Chromium and Compounds
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.
Green chromium oxide, iron chromite, potassium dichromate
and stains are compounds used by potters.
Chemical and Physical Forms:
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.
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 :
Chromous chloride CrCl2
Sodium chromate Na2CrO4
Potassium chromate K2CrO4
Sodium dichromate Na2Cr2O7
Potassium dichromate K2Cr2O7
Ammonium dichromate (NH4)2Cr2O7
Uses and Sources of Exposure :
Chromium is found
- the production of
- the production of
alloys resistant to corrosion: steel with chromium (ferrochrome);
plating: the metal part to be covered with chromium is placed
as an electrode in a chromic acid solution added with sulphuric
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 industry;
the use of trivalent derivatives: chromic anhydride used as pesticide
in wood preservation;
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
Chromium is present in trace amounts in many products (cements,
bleach, magnetic tapes....) which can cause skin allergy. Chromium
can also be found in tobacco smoke.
is an essential trace element and is present in tissues in its
I-Classification of Chromium and Compounds:
compounds vary greatly in their toxic and carcinogenic effects.
For this reason, ACGIH divides its inorganic compounds into a
number of groupings:
A-Chromium metals and alloys:
-other chromium-containing alloys.
B-Divalent chromium compounds (Cr2+) (Chromous compounds):
-chromous chloride (CrCl2);
-chromous sulfate (CrSO4);
C-Trivalent chromium compounds (Cr3+) (Chromic compounds):
-chromic sulfate (Cr2(SO4)3);
-chromic oxide (Cr2O3);
-chromic chloride (CrCl3);
-chromic potassium sulfate (KCr(SO4)2);
D-Hexavalent chromium compounds (Cr6+):
-chromium trioxide (CrO3);
-the anhydride of chromic acid chromates (e.g Na2CrO4),
(e.g., Na2Cr2O7), and polychromates.
Hexavalent salts are regarded as the most hazardous
Trivalent 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.
II-Routes of Absorption and Exposure:
of 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.
Hexavalent salts are
converted by gastric juice to the trivalent form prior to absorption.
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
Hexavalent salts generally
are absorbed well topically through intact skin.
can penetrate the skin and be transformed to trivalent chromium
which becomes an hapten and part of the allergic reaction causing
Trivalent salts are
poorly absorbed through intact skin but, once the dermal barrier
is broken, however, absorption may occur.
industry, workers may be exposed to trivalent and hexavalent chromium
compounds whose metabolic handling and toxicity are strikingly
toxicity is mainly due to hexavalent derivatives which, contrary
to trivalent ones, may penetrate the body by any possible route
including intact skin.
The principal carrier
protein for chromium is transferrin; albumin transports chromium
to a lesser extent.
pass through many tissues, including the red blood cell, kidney,
liver, spleen, and bone.
Inside cells, 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:
compartment (half- life of 7 hours).
is essentially excreted in the urine and in professionally exposed
personnel, its urinary concentration reflects mostly the amount
of recently absorbed soluble hexavalent chromium.
However, the 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.
IV-Symptoms and Signs:
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.
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.
secretions convert hexavalent chromium to trivalent chromium after
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 (shock).
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 ingestion.
the lethal dose for chromic acid by ingestion is estimated to
be between 1 to 3 g.
Even small ingestions
of dichromates have resulted in hemorrhagic gastro-enteritis and
renal failure may occur after large oral ingestions of hexavalent
chromium compounds and after dermal exposure.
of 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 ingestion.
necrosis may occur in acute intoxication by ingestion.
B- Chronic Toxicity:
Chronic toxic manifestations
are generally due to hexavalent compounds.
contact with skin, hexavalent chromium compounds act as both irritants
a-Exzematous Dermatitis (Allergic Contact Dermatitis)
This clinical entity
is characterized by erythematous, or vesico-papular, wet, pruriginous
lesions localised especially on the forearms (chromium bracelets).
It is very frequent
among individuals in contact with cement.
In practice, only
chromium hexavalent compounds are sensitizers.
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.
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.
Once induced, chromate
sensivity may produce difficulty in multiple settings.
Contact with 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 salts
In sensitized individuals,
the absorption of chromium by pulmonary and/or oral way could
cause an exzematous reaction.
only penetrates with much difficulty into the skin and the risk
of sensitizing is thus weak. Chromium metal is not in theory an
The allergy to chromium
is confirmed by skin patch testing.
Some authors claim
that the measurement of urinary chromium allows to confirm the
occupational origin of dermatitis in tanners.
cutaneous 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 industry.
c-Teeth and Skin:
discoloration of the tongue and teeth is a sign of chronic intoxication.
2-Irritation of 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.
Nasal septal 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 workers
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:
-potassium salts (potash
Symptoms of 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.
Exposure to chromic
acid (hexavalent) may cause chronic pharyngitis and laryngitis.
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
reaction may be of the delayed type and accompanied by an anaphylactoid
reaction including urticaria, skin swelling and an increase in
Inhalation of trivalent
chromium salts can also cause occupational asthma (chromium sulfate).
been observed also after exposure to chromite ore dust.
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 :
a-Water-soluble hexavalent chromium compounds:
2-chromic acid anhydrides;
3-monochromates and dichromates of:
b-Water-insoluble hexavalent chromium compounds:
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.
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 pigments.
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.
In the 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 exist.
Exposure 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 lesser risk.
According to Levy
et al., chromic acid (a very soluble compound) would be
a weak carcinogen.
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.
compounds have caused developmental effects in rodents in the
absence of maternal toxicity following oral administration.
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
per se is not genotoxic as demonstrated in epidemiologic
studies among which one conducted among exposed tannery workers.
Management of Acute Toxicity:
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 considered.
generally 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
Usually ascorbic 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
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.
evidence does not allow the conclusion that exchange transfusion
generally should be employed.
Hemodialysis and charcoal
hemoperfusion do not substantially enhance chromium removal from
the body if renal function remains normal. However, if renal failure
ensues, hemodialysis may be necessary for management of the renal
balance 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 indicated.
may be indicated to reduce the possibility of further renal injury.
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 proposed.
inhalation of hexavalent or trivalent chromium compounds, patients
should be removed from further exposure and assessed carefully.
If respiratory 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.
after the inhalation of other concentrated hexavalent, highly
soluble compounds are prudent.
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
The topical 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 compounds.
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.
is recommended that before work assignments, where hexavalent
chromium exposure is likely, that the following measures should
detailed 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.
base line standard chest x-ray film should be obtained and retained
indefinitely for future comparison.
should be obtained to minimally include FVC, FEV1 and the FEV1/FVC,
chiefly for base-line information.
tests to assure normal kidney and liver function should be performed.
should be obtained for the same reasons as in 5.
Once medically 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 eliminated.
A special attention
should be paid to the skin and nasal septum.
persons 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 creatinine, respectively.
values 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.
1-Biological exposure index (BEI):
has determined two (2) biological exposure index (BEI) measures
for hexavalent chromium compounds as a water-soluble fume.
the increase in total chromium in urine during a work shift, with
an upper limit of 10µg per g of creatinine.
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 creatinine.
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 damage.
chromium is excreted mostly in the urine.
researchers maintain that hexavalent chromium determination in
erythrocytes is a more useful estimation of the body burden of
hexavalent chromium after exposure.
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.
I-General Hygiene :
- to conduct all
dangerous operations (crushing of chromites, etc) in closed containement;
- 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
- 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
- an air adduction respiratory tract protection apparatus when
there are cancerogenic derivatives.
Exposure limits :
A-Quebec's exposure limits :
Valeur d’Exposition Moyenne Pondérée:
VI, certain water- insoluble compounds,
VI, water- soluble compounds,
= Confirmed carcinogen to humans
RP = Substance whose
recirculation is prohibited in accordance with the law
= Substance that should be kept at the lowest practicable level
B-NIOSH’s IDLH (Immediately Dangerous to Life
chromium compounds and chromic acid
toxicity varies with particular chromium compounds.
divalent, and trivalent chromium compounds generally are less
toxic than hexavalent compounds.
Trivalent 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.
Hexavalent chromium compounds are dangerous after acute substantial
chromium compounds have been demonstrated to be carcinogenic.
The optimal treatment
for chromium toxicity lies in its prevention, with the use of
good industrial hygiene practices, proper workplace industrial
controls and good personal hygiene measures.
M.D. (Occupational & Environmental Medicine)
Author of Substitutions
for raw ceramic materials
1-Occupational Medicine,Carl Zenz, last edition.
2-Clinical Environmental Health and Toxic Exposures, Sullivan
& Krieger; last edition.
3-Sax’s Dangerous Properties of Industrial Materials, Lewis C.,
et Intoxications Professionnelles, Lauwerys R. last edition.
of the Workplace, Proctor & Hughes, 4th edition.