Occupation and Cancer Risk
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Occupation and Cancer Risk

occupational cancer

Unfortunately, it’s not always easy to establish a link between occupation and cancer risk. Less than 2% of chemicals used in commerce have been tested for their potential to cause cancer. Further, the risk of developing cancer is influenced by a number of factors that are not clearly understood.

General Risk Factors for Cancer

According to the National Institute for Occupation Health and Safety (NIOSH), a person’s risk for developing cancer may be influenced by a combination of the following factors:

  • Personal characteristics, such as:
    • Age
    • Sex
    • Race
  • Family history of cancer
  • Lifestyle factors and personal habits such as:
    • Diet
    • Smoking
    • Alcohol consumption
  • Certain medical conditions
  • Exposure to cancer-causing agents in the environment
  • Exposure to cancer-causing agents in the workplace

These factors may act together or in sequence to cause cancer.

Establishing a Link

Sometimes, a number of people in a workplace will develop cancer within a relatively short period of time. However, this does not necessarily indicate that there is a cancer risk in the workplace. Cancer is a common disease, affecting one in two men and one in three women in the United States over the course of a lifetime.

In an effort to identify the role of possible occupational factors and cancer, scientists investigate cancer clusters. Clusters are defined as an unusual concentration of cancer cases in a defined area or time, according to NIOSH. Clusters may have a common cause or may be the coincidental occurrence of unrelated causes.

When evaluating a cancer cluster in the workplace, scientists tend to look for the following:

  • Several cases of the same type of cancer, especially if it is not common in the general population
  • The presence of a known or suspected cancer-causing agent, and, the occurrence of types of cancers that have been linked with exposures to these agents in other settings
  • Past exposures to possible cancer-causing agents in the workplace (often difficult to document)

However, according to Atul Gawande, writer for the New Yorker magazine article, “Cancer-cluster Myth,” examining cancer clusters hasn't shed much light on cancer.

"The problem is that when scientists have tried to confirm such causes, they haven’t been able to," says Gawande. "Raymond Richard, Neutra, California’s chief environmental health investigator and an expert on cancer clusters, points out that among hundreds of exhaustive, published investigations of residential clusters in the United States, not one has convincingly identified an underlying environmental cause.”

Cancers Associated With Occupational Exposures

The International Agency for Research on Cancer (IARC), an agency of the World Health Organization (WHO), has published information on cancer risks from individual chemicals, and mixtures of chemicals, in selected occupations or industries. They have classified chemicals and industrial processes in the following categories:

  • Group 1: Cancer causing (carcinogenic) to humans
  • Group 2A: Probably cancer causing to humans
  • Group 2B: Possibly cancer causing to humans

According to the IARC, cancers associated with various occupations or occupational exposures include the following:

Cancers Associated with Various Occupations or Occupational Exposures
CANCERSUBSTANCES OR PROCESSES
LungArsenic, asbestos, bis(chloromethyl) ether, chromium compounds, coal gasification, mustard gas, nickel refining, foundry substances, radon, soots, tars, oils, acrylonitrile, beryllium, silica
BladderAluminum production, auramine and magenta manufacture, rubber industry, leather industry, 4-aminobiphenyl, benzidine, naphthylamide
Nasal cavities and sinusesFormaldehyde, isopropyl alcohol manufacture, gas, nickel refining, leather dust, wood dust
LarynxAsbestos, isopropyl alcohol, mustard gas
PharynxFormaldehyde, mustard gas
Mesothelioma (type of lung cancer)Asbestos
Lymphatic and hematopoietic (blood cell producing) systemBenzene, ethylene oxide, chlorophenols, chlorophenoxy, herbicides, X-radiation
SkinArsenic, coal tars, mineral oils
Soft-tissue sarcomaChlorophenols, chlorophenoxy herbicides
LiverArsenic, vinyl chloride

The IARC evaluations are based on data from epidemiological studies in humans, bioassays in animals, and data from short-term tests and laboratory experiments.

Scientists Continue to Investigate Possible Cancer Risks in the Workplace

Efforts to identify and clarify occupational cancer risks continue. Although the majority of risks are associated with exposure to certain substances, particularly chemicals, scientists have looked at other factors, as well.

Women Working Night Shifts

For example, two studies published in the October 17, 2001 issue of the Journal of the National Cancer Institute found that women who worked night shifts (the “graveyard shift”) had significantly higher rates of breast cancer than women who did not. The occupational risk was not linked to exposure of chemicals on the job, but possibly to exposure to light and not sleeping during the night.

Airline Pilots and Flight Attendants

In the January 1998 issue of Radiation and Environmental Biophysics, researchers looked at data on cancer risk in pilots and flight attendants. While some studies found an elevated risk in this occupational group, other studies have not. Some scientists hypothesized that airline workers might have a higher risk for cancer due to cumulative radiation dose from increased exposure to cosmic rays. However, airline workers are subjected to numerous lifestyle factors that could also play a role in their risk, such as irregular working hours, inadequate diet, and disruption in circadian rhythms. To date, no conclusive evidence has been established on cancer risk in airline workers.

What Can You Do to Decrease Your Risk?

Identifying occupational risks for cancer is an ongoing process. Since it is often difficult to know if we are being exposed to cancer risks in the workplace, the best we can do is use the knowledge already at hand, and control the risk factors that we know we can control.

For example, we are largely in control of diet, smoking, alcohol use, and exposure to known cancer-causing agents. We can also get regular medical check-ups and follow the national guidelines regarding preventive tests like colonoscopy or mammography. The resources below can assist you in finding more information on cancer-causing agents.

RESOURCES:

International Agency for Research on Cancer
http://www.iarc.fr

The National Cancer Institute
http://www.cancer.gov

The National Institute for Occupational Health and Safety
http://www.cdc.gov/niosh/homepage.html

Occupational Safety and Health Administration
http://www.osha.gov

CANADIAN RESOURCES:

BC Cancer Agency
http://www.bccancer.bc.ca/default.htm

Canadian Cancer Society
http://www.cancer.ca

References:

Blettner M, Grosche B, Zeeb H. Occupational cancer risk in pilots and flight attendants: current epidemiological knowledge. Radiat Environ Biophys. 1998; 37:75-80.

Centers for Disease Control and Prevention, National Institute for Occupational Health and Safety, Occupational Cancer website. Available at: http://www.cdc.gov/niosh/occancer.html . Accessed on April 25, 2003.

Gawande A. The cancer-cluster myth. The New Yorker . February 8, 1999:34-37.

National Cancer Institute website. Available at: http://seer.cancer.gov/publications/raterisk/risks97.html . Accessed on April 25, 2003.



Last reviewed May 2008 by Igor Puzanov, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.


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