What are Carcinogens?
What are Carcinogens?
By Ina Woolcott
A carcinogen is a substance that can bring on cancer in humans or animals. They can be chemicals, hormones, viruses, ionizing radiation, or solid materials. Substances that are known to aggravate or increase cancer risks, but don’t necessarily cause cancer, are also known as carcinogens. Although many things are considered to cause cancer, a substance is only considered carcinogenic if there is substantial evidence of its carcinogenicity.
Cancer is caused by the information that cells receive from their DNA being changed. Immature cells then gather in number in the body rather than differentiate into normal functional cells.
Carcinogens may be genotoxic, meaning that they physically interact with DNA to impair or change its structure. Ionizing radiation is genotoxic carcinogen.
Other carcinogens can change how the DNA conveys its information without changing its structure directly. Or situations may be brought about in a cell or tissue that makes it more prone to DNA damage from other sources. These are referred to as nongenotoxic carcinogens, or promoters. Oestrogen and arsenic are nongenotoxic carcinogens.
Other carcinogens e.g. nickel, may tamper with or increase the speed of cell division, changing structure or number of chromosomes in new cells after a cell divides.
Several changes in a cell’s DNA are generally required to change a normal cell into a cancer cell. Such changes can amass over time. Sometimes they can be repaired. It is also possible for cells to die before enough change occurs to make them cancerous. The places that change in the DNA of cancer cells are known as oncogenes and tumour suppressor genes. Oncogenes and tumour suppressor genes are particular locations on DNA that control a cell’s faculty to conduct its biological functions and to control its growth. Susceptibility to the action of carcinogens is complex and is affected by an individuals unique genetic make-up, by factors such as genetic heritage, nutrition, external exposures, physiology, and behaviour.
Some chemicals are carcinogenic in their original form - aka direct carcinogens - whilst some must be metabolised in the body to their active form - aka indirect carcinogens. In these instances, individual susceptibility to a chemical carcinogen is affected by the rate at which the chemical metabolises in the body into a cancer causing form or into a harmless form. The rate varies from one person to another.
Various carcinogens have been identified from studies on people in contact with various substances over time, including cancer in cigarette smokers and leukaemia in people inhaling benzene in the workplace. Asbestos, radon and certain pesticides are carcinogenic.
Chlorine is another carcinogen. It may be considered helpful for disinfecting water for bathing, drinking and swimming, but at the same time its by-products can cause a range of illnesses, including lung cancer.
Worryingly enough, carcinogens are to be found in everything from snack foods and drinks to certain plastics and everyday objects. Often, a substance isn’t identified as carcinogenic until it has been used or consumed by humans for many years. Many substances are possible carcinogens, and it can be hard to figure out just what is safe to eat, drink, breathe, or use, and what is not. And even more frequently when something is figured out as damaging to our health, it is played down by the producers as they don’t want to lose out on the big bucks.
Carcinogens have too been identified using laboratory animals exposed to them over a period of time. Saccharin was declared a carcinogen after experiments caused bladder cancer in rats, whilst aflatoxin was caused liver cancer in rats. Apparently some substances that are carcinogenic to laboratory animals are not carcinogens in people because of differences in how they are metabolised or differences in how they produce cancer.
It is important to remember that carcinogens do not lead to cancer after every exposure. Some cause cancer following high, prolonged exposure. Others may cause damage at lower levels and after shorter exposure periods.
Filed under: Dare 2B Aware, Health and Diet on November 28th, 2007
Leave a Reply