| Thinking
About Classroom Safety: The Various Dusts in FOSS Kits
By Sue Jagoda, FOSS Earth Science Specialist
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.
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 potentional health risk.
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.
|
| 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.
- 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
http://hazard.com/msds/
Cornell University MSDS Search
http://msds.ehs.cornell.edu/msdssrch.asp
|
