed Operations
Oak Ridge, Tennessee
TOXICITY OF CERTAIN HEAVY METAL CARBONYLS-NI(CO),, Mo(CO),, W(CO),, Cr(CO),
By Carl Voegtlin
Nickelckrbonyl was discovered in 1890 and has been widely used ever pince in the Mond process
for'the production of pure nickel.
Nt + 4 CO 4 Ni(CO),
Finely divided nickel is treated at room temperature with CO and yields a clear yellow liquid
Ni(CO),, which decomposes at 150C into Ni and CO. Decomposition begins at 60C, an indication of
the instability of the compound. The relatively high toxicity of nickelcarbonyl was recognized during
its early industrial use and four deaths occurred as a result of the accidental escape of gas from the
Immediately after exposure, there is giddiness, headache, and at times, dyspnoea and vomiting.
These symptoms pass off when patient is brought into fresh air. From 12 to 36 hours later, the dysp-
noea returns, cyanosis and leukocytosis appear, and the temperature begins to rise. Cough with more
or less bloodstained sputum occurs on second day or later. Pulse rate increases, but not in propor-
tion to the respiratory rate. Delirium and a variety of other signs of central nervous system disturb-
ance occur. Death in fatal cases occurs between 4 and 11 days.
Hepatization of lungs resembling changes produced by phosgene. Alveoli filled by fibrin with
very few cells. Changes in capillaries and arteriols explain presence of multiple small hemorrhages
in lungs and also the degenerative changes in brain, medulla, and upper spinal chord. Nickel can be
found in urine, blood, lungs, and brain.
History of exposure. Occurrence of immediate symptoms. Presence of nickel in first 48-hour
Immediate rest is of importance. If asphexia is severe, give same treatment as for CO, i.e.,
95% oxygen plus 5% CO,. Warmth. Digitalin. 0.01 grain atropin sulfate subcutaneously is helpful.
Workers with pulmonary catarrhal conditions should not be employed. Monitoring: Blue alcohol
flame is changed to yellow by toxic concentrations. This test detects 1 part in 400,000 parts of air.
Place a constant CO recorder in various parts of plant. During breakdown of enclosed system,
workers should wear compressed air masks.
The mechanism of the toxic action of nickelcarbonyl is incompletely understood. It is believed
that the vapor is readily absorbed by the very large respiratory surface and the high solubility in
lipids. Following absorption decomposition of the carbonyl may take place locally in the lungs with
the formation of nickel protein complexes and CO hemoglobin. With heavy exposure, it is perhaps
possible that some of the compound may reach the central nervous system.
Exposure of animals to the vapors showed that 64 of 77 rabbits were killed by exposure for 65
minutes to 0.018 to 0.0188 volume per cent. Cats are somewhat less sensitive and dogs die after In-
haling air containing 0.036 volume per cent for 75 minutes. The symptomatology and pathological
findings in animals resemble those described for man.
Nickelcarbonyl is said to be at least five times as toxic as CO. The American Standards Associ-
ation has adopted the following maximum allowable concentration for CO: 100 ppm of air by volIme
with atmospheric q not below 19% by volume for exposures not exceeding a total of 8 hours daily,
and 400 ppm of air by volume for exposures not exceeding a total of 1 hour daily. These standards
are given in view of the fact that recently the Mond process may employ CO under pressure, which in
a breakdown of the system would release considerable amounts of CO into the factory air.
Mo(CO)6, W(CO),, and Cr(CO)
A search of the literature revealed no information concerning the toxicities of these compounds.
They are crystalline substances which are remarkably stable. The following tabulation shows that
they have a lower vapor pressure and higher decomposition temperature than nickelcarbonyl.
Vapor Pressure Begins to decompose at C
Ni(CO), 261 at 15"C 60
Cr(CO), 1 at 480C 130
Mo(CO), 2.3 at 55"C 150
W(CO), 1.2 at 67C 150
They are stable toward alkali and such strong reagents as bromine and iodine, but are decom-
posed by concentrated nitric acid. The industrial use of these compounds should not present any.
serious health hazards if the operation does not involve temperatures exceeding ordinary atmosphere
conditions and the inhalation of the compounds in the form of dust. Occupation and Health, Issued by
the International Labor Office, Geneva, states that Mo(CO), is toxic to the nervous system and liter,
but gives no further details.
As to the toxicity of Cr, Mo, and W in ionized compounds, it should be remembered that Cr as
chromic acid can produce perforation of the nasal septum and other local reactions. The toxicity of
Mo and W, as shown by a few experiments on animals, may be regarded as relatively low. There'is
no evidence of industrial tungsten poisoning in spite of its extensive use.
TOXICITY OF HEAVY METAL ALKYLS- Pb(CH,),, Zn(CH,),, Sn(CH4,
The literature contains very little concerning the toxicity of these compounds. Henderson and
Haggard in Noxious Gases, 1943, state that the action of volatile organo metallic compounds depends
upon that of the metal with which the organic group is combined; but their effects a-e usually far more
acute than those of any other compounds of the metals. Their volatility results in their absorption
from the lungs and thus renders the poisoning much more rapid than ordinarily occurring when salts
of the heavy metals are taken in through the alimentary tract. Chronic poisoning is essentially simi-
lar to that induced by the heavy metals.
Acute poisoning from tetraethyl lead is well known and is characterized by lead encephalopathy
with symptoms of increased intracranial pressure, meningeal irritation, and acute mania. Chronic
poisoning resembles the common chronic forms of lead poisoning.
Tetramethyl lead boils at 110C as compared with tetraethyl lead at 200C. The higher volatility
of the former compound would presumably increase its toxic action under similar conditions. German
toxicologists consider the toxicity of tetramethyl lead to be of the same order as that of tetraethyl
lead. Kehoe has carried out some unpublished experiments with tetramethyl lead, the results of
which, he will furnish me during a visit to his laboratory. Buck and Kumso (J. Pharmacology, 1930-
38, 169), found that the compound in olive oil injected intraperitoneally into rats caused lacrimation,
decrease in body temperature, loss of weight, and slight cerebral symptoms. MLD 70 to 100 mg.'kilo.
I~albits injected intravenously developed cerebral symptoms, MLD 70 to 100 mg/kilo for tetraethyl
lead. This information is sufficient to emphasize the precautions to be taken in the handling of tetra-
methyl lead. These are: closed system manufacture; mild poisoning should be treated by termination
of exposure, high intake of water, good diet and saline cathartics; severe cases should receive ade-
quate water intake with intravenous saline infusion, if necessary, for delerium 2 to 4 g magnesium
sulphate has been given intravenously in cases of tetraethyl lead poisoning. Insomnia may be bene-
fited by 1 g daily of pentobarbital, given by mouth.
No information concerning the toxicity of Dimethyl zinc could be located. Dr. Kehoe in a letter
to me states: "I have the feeling that all of the alkyl metal compounds are rather comparable in
As regards tetramethyl tin, nothing is known of its toxic action. It is probable that the inhalation
of the vaporized compounds may cause toxic symptoms. This assumption receives sor.e support from
the experience of two pharmacologists who worked with a related compound-triethlyl tin. During the
synthesis of this compound they inhaled some of its vapors. Both workers complained of severe head-
ache, nausea, diarrhea, and weakness lasting for two days. When the compound was injected intra-
venously into dogs in doses of approximately 25 mg per kilogram body weight, the tox:ic symptoms
resembled those following exposure to alkyl lead compounds, namely: nervous irritability, vomiting,
In conclusion, it may be said that proper precaution should be taken to avoid-exposure of workers
to the-vapors of the foregoing alkyl metal compounds.
UNIVERSITY OF FLORIDA
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