Top image: In the FOSS Mixtures and Solutions Module students pour a small mixture of diatomaceous earth and water through a filter to determine whether it is a solution. Mixing diatomaceous earth with water eliminates any potential health risk.

If FOSS kits are well-used, there should be no concern for dust on the outside of the boxes, but it is the "dust" (also called fine particulates) inside the boxes that has our attention once more. There have been some questions about possible health issues surrounding the diatomaceous earth and powdered clay in some FOSS kits. Diatomaceous earth was once used in the stream tables that are part of the Landforms Module and is still used in small quantities in the Mixtures and Solutions Module. Powdered clay replaced diatomaceous earth in the stream tables where it is now used in small quantities mixed with fine-grained sand.

Our current information was that there are no health concerns associated with the use of these materials in the classroom. To update our information, the FOSS staff contacted Christine Parks, a researcher at the National Institute for Environmental Health Sciences in Research Triangle Park, North Carolina. She, in turn, connected us with Dr. David Goldsmith, an associate research professor at the Department of Environmental & Occupational Health at George Washington University in Washington, D.C. His primary research involves cancer prevention, pesticides, and risk assessment for airborne silica dust. Dr. Goldsmith happened to be in the Berkeley area and generously agreed to spend some time with us at LHS to answer our questions about these materials.

Dr. Goldsmith's research on silicosis and the materials that contribute to it has focused mainly on occupational hazards. Certain occupations, such as mining, sandblasting, sculpting, road construction, and silica-rock processing, place workers at risk because of the great exposure to airborne silica. These occupations are sometimes called the "dusty trades." In these occupations workers are exposed to large amounts of dust over long periods of time. Good ventilation and devices such as air filters, respirators, breathing masks, safety goggles, and protective clothing can reduce the exposure and lessen the risk. If silica, such as that found in diatomaceous earth and clay, is an occupational health hazard, is it safe to use in the classroom?

According to Dr. Goldsmith, the methods and techniques in which these materials are used in FOSS essentially eliminate any hazard. In FOSS investigations,

• Exposure time to silica-containing materials is limited.
• The quantity of silica-containing materials is limited.
• If used according to instructions, the silica-containing materials are mixed with water. There should be no dust, as the silica bonds with the water.

The powdered clay and diatomaceous earth used in various FOSS modules have been specifically chosen so as to have as little crystalline silica as possible. Labeling on bags and bottles in the kits will provide information on hazards and use.

There are other provisions you can make to eliminate flying dust in the classroom. These are:

Students can move the damp earth material in the stream table with craft sticks and wooden blocks in the Landforms Module.

• In the Landforms Module, the earth material, consisting of sand and powdered clay, should be mixed in a closed zip bag. Water should be added to the earth material in the bag to cut down on flying dust.
• Contact lens wearers should remove their lenses before mixing the material. Use safety glasses for further protection. (Note: If the material is mixed in a closed bag as described earlier, there should be little or no dust to worry about.) Airborne silica dust particles may get lodged behind the lens andirritate corneas. If eye contact occurs, immediately flush the open eye with lukewarm, gently flowing water for at least 10 minutes. If irritation continues, obtain medical attention.
• Some students may experience mild, temporary skin irritation when handling the stream table earth material, especially if humidity is particularly low in your area. If this is a concern, make sure students use the wooden blocks supplied in the kit to manipulate the material in the stream table. Before handling the material, it also helps to wash hands and apply a skin location. Dry skin is more susceptible to irritation. If irritation occurs, rinse the irritated area with plenty of clear water.
• To clean up, do not dry-sweep powdered clay or diatomaceous earth. Whenever possible, sweep up the material when damp or spray with water before you sweep to cut down on the amount of airborne dust. Have students conduct their investigations over old newspapers that can then be rolled up and tossed, containing any dust spills.

By following the guidelines above and those included in the FOSS teacher guide, you should have no problems with the use of these materials in your classroom.

Resources

Dr. Goldsmith has agreed to be a continuing resource for further questions you might have about silica and its health hazards.

• David F. Goldsmith, MSPH, PhD
  Associate Research Professor
  Department of Environmental & Occupational Health
  George Washington University
  2300 K Street NW, Suite 201
  Washington, DC 20037
  Tel: 202-994-1734; fax 202-994-0011
  email: eohdfg@gwumc.edu
  website: http://www.OccupationalEpi.com

Materials Safety Data Sheets (MSDS) Online

There are a variety of websites where you can download MSDS for substances you might have in the classroom. Before doing so, make sure you have as much product information as possible, as MSDS may vary from one manufacturer to another and from one version of a substance to another (e.g., calcined versus amorphous diatomaceous earth). Some sites to browse include:

• Vermont SIRI MSDS collection