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Unformatted text preview: lab, and do not put your hands or fingers in your mouth. A toxic
chemical can also enter your body in other ways. Until you have washed your hands
and have left the laboratory, keep your hands away from your eyes, ears, and nose.
Keep your hands away from any cuts, bruises, or other places where your skin has been
broken. If it is necessary to use needles or to handle broken glass, exercise care to avoid
puncturing your skin or cutting yourself.
4Strictly, an acute exposure is an exposure to a toxic substance that lasts 24 hours or less; a chronic exposure is a
repeated exposure that takes place for a duration of three months or longer. Repeated exposures that occur for a
period of less than one month are called sub-acute exposures, and those lasting from one to three months are
called sub-chronic exposures. 11 students short index 1/15/03 12:45 PM Page 12 Some toxic chemicals can be absorbed directly through intact skin. If that is the
case, both the label and the Material Safety Data Sheet will warn of this hazard. For
such chemicals, be sure to wear gloves that are impervious to the chemical; discard the
gloves after use as directed by your instructor. Wash your hands thoroughly after you
have discarded the gloves.
If you spill a chemical on your skin or clothing, wash it off immediately and thoroughly. Always wash your hands thoroughly before leaving the laboratory.
There is only one other way that you can be exposed to a toxic chemical: by
breathing. We all breathe and therefore could sometimes inhale the vapors, dust, and
mist in the air in the laboratory. You will be in the laboratory for only a few hours
each week, and if your instructor ensures that the concentrations of toxic vapors,
dusts, and mists are kept well below the threshold limit value (TLV) or permissible
exposure limit (PEL), you are unlikely to be harmed by an inhalation exposure. The
terms TLV and PEL are defined in the “Understanding an MSDS” section at right. Sources of Information
Material Safety Data Sheets (MSDSs)
The U.S. Occupational Safety and Health Administration (OSHA) has defined a
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This document was uploaded on 02/27/2014 for the course PHYS 1B at UCSD.
- Spring '07