Cancer Facts and Cancer Clusters
version of this fact sheet (PDF,
What is cancer?
Cancer is a group of more than 100 different diseases characterized by
uncontrolled growth and spread of abnormal cells. Each type of cancer has
a different rate of occurrence, causes, and chances for survival.
Therefore, no one should assume that all types of cancer in a neighborhood
or community share a common cause.
How common is cancer?
Cancer is the second leading cause of death in the United States,
following heart disease. According to the American Cancer Society, about
30% of Americans now living will eventually develop cancer. Over the
years, cancer will strike about three out of four families. Given these
statistics, it is not surprising to know several people in a neighborhood
or workplace who have cancer.
How does age affect cancer rates?
While cancer occurs in people of all ages, cancer rates rise sharply
among people over 45 years of age. In communities where the majority of
residents are over 60 years of age, scientists would expect more cancer
than in a neighborhood of mixed ages.
What causes cancer?
The causes of most cancers are not well understood. Scientists know
that many cancers are influenced by a combination of factors, including
the environment, heredity, and behaviors related to how we live, called
lifestyle behaviors. Lifestyle behaviors that increase cancer risk
- Tobacco use, such as smoking or chewing tobacco
- Drinking more than two alcoholic beverages per day
- Nutrition – a diet lacking fresh fruits, vegetables and whole
- Physical inactivity
- Excessive exposure to sunlight
Other factors that can increase a persons cancer risk are a family
history of cancer, certain infectious diseases (e.g., hepatitis B, human
immunodeficiency virus (HIV), human papillomavirus (HPV)) and hormonal
factors (for women, high cumulative exposure to estrogen). Finally, work
exposure to some chemicals increases the risk for certain cancers.
How do environmental factors affect cancer deaths?
Many people believe that cancer is usually caused by exposure to toxic
substances in the environment. However, most cancers are affected by
lifestyle factors. It is not known the exact impact of environmental
pollutants on cancer development, but estimates suggest less than 10% of
cancers are related to environmental factors.
Is cancer related to exposures that happened many years ago?
Cancer does not develop immediately after contact with a cancer-causing
agent. Often there is a long time period, such as 15 to 30 years, between
the exposure to a carcinogen (a cancer-causing substance) and medical
diagnosis of cancer. This makes it very difficult to track what caused the
cancer. Cancers are usually related to long-term lifestyle factors (like
smoking) or significant exposure to a carcinogen for many years.
What is a cancer cluster?
A cancer cluster is an unusual number of the same type of cancers
occurring over a given time among people who live in the same geographical
area or workplace. The concern that a cancer cluster may exist usually
occurs when someone's spouse, neighbor, or friend is diagnosed with
cancer. This often brings an awareness of others who have any type of
cancer and a desire to answer the question, "Why?"
Has an environmentally related cancer cluster been found in Wisconsin?
To date, the Department of Health Services (DHS) has not
identified an environmentally caused cancer cluster in Wisconsin. It is
not uncommon for people to suspect that the cause of all cancers is some
toxic substance in the environment or workplace.
Even if there is an unusual number of a certain cancers in a community,
it shouldn’t be assumed the cluster was caused by exposure to an
environmental carcinogen. This cluster may have occurred simply by chance
or from unrelated causes-- such as smoking. It is hard to investigate a
cancer cluster and track past environmental exposures because people often
change their residence. For example in the 1990 census, over 50% of people
reported living somewhere else five years ago.
What is being done about cancer in Wisconsin?
The DHS, hospitals, and other agencies are actively tracking cancer
rates and locations. Health professionals at DHS and other organizations
are committed to promoting cancer prevention behaviors, while
investigating other possible causes of cancer. The public should also
continue to report environmental contamination to the Department of
Natural Resources for appropriate action.
For more information (including what you can do to prevent cancer)
Back to Environmental Health Resources