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Chromium - to take or not to take
The Sun, Tuesday, January 23,1996
A RECENT STUDY ON THE TRACE element chromium has triggered a furious debate between researches and health-conscious consumers.
It has been reported that chromium picolinate, a trivalent compound of chromium, can cause damage to chromosomes. Critics and researches are still arguing on the doses used in carrying out the experiments. While one reiterated that the dose under study was far higher than one gets from dietary intake, the other believed that the doses used were realistic.
So, what is chromium and how could it affect our health?
Chromium is a naturally occuring element found in soil, rocks and plants. it also occurs in volcanic dust and gases. Another source of chromium is chemical emissions in the manufacturing industry. Undoubtedly, this source leads to a significant difference in the concentration of chromium in rural areas compared with industrial sites. In some cases, the concentrations range from 0.1 nanogram per cubic metre in rural areas to 0.03 microgram per cubic metre in industrial cities.
Chromium normally exists in oxidation states ranging from chromium (II) to chromium (VI). However, the three major forms of chromium that commonly exist in the environment are chromium (O), chromium (III) and chromium (VI). Only the trivalent (III) and hexavalent (VI) forms are of biological significance.
The trivalent is the most common form found in nature. All forms of chromium can be toxic at high levels, but hexavalent compounds are more toxic than its trivalent form. Metallic chromium (O) is relatively non-toxic.
Chromium is extensively used in industries. Generally, the hexavalent form of chromate compounds are of greater industrial importance. Sodium chromate and dichromate are the principal substances engaged for the production of all chromium chemicals.
Some common uses of chromium and chromate compounds include:
in chemical synthesis;
for making steel and other alloys;
in the manufacturing of dyes and pigments;
in leather tanning;
for making bricks in furnaces.
In general, the two largest sources of chromium emission in the environment come from the chemical manufacturing industry and combustion of natural gas, oil and coal. Further potential sources of human exposure may also come from consumer products, industrial wastes and the working enviroment.
Some of the sources include:
cement-producing plants;exhaust emission from catalytic converters in automobiles;
waste from electroplating, leather tanning and textile industries indiscriminately discharged into lakes and rivers;
solid wastes from the manufacture of chromium compounds;
consumer products such as inks, paints and papers;
stainless steel and a few other alloy metals;
some toner powders used in copying machines.
Higher exposure to chromium may occur to those who work in related chromium industries and those who smoke cigarettes.
Physiologically, chromium is considered a trace element. It is an essential micro-mineral neededby the body. It is required for maintenance of normal metabolism of glucose, cholesterol and fat in humans.
Chromium is reported to be essential for optimum function of insulin in mammalian tissue. Chromium supplements improve or normalise glucose tolerance in diabetics and malnourished children who have chromium deficiency. Its concentration in human tissues decline with age.
Signs of chromium deficiency in humans include weight loss and impairment of the body's ability to remove glucose from the body. Once chromium is taken up by cells, it is very slow to leave.
Urinary excretion is generally less than 10 micrograms per day. Thus a certain amount of chromium may accumulate unnecessarily if its intake exceeds our daily requirements.
In one study, it was found that a single dose of chromium is retained in the liver of mice for at least 60 days. Normal levels of blood chromium concentration in humans is between 20 and 30 micrograms per litre.
Many nutritionists recommend that people should get all their chromium requirements they need from food. Although the minimum human daily requirement of chromium for optimal health is not known, an intake of 50 to 200 micrograms per day is regarded to be safe and adequate.
It is estimated that the average daily human intake of chromium is less than 100 micrograms per day. This is mostly obtained from food and water.
Chromium in food is mainly in the trivalent form. It is found in various types of food, including brewer's yeast, calf liver, cheese and wheat germ. It is thought that this type of chromium is an essential food nutrient when ingested in small amounts, although very large doses may be harmful.
The known harmful effects of chromium in humans have been attributed to be hexavalent form of chromium. Examples of hexavalent compounds are chromium trioxide, chromium anhydride, chromic acid and dichromate salts.
Hexavalent chromium is corrosive and causes chronic ulceration of skin surfaces. They produce corrosive burns by denaturation of tissue protein. Most reports describe the toxicity of chromium (VI) in the form of chromate of dichromate.
Chromium (VI) are soluble and are most readily absorbed from the gastrointestinal tract, skin and lungs. They have also been implicated as responsible for effects such as asthma, discoloration of teeth and inflammation of the skin.
In sensitive individuals, allergic chromium skin reactions occur readily with exposure and are independent of dose. People who are allergic to chromium may also have asthma attacks after breathing in high levels of either chromium (VI) or (III) fumes.
Systemic toxicity to chromium compounds occur largely from accidental exposures. The major acute effect from ingested chromium is kidney failure. The estimated fatal dose of a soluble chromate such as potassium chromate, potassium dichromate or chromic acid is approximately 5g.
Acute poisoning results in symptoms such as dizziness, intense thirst, abdominal pain, vomiting and shock. Ingestion of 0.5g of hexavalent chromium can result in serious toxicity.
In acute poisoning, death may occur due to the presence of urea in the blood. Chronic exposure from repeated contact of chromium to the skin can lead to inflammation of the skin with oedema.
Inhalation of chromium fumes over a long period of time causes irritation and ulceration. The most serious effect is development of lung cancer, which may occur 20 to 30 years after exposure.
One study showed that the death rate from lung cancer among workers exposed to chromium is 29 times that of the normal population. Animal studies have effectively demonstrated that chromium (VI) is a carcinogen. Animal studies also support the theory that the most potent carcinogen chromium compunds are the slightly soluble hexavalent compounds.
A review of chromium and cancer concluded that all hexavalent salts of chromium should be considered carcinogen. Highly water-soluble chromates may be more potent carcinogens than low-water-soluble salts. In contrast, chromium(III) compunds are found to be considerably less toxic than chromium (VI) compounds and are neither irritating nor corrosive. Long-term exposure of animals to chromium compounds, particularly chromium (III) compounds in drinking water or in the diet, has not resulted in any adverse effects.
The writer is a pharmacist at the National Poison Centre, Universiti Sains Malaysia, Penang.
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