Cancer Concerns: in my community

Concerns regarding a possible cluster of cancer usually occur when someone’s family member or neighbor is diagnosed with cancer. This close contact with cancer often brings an awareness of others who also have cancer and may lead to the perception that there are an unusually large number of individuals with cancer in one’s community. Some people contact the New Jersey Department of Health and Senior Services or their local health department because of increased awareness about cancer and the search for cancer causes. This information addresses some key issues in evaluating cancers in communities.

Topics
Cancer is more common than many people realize
Cancer is not just one disease
The risk of having cancer is related to age
More than half of all cancers are related to lifestyle factors
Toxic substances and cancer
Cancers today are usually related to events that happened years ago
Most cancer clusters occur by chance
Experience in the US with cancer cluster investigation
Contact us about a cancer cluster concern

Cancer is more common than many people realize.      [top of page]

According to the American Cancer Society, more than one out of three Americans now living will eventually have cancer. As a result, over the years, cancer will strike most households. Because public health and medicine have conquered many infectious diseases, cancer has become the second leading cause of death in the United States, following heart disease. Given these statistics, it is not surprising to know several people in one’s neighborhood or workplace who have cancer.

Cancer is not just one disease.      [top of page]

Cancers are a group of more than 100 diseases characterized by uncontrolled growth and spread of abnormal cells. Different types of cancers have differing rates of occurrence and different causes. We cannot assume that all the different types of cancers in a community or workplace share a common cause.

The risk of having cancer is related to age.      [top of page]

While cancers occur in people of all ages, incidence rates for most types of cancers rise sharply among people who are over 45 years of age. When a community, neighborhood, or workplace consists primarily of people over the age of 45, and particularly over the age of 60, we would expect to see many more cancers than in a neighborhood or workplace with diverse ages. It should be noted, however, that cancer is also the second leading cause of death in children, with accidents the most frequent cause.

More than half of all cancers are related to lifestyle factors.      [top of page]

Cancers may be caused by a variety of factors acting alone or together, usually over a period of many years.

Scientists estimate that more than half of all cancers are due to lifestyle factors including cigarettes, drinking heavily, and diet (for example, excess calories, high fat, and low fiber). Other risk factors for some cancers include reproductive patterns, sexual behavior, lack of exercise, and sunlight exposure. A family history of cancer may increase a person’s chances of getting a cancer.

Toxic substances and cancer.      [top of page]

Although many people are aware that toxic substances in the home, community, or workplace can cause some cancers, most environmental health scientists currently believe that a relatively small proportion of all cancers are related to toxic substances. In order for environmental contaminants to cause cancers, or any other disease, there must be a completed pathway through which the contaminants could travel from their source, through the environment, to enter the human body through air, water, food, or direct contact with the skin. It is important that any environmental contamination that violates federal or state standards be rectified properly, whether or not such pollution is found to cause disease.

Cancers today are usually related to events that happened many years ago.      [top of page]

When a cancer is due to a contact with a cancer-causing agent, the disease does not develop immediately. For adults, there is often a long period, 10 to 30 years or even more, between the exposure and diagnosis of cancer. Since the cancers we see now are generally related to a lifetime of certain habits or exposures to carcinogens, it is usually very difficult to pinpoint what caused a specific case of cancer.

Most cancer clusters occur by chance.      [top of page]

Cancer, and other diseases, do not occur evenly over time and place. The vast majority of occurrences of increased or decreased rates of cancer are due to random variation, even when unusually high or low rates can be statistically confirmed. Therefore, we can rarely conclude that a statistically significant increase was caused by exposure to local environmental factors. Additionally, when the numbers of cancer cases are small, it is particularly difficult for statistical analyses or scientific studies to yield useful or valid information.

Experience in the United States with cancer cluster investigations.      [top of page]

In the 1970s, when state cancer registries were first being organized, many public health scientists and others hoped that observations of clusters of cancer in the community might lead to the discovery of specific causes of these cancers. Since then, thousands of statistical analyses and countless intensive studies have taken place throughout the U.S., mainly conducted by state, local, or federal agencies. With two possible exceptions, none of these cluster investigations has led to the identification of specific causes, even when scientists were able to show that there was a statistically increased number of cancers in a geographic area. The New Jersey Department of Health and Senior Services does active surveillance of geographic patterns of cancer, made possible in part by electronic reporting and the high reliability of the New Jersey State Cancer Registry. We hope that future surveillance of cancers in the population will lead to new opportunities for prevention and control of cancers.

Revised February 2005