Applications
Chromium main uses are in alloys such as stainless steel, in chrome plating and
in metal ceramics. Chromium plating was once widely used to give steel a
polished silvery mirror coating. Chromium is used in metallurgy to impart
corrosion resistance and a shiny finish; as dyes and paints, its salts colour
glass an emerald green and it is used to produce synthetic rubies; as a catalyst
in dyeing and in the tanning of leather; to make molds for the firing of bricks.
Chromium (IV) oxide (CrO2) is used to manufacture magnetic tape.
Chromium in the environment
Chromium is mined as chromite (FeCr2O4) ore. Chromium ores are mined today in
South Africa, Zimbabwe, Finland, India, Kazakihstan and the Philippines. A total
of 14 million tonnes of chromite ore is extracted. Reserves are hestimated to be
of the order of 1 billion tonnes with unexploited deposits in Greenland, Canada
e USA.
Health effects of Chromium
People can be exposed to Chromium through breathing, eating or drinking and
through skin contact with Chromium or Chromium compounds. The level of Chromium
in air and water is generally low. In drinking water the level of Chromium is
usually low as well, but contaminated well water may contain the dangerous
Chromium(IV); hexavalent Chromium. For most people eating food that contains
Chromium(III) is the main route of Chromium uptake, as Chromium(III) occurs
naturally in many vegetables, fruits, meats, yeasts and grains. Various ways of
food preparation and storage may alter the Chromium contents of food. When food
in stores in steel tanks or cans Chromium concentrations may rise.
Chromium(III) is an essential nutrient for humans and shortages may cause heart
conditions, disruptions of metabolisms and diabetes. But the uptake of too much
Chromium(III) can cause Health effectsas well, for instance skin rashes.
Chromium(VI) is a danger to human health, mainly for people who work in the
steel and textile industry. People who smoke tobacco also have a higher chance
of exposure to Chromium.
Chromium(VI) is known to cause various Health effects. When it is a compound in
leather products, it can cause allergic reactions, such as skin rash. After
breathing it in Chromium(VI) can cause nose irritations and nosebleeds.
Other health problems that are caused by Chromium(VI) are:
- Skin rashes
- Upset stomachs and ulcers
- Respiratory problems
- Weakened immune systems
- Kidney and liver damage
- Alteration of genetic material
- Lung cancer
- Death
The health hazards associated with exposure to Chromium are dependent on its
oxidation state. The metal form (Chromium as it exists in this product) is of
low toxicity. The hexavalent form is toxic. Adverse effects of the hexavalent
form on the skin may include ulcerations, dermatitis, and allergic skin
reactions. Inhalation of hexavalent Chromium compounds can result in ulceration
and perforation of the mucous membranes of the nasal septum, irritation of the
pharynx and larynx, asthmatic bronchitis, bronchospasms and edema. Respiratory
symptoms may include coughing and wheezing, shortness of breath, and nasal itch.
Carcinogenicity- Chromium and most trivalent Chromium compounds have been listed
by the National Toxicology Program (NTP) as having inadequate evidence for
carcinogenicity in experimental animals. According to NTP, there is sufficient
evidence for carcinogenicity in experimental animals for the following
hexavalent Chromium compounds; Calcium chromate, Chromium trioxide, lead
chromate, Strontium chromate,and Zinc chromate. International Agency for
Research on Cancer (IARC) has listed Chromium metal and its trivalent compounds
within Group 3 (The agent is not classifiable as to its carcinogenicity to
humans.) Chromium is not regulated as a carcinogen by OSHA (29 CFR 1910 Subpart
Z). ACGIH has classified Chromium metal and trivalent Chromium compounds as
A4,not classifiable as a human carcinogen.
Environmental effects of Chromium
There are several different kinds of Chromium that differ in their effects upon
organisms. Chromium enters the air, water and soil in the Chromium(III) and
Chromium(VI) form through natural processes and human activities.
The main human activities that increase the concentrations of Chromium (III) are
steal, leather and textile manufacturing. The main human activities that
increase Chromium(VI) concentrations are chemical, leather and textile
manufacturing, electro painting and other Chromium(VI) applications in the
industry. These applications will mainly increase concentrations of Chromium in
water. Through coal combustion Chromium will also end up in air and through
waste disposal Chromium will end up in soils.
Most of the Chromium in air will eventually settle and end up in waters or
soils. Chromium in soils strongly attaches to soil particles and as a result it
will not move towards groundwater. In water Chromium will absorb on sediment and
become immobile. Only a small part of the Chromium that ends up in water will
eventually dissolve.
Chromium(III) is an essential element for organisms that can disrupt the sugar
metabolism and cause heart conditions, when the daily dose is too low.
Chromium(VI) is mainly toxic to organisms. It can alter genetic materials and
cause cancer.
Crops contain systems that arrange the Chromium-uptake to be low enough not to
cause any harm. But when the amount of Chromium in the soil rises, this can
still lead to higher concentrations in crops. Acidification of soil can also
influence Chromium uptake by crops. Plants usually absorb only Chromium(III).
This may be the essential kind of Chromium, but when concentrations exceed a
certain value, negative effects can still occur.
Chromium is not known to accumulate in the bodies of fish, but high
concentrations of Chromium, due to the disposal of metal products in surface
waters, can damage the gills of fish that swim near the point of disposal.
In animals Chromium can cause respiratory problems, a lower ability to fight
disease, birth defects, infertility and tumor formation.
