To describe environmental and hereditary factors that increase the chance of developing cancer.
Research shows that after education, students hold the misconception that human beings have cells inside of them, rather than being composed of cells themselves. As a result, students might perceive cancer as a group of foreign cells that are "invading" their normal cells, instead of knowing that cancer cells are simply normal body cells that have mutated. Students also might be unaware of the fact that all cells in every human being have the potential to become cancerous. Thus, students might think that cancer is a disease that you "catch" from others and the environment.
In this lesson, students read an article which describes communities in the United States that have been affected by high rates of cancer. The alleged causes for these cancers are environmental pollutants and industrial chemicals. Students will then read information about cancer written by scientists which describes hereditary factors that contribute to cancer development. Finally, students will read about some probable carcinogens and the risk factors for cancer. At the end of this lesson, students should be able to distinguish that there are both environmental and hereditary factors which influence a person's likelihood in developing cancer. Thus, it is difficult to say that any one thing is the cause of all cancers.
Before proceeding with this lesson, students should have an understanding of what cells are and that the genetic information is encoded within DNA. Students also should be familiar with the concept of genes and genetic mutations.
Tell students that the class will study cancer and look at the causes of the disease.
- What is cancer?
- Where have you heard of cancer?
- Who gets cancer?
- What causes cancer?
Discuss the fact that there are many types of cancer since cancer can develop in virtually any one of the body's tissues. Also point out that no race/gender/ethnicity/age group is excluded from developing cancer. When discussing question four, ask students to differentiate between hereditary and environmental causes of cancer.
Pass out a copy of the Cancer Risks student sheet to each student. Using the Cancer Risks student esheet, students will be directed to read the article, Toxicville.
Students should answer these questions individually as they read the article:
- What community/communities are being affected by cancer?
- Who is developing cancer?
- Explain the alleged causes of cancer according to the article.
- How have the communities reacted to the high incidence of cancer?
- How have local government and health agencies responded?
- What conclusions can you draw from the article about the relationship between cancer and the environment?
- What other types of information might you need to convince you that these cancers are due to chemicals and pollutants in the environment?
Allow students 5-10 minutes to share their findings and answers. Suggested responses and additional teacher suggestions are provided on the Cancer Risks teacher sheet. After this discussion, ask students:
- Besides the chemical pollutants in the environment, what other factors might have caused these students and children to develop cancer?
- Why doesn't everyone in these communities develop cancer?
To understand the hereditary causes of cancer, students should us their esheet to go to and read Understanding Gene Testing.
After completing this part of the lesson, discuss with students these questions from the student sheet:
- How do gene mutations occur?
- What are the factors that can determine the outcome of a gene mutation?
- Do most cancers result from random mutations in one's lifetime or from an inherited mutation?
Students have learned that cancer is caused by an abnormal change in a cell’s DNA. In the next part of the lesson, they will examine some of the things that can cause cancer and about environmental or behavioral factors that can increase a person’s risk for developing cancer.
Students will begin this part of the lesson by reading the following sections on the Known and Probable Carcinogens page of the American Cancer Society:
- What Is a Carcinogen?
- How Do We Determine if Something Is a Carcinogen?
Instruct students to answer the questions that pertain to this part of the lesson on their student sheet and discuss the answers with the class.
- According to the article, what causes cancer?
- What is a carcinogen?
- Do all carcinogens act directly on a cell’s DNA?
- Which two types of cancer studies are described in the article?
Using the esheet, students will then read Risk Factors. Instruct students to answer the questions that pertain to this part of the lesson on their student sheet and discuss the answers with the class.
- What is a risk factor?
- Describe some factors that are likely to play a major role in increasing a person’s risk of cancer.
- What are some behavioral choices that could affect your cancer risk?
- Describe some environmental factors that are discussed in the article.
Students should now have an understanding that all cells have the potential to become cancerous and that both environmental and hereditary factors contribute to the development of cancer. Moreover, students should be aware, after the readings, that it is difficult to correlate a single cause with cancer for any one person.
Assess student understanding by having students write in a journal or share their ideas with the class:
- Do you feel at risk for developing cancer? Why, or why not?
- Why does knowing about your environment help you understand your risk of developing cancer?
- If you are exposed to a certain industrial chemical or pollutant, does it mean that you will develop cancer?
- What choices might you make if you know that you have been exposed to such a chemical or pollutant or if you know that you carry a hereditary mutation?
Divide students into groups/teams and have them choose a media item, such as an advertisement for sunscreen, an anti-smoking commercial, or other item that makes a claim regarding cancer risks. Have the teams identify the various claims about cancer being made by each media item. Ask students to describe any evidence used by the media item to support its claims.
- Is this evidence satisfactory in supporting the claims made by this media item?
- What other evidence do you need?
- What experiments might you perform to test the claims of this media item?
- How do these advertisements affect the public's perception about cancer?
Cancer and the Environment: What You Need to Know and What You Can Do is a booklet that addresses concerns about the connection between cancer and exposure to toxic substances in the environment. Published by the National Institutes of Health, it contains information about which types of substances are either known to cause or likely to cause cancer. It also explains how scientists discover which substances are likely to cause cancer.