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Connections

Activity Plan, Science 4

Epidemiology

 

Lesson Summary: In this activity, students will act as both epidemiologists and citizens of the towns of Smogsville and Greensville.  Using the Epidemiology Card deck, the students will determine how many people are healthy and how many have asthma or ear infections in each of the two towns.  They will then use the Epidemiology Worksheet to calculate the risks of having asthma or ear infections in each town and the risk ratios between the towns.

           
Subject:

Science: Science as Inquiry, Life Science

Health: Health Promotion and Disease Prevention, Analyzing Influencing Factors on Health

 

Grade Level:

  • Target Grade: 7 
  • Upper Bound: 9
  • Lower Bound: 6

 

Time Required: One class period.

Materials:

  • Epidemiology Worksheet
  • Epidemiology Card deck

 

Lesson Plan:

  • Before class, cut out the Epidemiology Card deck into cards and make two piles, one with the Smogsville (high air pollution) cards and one with the Greensville (low air pollution) cards, making sure that both decks are arranged in numerical order.  Set aside until later in the activity.
  • Ask students if they have ever heard the word epidemic and if they know what it means. Go over the definition for epidemic which is found below.
  • Now ask students if they know what Epidemiology is and what Epidemiologists do. Epidemiology may sound unfamiliar, but it simply means the study of the relationship between populations (groups of people) and diseases.  Epidemiologists often perform studies to determine the causes of diseases.
  • Today the students will be acting as epidemiologists and studying the town of Smogsville.  Smogsville has lots of air pollution and the citizens there complain that the air pollution is causing asthma and ear infections.  You need to investigate and determine if the air pollution could be the cause of the illnesses in Smogsville.
  • Hand out a Smogsville citizen card to each student.  On it the student will find their exposure status and their outcome status.  All citizens of Smogsville will have an exposure status of High Air Pollution.  The possible outcome statuses include Healthy, Asthma, and Ear Infections.  When handing out the cards start with number 1 and continue numerically until all students have a card.  The numerical order is important to ensure that the proper ratios are obtained.  If there are more than 30 students, start again with number 1.
  • Ask all the students with asthma cards to raise their hands and write this number on the board.  Do the same for all the students with healthy cards and students with ear infections cards.
  • Hand out the Epidemiology Worksheet to each student.  Have students copy the number of people with each exposure into the appropriate boxes on the worksheet.
  • Go over the definition of risk, and explain how it is calculated.
  • Help the students work through question 1 on the worksheet to examine sore throats, and demonstrate how to calculate the risk of getting an ear infection in Smogsville.  In this example, a personís risk of getting an ear infection if he/she lives in Smogsville is determined by dividing the number of people with ear infections by the total number of people in Smogsville.
  • Now have the students attempt to determine the risk of asthma (question 2) themselves.
  • Ask students if they think that asthma and ear infections are caused by living in Smogsville and being exposed to air pollution.
  • Explain to them while it may seem like the air pollution is causing the illnesses, this information by itself is not enough to really know that.  In order to see if living in Smogsville is associated with asthma and ear infections, they need to know how many people typically have these illnesses when living in an area without air pollution.  For this, epidemiologists use a control group.  A control group is a group of people that are similar to the ones you are studying but who havenít been exposed to the questionable chemicals.  For your study, you will be using the citizens of Greensville.  The citizens of Greensville are similar to the citizens of Smogsville in age, education level, and the types of jobs they have, but Greensville has little air pollution.
  • Hand out a Greensville citizen card to each student.  All citizens of Greensville will have an exposure status of low air pollution.
  • Ask all the students with asthma cards to raise their hands and write this number on the board.  Do the same for all the students with healthy cards, and students with ear infection cards.
  • The number of students with ear infections should be the same for both towns.  This shows that while students who live in Smogsville have ear infections, it is not because they live in Smogsville.  However, the number of students with asthma should be higher for students who live in Smogsville than in Greensville, which shows that the high numbers of asthma cases are associated with living in Smogsville and being exposed to high levels of air pollution.  While some students may understand this simply by looking at the numbers, they still need to go through the process of determining the risks and risk ratios.
  • Have students answer questions 3-5 on the worksheet to determine the risks of ear infections and asthma in Greensville.
  • Go over the definition of risk ratio, how to calculate a risk ratio, and what different risk ratios mean.
  • Now have students answer questions 6-9, in which they determine the risk ratio for sore throats and asthma and interpret their results.
  • Ask the students if they can remember any of the air pollutants mentioned in the PowerPoint that cause cancer.  One of these is Benzene.  Both the Environmental Protection Agency and the Center for Disease Control say that Benzene causes cancer, especially a particular kind of cancer called Leukemia.  But how did they determine that Benzene is what caused the cancer and not something else?  They must use epidemiological studies to determine Relative Risks just as we have done for asthma and sore throats.  These studies showed that in groups of people who were exposed to Benzene, more people had leukemia than in groups that were not exposed.
  • Now have students finish the worksheet by answering questions 10-13 about benzene and risk ratios.

 

Vocabulary / Definitions:

  • Epidemic: An outbreak of a disease that spreads rapidly, widely, at a level above normal.
  • Epidemiology: The branch of medicine that deals with the study of the causes, distribution, and control of disease in populations.
  • Risk: The probability of experiencing harm, illness, or loss.  It is calculated by dividing the number of people with the illness by the total number of people in the population being studied.
  • Risk Ratio: The relative measure of the difference in risk between the exposed and unexposed populations.  It is calculated by dividing one risk (usually of exposed) by another (usually the control).  A Risk Ratio of 2 means that the numerator population is two times as likely as the denominator population to have the problem.  A Risk Ratio of 1/3 means that the numerator population is only 1/3 as likely to have the problem as the denominator population.  A Risk Ratio of 1 means that both groups are equally as likely.


References:

  • http://www.epa.gov/iris/subst/0276.htm.

 

TEKS:

Science:

7.2 (C) Organize, analyze, make inferences, and predict trends from evidence

7.3 (D) Evaluate researchís impact on scientific thought, society, the environment

7.4 (A) Collect, analyze, and record information to explain a phenomenon

7.4 (B) Collect and analyze information to recognize patterns

 
Health:
7.3 (B) Analyze risks for contracting specific diseases  
7.4 (A) Analyze and use health information   
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