To examine the clinical effects of environmental toxicants on living organisms by collecting and analyzing scientific data and identifying ways of detection and diagnosis.
This lesson is part of a three-part series on toxicology, the scientific study of poisons and their affect on biological systems. These lessons are based on Toxicology Enrichment Materials developed by Suzanne Conklin and found on the Society of Toxicology's website.
In the first lesson, Toxicology 1: Toxicology and Living Systems, students are introduced to the basic concepts and terminology of the science. Toxicology 2: Finding the Toxic Dose allows students the opportunity to conduct a toxicology experiment on a plant. Specifically, students determine the toxic dose of a chemical that will inhibit seed germination in Brassica rapa, a relative to cabbages and mustards. In the third lesson, Toxicology 3: Toxicology and Human Health, students investigate the effect of environmental tobacco smoke on human lung development. These lessons can be done in a series or they can stand alone.
In this lesson, students apply their knowledge about pollutants and human anatomy towards understanding ways in which normal body functioning is impaired by environmental toxicants. Students first review concepts in toxicology and lung anatomy using online problem sets. They then conduct an online investigation and analyze scientific data to examine the effect of environmental tobacco smoke on human lung development.
In this final lesson, students develop an understanding of how health and knowledge about the environment and substances are closely connected. Knowledge of science can inform our understanding of diseases, choices about nutrition and exercise, normal body functioning, and healthy practices. Research shows that some students may harbor misconceptions about health that are contrary to scientific fact. Middle- and high-school students’ wrong ideas about the causes of health and illness may derive from cultural knowledge. Students of all ages tend to believe that many factors they consider important to their health and life span are also beyond their personal control. (Benchmarks for Science Literacy, p. 346.)
The investigation requires that students know lung anatomy, including related vocabulary. The Lung Toxicology Problem Set is only a review of these concepts, including lung toxicology, diseases of the lungs, and environmental tobacco smoke. The activity also describes in basic terms the methodology employed for the environmental tobacco smoke experiment on mice. Thus, students should have an understanding of how microscopes are used in experiments, how slides are made, how data are collected, and how the scientific method is employed during experimentation.
The Lung Tissue Point Counting student sheet should be made into a transparency (preferably color) to demonstrate counting techniques to students before they begin the online investigation. If a transparency cannot be made, black-and-white copies of the sheet can be distributed to students.
Distribute the Toxicology Problem Set student sheet. This can be found on pages 6-9 of the Teacher’s Guide. Divide students into small groups of two to four. Have the students work with their group partners to answer all the pre-questions using their understanding of toxicology and knowledge gained through the past two lessons. These pre-questions expose students to the questions that they will need to answer online and get them thinking about toxicology. Do not grade the pre-question responses. Although students will work in groups, make sure that each student completes the student sheet.
Using the Toxicology and Human Health student esheet, students will go to the Toxicology Problem Set of the Chemicals and Human Health website, part of The Biology Project. Tell students that this problem set repeats the 11 topics on the student sheet. Each topic is associated with a multiple-choice question designed to help students learn the concepts. If the correct answer is selected, students will see the word "correct" along with reinforcing information. If an incorrect answer is selected, students will be given a tutorial page. Students can also go directly to the tutorial page by clicking on the tutorial button at the bottom of each page.
As students work through the online Toxicology Problem Set, they should record the correct answers to the questions in the second column of the table on their student sheets. Students will also explain the correct answers on their student sheets using guiding questions.
After students have completed the online activity, ask them to re-group with their partners. Have students compare their answers and explanations with those of their partners. Alternatively, students can turn in their sheets to be graded in accordance with the teacher’s guide.
- What are some examples of natural toxins?
- (Make a list of student responses.)
- What are some examples of man-made toxins?
- (Make a list of student responses.)
- Describe the main ways in which a toxin can enter the body.
- (Ingestion, inhalation, and absorption.)
- Which route may result in the greatest amount of toxicant in the blood?
- Why might ingestion and absorption not lead to the greatest amount of toxicant in the blood?
- (The stomach provides some protection against the toxicant when ingested. The skin is a protective barrier if a toxicant is being absorbed.)
- What does a dose-response curve tell us?
- (As the dose increases, the harm or response caused by the toxicant increases.)
- What questions did you get wrong in the pre-question section?
- (Answers will vary.)
- Did any of the answers surprise you?
- (Answers will vary.)
Tell students that they will work in pairs to conduct an online investigation on the effects of second-hand smoke on lung development. Before they begin the experiment, they will review lung anatomy and learn about lung development, respiratory toxicology, second-hand tobacco smoke, asthma, and lung cancer. Distribute the Lung Toxicology Problem Set (found on pages 4-6 of the teachers guide) to each student. Divide students back into their groups and have them answer the pre-questions.
Then refer students to the esheet again, which will guide them to the online version of the Lung Toxicology Problem Set. As they did with the first problem set, they will go through the problems online, correct their answers if necessary, and explain their answers. After completing the problem set, students should turn in their sheets to you to be graded in accordance with the rubric provided.
Tell students that they will do a virtual experiment online. As with any scientific endeavor, there will be a hypothesis, methods, data collection, results, and analysis associated with this experiment. Specifically, the experiment will look at the effect of second-hand smoke, or environmental tobacco smoke, on lung growth and development.
- What is second-hand smoke?
- (Second-hand smoke is a mixture of the smoke given off by the burning end of a cigarette, cigar, or pipe as well as the smoke that is exhaled from a smoker. Second-hand smoke is involuntary or passive smoking.)
- Who do you think is most affected by the ill effects of second-hand smoke?
- (Unborn babies in the womb, children and infants with developing lungs, people with respiratory problems such as asthma or lung cancer.)
- The experiment is looking at lung growth and development. Within a population, whose lungs are growing and developing?
- (Unborn babies in the womb, infants, and children.)
Place a transparency of the Lung Tissue Point Counting teacher sheet on an overhead projector for students to see. Tell students that this is what lung tissue looks like under the microscope. The white areas are the alveoli and the dark areas and boundaries are septal tissue. Tell students that point counting is a technique used for estimating three-dimensional structural data from two-dimensional data, in this case a flat image under the microscope. In point counting, a grid is laid over the sample image. Each cross hair represents a specific area. Point to the purple shaded box. Tell students that the area in this box is represented by one adjacent cross hair on the grid, marked with an orange dot. Thus, one can estimate how much space in the lung is taken up by septal tissue by counting the number of cross hairs that touch septal tissue. Tell students that in their online investigation, they will examine several microscopic lung tissue images with grids laid over them. They will measure septal tissue in the samples by counting each instance where a grid crosshair touches septal tissue.
Ask students to point out on the transparency instances where the grid crosshairs touch septal tissue. There are three instances (the grid crosshairs should be exactly on the septal tissue for a valid count).
Tell students that in their investigation, they will examine six samples of mouse lung tissue; three will be from the experimental group and three will be from the control group. Tell students that the methods of the experiment are described in detail online. Ask students:
- The experiment examines the effects of second-hand smoke on lung development, using mice as the study subject. How would you design such an experiment?
- (Allow students time to brainstorm ideas in the experimental methodology. Write students’ suggestions on the board, particularly if they suggest testing pregnant mice and newborn mice since their lungs are developing.)
- When conducting the experiment, how do you think treatment of the experimental group will differ from that of the control group of mice?
- (The experimental group will be exposed to second-hand smoke.)
- Do you expect there to be any differences between the lung tissues of the two groups? What do you expect?
- (It is expected that there will be some difference in the amount of septal tissue between the two groups. Students will probably say that they expect the experimental group exposed to second-hand smoke to have less septal tissue.)
- In a real-world scientific investigation, experimenters use 120 samples. Why do you think scientists use 120 samples when point counting?
- (Using more samples reduces variability in data collection.)
- As you count, you will know which slides are from experimental animals and which are from control animals. However, in the real world, a scientist would collect the counting data without knowing whether the slide is from a control or experimental animal. Why do you think scientists do this?
- (This prevents unconscious bias from occurring.)
Provide students with a copy of the Environmental Tobacco Smoke and Lung Development Activity student sheet. Divide students into pairs and have them conduct the online investigation. After students have completed the activity, discuss their answers to the questions on the student sheet.
Refer students to the “Understanding What You Learned” portion of the student esheet. Suggested answers for the questions posed in this section are provided below.
- Besides second-hand smoke, what are some everyday environmental pollutants that can affect our health?
- (Smog, ground level ozone, gasoline and diesel exhaust, cleaning supplies, pollen, insecticides, fungal spores from mold, and factory emissions.)
- Do you think that we experience chronic or acute exposures to these toxicants? Explain.
- (Most of our exposures to these common everyday pollutants are chronic. Acute exposure can come if someone is exposed to a heavy dose of cleaning supplies fume, for example.)
- What are some diseases or adverse health effects that can result from exposure to these types of toxicants?
- (Headaches, lethargy, asthma, emphysema, fatigue, nausea, dizziness, shortness of breath, coughing, allergies, fever, runny nose, watering eyes, vomiting.)
- Many of these symptoms can be caused by a lot of different things, including genetic diseases. How would a doctor be able to determine if the patient’s symptoms are related to exposure to an environmental toxicant?
- (The doctor would have to conduct a history and physical of the patient, asking him/her questions about what they do, what types of irritants they may be exposed to on an everyday basis, and what types of diseases he/she already has.)
What’s in My Backyard? is a three-part activity developed by the University of Arizona. It guides students through a basic database search for information on toxic substances in different geographical locations. Students use an Internet resource provided by the Environmental Protection Agency, called the “Toxic Release Inventory Query Form” which provides information about various facilities, including chemical reports, air emissions, surface water discharges, releases to land, underground injections, and transfers to off-site locations.
Have students conduct research on different types of diseases and disorders caused by exposure to environmental toxicants. Students can write papers, make Power Point presentations, diagrams, or class presentations to share their findings with the rest of the class.