Above: Image © Daniel Rodríguez Quintana, iStockphoto

In 2012, cancer was the number one cause of death in Canada.

This hasn’t always been the case. Cancer is actually an ancient disease that has affected humans for millennia. However, it’s only in the past century or so that cancer has become common in Canada and the rest of the Western world. In the 1920s, more people in Canada died from tuberculosis or the flu than cancer! The same is true for the United States.

So what changes have lead to the higher occurrence ofs cancer in these two countries? Carcinogens have something to do with it. But so does the fact that people live longer today than ever before.

Did you know? The Canadian Cancer Society states that roughly 40% of Canadians will develop cancer during their lifetimes.

The Causes of Cancer

Most of your cells contain DNA. This is a set of instructions that tells the cell what to do, when to divide, and when to grow. Cancer is most often caused by a buildup of mutations (errors) in DNA. Mutations in DNA can distort the instructions. This can result in a cell that behaves weirdly, and grows and spreads uncontrollably.

One cause of these mutations is carcinogens. Carcinogens are chemicals, substances, or exposures that can potentially cause cancer. Examples of carcinogens include cigarette smoke, UV radiation from the sun or tanning beds, and even some viruses (like HPV).

However, mutations can also happen spontaneously. These types of mutations happen during DNA replication, which happens as your cells divide. Most often, the cell fixes these errors before they become problems. If the error can’t be fixed, the body can either eliminate this cell or stop it from dividing. These steps prevent the cell from dividing uncontrollably and becoming cancerous. In rare cases, none of these fixes happen. That’s when the mutations can lead to cancer.

But wait. Carcinogens have always been around. And errors during DNA replication have always been a possibility. This means that humans have always been vulnerable to developing cancer. So why has the rate of cancer increased in the past century?

Cancer Today

Part of the reason why certain types of cancer have become more common is that people are more exposed to certain carcinogens.

For example, lung cancer used to be quite rare. But in the late 1800s and early 1900s, cigarette smoking became more popular. As smoking increased, so too did the rate of lung cancer. It is now responsible for over 25% of cancer deaths in Canada - far more than any other cancer.

Meanwhile, according to the Canadian Cancer Society, skin cancer is the most common cancer in Canada - and it’s on the rise. This increase, particularly for people under 30, has been linked to more time in the sun and an increased use of tanning beds. Both of these are sources of UV radiation, which is a carcinogen.

However, another big reason why the rate of cancer has increased is that people have been living longer. In fact, the life expectancy in Canada has increased from 50 years in 1900 to roughly 80 years in 2012! This increase is due to various human achievements such as better safety measures, improved sanitation, and widespread use of vaccines and antibiotics. Today, it is rare for someone to die during their childhood or adulthood of an infectious disease like tuberculosis, polio, or the flu.

Unfortunately, an older society means an increased rate of cancer. In fact, one of the biggest risk factors for developing cancer is old age. The older you are, the more chances your body has to accumulate mutations and be exposed to carcinogens.

Did you know? Of all cancer deaths in Ontario in 2006, only 6% were in people under the age of 50.

However, medical researchers are constantly looking at ways to develop new treatment options, better screening methods, and preventative measures. This means there is hope that more people will survive cancer and continue to live longer lives.

Learn More!

About Cancer:

Canadian Cancer Statistics (2015)
Canadian Cancer Society’s Advisory Committee on Cancer Statistics

Cancer (2015)
World Health Organization

What is Cancer? (2015)
Nathan Michaels, CurioCity

Cancer in Ontario: Overview, a Statistical Report (2010)
Cancer Care Ontario

Cancer Cell Development
Canadian Cancer Society

Cancer Statistics at a Glance
Canadian Cancer Society

Carcinogens and Specific Types of Cancer:

Known and Probable Human Carcinogens (2016)
American Cancer Society

Cancer Fact Sheets (2012)
GLOBOCAN, World Health Organization

The history of the discovery of the cigarette–lung cancer link: evidentiary traditions, corporate denial, global toll (2012)
R. N. Proctor, Tobacco Control 21

Daniel Tarade

A Bosnian immigrant, I moved to Canada during my childhood years. I completed an Honour’s Arts and Science degree with a major in biochemistry at the University of Windsor in my hometown. During my undergraduate years, I worked as a research assistant, evaluating the anti-cancer activity of various novel chemotherapeutics. My early exposure to research evolved into a passion for studying cancer and I am currently enrolled in a PhD program at the University of Toronto, studying the role of oxygen in cancer progression. In addition to research, I also enjoy reading, Frisbee, and going for walks.

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Avatar  sarah

Great article. Very interesting!