Part I—Lake County Emergency

At Lake County Community Hospital, Dr. Barbara Elliot raced to the emergency room. There, she found 6-year-old Suzy Smith, whom she had seen just yesterday with what the doctor had thought was a case of flu. Suzy’s mother, Jane Smith, sighed with relief when Dr. Elliot stepped into the room.

“Thank goodness you’re here! Suzy can’t seem to keep any food down. She’s so pale and weak … I’m worried about her.”

“Let’s have her spend the night, Jane, so I can keep an eye on her. I suspect there is something going on here besides the flu. I’d like to run a series of tests on her.”

After checking Suzy’s vital signs, the doctor got the little girl settled into a hospital room.

Dr. Barbara Elliot was new to Lake County, Colorado. During the year she had been practicing there, she had observed that a large number of her pediatric patients had similar symptoms: sleeplessness, stomachache, vomiting, diarrhea, and anemia. The doctor was becoming convinced that there was an underlying problem—some common cause.

When Dr. Elliot got back Suzy’s blood test results, she was alarmed to see that the blood contained elevated lead levels. Her thoughts immediately shifted to the abandoned mining district only a few miles away. Was it possible that this was the source of lead in Suzy’s blood? Could contamination from the old mines be responsible for the large number of sick children she had seen over the past year?

Background

The mining district of Lake County, Colorado, is about 120 miles west of Denver and was the site of gold mining as early as 1859. In the 1870s, silver and lead were also mined. During World War II, large amounts of zinc, lead, and copper were extracted at the site.

Mining at the location has since ceased, but there remains a large quantity of resultant waste at what is known as the “California Gulch Site,” a 15-square-mile area that serves as a watershed. Among the waste products from mining operations are mine tailings, slag piles, waste rock piles, and abandoned mine shafts.

Questions

1. (a) Describe a general process of mining lead from ore, including the name and formula for the primary ore that contains lead. (b) Define terms used in the process such as ore, smelt, gangue, refine, slag, and mine tailings.
2. During the smelting process, sulfur dioxide gas is produced. When dissolved into water, what compound is produced? Write the chemical equation(s) for this process.
3. What is a watershed? What might be some possible environmental effects of an area like this being mined for lead in light of your answers to questions 1 and 2? (Hint: What is the effect of an acid on an insoluble compound such as lead(II) sulfide?)
4. What are considered safe levels of lead in human blood in parts per million (ppm)?
5. What are some of the effects of overexposure to lead for adults? For children?
6. How are patients with high levels of lead in their blood treated?

Date Posted: April 21, 2008.

Copyright © 1999–2010 by the National Center for Case Study Teaching in Science.  Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.