Sue Jagoda September 06, 2001 | Safety
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,
NOTE: Some powdered clays and some forms of diatomaceous earth contain a higher percentage of silica. For example, calcined, or cooked, diatomaceous earth contains more crystalline silica. Natural diatomaceous earth (that is, uncalcined) is called amorphous. It has much less crystalline silica. Certain types of clay contain more silica than others. And when clay pottery is fired (i.e., calcined), more crystalline silica is formed.
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.
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.
Dr. Goldsmith has agreed to be a continuing resource for further questions you might have about silica and its health hazards.
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: