While misinformation abounds on the internet, there are reliable sources of information about cancer that you can trust. Here some of our favorites:

American Cancer Society

Centers for Disease Control and Prevention

American Associated for Cancer Research

American Institute for Cancer Research

Cancer Research UK

Dana-Farber Cancer Institute

International Agency for Research on Cancer

National Cancer Institute

National Institute for Environmental Health Sciences

Silent Spring Institute

Union for International Cancer Control

World Cancer Research Fund

Exposures, occupations, and other factors linked to cancer

The International Agency for Research on Cancer (IARC) determines whether exposures, compounds, nutrients, occupations, and other exposures are likely to cause cancer. They divide potential cancer-causing exposures into groupings based on the strength of the scientific evidence.

The IARC rating system is different than what is presented in the Cancer FactFinder because it considers a scientific review of specific exposures and occupations, while the FactFinder focuses on fewer topics that may be of interest to the general public, including topics that may represent misinformation.

The information provided by IARC may be difficult for the general public to understand, but it represents the best evidence available about whether a risk factor or exposure is related to cancer or not. Most of the topics studied by IARC are not in the FactFinder.

If you are exposed to anything on the IARC list that is likely to cause cancer, it does not mean you will get cancer. It only means is that there is evidence that you might be at increased risk of getting cancer, that we are not sure if the exposure causes cancer, and that more cancers would likely be seen in populations that are exposed. IARC does not have a category for “definitely does not cause cancer,” but the agency does note when a chemical has been well-studied without finding evidence that it causes cancer.

Usually, exposures are thought to cause one or more specific cancer types. For example, there is no doubt that cigarette smoking can cause lung cancer, so tobacco smoking is listed in “Group 1” as “carcinogenic to humans.”

Some things on the list are exposures we have all had: For example, sun exposure is known to cause skin cancer and is listed by IARC in Group 1. However, some sun exposure can have benefits (like getting enough vitamin D) and being out in the sun for exercise has health benefits, too. Therefore, the IARC groupings are not guidelines: They do not tell us if or when some limited exposure to things on the list may be OK, or how to guide our choices to weigh risks and benefits from the exposure.