Sample Expository Essay: Carcinogens

Essay Expository Essay

Cancer is one of the most troubling kinds of disease that exists in this world. There exist more than a hundred types of cancers and they can be found all over the body. In the United States alone, one out of three people is affected by cancer. About 600,000 people die of cancer each year. Many people lose their children, spouses, parents, relatives, and friends to this disease. This research paper will delve into one of the causes of cancer – carcinogens.

What are the causes of cancer?

Cancer is caused by certain changes or mutations to the DNA that is part of a cell. It may be caused due to the occurrence of uncontrollable cell division which spreads to surrounding cells, then progresses to surrounding tissues. The development of cancer cells is triggered by multiple changes in one’s genes.

These changes can be caused by different things like smoking, certain diet and physical activities, prolonged exposure to the sun, genetics, and carcinogens. More often than not, there is no obvious cause as to how an individual developed cancer.

What is a carcinogen?

A carcinogen can be defined as an agent responsible for endorsing cancer to one’s body.  The carcinogenic agent could be a substance, radionuclide, or radiation that promotes the development of cancer cells and helps in their propagation. This results from the damage of the genome or hampering of the metabolic processes of the cells.

A number of radioactive elements come in the carcinogens category but their cancer-causing characteristics depend on their radiation of gamma rays, alpha particles, etc. The amount of time a person is exposed to the substance, how the person was exposed, and the current health of an individual are also factors to how much a carcinogen can affect the body and cause cancer cells. The most commonly used and inhaled carcinogens are asbestos, some dioxides, and tobacco smoke.

Cancer can be defined as a disease in which damaged cells of the patient’s body do not die when they are supposed to, the growth of those cells becomes uncontrollable, and they alter the process of metabolism. Carcinogens are responsible for the proliferation of the risk of getting cancer by changing the metabolism of cells and damaging the DNA directly in cells.

Consequently, this hampers biological processes inducing uncontrolled cell divisions, which eventually lead to the formation of tumors. Damage to the DNA in usual cases would lead to a scheduled death of the cell; however, if there has been some damage to the programmed cell death pathway then the cell would not be able to prevent itself from becoming a cancer cell.

However, it should be noted that being exposed to carcinogens does not immediately and necessarily equate to the individual developing cancer. But, it is also not an impossible occurrence. It should be kept in mind that there are many factors that can influence the possibility of cancer cells developing due to carcinogens.

Historical Overview of Carcinogens

The early twentieth century marked the recognition of cancer-causing chemicals. Tobacco was the first one to be suspected as a cancer-causing agent but studies are yet to be conducted. Because, during that time, specific cancer-causing molecules had not been identified individually and their cellular targets were unknown.

At that time, it was clearly realized that it is impossible to reverse carcinogenesis happening in cells. The initial research lacked information on methods by which carcinogens cause cancer and they also lack information on changes in the molecule that ultimately led up to the development of tumors. Epidemiologic interpretations and animal experiments were responsible for the identification of carcinogens and they eventually led to experiments that established molecular mechanisms and reduction of exposure in humans.

Carcinogens history could be traced back to the recognition of scrotal cancer among chimney sweepers by a surgeon in London Percival Pott. He later characterized it as the constant irritating effect of soot and this was among the initial identification of occupational cancer. Later came the identification of lung cancer among miners of Black Forest in 1879 and urinary bladder cancer among workers of dye factories in 1895. This led to the research for substances causing cancer.

In 1930, a research group in London realized chemicals such as polycyclic hydrocarbons as responsible for cancer. The list has continued to grow since then. The beginning of the twentieth century marked the identification of carcinogenic action caused by radiation. Researchers of that time believed that the preemptive measures had not been taken properly.

However, this belief changed drastically after the bombing of Hiroshima and Nagasaki caused by the World War in 1945. A study on the survivors of the attack indicated that the exposure of the test cases to the ionizing radiations had resulted in the production of myelocytic leukemia and an increase in thyroid and other forms of cancer.

Tobacco was among the carcinogens that were identified at the initial level; however, the medical profession pays little attention to their threat when it was first identified. This situation also changed after World War II – when the mortality rate due to lung cancer increased drastically. Several cases in Britain and the United States of America indicated the rise in lung cancer as a consequence of cigarette smoking, which had gained popularity during the twentieth century, especially during the 1940s.

In 1962, the previous events led to the official linking of smoking with cancer in both the United States and England. With increasing evidence regarding cigarette smoking causing cancer, it eventually led to the burgeoning of regulations and large financial claims in courts that were working towards limiting the consumer’s access to cigarettes. These resulted in bringing the rate of cigarette smokers in America down from 40% to 20% during the 1980s to the 1990s and soon led to the decline of lung cancer contracted by cigarette and tobacco smokers.

The 1960s and the 1970s marked the increase in the enthusiasm towards helping save the environment as well as proper classification of toxicology and carcinogenic substances. A large amount of publicity was given to mesothelioma resulting from asbestos and angiosarcoma of the liver resulting from vinyl chloride. Aniline dyes were recognized as responsible for the cancer of the bladder and aflatoxin was found in peanut mold for liver cancer. More attention was given to sun exposure resulting in melanoma or skin cancers.

However, proper formulation of toxicology and the reduction in the usage of environmental carcinogens remained controversial and it is still a matter of debate. Certain viruses were also characterized as carcinogenic. Cancers may also result from usual viruses. According to an estimate, studies indicate that 15-20% of all cancers result from constant infection with common viruses or other microbial organisms.

Cancer-Causing Substances

Various substances have proven to be carcinogenic with time. Those substances include Aflatoxin B1. This is produced by the fungus Aspergillus flavus which grows on stored grains, nuts, and peanut butter. This carcinogen is a naturally-occurring microbial carcinogen. Research has indicated that certain viruses such as Hepatitis B and human papilloma viruses are also carcinogenic.

The first evidence of these carcinogenic viruses to be found in animals was the Rous sarcoma virus. Peyton Rous discovered it in 1910. Other carcinogenic elements include Benzene, kepone, EDB, asbestos, and the waste rock from oil shale mining. During the 1930s, smoke from industrial zones and tobacco were characterized as carcinogenic including benzo-pyrene, nitrosamines found specifically in tobacco such as nitrosonor-nicotine.

Others included reactive aldehydes such as formaldehyde, which result from making plastics. Vinyl chloride is also carcinogenic and used in the manufacture of PVC. Another class of carcinogenic agents is Co-carcinogens; these substances individually do not cause cancer but combine to do so. 

Classification of Carcinogens

One of the jobs of the International Agency for Research on Cancer (IARC) is to identify the causes of cancer. Scientists of the IARC have classified carcinogens into various groups and the system they have developed is the most widely used classification system. The over 1000 cancer-causing agents have been grouped into four:

  • Group 1 – Carcinogenic to humans

This group includes a recorded 111 substances which show sufficient evidence of being able to cause cancer in human beings.

  • Group 2A – Probably carcinogenic to humans

This group includes 66 substances that can cause cancer in humans. However, there is limited or inadequate evidence as to the evidence of carcinogenicity for humans but shows sufficient levels of carcinogenicity for some animals.

  • Group 2B – Possibly carcinogenic to humans

This group includes 285 substances that might cause cancer. There is a limited amount of evidence of whether these substances are actually harmful to humans and even less sufficient evidence to prove their cancer-causing tendency in animals.

  • Group 3 – Not classifiable as to its carcinogenicity in humans

This group includes about 500 substances that are not responsible for causing cancer in humans but they can probably cause cancer in animals. However, evidence for these substances acting as a carcinogen for animals is also currently limited or inadequate.

  • Group 4 – Probably not carcinogenic to humans

This group includes those carcinogenic elements that have a high probability of not causing cancer in humans.

Types of Carcinogens

What are the types of carcinogens?

Humans can experience occupational, environmental, medical, and lifestyle exposures to carcinogenic substances. Some encounter these cancer-causing agents more than others due to their profession, habits, or where they live or work. Here are some types of carcinogens that everyone should be aware of:

  • Pollution. Indoor and outdoor pollution contains traces of carcinogens. Aside from the exhaust coming from vehicles, polluted air contains traces of metal and solvents. The dust that everyone is exposed to every day may also contain certain carcinogenic microscopic specs of certain harmful substances. Pollution is one of the only causes of cancer that cannot be completely avoided as it is a permanent part of today’s society.
  • Lifestyle habits. Factors like smoking, obesity, eating too much-processed food, drinking alcohol, and eating burnt food can be responsible for cellular changes that may lead to the development of cancer. Smoking or even breathing in someone’s smoke from a cigarette or tobacco can harm health. Excessive consumption of food – or processed and burnt food – may also cause cancer. 
  • Chemicals or substances. Some chemicals or substances that can be found and used at home or work may be carcinogens. An example of this is asbestos – a product that strengthens car parts, roofing, and the ceiling. Another example is formaldehyde which is used as an ingredient in many household products and may also be present in the furniture.
  • Environmental radiation. Ultraviolet rays caused by the sun or a tanning bed can cause severe damage to skin cells and thus produce cancer. Radon – a gas that naturally occurs in small amounts – is considered harmless but once it gets trapped in an enclosed space and is breathed in, may damage the lungs and lead to lung cancer.
  • Medical radiation. Some medical professionals are exposed to radiation in each of their shifts. Radiation can come from medical equipment like x-ray machines, ultrasound, ultraviolet, and even those that are used to treat cancer patients are carcinogenic.
  • Some medications. Certain drugs or medications especially those that are used for hormonal therapy and chemotherapy have a chance of raising the risk of developing cancer. However, this side effect does not affect everybody and should not discourage one from getting the needed treatment unless otherwise suggested by the doctor.
  • Viruses. Researchers have found certain viruses that damage the DNA, alter the immune system, disrupts the normal process of cell division, or cause chronic inflammation such as the human papillomavirus (HPV), hepatitis B and C, and human immunodeficiency virus (HIV).

Carcinogens are everywhere. It can be encountered in one’s daily life – or at some point in one’s life. Carcinogens can come from the sun’s rays, popular food products, home cleaning products, and even materials used to build one’s home. To fully protect oneself – even if the risk of developing cancer is not that high – it is recommended to restrict oneself from getting exposed to known carcinogenic or at least limit one’s exposure to them.

Avoiding getting sick in college is one of the major concerns of students. Even the slightest trace of an onset headache can be troubling as this feeling under the weather can disrupt at least a day’s worth of planned activities which includes extracurricular activities , doing projects, and studying up for upcoming exams. This is exactly why it is important to learn about carcinogens and other possible sources of sickness so that it can be avoided at all costs.

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Eldridge, MD, L., & Paul, MD, D. (2019, December 1). Types and Ratings of Different Carcinogens in Our Environment. Verywell Health.

National Cancer Institute. (2019, June 26). Environmental Carcinogens and Cancer Risk.

The American Cancer Society medical and editorial content team. (2020, November 6). What Is Cancer? American Cancer Society.

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