Introduction / Background
This case was developed for use in a physical geology course. The class has fewer than 20 students; most of them are not science majors and are taking the course to meet general education requirements. Minerals are the first major topic covered in the semester, and this case is the last component of the class discussion of minerals. The case also could be used in environmental science, environmental geology, and environmental health courses, or even in mineralogy.
My students found this case interesting for two reasons. First, they have (almost) all heard of asbestos, but know little about it. Second, our community college is located in Madison County, Illinois, the litigation capital of the country. The case is based on an actual case tried in Madison County and reported about in the Madison County Record.
The main purpose of the case is for students to relate mineral properties to their real-life uses and hazards. While doing this, students are forced to think about the relative health hazards of the different asbestos minerals, the importance of exposure amount and time, and how to assign responsibility in asbestos exposure cases.
Objectives
Upon completion of this case, students will be able to:
- Distinguish between asbestiform minerals, non-asbestiform fibers, and asbestos as defined by laws and regulatory agencies.
- Compare and contrast the five different varieties of amphibole and one type of serpentine that are regulated as asbestos. Comment specifically on each mineral’s structure, how the mineral forms fibers, and the qualities of each mineral’s fibers.
- Identify the properties that make asbestos useful and the properties that make it harmful. Discuss how specific mineral properties lead both to the usefulness and harmfulness of asbestos.
- Describe (in general) how asbestos enters the body and causes harm. Summarize the conditions under which asbestos exposure most likely will lead to disease.
These objectives are examined in greater detail in a separate password-protected Detailed Analysis.
Classroom Management
This case takes about 1.5 class periods to teach. Table 1, below, summarizes the timing of the case. The table is followed by a detailed description of the activities summarized in it.
| Time | DAY 1 (30 minutes) |
|---|---|
| 2 mins | Students read case |
| 10 mins | Students brainstorm in groups |
| 5 mins | Students share questions with class; instructor lists questions on board |
| 5 mins | Instructor assigns questions to groups. |
| 8 mins | Instructor discusses: • Minerals that form asbestos • What fibers are and how they form (cleavage, growth habit, rolled sheets) • How fibers get into the lungs, and why they aren’t removed |
| Time | DAY 2 (40 minutes) |
| 5 mins | Student groups formulate answers to the assigned questions |
| 15 mins | Students present answers to class |
| 15 mins | Instructor poses the following question to students for discussion: “Do you think that Adelaide Martin will win her lawsuit? Why or why not?” |
| 5 mins | Instructor assigns follow-up assignment |
Day 1
During the first day, only a half-hour is required for the case.
1. After students have read the case, the instructor should arrange them into groups of 4–5 to discuss the two questions at the end of the case.
2. Next the instructor asks the students to share their answers to the first question (“What questions do you think Cheri might have about asbestos?”) as a class while writing their responses on the board. Table 2 lists the categories of questions about asbestos that are likely to result from the students’ brainstorming session. If students are reluctant to participate, the instructor can prod the students to come up with all of the questions in the table below. The last column lists useful resources that are listed by number in the Website Suggestions for Students section of the References. (The password-protected Detailed Analysis provides answers for these questions.)
| Category | Representative Questions | Resource |
|---|---|---|
| Health effects of asbestos | How are people exposed to asbestos? What happens to lungs exposed to asbestos? How long must a person be exposed to asbestos in order to develop lung disease? |
Websites 1, 2, 3, 4 |
| Characteristics of asbestos minerals and differences between the minerals | What minerals are the various kinds of asbestos? What properties of these minerals make them harmful? Are all asbestos minerals equally harmful? | Instructor answers these |
| Use of asbestos | What products contained asbestos? What properties of asbestos made it useful? Why would asbestos be used in drywall joint compound? Who is at risk for asbestos exposure? | Website 6 |
| Safety of asbestos replacements | What do today’s joint compounds contain? Are they safe? If not, are there ways to handle them safely? | Website 5 |
| Problems in determining causes of health problems and determining liability | How can we determine the cause of lung disease? What is the length of time between asbestos exposure and lung disease? | Website 1 |
| History of asbestos use | When did people first learn that asbestos caused problems? When was its use banned? | Website 6 |
3. Next, assign each group approximately three questions to answer before the next class period. Direct the student groups to decide among themselves who in the group will be responsible for attempting to answer which questions at home. Groups may also be encouraged to assign more than one person to look for answers to the same question so that the answers can be compared and formulated into a group answer. The instructor also should provide suggestions of helpful websites that students can use to look for answers (e.g., OSHA, EPA, etc.).
4. During the remainder of the class, the instructor answers some of the questions that may be difficult for students to answer. Specifically, the instructor defines the minerals involved, summarizes the characteristics of these minerals, and summarizes how the fibers enter the lungs. As part of this, the instructor can show visuals of asbestos minerals (USGS, 2008).
Day 2
On the second day, about 40 minutes will be needed for the case; in a larger class, more time might be needed for discussion
1. In their groups from the previous day, have students share and compare the answers they found to their assigned questions. Tell them they need to prepare an answer to present to the entire class.
2. Ask student groups to present their answers to the class.
3. As a class, discuss the question, “Do you think that Adelaide Martin will win her lawsuit? Why or why not?” Some of the guiding questions in Table 3 can be used to further the class discussion. (The password-protected Detailed Analysis provides possible answers.)
| Question 1: | What information would you want to know if you were on the jury? |
| Question 2: | Why is it hard to establish the liability of the Bind-It-Right Company? |
| Question 3: | How would this case differ if Adelaide’s husband worked for a company that made brake linings? |
| Question 4: | Imagine a case where there is almost no doubt that asbestos caused a person’s lung disease. Describe the plaintiff and the case. |
The following topics should come up in the discussion:
- Asbestos type: The joint compound contained chrysotile asbestos. Students should recall from the discussion that chrysotile is the least harmful type of asbestos and may not even cause mesothelioma.
- Exposure: Students should question if washing clothes would expose Mrs. Martin to harmful amounts of asbestos. When asked guiding question #1 from Table 3, students should wonder about such things as the cause of Mrs. Martin’s husband’s death, whether Mrs. Martin washed clothes in a way that would suspend the asbestos in the air, etc.
- The source of asbestos: The joint compound contained chrysotile asbestos, and most mesothelioma is linked to amphibole asbestos exposure. The class should wonder if Mrs. Martin might have been exposed to asbestos some other way. Students also might wonder how Mrs. Martin knew which product her husband used at work. Guiding questions #1 and #3 in Table 3 should help bring out some of these concerns.
- Time: More than 30 years have passed since Mrs. Martin’s husband worked with the joint compound.
4. The instructor should close the discussion by asking students if they think there is enough evidence to hold the Bind-It-Right Company liable for Mrs. Martin’s mesothelioma. Be prepared for students to ask about the real case. A summary of two examples of asbestos litigation similar to this case that the instructor may share with students is provided in the password-protected Detailed Case Analysis.
Follow-up Assignment
A possible follow-up assignment is to have students apply what they have learned about asbestos from the case to a different question, such as: A school board learns that a local elementary school building contains asbestos. What should the school board do? The students’ task is to write a plan that could be submitted to the school board. (See handout for the text of the assignment.)
Their plans should include the following:
- Asbestos is only harmful if airborne and inhaled. In their plans, students should mention that the site should be inspected in order to determine if the asbestos has been disturbed. They also should mention that large-scale asbestos removal may greatly increase the number of fibers in the air.
- The response will depend on several factors, including the condition of the asbestos and the type of asbestos.
- Any plan should involve educating the public about asbestos, especially the health effects of asbestos, that health risk increases with exposure amount, and that undisturbed asbestos is not harmful.
Blocks of Analysis
Definitions
Asbestos can be any mineral fiber. There are two main minerals that form asbestos: amphibole and serpentine. There are over 80 varieties of amphibole, but only seven grow as fibers, and only five are regulated (see Table 4; Gunter et al., 2007). Of these, grunerite and riebeckite were mined as asbestos; amosite and crocidolite refer only to asbestiform varieties of those two minerals. Anthophyllite, tremolite and actinolite exist as impurities in other mined industrial minerals, such as talc (Gunter et al., 2007). Similarly, there are several serpentine varieties. Of the three most common types, chrysotile is the only one that grows as fibers and was mined as asbestos (see Table 4). Chrysotile is almost always asbestiform.
| Mineral | Name of Asbestiform Variety | Mineral Formula |
|---|---|---|
| Amphibole | Grunerite (aka amosite, brown asbestos) | (Fe2+)2(Fe2+,Mg)5Si8O22(OH)2 |
| Riebeckite (aka crocidolite, blue asbestos) | Na2(Fe2+,Mg)3Fe3+2Si8O22(OH)2 | |
| Anthophyllite | Mg7Si8O22(OH)2 | |
| Tremolite | Ca2Mg5Si8O22(OH)2 | |
| Actinolite | Ca2(Fe2+,Mg)5Si8O22(OH)2 | |
| Serpentine | Chrysotile (aka white asbestos) | Mg3Si2O5(OH)4 |
Definition of mineral: Any natural, chemically homogeneous, and crystalline solid that usually forms inorganically.
Definition of fiber: There are different definitions of fibers. Historically, geologists considered fibers to have not only a large aspect ratio (ratio of length to width), but also to be flexible and possess a high tensile strength (Gunter et al., 2007). Regulatory agencies define fibers simply based on the aspect ratio; particles with an aspect ratio >1 are considered fibers. OSHA regulates fibers that are ≤5 microns long with an aspect ratio ≥ 3. Many asbestos minerals have aspect ratios greater than 20, and even as high as 1000 (Skinner et al., 1988).
Asbestiform minerals are fibers with longitudinal parting; they spall into individual fibers. Some non-asbestiform mineral fragments might meet the regulatory definition of fiber, but will lack the flexibility and strength of a fiber as defined by geologists.
Health Hazards of Asbestos
The processes that keep particles out of the lungs and clear particles from the lungs must be summarized in order to pinpoint the reasons why asbestos is problematic. First, large inhaled particles are trapped in the mucous and cilia found in the nose and throat, where they can be coughed back to the mouth. If small particles are inhaled into the alveoli, special white blood cells called macrophages encapsulate and phagocytize the particles. These processes clear approximately 99% of all inhaled particles (Gunter et al., 2007). However, fibers are more likely than other particles to elude clearance. Also, carbon monoxide from cigarette smoke impedes the body’s clearance mechanism, explaining why smokers are more likely to contract asbestos-related disease than non-smokers (Skinner et al., 1988). See Fubini and Fenoglio (2007) for an overview of what happens to inhaled particles in the lungs.
There are two characteristics of fibers that allow their entry into the alveoli. First, asbestiform fibers can easily be broken into smaller fibers. Fibers less than 5 µm in diameter can be suspended in air, and particles less than about 3 µm in diameter may reach the alveoli. Mid-size particles are captured in cilia of the nose and throat and removed with mucous. Small particles that reach the lungs are encapsulated by macrophages; the phagocytized particles cannot cause harm. However, macrophages, which have diameters of about 15–20 µm, cannot surround and encapsulate fibers with large aspect ratios (Gunter et al., 2007). Even though the fibers have very small diameters, their lengths give them an overall surface area exceeding the size of the macrophage.
Once in the alveoli, the fibers lodge into lung tissue, causing inflammation and scarring (asbestosis). The damaged tissue loses some of its gas exchange effectiveness. If the minerals dissolve or leach out of the tissue, lung damage will be halted and lungs may even heal. More insoluble minerals will remain in the lungs indefinitely. Exposure can lead to lung cancer, and occasionally to malignant mesothelioma, in patients with or without asbestosis. Cancers arise in patients about 30 years after being exposed to asbestos. Mesothelioma is fatal, and patients live only about a year after being diagnosed with the disease.
Most mesothelioma is a cancer of the pleural mesothelium (the lining of the lung cavity), although there is a more rare cancer of the peritoneum (abdominal cavity lining). Asbestos exposure is the main cause of pleural mesothelioma, and other factors, such as genetics, may determine whether or not someone contracts the disease (see reviews by Bianchi and Bianchi, 2007 and Hodgson and Darnton, 2000, and references therein). Some people (primarily women) with mesothelioma had no known exposure to asbestos. Inhalation of other particles (e.g., metals, rubbers, sugar cane) and minerals (e.g., zeolites), ionizing radiation and lung infections are just a few other possible causes of mesothelioma (Lange, 2004).
Although there is a strong link between occupational exposure to amphibole asbestos and lung cancer and mesothelioma (Hodgson and Darnton, 2000), researchers still debate whether or not exposure to chrysotile only causes lung cancer and/or mesothelioma (e.g., Yano et al., 2001; Yarborough, 2006).
Health Impacts of Different Types of Asbestos
Asbestos minerals are harmful only if they form fibers. This suggests that fiber shape and size are more important than chemical make-up in determining the safety of these minerals. Fibers must be small in order to be inhaled, but have high aspect ratios in order to survive the lungs’ clearance mechanisms. Because spalling reduces a fiber’s diameter but not its length, asbestiform fibers are the most hazardous.
The different structures of serpentine and amphibole explain their different fiber characteristics. Serpentine is a sheet silicate. Seemingly due to a size mismatch, the double sheets in chrysotile roll into fibers with diameters of about 25 nm (Skinner et al., 1988). Amphibole is a double-chain silicate, and in certain conditions crystal growth occurs primarily in the long-direction of the chains, forming fibers. The diameters of chrysotile fibers are larger than those of the asbestiform amphiboles, giving chrysotile larger aspect ratios. However, because amphibole fibers are more brittle than the flexible chrysotile, amphibole can break into very small pieces. Chrysotile often forms curved fibers whereas amphibole forms straight fibers. Fibers with curved shapes are more likely to get trapped in the skin of the throat and coughed back to the mouth (Skinner et al., 1988). Also, the short, curly, flexible chrysotile fibers are phagocytized by macrophages and removed from the body sooner than amphibole fibers; the straight non-flexible amphibole fibers are more likely to pierce lung tissue and migrate to the mesothelium (Plumlee et al., 2006). In addition to growing into fibers (growth habit), amphibole can break along the two cleavage planes parallel to the double chains, forming non-asbestiform fibers. Studies show, however, that these cleavage fragments do not cause health problems (Ilgren, 2004).
Another mineral property that determines the health impacts of asbestiform fibers is solubility; chrysotile is more soluble than amphibole within the lungs (Gunter et al., 2007). For example, Wood et al. (2006) found that chrysotile completely dissolved in simulated lung fluid (pH 6.5) in about 50 days. Tremolite, an amphibole, remained after 80 years. Chrysotile is believed to cause less harm than asbestiform amphibole because chrysotile remains in the lungs for a shorter time, due both to its faster dissolution rate and its more easily phagocytized morphology.
| Serpentine | Amphibole | |
|---|---|---|
| Structure | sheet silicate | double-chain silicate |
| Solubility | more soluble | less soluble |
| Size and Shape | larger diameter, curved | higher aspect ratio, straight, more brittle, so are more likely to break into smaller pieces |
| Formation of Fibers | rolled sheets | fibrous habit or cleavage products |
| Origin of Mineral | metamorphic rocks | fibers are found mostly in metamorphic rocks (Gunter et al., 2007) |
Detailed Analysis
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References
Cited References
- Bianchi, Claudio, and Tommaso Bianch. 2007. Malignant mesothelioma: Global incidence and relationship with asbestos. Industrial Health 45:379–387.
- Fubini, Bice, and Ivana Fenoglio. 2007. Toxic potential of mineral dusts. Elements 3(6): 407–414.
- Gunter, Mickey E., Elena Belluso, and Annibale Mottana. 2007. Amphiboles: Environment and health concerns. Reviews in Mineralogy and Geochemistry 67:453–516.
- Hodgson, John T., and Andrew Darnton. 2000. The quantitative risks of mesothelioma and lung cancer in relation to asbestos exposure. The Annals of Occupational Hygiene 44(8): 565–601.
- Ilgren, E.B. 2004. The biology of cleavage fragments: A brief synthesis and analysis of current knowledge. Indoor and Built Environment 13:343–356.
- Lange, John H. 2004. Letter to the Editor Re: Mesothelioma trends in the United States: An update based on surveillance, epidemiology, and end results program data from 1973 through 2003. American Journal of Epidemiology 160(8): 823.
- Plumlee, Geoffrey S., Suzette A. Morman, and Thomas L. Ziegler. 2006. The toxicological geochemistry of earth materials: An overview of processes and the interdisciplinary methods used to understand them. Reviews in Mineralogy and Geochemistry 64:5–57.
- United States Geological Survey, Denver Microbeam Laboratory. “Image Gallery II: Images of Fibrous and Asbestiform Minerals.”
- http://usgsprobe.cr.usgs.gov/picts2.html (Last accessed: February 1, 2008).
- Wood, Scott A., Anne E. Taunton, Charles Normand, and Mickey E. Gunter. 2006. Mineral-fluid interaction in the lungs: Insights from reaction path modeling. Inhalation Toxicology 18:975–984.
- Yano, Eiji, Zhi-Ming Wang, Xiao-Pong Wang, Mian-Zheng Wang, and Ya-Jin Lan. 2001. Cancer mortality among workers exposed to amphibole-free chrysotile asbestos. American Journal of Epidemiology 154(6): 538–543.
- Yarborough, C.M. 2006. Chrysotile as a cause of mesothelioma: An assessment based on epidemiology. Critical Reviews in Toxicology 36(2): 165–187.
Example of Asbestos Litigation
This case is loosely based upon a case tried in Madison County courts. Three articles published in the Madison County Record (all written by Steve Gonzalez and listed below) summarize the case. They are available online at: http://www.madisoncountyrecord.com).
- Gonzalez, Steve. March 2, 2006. Jury reaches defense verdict in Madison County trial. Madison County Record.
- Gonzalez, Steve. February 24, 2006. Bondex and Georgia Pacific begin defense in asbestos case. Madison County Record.
- Gonzalez, Steve. February 16, 2006. Laundry caused 84-year old’s asbestos illness, lawyers claim in Madison Country trial. Madison County Record.
- Supreme Court of Michigan. 2007. Miller v. Ford Motor Co. (In re Certified Question), No. 131517, 479 Mich. 498; 740 N.W.2d 206; 2007 Mich. LEXIS 1625, May 10, 2007, Argued, July 25, 2007, Decided, July 25, 2007, Filed.
General Information about Asbestos
- Demers, R., K. Gehle, T. Nastoff, and V. Rush. 2000. Asbestos toxicity. Case Studies in Environmental Medicine. US Dept. of Health and Human Services, Agency for Toxic Substances and Disease Registry, Division of Toxicology and Environmental Medicine. Available online at:
- http://www.atsdr.cdc.gov/HEC/CSEM/asbestos/index.html
- U.S. Environmental Protection Agency. “Air quality planning and standards.”
- http://www.epa.gov/oar/oaqps (accessed February 10, 2008).
- U.S. Department of Labor Occupational Safety and Health Administration. “Safety and Health Topics: Asbestos.”
- http://www.osha.gov/SLTC/asbestos/index.html (accessed February 10, 2008).
- Skinner, H.C.W., M. Ross, and C. Frondel. 1988. Asbestos and Other Fibrous Minerals. New York: Oxford University Press.
- Virta, Robert L. Some facts about asbestos. USGS Fact Sheet FS-012-01.
- Virta, Robert L. 2002. Asbestos: Geology, Mineralogy, Mining and Uses. U.S. Geological Survey Open File Report 02-149. 28 pgs. Available on-line at
- http://pubs.er.usgs.gov/usgspubs/ofr/ofr02149
Website Suggestions for Students
- 1. Agency for Toxic Substances and Disease Registry. “Asbestos.”
- http://www.atsdr.cdc.gov/asbestos (Last accessed: January 24, 2008).
- 2. Centers for Disease Control and Prevention. “Asbestos.”
- http://www.cdc.gov/health/asbestos.htm (Last accessed: January 24, 2008).
- 3. National Cancer Institute. “Asbestos Exposure: Questions and Answers.”
- http://www.cancer.gov/cancertopics/factsheet/Risk/asbestos (Last accessed: January 24, 2008).
- 4. National Cancer Institute. “Mesothelioma: Questions and Answers.”
- http://www.cancer.gov/cancertopics/factsheet/Sites-Types/mesothelioma (Last accessed: January 24, 2008).
- 5. National Institutes of Health National Library of Medicine. “Household Products Database.”
- http://hpd.nlm.nih.gov/health.htm (Last accessed: January 24, 2008).
- 6. U.S. Environmental Protection Agency. “Asbestos.”
- http://www.epa.gov/opptintr/asbestos (Last accessed: January 24, 2008).
Acknowledgements: This case was developed with support from the National Science Foundation under CCLI Award #0341279. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Date Posted: July 29, 2008.
Originally published at http://www.sciencecases.org/asbestos/asbestos_notes.asp
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