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Did cancer exist before man-made chemicals were around to create it?
Category: Health
Published: March 27, 2015
By: Christopher S. Baird, author of The Top 50 Science Questions with Surprising Answers and physics professor at West Texas A&M University
Yes, cancer existed long before humans were able to create synthetic substances that cause cancer (cancer-causing agents are called "carcinogens"). Unfortunately, cancer is a natural part of life. Every multicellular creature on earth can get cancer, even in the remotest locations (yes, even sharks get cancer). While some man-made chemicals can indeed cause cancer, they are not the only causes. Strictly protecting yourself from every man-made carcinogen will not guarantee that you will never get cancer.
First of all, cancer is an umbrella term that encompasses hundreds of different diseases. What all of these diseases have in common is that normal cells are changed so that they begin to reproduce in an abnormal way, spreading through the organism and harming it. There is a vast array of mechanisms which can lead to cells reproducing abnormally. As with other biological processes, cell reproduction is ultimately controlled by the DNA of the cells. When a cell's DNA is changed, the cell is said to be mutated. Mutations are often harmless. However, if a mutation occurs in a portion of the DNA that controls cell reproduction, it can cause the cell to reproduce abnormally and pass on its mutation to the daughter cells. Any agent that leads to the mutation of DNA has the potential to cause cancer. Cancer-causing agents include (see the Notes Section at the end for more details):
- Natural chemical carcinogens such as tobacco, alcohol, arsenic, and lead
- Natural biological carcinogens such as the hepatitis B virus, human papillomavirus, and helicobacter pylori
- Natural mechanical carcinogens such as asbestos
- Natural radiological carcinogens such as radon, cosmic rays, and solar radiation
All of these carcinogens existed before humans developed the technology to create synthetic chemicals. Although human industrial activity can increase a person's exposure to natural carcinogens, this does not change the fact that these carcinogens are natural.
Even if you were somehow able to protect yourself from 100% of the carcinogens; whether natural or man-made; you could still get cancer. Cancer can form even when no harmful agents are present. Every time a cell reproduces, it must make copies of its DNA for its daughter cells. Due to the random fluctuations present in all molecular movements, copy errors can result during DNA replication even when no carcinogens present. In this way, DNA mutation is a natural part of cell replication. Many mutations are harmless. Some mutations are even beneficial and help drive evolution. However, mutations sometimes lead to cancer. Because of the presence of natural carcinogens in the environment, and because mutation is a natural part of cell replication, cancer happens even in the absence of man-made chemicals. Despite the fact that cancer is natural, we can certainly reduce our risk of cancer by avoiding tobacco, alcohol, arsenic, radon, ionizing radiation and other carcinogens; by eating more fruits and vegetables; by exercising regularly; by getting vaccinated; and by using sunscreen.
NOTES
Alcohol (ethanol), such as found in beer and wine, is the natural byproduct of yeasts fermenting sugar and can thus be found anywhere that yeast is found, including in overripe fruit and in palm tree sap. Alcohol is known to cause cancers of the mouth, throat, laryx, esophagus, liver, colon/rectum, and breast (source).
Arsenic is a chemical element found in many natural minerals. Natural arsenic is known to seep into groundwater, contaminating water sources used by humans, especially in regions of the world where natural arsenic levels are high. Arsenic has been found to cause cancers of the lungs, bladder, kidney, and skin (source).
Asbestos is a naturally-occurring silicate mineral that contains small, strong, needle-like fibers. When asbestos dust is inhaled, the fibers irritate and puncture lung cells, causing scarring and chemical imbalance that can lead to cancer. Asbestos is a mechanical carcinogen rather than a chemical carcinogen since it is the small size and hard, needle-like shape of the asbestos that enables it to damage cells rather than its chemical makeup. All minerals that have small, hard, needle-like fibers are suspected to be carcinogenic. Asbestos is known to cause cancers of the lungs, pleura, larynx, and ovaries (source).
Cosmic rays are high-energy particles emitted by distant supernovae outside of our solar system. Cosmic rays constantly rain down on the earth and have enough energy to ionize the atoms in biological cells, thereby potentially causing cancer. The earth's atmosphere provides somewhat of a shield against cosmic rays. However, people who spend a lot of time on airplane flights do not benefit as much from atmospheric shielding and have increased exposure to cosmic rays and solar radiation (source).
Helicobacter pylori (H. pylori) is a bacterium that grows in the mucus layer of the stomach. H. pylori has been found to cause stomach cancer (source).
Hepatitis B virus is a virus that affects humans who are exposed to infected bodily fluids. This virus has been found to cause liver cancer (source).
Human papillomavirus (HPV) is a virus that has been found to cause about 70% of cervical cancer cases. Additionally, HPV has been found to cause cancers of the vulva, vagina, penis, oropharynx, and anus (source).
Lead is a chemical element that occurs naturally in minerals, soil, plants, and animals. Since lead is a stable, solid metal under standard conditions, exposure to lead usually occurs through ingestion or inhalation. Lead likely causes lung cancer and stomach cancer, although the evidence is not yet conclusive (source).
Radon is a natural radioactive chemical element that is produced by the decay of radium in soil and rocks. As a gas, radon tends to collect in enclosures close to the ground, such as basements. Radon decays to other radioactive isotopes which decay and emit ionizing radiation. Radon is known to cause lung cancer (source).
Solar radiation contains ultraviolet radiation which damages skin cells. Ultraviolet radiation is also emitted by tanning beds. Prolonged exposure to ultraviolet radiation is known to cause skin cancer (source).
Tobacco, such as found in cigarettes and cigars, comes from the leaves of the tobacco plant. Tobacco is known to contain at least 50 different chemicals that cause cancer. Tobacco is the leading cause of preventable cancer. It has been found to cause lung cancer as well as cancers of the mouth, lips, nose, sinus, larynx, throat, esophagus, stomach, pancreas, kidney, bladder, uterus, cervix, colon/rectum, ovary, and blood (source).