According to the Centers for Disease Control and Prevention (CDC), millions of workers in the United States are exposed to carcinogenic substances. Occupational cancer is considered one of the leading causes of work-related deaths worldwide, with up to six percent of all cancers being linked to occupational exposure to carcinogens. In 2012, in the United States alone, there were between 45,872 and 91,745 new cancer cases that were caused by past exposure in the workplace.

Due to the latent nature of the disease, it is often difficult to determine the true figures related to occupational cancer. Nonetheless, reducing the levels of known or suspected carcinogens in the workplace can prevent cancers that occur as a result of occupational exposure.

What Is Occupational Cancer?

The Canadian Centre for Occupational Health and Safety (CCOSH) defines occupational cancer as "cancer that is caused wholly or partly by exposure to a carcinogen at work."

What Is a Carcinogen?

A carcinogen is a substance, mixture, or agent that can cause cancer or increase the risk of developing cancer. There are three different types of occupational carcinogens:

  1. Biological carcinogens – These include microorganisms such as viruses (e.g., hepatitis B and HIV). Viruses have been known to cause cancer either by decreasing the body's ability to control abnormal cells or by directly damaging cells.
  2. Chemical carcinogens – These chemicals may occur naturally (e.g., asbestos), be manufactured (e.g., vinyl chloride), or be by-products of industrial processes (e.g., polycyclic aromatic hydrocarbons).
  3. Physical carcinogens – These include agents such as ionizing radiation (e.g., X-rays and gamma radiation) and ultraviolet (UV) radiation.

What Are the Common Occupational Cancers?

The most common types of occupational cancer in the United States are:

  • Lung cancer (6.3-13%)
  • Bladder cancer (3-19%)
  • Mesothelioma (85-90% in men; 23-90% in women)

For a more comprehensive list of cancers associated with occupational exposures and their known carcinogens, check out: Cancer Sites Associated with Occupational Exposures.

What Are the Substances or Agents That Can Cause Occupational Cancer?

While identifying carcinogens may be a complicated process, there are, according to CCOHS, several reputable organizations that have complied and published lists of carcinogens known to cause occupational cancers.

1. The International Agency for Research on Cancer (IARC)

This is an agency of the World Health Organization (WHO). The IARC has classified substances and agents into five groups based on the strength of scientific evidence for carcinogenicity. These groupings are as follows:

  • 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
  • Group 4 - Probably not carcinogenic to humans

The IARC website provides lists of carcinogens organized alphabetically, by CAS Registry Number, and by cancer site.

2. The American Conference of Governmental Industrial Hygienists (ACGIH)

The ACGIH is an independent US organization responsible for assigning chemicals or agents to one of the following five categories:

  • A1 - Confirmed human carcinogen
  • A2 - Suspected human carcinogen
  • A3 - Confirmed animal carcinogen with unknown relevance to humans
  • A4 - Not classifiable as a human carcinogen
  • A5 - Not suspected as a human carcinogen

The ACGIH publishes its annual Guide to Occupational Exposure Values, a reference work that includes the carcinogenicity of various substances.

3. US National Toxicology Program (NTP)

The NTP is a US inter-agency program that publishes an annual list of agents they have evaluated and assigned to one of two categories:

  • Known to be a human carcinogen
  • Reasonably anticipated to be a human carcinogen

What Can Employers Do to Reduce Workers' Risk of Exposure?

Here are a few simple but effective steps employers can take to protect their employees:

  • Inform workers about the potential carcinogens that may exist in the workplace and educate them about the different types of cancers associated with them.
  • Eliminate or reduce workers’ exposures to carcinogens in the workplace by using a different agent or substance or by making changes to the work process.
  • Provide workers with the appropriate personal protective equipment or clothing. Remember, the use of personal protective clothing or equipment as a control measure should be a last resort.
  • Develop and implement education and training programs tailored to workers who are exposed to hazardous products or substances.
  • Ensure that all products are labeled and that a Material Safety Data Sheet (MSDS) is present for each product and they are readily available to workers.

What Can Workers Do to Reduce Their Risk of Exposure to Carcinogens?

Workers can undertake the following activities to help reduce their risk of occupational exposure to carcinogens:

  • Correctly use all the personal protective equipment and clothing provided by the employer when carrying out assigned job tasks (see What PPE Does My Employer Need to Provide? to learn about your right to safety equipment).
  • Follow the employer’s safety instructions when handling, storing, transporting, and disposing of hazardous substances and materials.
  • Follow the manufacturer’s guidelines for handling, storing, transporting, and disposing of hazardous substances and materials. Refer to the MSDS printed on the packaging. The MSDS contains information regarding potential hazards and health and environmental effects, as well as instructions for working safely with the material.
  • Participate in training programs regularly.
  • Immediately report any accidental exposure.

All cancers that originate from occupational exposure are preventable. While most occupations in the United States do not present a major risk for developing cancer, the cancer risk in some industries, such as chemical manufacturing and mining, can be significant. Protecting workers from workplace carcinogens, therefore, is essential and should involve a combination of education, training, surveillance, and strong regulatory control.