Edouard Bastarache Inc. on mon 15 dec 03
Chronic Chromium Toxicity :
Chronic toxic manifestations are generally due to hexavalent compounds.
1-Skin symptoms :
On contact with skin, hexavalent chromium compounds act as both irritants
and sensitizers.
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.
Hexavalent 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.
Chromate 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.
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.
Trivalent 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.
Some authors claim that the measurement of urinary chromium allows to
confirm the occupational origin of dermatitis in tanners.
b-Chrome ulcers :
After 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 :
Yellowish 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 :
-arsenic,;
-mercury fulminate;
-chlorine;
-cement dust;
-potassium salts (potash mines).
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.
Oesophagitis, gastritis and stomach ulcers have been described among workers
exposed to hexavalent chromium salts.
3-Respiratory Tract :
Occupational 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 fumes.
The bronchospastic reaction may be of the delayed type and accompanied by an
anaphylactoid reaction including urticaria, skin swelling and an increase in
serum histamine.
Inhalation of trivalent chromium salts can also cause occupational asthma
(chromium sulfate).
Pneumoconiosis has been observed also after exposure to chromite ore dust.
4-Carcinogenesis :
Certain 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,
hexavalent chromium compounds are subdivided into two sub-groups by ACGIH :
a-Water-soluble hexavalent chromium compounds :
1-chromic acid;
2-chromic acid anhydrides;
3-monochromates and dichromates of :
-sodium,
-potassium,
-ammonium,
-lithium,
-cesium,
-rubidium.
b-Water-insoluble hexavalent chromium compounds :
1-zinc chromate,
2-calcium chromate,
3-lead chromate,
4-barium chromate,
5-strontium chromate,
6-sintered chromium trioxide.
Chronic 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.
Epidemiologic 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 pigments.
Among individuals 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.
Trivalent chromium compounds and metallic chromium generally are considered
to be very weak carcinogens or noncarcinogenic.
5-Genotoxicity :
Hexavalent 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.
Hexavalent chromium 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 chromium.
Trivalent chromium per se is not genotoxic as demonstrated in epidemiologic
studies among which one conducted among exposed tannery workers.
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
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