It is a
grey-white metal very resistant to wear. Chromium is produced from
chromite, FeO.Cr2O3, by roasting and extraction in the form of
chromate which is then reduced to chromium metal.
oxide, iron chromite, potassium dichromate and stains are
compounds used by potters.
Chemical and Physical Forms :
Chromium has a
molecular weight of 52. Most chromium compounds are solids at room
temperature, altough one notable exception is chromyl chloride, a
hexavalent chromium compound that is a fuming liquid.
The chemical and
toxicologic properties of chromium differ markedly, depending on
the valence state of the metal. Chromium occurs in its metallic
state (valence 0), and in valence states 2+ through 6+, but only
the trivalent (3+) and hexavalent (6+) are commonly found.
Chromium in its 2+ state frequently oxidizes rapidly to 3+ form,
and the 4+ and 5+ states are found only as intermediates in the
conversion between 3+ and 6+ states.
Some Common Chromium Compounds :
Uses and Sources of Exposure :
Chromium is found
- the production
of chromium metal;
- the production
of alloys resistant to corrosion: steel with chromium
chromium plating: the metal part to be covered with chromium is
placed as an electrode in a chromic acid solution added with
Thick chromium plating (hard type-thickness
5-10µm) can cause significant exposure to chromium whereas
thin chromium plating (bright type-thickness
0.5-1µm) does not cause any significant risk of excessive
exposure to chromium;
- the manufacture
of chromates and dichromates from iron chromate. These have many
applications in lithography, textile industry, printing, tannery,
dyeing, photography, and the paint industry;
- the manufacture
refractory bricks for the furnaces of the metallurgical
- the use of
trivalent derivatives: chromic anhydride used as pesticide in wood
- welding alloys
containing chromium. Welding of stainless steel by the manual
metal arc process releases particles which, after deposition in
the respiratory tract, allows the progressive solubilization of
chromium. On the other hand, the particles released by welding
under inert gas (MIG) are not very soluble.
dioxichloride (Cl2CrO2) is a volatile liquid compound of
hexavalent chromium used in a great number of synthesis processes
: olefinic hydrocarbon polymerization, hydrocarbon oxidation,
production of aldehydes and ketones
present in trace amounts in many products (cements, bleach,
magnetic tapes....) which can cause skin allergy. Chromium can
also be found in tobacco smoke.
Clinical Toxicology :
Chromium is an
essential trace element and is present in tissues in its trivalent
I-Classification of Chromium and Compounds
compounds vary greatly in their toxic and carcinogenic effects.
For this reason, ACGGIH divides its inorganic compounds into a
number of groupings :
-the anhydride of
chromic acid chromates (e.g Na2CrO4), dichromates,
are regarded as the most hazardous ones.
chromium is absorbed poorly by inhalation and throught intact
skin, resulting in a low order of systemic toxicity. However,
should trivalent chromium gain access to the systemic circulation,
toxic effects may develop.
Absorption and Exposure :
highly water-soluble hexavalent chromium salts, such as chromic
acid, sodium dichromate, and potassium dichromate, may result in
substantial systemic absorption.
water-soluble salts are unlikely to produce systemic effects but
may produce pulmonary effects.
and chromous or chromic salts (valences 0, +2, +3) are absorbed
minimally after inhalation. Local pulmonary deposition of these
salts has been reported after exposure but without evidence of
adverse systemic effects.
are converted by gastric juice to the trivalent form prior to
chromium salts are absorbed after ingestion, but only 1% to 25% of
the dose ingested is absorbed.
The extent of
absorption varies with the particular salt ingested and the
circumstances of ingestion.
generally are absorbed well topically through intact skin.
chromium can penetrate the skin and be transformed to trivalent
chromium which becomes an hapten and part of the allergic reaction
causing exzematous dermatitis.
are poorly absorbed through intact skin but, once the demal
barrier is broken, however, absorption may occur.
workers may be exposed to trivalent and hexavalent chromium
compounds whose metabolic handling and toxicity are strikingly
is mainly due to hexavalent derivatives which, contrary to
trivalent ones, may penetrate the body by any possible route
including intact skin.
carrier protein for chromium is transferrin; albumin transports
chromium to a lesser extent.
compounds pass through many tissues, including the red blood cell,
kidney, liver, spleen, and bone.
hexavalent chromium is reduced to the very reactive pentavalent
chromium and the trivalent one.
Only these two
forms may alter DNA.
is distributed in two compartments :
elimination compartment (half- life of 7 hours).
essentially excreted in the urine and in professionally exposed
personnel, its urinary concentration reflects mostly the amount of
recently absorbed soluble hexavalent chromium.
presence of a slow elimination compartment explains why those who
have been away from exposure, even for many months, have levels of
urinary chromium above normal values.
and Signs :
After oral or
dermal exposure, hexavalent chromium compounds, including chromic
acid, the chromates and dichromates, are potentially the most
toxic of the chromium compounds commonly encountered. Ingestion of
dichromates has proved fatal in many instances; the oral lethal
dose is estimated to be 0.5 to 5 g.
chromium compounds may be absorbed percutaneously, even through
intact skin and acute renal failure may occur after a dermal burn
of 10% body surface or less.
In a case, 70%
total body thermal burn from hot chromic sulfate (trivalent) mixed
with sulfuric acid (broken skin barrier) produced chromium
poisoning with acute renal failure.
Fumes of chromium
dioxichloride are very irritating to the skin.
2-Gastrointestinal System :
secretions convert hexavalent chromium to trivalent chromium after
In this process,
the gastric and intestinal mucosa are in grave danger of severe
injury caracterized by massive inflammation and necrosis from the
mouth to the jejunum causing :
These rapid onset
manifestations may cause death by circulatory collapse
If the outcome is
not rapidly fatal, 12 to 20 hours later, manifestations of hepatic
and renal necrosis will appear.
distress syndrome has been reported after substantial
treatment, the lethal dose for chromic acid by ingestion is
estimated to be between 1 to 3 g.
ingestions of dichromates have resulted in hemorrhagic
gastro-enteritis and death.
failure may occur after large oral ingestions of hexavalent
chromium compounds and after dermal exposure.
concentrated chromic acid mist has been reported to result in
pulmonary edema, which may be delayed up to 72 hours after
Fumes of chromium
dioxichloride are very irritating to the mucous membranes.
distress syndrome has been reported after substantial
may occur in acute intoxication by ingestion.
manifestations are generally due to hexavalent compounds.
On contact with
skin, hexavalent chromium compounds act as both irritants and
entity is characterized by erythematous, or vesico-papular, wet,
pruriginous lesions localised especially on the forearms (chromium
It is very
frequent among individuals in contact with cement.
In practice, only
chromium hexavalent compounds are sensitizers.
chromium can penetrate the skin where it is reduced to trivalent
chromium which plays the role of an hapten; when fixed on a
protein, it becomes a complete antigen.
sensivity has proved fairly persistent once developed. In one
study, 92% of the study patients with dichromate sensivity induced
by exposure to Portland cement continued to display contact
dermatitis 10 years after initially developed symptoms.
chromate sensivity may produce difficulty in multiple
textiles colored with chromate-based pigments can be sufficient to
exacerbate the dermatitis. The wearing of leather shoes tanned
with chromates can produce dermatitis of the feet if these are
allowed to remain sweaty. " Housewife exzema " may be largely a
chromate sensitivity phenomenon, as detergents and bleaches in
some areas contain more than trace amounts of chromate
individuals, the absorption of chromium by pulmonary and/or oral
way could cause an exzematous reaction.
chromium only penetrates with much difficulty into the skin and
the risk of sensitizing is thus weak. Chromium metal is not in
theory an allergen
The allergy to
chromium is confirmed by skin patch testing.
claim that the measurement of urinary chromium allows to confirm
the occupational origin of dermatitis in tanners.
exposure to chromic acid, erosions of the skin may occur. These "
chrome holes " initially appear as papular lesions , either singly
or grouped, with central ulceration. They occur chiefly on the
hands and forearms where there has been a break in the epidermis;
they are believed to be due to a direct necrotizing effect of the
chromate ion. These ulcers are from 5 to 10 mm in diameter,
painless, with sharp edges, sometimes itchy and have the
possibility of extending into joints; they heal slowly and produce
a characteristic depressed scar.
These ulcers are
observed mainly among workers of the electrolytic chromium plating
c-Teeth and Skin
discoloration of the tongue and teeth is a sign of chronic
mucous membranes :
Atrophy of the
nasal mucous membrane followed by ulceration and perforation may
occur. It is generally painless and is found at medical
examination. It may be found in nearly 50 % of workers exposed to
chromates and may be associated to anosmia.
ulcerations were observed after only 2 weeks of exposure to 1mg/m3
of zinc chromate whilst 18 months of exposure to 0.02-0.1 mg/m3
did not cause any perforation or ulceration. These ulcerations
were obseved mainly among electrolytic chromium plating
In one study of
chromic acid workers, the incidence and severity of nasal injury
was related both to lenght of exposure and the laxity of
industrial hygiene practiced by individual workers.
Let us remember
that perforation of the nasal septum is also associated with
exposure to many other industrial toxicants :
rhinitis, conjonctivitis, shortness of breath and pruritus are
more frequent among electolytic chromium plating workers. Workers
of the same type of industry, excreting more than 15 µg / g
of creatinine of chromium, have impairments of spirometric
measurements, for instance a reduction of FEV1.0. Therefore, it is
logical to conclude that chronic exposure to chromic acid fumes
may cause chronic obstructive pulmonary disease.
chromic acid (hexavalent) may cause chronic pharyngitis and
gastritis and stomach ulcers have been described among workers
exposed to hexavalent chromium salts.
asthma has occurred among workers exposed to chromic acid fumes,
to hexavalent chromium compounds present in bauxite used in the
production of aluminium, and from hexavalent chromium in welding
bronchospastic reaction may be of the delayed type and accompanied
by an anaphylactoid reaction including urticaria, skin swelling
and an increase in serum histamine.
trivalent chromium salts can also cause occupational asthma
has been observed also after exposure to chromite ore dust.
hexavalent chromium compounds have been demonstrated to be
carcinogenic on the basis of epidemiologic investigations of
workers and of experimental studies with animals.
In general, these
compounds tend to be of low solubility in water and, thus, are
subdivided into two sub-groups by ACGIH :
hexavalent chromium compounds :
and dichromates of :
hexavalent chromium compounds :
inhalation of hexavalent chromium compounds presents an increased
risk of lung cancer, with the degree of risk depending on the
particular salts and their solubility under biological conditions,
on the circumstances of exposure, and on such concomitant risk
factors as cigarette smoking.
studies conducted in the USA 40 years ago, demonstrated a 10 to 30
fold- increased risk of lung cancer among workers of the chromate
industry compared to the general population. Many studies have
confirmed the carcinogenic risk among workers employed in the
manufacture of chromates and the use of chromium-based
who have been severely exposed, the increased risk of lung cancer
is still detectable 20 years after cessation of exposure. In most
studies, a positive correlation between duration of exposure and
lung cancer death was found.
electrolytic chromium plating industry, mainly of the " hard type
", the cancer (mainly lung cancer) risk is quite lower than in the
chromate industry; this is explained by the fact that soluble
hexavalent chromium is used in the former while rather insoluble
compounds are used in the latter.
The cancer risk
among stainless steel welders, exposed to soluble hexavalent
chromium compounds has not been precised.
In the production
of ferrochrome, workers are exposed mainly to metallic and
trivalent chromium and lightly to hexavalent compounds, under
these circumstances an increased lung cancer risk does not seem to
chromates would also favor cancers of other sites such as nasal
cavities, larynx and stomach.
Zinc chromate is
the most potent carcinogen among chromates commonly found in
industrial settings; calcium chromate and lead chromate pose a
According to Levy
chromic acid (a very soluble compound) would be a weak
The risk of lung
cancer appears non-existent among tanners using mainly trivalent
chromium compounds and metallic chromium generally are considered
to be very
weak carcinogens or noncarcinogenic.
chromium compounds have been consistently genotoxic, inducing a
wide variety of effects, including DNA damage, gene mutation,
sister chromatid exchange, chromosomal aberrations, cell
transformation, and dominant lethal mutations.
chromium compounds have caused developmental effects in rodents in
the absence of maternal toxicity following oral
As in the case of
chromium exzematous dermatitis, it appears that the genotoxic
substance is pentavalent chromium or trivalent chromium produced
from the intracellular reduction of hexavalent chromium after
penetration into the cell. According to Molyneux and Davies, it is
the re-oxidation of pentavalent chromium by hydrogen peroxide, or
eventually by other peroxides, that would cause the production of
hydroxyl radicals responsible for DNA alterations induced by
chromium per se is not genotoxic as demonstrated in epidemiologic
studies among which one conducted among exposed tannery
Management of Acute Toxicity :
No matter the
route of exposure, the initial approach to an affected individual
includes a brief assessement of his clinical status followed by
support of basic cardiopulmonary functions.
Once the airway
has been stabilized and cardiopulmonary support has been
instituted as indicated, further measures can be
should not be induced in the patient exposed to chromium via
ingestion, owing to the potential corrosive effect of the chromium
compound and the potential for rapid deterioration of the
acid should be administered orally or nasogastrically, if the
patient still has chromium in his stomach. Ascorbic acid has been
shown to ameliorate the effects of topical human exposure to
chromates. Ascorbic acid acts chemically by reducing Cr6+ to Cr3+,
the form less toxic to the gastric and intestinal mucosa.. The
ascorbic acic dosage for treatment of hexavalent chromium
ingestion varies with the salt ingested.
Dilution of the
ingested agent may be appropriate if dilution can be accomplished
within minutes after ingestion, particularly if the ingested
material's pH is fairly low (e.g. chromic acid) or fairly high
(e.g. ammonium dichromate).
Dilution may be
accomplished with water or with fluids that also serve as
demulcents, such as milk. The use of demulcent compounds (e.g.
antacids, corn starch, or milk) in addition to those used for
dilution has been recommneded and seems reasonable but have not
been studied formally.
Gastric lavage to
reduce the ingested dose may be desirable if chromium is likely to
be present in the stomach. But, there is a risk of perforation of
the injuried oesophagus and stomach; if the decision to proceed to
lavage is made, a soft tube is preferable.
does not allow the conclusion that exchange transfusion generally
should be employed.
charcoal hemoperfusion do not substantially enhance chromium
removal from the body if renal function remaims normal. However,
if renal failure ensues, hemodialysis may be necessary for
management of the renal failure itself.
must be maintained. Affected patients should be monitored
carefully for evidence of gastrointestinal bleeding,
methemoglobinemia, hemolysis, coagulopathy, seizures, or pulmonary
dysfunction. Appropriate supportive measures should be employed as
may be indicated to reduce the possibility of further renal
It should be
treated with methylene blue if the methemoglobin level exceeds 30%
or if signs or symptoms of methemoglobinemia are present.
The use of the
chelating agent dimercaptopropane sulfonate has been
of hexavalent or trivalent chromium compounds, patients should be
removed from further exposure and assessed carefully.
distress or cyanosis is noted, oxygen should be administered.
Bronchospasm should be treated with bronchodilatators.
If the inhaled
agent was chromic acid, continued observation and
assessement should be considered, to note any developement of
pulmonary edema up to 72 hours after exposure.
precautions after the inhalation of other concentrated hexavalent,
soluble compounds are prudent.
In cases of
dermal absorption, the skin should be irrigated copiously with
water. The affected area should be evaluated for the presence of
chemical or thermal burns, and treatment should be provided as
application of a freshly made 10% ascorbic acid solution or of a
barrier cream containing 2% glycine and 1% tartaric acid has
proved beneficial in some industrial settings in reducing the
consequences of topical exposure to hexavalent chromium
measurements of chromate levels after exposure have not been shown
to have prognostic or therapeutic value. However, it may allow
further documentation of exposure and assessement of the efficacy
of measures to enhance elimination.
Medical Measures :
A-Pre-employment examination :
It is recommended
that before work assignments, where hexavalent chromium exposure
is likely, that the following measures should be taken.
personal medical and work history should be reviewed by a
physician familiar with the potential health risks of exposure to
the specific chromium compounds.
general physical examination should be done, with a special
attention to the skin, mucous membranes, and lungs. Those with
skin lesions and chronic bronchitis should be discarded.
A base line
standard chest x-ray film should be obtained and retained
indefinitely for future comparison.
be obtained to minimally include FVC, FEV1 and the FEV1/FVC,
chiefly for base-line information.
Blood tests to
assure normal kidney and liver function should be
be obtained for the same reasons as in 5.
approved for hexavalent chromium compounds exposure, items 1, 2 4, 5, 6
should be repeated annually. Also, beginning with the tenth year
of exposure to carcinogenic chromium compounds, a standard chest
x-ray and sputum cytology may also be helpful to verify that lung
cancer has not developed.
If it is known
with absolute certainty that the worker has never been exposed
above the maximum allowable concentration, is a non-smoker, and
has meticulous work habits, this precaution may be
attention should be paid to the skin and nasal septum.
non-occupationally exposed to chromium, the concentration of
chromium in serum or plasma and in urine usually does not exceed
0.05µg/100ml and 5µg/ g ss#creatinine,
reported by WHO (1988) and based on the data of the U.S. EPA
(1978) range from 0.02 to 7 µg/100 ml in serum and plasma,
and 0.5µg to 5.4µg/100 ml in red blood cells.
exposure index (BEI):
determined two (2) biological exposure index (BEI) measures for
hexavalent chromium compounds as a water-soluble
increase in total chromium in urine during a work shift, with an
upper limit of 10µg per g of creatinine.
Samples the total
urinary chromium at the end of the shift at the end of the work
week, with an upper limit of 30 µg per g of
Studies show that
the predominant form of chromium recovered in blood and tissues,
even after exposure to hexavalent chromium, is trivalent chromium
because the hexavalent form is reduced to the trivalent form in
tissues in biological media. Reduction of Cr6+ to Cr3+ decreases
the entry of chromium into cells and lessens intracellular and DNA
chromium is excreted mostly in the urine.
maintain that hexavalent chromium determination in erythrocytes is
a more useful estimation of the body burden of hexavalent chromium
When low chromium
levels are found in the erythrocytes along with high urine
chromium concentrations, extracellular reduction of hexavalent
chromium is assumed to be sufficient for detoxification.
Technical Measures :
- to conduct all
dangerous operations (crushing of chromites, etc) in closed
- to carry out
aspiration of fumes and dusts above the vats of electrolysis or to
prevent the release of chromic acid mist by covering the bath of
electrolysis by a liquid or solid screen . Suppressors of mist
over the vats of chromium plating are currently used. They act
either by reducing the surface tension of the liquid or by forming
a thick foam barrier.
- to mechanically
place and withdraw parts to be chromium plated;
- to add 0.1 to
0.2% ferrous sulphate to Portland cement to reduce the hexavalent
chromium it contains. It was shown that this measure had a
beneficial effect on exzematous contact dermatitis in Denmark.
- to add 1% zinc
in welding wire, which causes a significant reduction in
hexavalent chromium in welding fumes.
Depending on the
type of compounds used, type and severity of exposure, it may be
necessary to wear:
clothing: gloves, aprons;
- a hand cream or
solution based on 10% ascorbic acid, or on sodium dithionite
(Na2SO4), or on an ion exchange resin and or tartaric acid.
60% of the
subjects sensitized to chromium can be protected completely or
partially by the following formulation : silicone 10%, lactate of
glycerol 2%, glycine 2%, tartaric acid 1%, excipient ad 100%
.These preventive cutaneous treatments would be indicated in
subjects allergic to chromium and who cannot, for various reasons,
avoid any contact with chromium.
A zinc oxide or
10 % ascorbic acid ointment is also recommended to protect the
nasal mucous membrane.
- an air
adduction respiratory tract protection apparatus when there are
Exposure limits :
exposure limits :
VEMP : Valeur
d'Exposition Moyenne Pondérée :
II, compounds,as Cr.
III, compounds,as Cr.
VI, certain water- insoluble compounds,as Cr.
VI, water- soluble compounds,as Cr.
C1 = Confirmed
carcinogen to humans
RP = Substance
whose recirculation is prohibited in accordance with the
EM = Substance
that should be kept at the lowest practicable level
(Immediately Dangerous to Life and Health) :
Hexavalent chromium compounds and chromic
varies with particular chromium compounds.
chromium, divalent, and trivalent chromium compounds generally are
less toxic than hexavalent compounds.
compounds, such as green chromium oxide used by potters, do not
appear to cause other effects associated with the hexavalent
chromium compounds, such as chrome ulcers (hands and forearms),
nasal septal perforation, lung cancer, etc.
chromium compounds are dangerous after acute substantial exposure.
hexavalent chromium compounds have been demonstrated to be
treatment for chromium toxicity lies in its prevention, with the
use of good industrial hygiene practices, of proper workplace
industrial controls and good personal hygiene measures.
-Occupational Medicine,Carl Zenz, last edition.
Environmental Health and Toxic Exposures, Sullivan & Krieger;
Dangerous Properties of Industrial Materials, Lewis C., last
Industrielle et Intoxications Professionnelles, Lauwerys R. last
Hazards of the Workplace, Proctor & Hughes, 4th
Article by Edouard Bastarache Edouard Bastarache is a well known doctor that has written many articles on the subject of toxicity of ceramic materials and books on technical aspects of ceramics. He writes in both English and French.