Carcinogens and heavy metal pollution

Cancer is a group of related diseases that begin in cells of the body. Normally cells divide to produce more cells when body needs them for development, growth and repair of cell damage. The process of continuous division and growth of cells keeps the body healthy and normal. However, at times, cells keep on dividing even when new cells are not required. These cells form a mass of tissue known as a tumour. The tumours can be either benign or malignant.

• Benign tumors: Benign tumours are not harmful all the time and can be removed surgically and they do not reappear. These do not endanger life.
• Malignant tumors: Malignant tumours are cancerous. Cells of these tumours are abnormal and they divide and re-divide without any control. They can invade and damage nearby tissues and organs. Cells from these tumours can break away and enter the blood stream or lymphatic system and spread from the original site to form new tumours in other organs.
• Leukemia and lymphoma are cancers which are initiated in blood-forming cells. Most cancers are named after the organ concerned e.g. Cancer that begins in lungs is lung cancer and the one in skin is known as melanoma.
• Carcinogens: The cancer-causing agents are known as carcinogens. Agents present in the environment are the environmental carcinogens.

Following are the major carcinogens we are continuously exposed to:

Tobacco

• Tobacco is a major carcinogen responsible for multiple cancers like stomach, liver, prostate, colon and rectum.
• Smoking tobacco or being regularly exposed to tobacco smoke is responsible for about 85 per cent of all cancer deaths.
• Smokeless tobacco like chewing tobacco and snuff cause cancer of the mouth and throat.
• Passive smoking: Exposure to environmental tobacco smoke also increases the risk of lung cancer for non-smokers.

Ultraviolet (UV) radiation

• Sun rays have a great amount of UV rays which are potential agents of skin cancer.
• Ozone which reflects back ozone rays from the atmosphere is being damaged by compounds like- chlorofluorocarbons and others.
• Avoiding exposure to direct midday sun light is perhaps the best way of reducing the risk of skin cancer. Wearing of a broad-brimmed hat, use of UV absorbing sunglasses and clothing to cover the body adequately also offers protection against UV.

Ionising radiation

• High levels of radiation like those from radiation therapies and X-rays, and from radioactive substances can damage normal (somatic) cells and increase the risk of developing leukemia and cancers of the breast, thyroid, lung, stomach and other organs.

Toxic metal poisoning What are Toxic metals?

Not all metals are compatible with organic compounds as human body is made up of organic compounds they pose a serious threat to life. Concentration of toxic metals can cause irreversible changes in human body.

• Toxic metals are dispersed in the environment through metal smelting industrial emissions, burning of organic wastes, automobiles and coal based power generation.
• Heavy metals can be carried to places far away from their source of origin by winds when they are emitted in gaseous form or in the form of fine particulates. Rain ultimately washes the air of metallic pollutants and brings them to the land and water bodies.
• Heavy metals may endanger public health after being incorporated in the food chain.
• Heavy metals cannot be destroyed by biological degradation. Incidence of heavy metal accumulation in fish, oysters, mussels, sediments and other components of aquatic ecosystems have been reported from all over the world.

The heavy metals often encountered in the environment include lead, mercury, arsenic, chromium.

• These are known to cause toxic effects in living organisms.

Lead

• Lead enters the atmosphere from automobile exhaust.
• Tetraethyl lead (TEL) was added to petrol as an anti-knock agent for smooth running of automobile engines.
• TEL has now been replaced by other anti-knock compounds to prevent emission of lead by automobiles.
• Lead in petrol is being phased out by introduction of lead free petrol.
• Many industrial processes use lead and it is often released as a pollutant.
• Battery scrap also contains lead.
• It can get mixed up with water and food and create cumulative poisoning.
• It can cause irreversible behavioural disturbances, neurological damage and other developmental problems in young children and babies.

Mercury

• Mercury kills cells in the body and damages organs that come in contact with mercury and thus impairs their functioning.
• Inhalation of mercury vapours is more dangerous than its ingestion.
• Chronic exposure causes lesions in the mouth and skin and also leads to neurological problems.
• Typical symptoms of mercury poisoning are irritability, excitability, loss of memory, insomnia, tremor and gingivitis.
• Exposure to mercury can be prevented by taking care that mercury is not released in the environment as well as by replacing mercury by other materials.
• Even mercury thermometers used earlier are being replaced by mercury free thermometers as the former pose a threat too.

Arsenic

• Arsenic is associated with copper, iron and silver ores.
• Arsenic is emitted from fossil fuel burning.
• Liquid effluents from fertiliser plants also contain arsenic.
• Ground water contamination with arsenic is very common in areas where it is present.
• People depending on ground water majorly get exposed to this pollutant.
• Chronic arsenic poisoning leads to loss of appetite, weight, diarrhoea, gastrointestinal disturbances and skin cancer.
• The water from underground sources contaminated with arsenic should not be used for drinking and cooking purposes.
• Surface waters are generally free from arsenic pollution and should be preferred for drinking and cooking.
• Alternatively the tube well/ hand pump water should be purified to remove arsenic before consumption.
• Techniques for removing arsenic from water are available.

Cadmium

• Mining especially of zinc and metallurgical operations, electroplating industries, etc. release cadmium in the environment. It may enter the human body by inhalation or from aquatic sources including fish, etc.
• It may cause hypertension, liver cirrhosis, brittle bones, and kidney damage and lung cancer.

Other Heavy metals

• Metals such as zinc, chromium, antimony and tin enter food from cheap cooking utensils.
• Preserved foods stored in tin cans also cause contamination by tin.
• Zinc is a skin irritant and affects pulmonary system.
• Problems of heavy metal toxicity can be prevented by avoiding the use of utensils made from materials containing these heavy metals or use of drinking water and fish polluted by the heavy metals.