Cancer and the Environment

Since cancer is not a single disease, it does not have a single cause. There are a variety of causes (better known as “risk factors”). These factors act over many years to increase an individual’s chance of developing cancer. They can include such things as age, race, gender, other genetic factors, exposure to tobacco, diet, physical inactivity, some viruses, radiation, medications, reproductive history and chemical exposures.

• Genetics play a role in most cancers. This means that a family history can be a risk factor for some types of cancers such as melanoma, prostate, breast and colon cancer. It is not unusual for several cases to occur within a family.
• Things we do in our daily lives can increase our chance of developing cancer. These factors, sometimes called “lifestyle factors,” include: cigarette smoking; heavy drinking; and having a diet that has excess calories, is high in fat, and contains few vegetables and fruits. Other lifestyle factors that increase risk have to do with reproductive patterns, sexual behavior, physical inactivity and excessive unprotected sunlight exposure.
• Cigarette smoking is a leading cause of cancer deaths in the U.S. today. In addition to being responsible for 80 to 90 percent of lung cancers, cigarette smoking is also associated with leukemia and cancers of the mouth, pharynx, larynx, stomach, esophagus, pancreas, kidney, bladder, cervix, and endometrium(lining of the uterus).

In the U.S.

From the 1930s until 1991, there was a steady rise in the overall cancer death rate in the U.S. The major cause of this rise was the increase in lung cancer; this was strongly associated with increasesin smoking. Death rates for many cancers—otherthan lung cancer—declined significantly between 1950 and 2008. These decreases are due to improvementsin the early detection and treatment of specific types of cancers,such as breast, colon, and cervical cancers. Even lung cancer rates for males have begun to decline since 1990. Between 1998 and 2008 the national cancer death rate fell 12.4 percent.

In Minnesota

The incidence of cancer (new cases) is monitored by the Minnesota Cancer Surveillance System. Created by the Minnesota Legislature in 1987, this statewide system collects information on all new cancers diagnosed in Minnesotans.

Minnesota’s cancer rates are similar to the national rates for most types of cancer. However, our lung cancer rates are lower compared to the U.S. population. This may be due to the fact that smoking prevalence in Minnesota was lower years ago. Today our smoking rate is similar to the national average and the gap between the national lung cancer rate and Minnesota’s rate is closing.

• In men, cancer incidence has declined in Minnesota since peaking in 1992, largely due to decreases in colorectal, stomach, prostate and lung cancer.

Odds of Cancer in Minnesota Males

	Diagnosis	Death
Prostate	1 in 5	1 in 30
Lung	1 in 14	1 in 15
Colo-rectal	1 in 18	1 in 45
Bladder	1 in 22	1 in 111
Any Cancer	1 in 2	1 in 4



• In women, overall cancer incidence rates increased slightly, largely due to increasesin melanoma, kidney, thyroid and lung cancer, which outweighed decreasesin colorectal, stomach, ovarian and cervical cancer. Despite these increases, breast cancer deaths decreased due to earlier diagnosis and improved treatment.

Odds of Cancer in Minnesota Females

	Diagnosis	Death
Breast	2 in 15	1 in 34
Colo-rectal	1 in 19	1 in 50
Lung	1 in 16	1 in 19
Uterine	1 in 32	1 in 167
Any Cancer	8.5 in 20	1 in 5

• Racial differences have been observed In Minnesota, as in other parts of the country. American Indian men have the highest cancer rates in Minnesota followed by African Americans. Among American Indians, smoking- related cancers of the lung, larynx, and oral cavity, as well as prostate, colorectal and cervical cancers are unusually common.

In Children

Many pediatric cancers occur early in life. Nearly 1 in 450 children will be diagnosed with cancer before the age of 15. Although some childhood cancers are associated with specific genetic and prenatal factors, in most cases the causes remain largely unknown.

It is believed that the organ systems of children are especially vulnerable to injury when undergoing periods of rapid growth and development. Factors that have been studied which play a role in childhood cancers include genetics, infectious diseases, prenatal conditions, environmental pollutants, and radiation. However, few studies have been able to show a consistent association between childhood cancer and these factors.

The types of cancer most often seen in children are different from those seen in adults.

The most common types of cancer in children:

• Leukemias
• Tumors of the brain and nervous system
• Lymph node cancers

The most common types of cancer in adults:

• Prostate cancer
• Breast cancer
• Lung
• Colo-rectal cancer

Some chemicals have been shown to cause cancer in animals, but there is not enough evidence to show that these chemicals cause cancer in humans. These chemicals are classified by IARC as “possible or probable (suspected) human carcinogens.”

Most of what we know about chemicals and cancer in humans comes from scientists’ observations of workers. Historically,the most significant exposures to cancer-causing chemicals have occurred in workplaces where large amounts of toxic chemicals were used. That is why safe work practices, personal protection, ventilation, and other controls are so important in protecting workers.

The amount of toxic chemicalsfound in food, air, soil, and drinking water are typically much lower than in the work environment. Therefore, cancer risk from environmental exposures is thought to be very low compared to the risk in occupational settings. In fact, the cancer risk from environmental exposures is so low that it is difficult to measure in scientific studies. It is not possible to determine the health of the environment by looking at cancer incidence or mortality in any given community. This is due to the many other significant factors (other than man-made pollutants) that determine a community’s cancer rates.

Scientists have compiled a list of substancesthat are either known or suspected of causing human cancer in The 14th Report on Carcinogens published in 2016. The report also describes where these substances are found in our environment.

There are several principles to keep in mind when you read an article or hear a news report about a new scientific study:

• A single study on the causes of cancer is seldom conclusive.

  There are many examples where one study identifies a risk, but later studies do not confirm it. Scientists look for multiple studies with consistent results before drawing conclusions. Each new study that you hear or read about adds to the body of evidence that scientists use for understanding the causes of cancer.

• The dose determines the poison.

  Scientific results are usually specific to a particular dose and route of exposure to a specific population being studied. Each individual’s chance of getting cancer from an exposure will be different depending on:

  • The amount of contaminant to which a person is exposed
  • The length of time a person is exposed
  • The number of times a person is exposed
  • How the person was exposed, such as by eating, breathing, or touching the substance
• Realize that uncertainties are always present in any study of environmental exposure and cancers.

  Due to the long latency period of cancer development, it is often difficult to collect information regarding exposures years or decades after they occur. Individual genetic differences, age, gender, and health status interact with lifestyle habits, as well as environmental exposures -- causing some people to be more sensitive to developing cancer than others. Because it is difficult to account for all of these variables and how they interact, “uncertainties” exist in the study of cancer and environmentalrisk factors.

• “Safety factors” or “uncertainty factors” are used to set acceptable levels of exposure.

  These factors take into account that certain individuals might be more sensitive to chemicals because of age (children and the elderly), genetic make-up, gender, diet, or health status. In addition, if mice or rats were used to test the chemical, the possibility is considered that people may be more sensitive to the cancer-causing effects of the substance than the rodents. To ensure that the acceptable level of exposure will protect the public, government agencies use safety factors that result in setting acceptable levels of exposure as much as 10,000 times lower than the levels used to observe cancers in mice and rats.

• Sometimes it is necessary to weigh risks vs. benefits.

  Some drugs are prescribed even though they may increase the risk of cancers in later years. An example is the use of certain drugs to treat cancer that increase the risk of secondary cancers. In these situations, the immediate benefits of treating an often imminently life-threatening disease have been determined to outweigh the risks of developing another cancer several years later.

Strict federal and state standards have been set to minimize our exposures to cancer-causing chemicals.

• At the Federal level: the U.S. Environmental Protection Agency (EPA) is charged by the U.S. Congress to set environmentalregulatory standards to protect human health and the health of the environmentfrom substances released into air, water or soil.
• In the State of Minnesota: the Minnesota Pollution Control Agency (MPCA) and the Minnesota Department of Health (MDH) have state programs to meet or exceed the federal standards to protect human health and the health of the environment. Activities include monitoring of air, water, and soil; conducting scientific research,setting standards, proposing rules, and enforcement.

The MDH Division of Environmental Health protects people from environmental hazards in drinking water, the home, workplace, and community by:

• monitoring health trends,
• assessing environmental exposures in communities,
• evaluating the scientific evidence and recommending safe exposure levels or other actions to protect public health,
• establishing standards for chemicalsin air (called Health Risk Values) and water (called Health Risk Limits) specifying levelsthat are considered safe, and
• providing education about hazardous substances for communities and health professionals.

Many hazardous substances,such as certain pesticides and metals, continue to be found in our environment from past and current use. Dioxin, for example, is widespread and persistent in the environment. Small amounts of dioxin can be found in our food and in our bodies. It will take many years for such persistent chemicalsto break down or be removed from the environment.

Ironically, one of the most potent and well-known cancer-causing chemicals, tobacco, is still largely uncontrolled. There are over 40 known or suspected carcinogens present in tobacco smoke. Progress has been made, however, in controlling exposure to secondhand smoke in public buildings and on the job.

Some carcinogensin the environment occur naturally and are much more difficult to control. Arsenic in underground rock can get into drinking water wells. Radiation from the sun is also a strong skin cancercausing agent. Sometimes our own actions offer the best control for exposure. When necessary, we can purify drinking water or use clothing and sunscreen to protect ourselves from the sun.

Many other agencies work to protect the public from harmful environmental exposures. For a listing of some of these agencies, see Other Resources.

Cancer is a personal tragedy for those affected. But what may appear to be an “outbreak” of cancer does not, by itself, signal a special risk related to something in the environment. Unfortunately, cancer is common in our population. Nearly half of Minnesotans will be diagnosed with cancer in their lives. Seeing different types of cancer usually means there are different causes.

It is not unusual to observe many cases of cancer in a single community or neighborhood, particularly if the community is aging. In fact, using information from our cancer surveillance system, we know that cancers frequently occur in clusters. Clusters often occur by chance and cancer cases are not evenly distributed throughout the population.

At MDH, patterns of disease are investigated by epidemiologists who study the frequency, distribution, risk factors, and control of diseases in populations. Epidemiologistslook for an unusual pattern of a specific type of cancer, rather than several different types. They find out whether the specific type of cancer is a primary cancer or a cancer that is the result of metastasis (spread from another organ in the body).

Using statistical methods, epidemiologists can determine whether a reported excess of cancer in a population is really more than would normally be expected to occur. They must also take into account other characteristics of the population that can affect disease patterns,such as age, gender, and heredity.

Most of our knowledge about the causes of cancer in people comes from studying large populations. Even our best scientific methods cannot tell us the cause of cancer in an individual, or in a small group of individuals.

For a printable version of this information, see Cancer and the Environment (PDF).

The National Cancer Institute (NCI) is the largest cancer research organization in the country; supports research at universities, hospitals, foundations, and businesses throughout the U.S. and abroad.

• Cancer Causes and Prevention
• Resources for Researchers

  NCI's SEER Program is the most authoritative source of information on cancer incidence and survival in the U.S.

• NCI’s Toll-Free Cancer Information Service for information about cancer and to request publications: 1-800-4-CANCER/1(800) 422-6237

The National Institute of Environmental Health Sciences (NIEHS) was established to reduce human illness caused by unhealthy substances in the environment.Activities include biomedical research, prevention, and intervention programs along with training, education, and community outreach efforts.

• National Toxicology Program (NTP): Coordinates toxicology research and testing activities within the U.S. Department of Health and Human Services(DHHS). Publishes a biennial Report on Carcinogens.

The Centers for Disease Control and Prevention (CDC) is an agency of the U.S. DHHS that is charged with promoting health and quality of life by controlling disease, injury, and disability:

• National Center for Environmental Health (NCEH)
• National Report on Human Exposure to Environmental Chemicals

The Agency for Toxic Substances and Disease Registry (ATSDR) is an agency of the U.S. DHHS that advisesthe EPA on hazardous waste issues. ATSDR has educational fact sheets about toxic chemicals.

• ToxFAQs
• Chemicals, Cancer, and You (PDF)

The International Agency for Research on Cancer (IARC) is part of the World Health Organization (WHO) and has a mission to coordinate and conduct research on the causes of human cancer.

The Environmental Protection Agency (EPA) is a government regulatory agency charged by the U.S. Congress to protect human health and safeguard the natural environment

• Indoor Air Quality (IAQ)
• Envirofacts
• National Pesticide Information Center
• EPA Hotlines

The American Cancer Society is the nationwide, community-based, voluntary health organization dedicated to eliminating cancer as a major health problem by preventing cancer, saving lives, and diminishing suffering from cancer, through research, education, advocacy, and service.

The Food & Drug Administration (FDA) monitors productsfor safety and helps safe and effective products reach the market in a timely way.

• The National Center for Toxicological Research
• FDA Consumer Hotline: 1(888) 463-6332

The Occupational Safety and Health Administration (OSHA) is an agency of the U.S. Department of Labor charged with preventing work-related injuries, illnesses, and deaths

The National Institute for Occupational Safety and Health (NIOSH) is an agency of the CDC that researches and makes recommendationsto prevent work-related disease and injury.