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What You Need to Know. What You Can Do.
Cover Page

Key Concepts

  • At least two-thirds of all cancers are caused by environmental factors.
  • One-third of all cancer deaths in the United States could be prevented by eliminating the use of tobacco products.
  • After tobacco, overweight or obese appears to be one of the most important modifiable causes of cancer.
  • Excessive alcohol consumption, poor diet, and physical inactivity are also factors that contribute to cancer.
  • Precautions can be taken in the home and workplace to reduce other harmful, possibly cancer-causing exposures.


This training addresses concerns about the connection between cancer and exposure to toxic substances in the environment. It contains information about which types of substances are known either to cause or likely to cause cancer, and what can be done to reduce exposures to them. It also explains how scientists discover which substances are likely to cause cancer. Although toxic substances may cause other health effects, cancer is the focus of this training.

At the end of this training, you will find information about the federal government agencies responsible for reducing exposures to harmful substances and where to go for more information. These agencies develop policies to limit our exposure to agents that can be hazardous to our health such as lead in gasoline and paint, asbestos in building insulation, bacteria in our water supplies, air pollutants, and pesticides. Some harmful exposures, however, result from personal choices or lifestyles.

The good news is that a large number of cancers can be prevented. It is estimated that as many as two-thirds of all cancer cases are linked to environmental causes. This number may even be higher. Many of these are linked to lifestyle factors that can be modified. For example,

  • We know that one-third of all the cancer deaths in this country could be prevented by eliminating the use of tobacco products.
  • In addition, about 25 to 30 percent of the cases of several major cancers are associated with obesity and physical inactivity.

National Cancer Institute (NCI)

National Institute of Environmental Health Sciences (NIEHS)

National Institutes of Health (NIH)

This training was created by scientists at the National Cancer Institute (NCI) and the National Institute of Environmental Health Sciences (NIEHS) in response to many public requests for information. The content has been guided by responses from a series of focus groups that were conducted prior to producing the booklet. People from local communities throughout the country participated in these groups.

NCI and NIEHS are 2 of the 27 institutes/centers that make up the National Institutes of Health (NIH), an agency of the Federal Government’s Department of Health and Human Services supported by your tax dollars. NIH is the major supporter of medical research in universities and academic centers throughout the country. To date, 102 Nobel Prize winners have been supported by funds from NIH, more than any other scientific institution in the world. For details, go to the NIH Web site at

NCI was established by Congress in 1937 as the Federal Government’s principal agency for cancer research and training. Research projects include a broad range of topics:

  • The cellular events in the development of cancer;
  • The role of infectious agents or other agents in the environment or workplace;
  • The role of genetic and hormonal factors;
  • The interactions between environmental agents and genetic factors in the development of cancer;
  • Improved imaging techniques and biomarkers in the blood or urine for the early detection of cancer; and
  • The role of diet and other chemicals in preventing cancer.

Additional activities include

  • Tracking cancer trends,
  • Coordinating studies to test new drugs, and
  • Supporting new drug and vaccine development.

Since the passage of the National Cancer Act in 1971, which broadened NCI’s responsibilities, the institute has built an extensive network that includes

  • Regional and community cancer centers,
  • Specialized cancer physicians, and
  • Cooperative groups of researchers throughout the country and abroad to test new prevention and treatment agents.

NCI’s mission also includes

  • The collection and dissemination of health information,
  • Programs to promote the incorporation of state-of-the-art cancer treatments into care of cancer patients, and
  • The continuing care of cancer patients and their families.

For more information, go to NCI’s Web site at

NIEHS was established by Congress in 1966 to reduce human illness caused by hazardous substances in the environment. The National Toxicology Program, which is headquartered at NIEHS,

  • Helps coordinate toxicology studies among Federal agencies and
  • Identifies substances that might cause cancer.

NIEHS conducts and supports

  • Extensive biomedical research,
  • Disease prevention, and
  • Intervention programs,

as well as

  • Training, education, and
  • Community outreach efforts.

NIEHS is a leader in understanding the effect of environmental pollution on

  • Birth and developmental defects,
  • Sterility,
  • Alzheimer’s and other brain and nerve disorders,
  • Pulmonary diseases,
  • Poverty and health, and
  • Cancer.

For more information, go to the NIEHS Web site at

The authors dedicate this publication to Dr. Susan Sieber Fabro (1942-2002), a scientist at NCI, who provided the leadership to make the booklet a reality.


Agency for Toxic Substances and Disease Registry (ATSDR)

The Agency for Toxic Substances and Disease Registry (ATSDR) acknowledges the work that the writers, editors, and reviewers have provided to produce this educational resource.


The use of trade names and commercial sources is for identification only and does not imply endorsement by ATDSR or the U.S. Department of Health and Human Services.

Web links to non-federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by the Centers for Disease Control and Prevention (CDC), ATSDR, or the federal government, and none should be inferred. CDC and ATSDR are not responsible for the content of the individual organization Web pages found at these links.


The original publication [PDF - 614 KB] and the instructional content of this training course are in the public domain. You are free to use text from the publication and adapt it to your needs. Please credit the NCI publication or the ATSDR training course as your source. Illustrations in this publication, however, may be owned by the artist. To inquire about permission to use any of the illustrations, please contact NCI's Office of Communications Services at (301) 496-4394 or write to

For more information about copyright permissions related to the use of NCI materials, refer to the NCI Web page “ Copyright and Reuse of Graphics and Text

Department of Health and Human Services

U.S. Department of Health and Human Services
Agency for Toxic Substances and Disease Registry
Division of Toxicology and Environmental Medicine
Environmental Medicine and Educational Services Branch

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