In the Classroom
Service–Learning General Chemistry: Lead Paint Analyses Laya Kesner and Edward M. Eyring* Department of Chemistry, University of Utah, Salt Lake City, UT 84112; *
[email protected] The concept of service–learning continues to gain importance in secondary and higher education (1–4 ). Service– learning attempts to form a connection between the knowledge a student acquires in the classroom and an application of that knowledge that benefits the community at large. It is this connection between the classroom learning and the service that differentiates service–learning from other volunteer activity. Such a connection may yield a variety of desirable results: The student who recognizes an immediate use for knowledge may become a more motivated learner and may voluntarily acquire advanced skills in the performance of her or his service. The student may enjoy a closer working relationship with the instructors than is usually possible in large undergraduate classes. The student may be evaluated (graded) on an activity more directly connected to future employment than the typical undergraduate exams. The student may receive personal satisfaction from performing useful service. The elements in the community benefiting from a service–learning project may be inclined more favorably toward the academic institution and toward advanced learning in general.
We report here a community service project carried out by general chemistry students at a Research I university that could be adapted for use almost anywhere and that definitely enhances student laboratory learning. Service–learning at the University of Utah is fostered by the Lowell Bennion Community Service Center. The Center encourages academic departments to create service–learning courses and sets quality standards for the classes. The Center also raises funds to maintain a staff and to provide an undergraduate teaching assistant for each service–learning course the first time it is taught. In the service–learning project described in this paper, the Salt Lake City/County Health Department was the agency served by the freshman students. First-term general chemistry students were selected for pedagogical as well as pragmatic reasons. A pedagogical goal of service–learning is to motivate students to learn by showing them an immediate use for the knowledge. It is advantageous, therefore, to expose them to the service–learning as early as possible in their chemical education. Many of the students major in subjects other than chemistry and will not progress to the sophomorelevel analytical chemistry class. The pragmatic reason is that because first-term students do not have a full schedule of weekly experiments, the service learning can be added without interfering with the regular laboratory schedule. The service–learning guidelines at the University of Utah require that the project be useful to a particular nonprofit agency. In this project, the City/County Health Department was interested in assessing the scope of the lead-paint problem in older neighborhoods and educating the public about the hazards of lead paint. Federal regulations in the United States 920
going back to 1979 prohibit the use of more that 0.06 wt% lead in house paint. Older homes are usually coated on their interior and exterior surfaces with multiple layers of paint. The earlier, deeper layers typically contain significant amounts of lead. Lead-paint surfaces in homes pose no significant health threats until either they are abraded by normal wear and tear or the house is remodeled. Boeckx (5) has described lead poisoning in children. Infants and pregnant women are particularly at risk when lead-paint dust is in their environment. The rapid growth of children facilitates the substitution of lead for calcium in their bodies, with the potential for long-term storage of the lead in bones. Chelation therapies exist for the removal of lead from the human body (5), but they cannot reverse permanent damage to the brain arising from chronic lead poisoning. Students can provide assistance in determining the extent of the lead problem in targeted neighborhoods and can distribute educational materials to the residents. The Environmental Coordinator of the local Health Department identified the geographical areas of interest in the city and provided lecturers to educate the students about the lead-paint issue. Recent papers (6, 7) describe undergraduate laboratory experiments that examine lead-based paints. The novelty of the present paper lies in the marriage of such student experiments with the service–learning concept. Preparations and Field Work The lead-paint service–learning project has been carried out twice, in the autumn of 1996 and the autumn of 1997, in different neighborhoods of Salt Lake City. Twenty-five students the first time and 40 students the second time (each group constituting approximately 15% of a large lecture class) registered for special laboratory sections in order to participate in the project. The service–learning students visit homeowners and collect samples on their own time. Sample preparation is carried out during weeks when there is no assigned laboratory exercise for the remainder of the lecture class. A team of two friendly students can do a particularly effective job of communicating the lead-paint biohazard to householders by canvassing an assigned neighborhood doorto-door. Shortly after the school term begins, our students prepare for this task by researching and writing a short (400word) essay about lead poisoning. They are required to include in their essay citations of at least two published, non-Internet references that describe particular lead health hazards. In addition, each student keeps a longhand journal (8) chronicling the service–learning experience. The journal provides an opportunity for introspection as well as a place for recording events in the service project. The journals were collected twice during the term and were read and annotated by the instructors. The students also attend a one-hour lead hazard lecture given by two college graduates employed by the City/County Health Department. Armed with this information and onepage explanatory flyers, the students then go into an assigned
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In the Classroom
older neighborhood. They take with them a neighborhood map, a razor for sampling exterior house paint, plastic baggies for paint samples, a black marking pen for labeling baggies, four “Lead Check” swabs (HybriVet Systems, Inc., Natick, MA 01760), and a “Lead Check” test confirmation card. At each house they explain the lead-paint hazard to the person answering the door or they leave a flyer if no one is home. At no fewer than four houses, each team obtains permission to sample exterior paint. Wooden window casings, stairs, railings and porches are surfaces suggested. Liability issues preclude students entering homes. The paint samples should include all layers of paint present, if possible. Students record the location from which the sample was taken and the appearance of the sample. Samples collected are typically one inch square and weigh between 0.5 and 1.0 g. While still in the field, the students verify that at least four of their paint samples contain some lead by rubbing the front and back of the paint-chip and as many exposed layers as possible with a “Lead Check” swab. A distinctive pink color appears on the paint where it has been rubbed with the swab (containing sodium rhodizonate) if the element lead is present in the paint. Negative tests are confirmed by using the swab to obtain a positive test on a known sample of lead provided by HybriVet Systems. Students are cautioned to wash their hands well after completing sample collection and testing. Students collect their paint samples during the first two or three weeks of the school term. They then participate in an hour-long “reflections” session (9, 10) in which there is an exchange of ideas about community service as well as an occasionally amusing commentary on the responses of householders to this service activity. In two school terms in two entirely different neighborhoods our students have seldom encountered rude householders, and no student has been bitten by a dog. (The University insists on collecting liability release forms signed by the students before the service project begins.) The educational value of the sample collection exercise was significant. In a typical freshman laboratory experiment, students receive and treat samples with no consideration of their source or representative nature. In the service–learning course, students experienced the difficulty of extracting a small sample that would be representative of the site as a whole. In fact, we have no guarantee that the student samples of a site are totally representative. Because some students failed to maintain a careful “chain of custody”, all students became aware of the importance of meticulous record keeping. Laboratory Work Our department postpones checking first-term general chemistry students into the student laboratory lockers until several weeks after the school term has begun. This delay accommodates a high dropout rate in the first few weeks of the term and facilitates a more efficient use of graduate teaching assistants in the laboratories. We recognized those first few weeks without laboratory activity as an opportunity for a service–learning experience for interested students. Having completed their field work, these novice chemists next complete two or more standard general chemistry laboratory experiments that familiarize them with single pan balances and laboratory glassware. With this much preparation they are ready to digest their paint samples for atomic
absorption spectroscopic (AAS) quantitative analysis for the element lead. Sample Processing for Quantitative Analysis Only paint samples that give a positive test with the Lead Check swabs are subjected to quantitative analysis. Students are given a four-page handout1 containing detailed instructions for the laboratory procedure as well as a brief introduction to AAS analysis. The method is a wet ash procedure followed by filtration to remove insoluble material. Some type of wet ash procedure is a standard method to isolate a metal from a complex, largely organic substance for quantitative analysis. The wet ash procedure was the means to the end—a preparation of lead that could be analyzed quantitatively by AAS. The wet ash procedure and the subsequent AAS analysis were recommended by our partner agency, the Health Department. Students are issued latex gloves to protect their hands from the nitric acid and hydrogen peroxide, and the digestions are carried out in the fume hood. Eye protection is required throughout the experiment. The students weigh a 0.5–0.7-g sample of a paint chip that has given a positive test for lead with the Lead Check swab. If a student has collected a smaller weight of sample, she or he is instructed to use the total sample and compensate for the low weight later in the procedure. At each step in the procedure, students are cautioned to mark the container with a laboratory marker to preserve an unequivocal “chain of custody” for the sample. The written instructions advise that three wet ash procedures be carried out on each sample. Pulverized paint-chip samples are digested in concentrated HNO3 and 30% H2O2 in a beaker covered by a watch glass and placed on a hot-plate in a fume hood. If large flakes of paint remain after three repetitions of evaporation to near dryness, students are encouraged to carry out additional wet ashing. The residue is dissolved in nitric acid and then transferred to a 250-mL volumetric flask. The mixture is diluted to volume and mixed, and a portion is filtered into a polyethylene bottle. If the sample is small, the student compensates at this point by using a proportionately smaller volumetric flask. Some students are assigned the task of preparing a reagent blank by performing the entire procedure with no sample present. More than 70 sample solutions and blanks were submitted for AAS analysis in autumn 1997. The samples were analyzed using a Perkin-Elmer 3100 Atomic Absorption Spectrophotometer. A zero intercept, nonlinear calibration plot was prepared using lead standards of 50, 100, 250, 500, 750, and 1000 ppm at a wavelength setting of 283.3 nm. The deviation from linearity of the calibration curve was minimal: when a linear regression with a zero constant was carried out on the calibration data, the most divergent calibration point deviated about 6% from the regression line value. All student samples were within the concentration range of the calibration plot. Each AAS concentration reading was the average of three determinations. The chemical education of freshman students is enriched by the sample processing activity. Students learn safety procedures for working with hazardous substances, in this case nitric acid and hydrogen peroxide. They carry out a wet ash experiment, an opportunity seldom provided in freshman chemistry. Most students successfully complete the sample processing. Accidental spillage at some point in the procedure is the most
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In the Classroom
common difficulty. The students appear to be concerned about obtaining reliable results because the service–learning experiment answers a real-world question. The sample processing operation consumes most of two 3-hour laboratory periods. After the student work is completed, the AAS analysis is carried out by the freshman laboratory supervisor, who explains the operation of the instrument and demonstrates its use. Thus students are introduced to a method of analysis that they would normally encounter only in an advanced course. Data Analysis and Reporting The mass of sample, total dilution volume, and AAS lead concentration are used to calculate a weight per cent lead for each sample The equation used in this calculation is shown below. % Pb =
a mg Pb 1g × 1L × × b mL × c1g × 100 (1) L 1000 mL 1000 mg
where a is the lead concentration from AAS in ppm, b is the volume to which the student dilutes the sample after the wet ash procedure, and c is the mass of the paint chip. The calculations were done on a spreadsheet by the lab supervisor. It would be beneficial to have students work through their own calculations in the future. Students did not write a formal lab report. Requiring a formal lab report would diminish the pool of volunteers for this service activity. Equation 1 is used to reinforce dimensional analysis, which the students learn in the introductory course. The paint-chip samples, collected in autumn 1997, contained a range of from less than 1% lead (indistinguishable from the reagent blanks) to more than 27% lead. Approximately 80% of
the exterior paint samples collected in 1996 and 1997 by students in two older neighborhoods of Salt Lake City contained detectable lead. The random geographic distribution of lead found in exterior paint in one Salt Lake City neighborhood is depicted in Figure 1. By using colored push-pins on a map to mark the homes where students did and did not find lead paint, all the students gain an appreciation for the magnitude of this health threat as well as for the value of having many hands come together to carry out this service project. (The students used a full-color map published by the city that had been photoenlarged and pasted on poster board.) Students did discuss and were very interested in the numbers and the push-pin map. The results of the student project were communicated to the Health Department by mail in a written report composed by the professor. (On a 10-week academic quarter schedule it was difficult to get all the sample collecting, laboratory work, data analysis, and reflection sessions completed before the school term ended. The final report was written after the students had scattered for the winter holidays.) The professor sent letters to all participating householders by U.S. mail reporting results for the neighborhood as a whole as well as for the home of the householder. In none of these reports were specific street addresses given, as per the original understanding with householders when the students solicited permission to collect an exterior paint sample.2 Our university shifted to a semester system in the 1998– 99 academic year. We anticipate that the longer duration of the academic term will enable the students to assume ownership of the service–learning project with full responsibility for the required reports to the Health Department and householders. So far, the best student experience along these lines has been an oral project report by two students to a county committee composed of professionals with environmental sciences backgrounds. Discussion
Figure 1. Map of an older “East Bench” Salt Lake City neighborhood surveyed for lead in exterior house paint in autumn 1997. Closed circles locate houses where lead paint was found. Open circles locate houses where a single sample showed no evidence of lead.
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A faculty colleague in sociology has used before and after surveys of our service–learning students to confirm a statistically significant increase in enthusiasm for service projects among students who participated in the lead paint project. Teachers of chemistry are more interested in assessing whether the service–learning students performed at a higher level on their chemistry examinations than the much larger number of students who did not volunteer for service–learning. No significant difference in performance on objective midterm and final general chemistry examinations was found between the two groups of students. Service–learning students learn more chemistry, but when it comes to the chemical topics taught to both groups the service–learning students do not demonstrate a better grasp of the material. Of the several possible desirable results of a service– learning class listed in our introduction, some (motivated learner, advanced laboratory skills, closer relationship with instructors, personal satisfaction from performing service) definitely materialized. For instance, the students clearly showed more motivation in carrying out the lead-paint sample preparation than in their other student laboratory experiments. They seemed to view this as more important because they were not getting a previously analyzed “unknown” sample, as in the other experiments. Other projected benefits
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In the Classroom
(evaluation more related to future employment, and more favorable attitude of the community toward the university) are unproven. The university continues to advertise this and other service–learning projects in the community in the hope that the information will favorably influence opinion makers. The freshman students who participated in the service– learning project experienced a balanced, methodical evaluation of an environmental problem. The resident whose home was found to be contaminated with a high percentage of lead in exterior paint was neither alarmed nor overly reassured. The resident was alerted to the presence of lead, but informed that intact paint that is not peeling or flaking is a negligible hazard. Only deteriorating paint and its dust that may cause exposure of young children to lead are immediately dangerous. However, the lead content of the paint should be considered serious during remodeling plans. Young children should be present as little as possible during construction and workers should take adequate precautions. The Health Department provides detailed instructions on appropriate precautions to be taken during remodeling. Some interesting, still-unsolved challenges have arisen in this service–learning project: 1. Occasionally a student goes door-to-door alone, incurring personal safety risks. 2. Some students cannot read city maps and mistakenly go door-to-door on a street assigned to another team of students. 3. Chain-of-custody problems arise when students mislabel samples or fail to obtain a legible signature of a householder on the permission-to-sample-paint form. 4. “Reflections sessions” (9, 10) (required by service– learning administrators) can have a “touchy-feely” aspect that some science students find awkward. 5. The University of Utah encourages enrollment in service– learning classes by annotating a student’s transcript with the letters SL next to a student’s grade but expects the student’s investment in the service project to exceed 20 hours for the school term, a large number of hours for undergraduates carrying a full load of courses. 6. If many students (say more than 35) elect to participate in the service–learning project, the logistics of reading lead essays, coordinating reflections sessions, preparing field testing kits for lead, watching for risky technique with powerful oxidants in the lab, doing the AAS analyses, and writing letters to householders reporting the results can keep the instructors very busy.
In future offerings of this service–learning course we intend to address the first three challenges with better and oftrepeated instructions. A fertile area for development in our service–learning project is use of the reflection sessions to personalize learning (9). First, the students can develop empathy for the homeowner’s experience. The homeowner wants to protect his or her family from lead poisoning but not to uncover information that will devalue the property. It may be possible to extend these considerations to examine the place of scientific knowledge in our society. While the findings of science may be ethically neutral, they can be used for good or for evil. Is it moral for scientists to divorce themselves from the uses of their findings? Will moral concerns about uses undermine scientific objectivity? Second, students in the sciences can be intimidated by the large body of knowledge they are
expected to master. In the reflections sessions, we can introduce a deeper understanding of the scientific aspects of the project with the goal of empowering the students. Students will realize that they can comprehend a scientific question and gather data to answer it. Because scientific questions are understandable, students may come to realize that it is not always necessary to leave policy decisions to the “experts”. We do not see a workable increase in the number of service hours required above the present 20 hours per student per school term, because the integrity of the chemical content of the general chemistry course could be compromised by too large an investment of student time in the service project. To address the challenge of instructor overload, we believe the students can assume many of these tasks with a consequent desirable feeling of increased ownership of the project. This will necessitate reallocating some of the 20-hour student commitment away from researching the essay and on to the business of reporting results. We have found the task of running this service–learning project rewarding. In a city of half a million people the opportunities for repeating this project are nearly inexhaustible. The essential element is close cooperation with a government or nonprofit private agency so that students provide a requested community service. Acknowledgments We thank Linda Bonar, Stephanie Peterson, and Stephanie Adams of the Lowell Bennion Community Service Center and Gordon Lund of the Salt Lake City/County Health Department for their help in carrying out this service–learning project. Graduate teaching assistants Coby Carlson, Wendy Hoffman, and Alice Mitchell facilitated the student laboratory work. A small SEAMS grant from the national office of Campus Compact is gratefully acknowledged. Notes 1. We will provide copies of this handout to interested readers upon request. 2. We will provide copies of the reports and letters to interested readers upon request.
Literature Cited 1. Jacoby, B., and Associates, Service–Learning in Higher Education, Concepts and Practices; Jossey-Bass: San Francisco, 1996. 2. Giles, D. E. Jr.; Eyler, J. Mich. J. Commun. Serv. Learn. 1994, 1, 77. 3. Liu, G. Mich. J. Commun. Serv. Learn. 1995, 2, 5. 4. Bonar, L.; Buchanan, R.; Fisher, I.; Wechsler, A. Service–Learning in the Curriculum: A Faculty Guide to Course Development; Lowell Bennion Community Service Center, University of Utah: Salt Lake City, 1996. 5. Boeckx, R. L. Anal. Chem. 1986, 58, 274A. 6. Markow, P. G. J. Chem. Educ. 1996, 73, 178. 7. Sundback, K. A. J. Chem. Educ. 1996, 73, 669. 8. de Acosta, M. J. Mich. J. Commun. Serv. Learn. 1995, 2, 141. 9. Morton, K. In Rethinking Tradition: Integrating Service with Academic Study on College Campuses; Kupiec, T. Y., Ed.; Campus Compact, Brown University: Providence, RI, 1993; pp 89–97. 10. Eyler, J.; Giles, D. E. Jr.; Schmiede, A. Practitioner’s Guide in Service Learning: Student Voices Reflections; Vanderbilt University: Nashville, TN, 1996; pp 13–21.
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