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Are You Being Poisoned by Your Dishes?

Barbara Mannion
1991 Woodrow Wilson Biology Institute


BACKGROUND:

Human activities are mainly responsible for the increase of lead in the ecosystem. From paints to ceramic ware, crystal, batteries, solder, and plumbing, to pesticides and leaded gasoline, all forms contribute to an increase of lead worldwide.

Lead poisoning plays a special role in history in which even the fall of Rome is possibly correlated with the increased levels of lead in tissues. The prediction of lead concentrations in snow by the year 2000 are above the 250 parts per trillion.

As lead is concentrated through accumulation in human tissue, certain stress such as fever can release the lead in toxic proportions into the blood. The following data present an overview of lead concentration and its effect on human tissues:

  • ENZYME INHIBITION: starts at 20 micrograms at a blood level of 40 micrograms/100 g; at this point 20% of the people have 70% inhibition.
  • RBC ANEMIA: approx. 50 micrograms/100 ml
  • COGNITIVE DEFICITS: FATIGUE, NERVOUSNESS, SLEEP DISTURBANCE: approx. 60 micrograms/100 g
  • SLOWING OF NERVE CONDUCTION 50-59 micrograms/100 g
  • KIDNEYS: 2/3 KIDNEY FUNCTION IS DESTROYED (25% REQUIRE DIALYSIS): 40 micrograms/100 ml
  • REPRODUCTIVE SYSTEM: DECREASED QUANTITY AND QUALITY OF SPERM: 41 micrograms/ 100 ml
  • ABORTION (MISCARRIAGES)

OBJECTIVE:

The purpose of this experiment is to discover if any of your ceramic ware is leaching lead which might cause lead poisoning.

PROCEDURE:

  1. Obtain two or more empty film canisters, which will need to be labeled with your name and object tested. One film canister is to be filled with untested vinegar and will be your vinegar blank.
  2. Select the object(s) to be tested for lead. Older glazed items preferably made before 1971 such as cups and bowls are likely suspects for lead. Also of interest are those items that are homemade or imported especially those that are brightly colored, worn down, or scratched.
  3. Cover the surface of the item being tested with white distilled vinegar. Cover with a lid of some type to prevent evaporation. Allow the vinegar to stand at room temperature for 24 hours.
  4. After 24 hours, pour the vinegar from each object into a separate film canister and label with your name and object tested. MAKE SURE THE LID IS ON TIGHTLY!
  5. You will now prepare a set of standards to compare your sample with when you bring it back to class tomorrow. Select seven 6 x 50 mm culture tubes and place them in the first row of your 96 well plate. Add 20 drops of .5 M Pb(NO3)3 to the first test tube.
  6. Add 18 drops of distilled water to the second culture tube and add two drops of .5 M Pb(NO3)3 to this. What is the new concentration of the second tube? You can figure this out by using the following relationship: M1 x V1 = M2 x V. Using the correct numbers the equation should now look like this:2 drops .5 M Pb(NO3)3 = 20 drops of X Molar solving for X will give you a new concentration of . 1 M Pb(NO3)3 in the second test tube
  7. Add 10 drops of distilled water to the third culture tube and 10 drops of Pb(NO3)3 from the second test tube. Write this new concentration on the data table.
  8. Add 18 drops of distilled water to the fourth culture tube and 2 drops of the Pb(NO3)3 from culture tube number three. Write the new concentration on the data table.
  9. Add 10 drops of distilled water to the fifth culture tube and 10 drops of the lead nitrate solution from the fourth culture tube. Record the new concentration on the data table.
  10. Add 18 drops of distilled water to the sixth culture tube and 2 drops of the lead nitrate from the fifth culture tube. Record the new concentration on the data table.
  11. Add 10 drops of distilled water to the seventh culture tube and 10 drops of the lead nitrate solution from the sixth culture tube. Record the new concentration on the data table.

    Data Table

    Test Tube NumberConcentration in
    moles/liter
    Color of PrecipitateParts per Million
    of Lead
    one


    two


    three


    four


    five


    six


    seven


    vinegar


    sample # one


    sample # two


  12. Add 1 or two drops of 1 M Na2S to each of the culture tubes and record the color of the precipitate on the data table.
  13. Do the following steps IN THE FUME HOOD!!!!!! In a clean culture tube add 8 drops of vinegar. Add two drops of 1 M Na2S and record your results on the data table.
  14. Test your sample and one other from any of your classmates. Determine the parts per million of lead found if any in these samples.

    [Caution: This test will give off small amounts of hydrogen sulfide gas (rotten egg odor). Prolonged exposure to low concentrations (0.01%) can cause headaches and nausea. Development of a color indicates the presence of a heavy metal sulfide. The test is not specific for lead, since some other metals give dark, insoluble sulfides. However, metals should not be leaching out of such surfaces and lead is the most likely candidate from your samples. Assuming the color is due to lead sulfide, there is a rough correspondence between color and parts per million (ppm) lead concentrations.

    In the following table record the following information: Sample, type of object, coating type, source, test result, color of glaze, origin if known, & age.

    Blank
    sample # one
    sample # two
    sample # three
    sample # four
    sample # five

    IF YOU GET A POSITIVE TEST, DO NOT USE THE OBJECT FOR FOOD!!! The 1971 FDA "action levels" for lead (which may be reduced) range from 2.5 to 7 ppm, depending on the use of the object.

  15. Turn in the remaining vinegar from any positive tests to the appropriate box for possible follow-up testing. If the object tested was part of a set, you may wish to test additional items from the set.
  16. Pour the test solutions down the drain in the hood sink and place the test well strips in the container of water that is IN THE HOOD.
  17. Place the negative test canisters in the appropriate box.


TEACHERS GUIDE

TITLE OF EXPERIMENT: ARE YOU BEING POISONED BY YOUR DISHES?

LEVEL OF EXPERIENCE: None

REFERENCE: University of Washington, Department of Chemistry,Student Environmental Testing, Lead From Ceramic Ware,Sulfide Precipitate Screening Program.

LIST OF REAGENTS:

  • 100 ml of 1 M Na2S (7.8 g per 100 ml H2O)
  • White distilled vinegar.
  • .5 M Pb(NO3)3 ( 19.68 g per 100 ml H20)

LIST OF EQUIPMENT:

  • film canisters - approximately 4 per student
  • 96 well plates or the same sized well strips
  • microscale pipets or eye droppers
  • large container of water for used test strips
  • two boxes or container labeled for positive and negative tested canisters

ANSWERS TO POSSIBLE QUESTIONS: Did this experiment at the Chemistry Institute at the University of Washington, Summer 1989 and received very good results. The Department of Chemistry is willing to run positive results through the ICPAES (inductively coupled plasma atomic emission spectroscopy).

Sample results

Data Table
Test Tube NumberConcentration in
moles/liter
Color of PrecipitateParts per Million of Lead
one


two


three


four


five


six


seven


vinegar


sample # one


sample # two


The chemistry portion of this lab was designed by two of my colleagues and I thank them for permitting me to use this for a biological application.

Kelly Farmer
Revisions by John J. Mauch Pasco High School
Manson High School
PO Box A
Manson, WA 98831
(509) 687-9585


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