What are carcinogens and why are they dangerous? You probably have been advised to avoid carcinogenic material in daily life, but have you ever wondered what it is and why it can be so dangerous? The definition of a carcinogen is a substance which can cause cancer (the “uncontrolled division of abnormal cells in a part of the body”) in living tissue. Carcinogens come in groups, defined as the following by the International Agency for Research on Cancer (IARC): Group 1: Carcinogenic to humans Group 2A: Probably carcinogenic to humans Group 2B: Possibly carcinogenic to humans Group 3: Not classifiable as to its carcinogenicity to humans Common carcinogens include tobacco, ultraviolet radiation and alcohol, all of which are Group 1 carcinogens. What makes these unsafe is the chemicals that they contain or release when used. At least 70 chemicals found in tobacco are confirmed to be carcinogenic, 3 of which are formaldehyde, arsenic and benzene. Formaldehyde is a colourless gas with a strong smell. It is frequently found in pressed-wood products, glues, the coatings of paper products and, tobacco. It has been deemed carcinogenic because studies have shown that workers who have been exposed to formaldehyde have a higher risk of myeloid leukaemia (the cancer of the white blood cells). Another study has shown that these workers had abnormal levels of mutations in their chromosomes of early white blood cells in their bone marrow. This suggests that there is likely a link between exposure to formaldehyde and developing leukaemia. Based on this evidence, the National Toxicology Program (NTP), a section of the United States' Department of Health and Human Services, listed formaldehyde as a known human carcinogen. Benzene exposure is also similar – it has been proven to be linked to the cancers of blood cells. The IARC has deemed arsenic to be a carcinogen, able to cause lung, bladder and skin cancer. Inorganic arsenic compounds have proved they cause cancer by affecting DNA repair mechanisms, and chromosomal anomalies are seen in those exposed to arsenic. The smoking of tobacco causes 15% of the UK’s cancer cases. UV radiation contains three main groups: UVA rays, UVB rays, and UVC rays, in order from lowest to highest energy. UVA rays have the least energy, meaning they can indirectly damage the DNA in cells and are usually responsible for ageing skin cells. The damage they cause is over long-term in most cases; however, it is suggested that they contribute to certain skin cancers. UVB rays have more energy than UVA rays, and they damage DNA more directly – this makes them cause the majority of skin cancers, in addition to being responsible for
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