Ultraviolet
light (UV)
UV radiation used for visualizing stained DNA is hazardous, in particular
to the eyes. Protective UV-blocking goggles and safety mask should be worn.
Also, the UV source should be adequately shielded.
Acrylamide
Acrylamide and bis-acrylamide are powerful neurotoxins that have
cummulative effects and can be absorbed by the skin. Gloves and mask should
be worn when weighing acrylamide or methylene- bisacrylamide
and when handling solutions containing any of those chemicals. Though
polyacrilamide is supposed to be harmless, preacautions should be taken
when handling it as it may have minute quantities of toxic unpolimerized
acrylamide.
Ethidium
Bromide
Ethidium bromide (Et Br), commonly used for DNA staining in
electrophoresis, is highly mutagenic and moderately toxic. Et Br
contains a planar group that intercalates in the DNA molecule and makes
the dye bound to the DNA and display an increased fluorescence. This property
of intercalating in the DNA makes Et Br a very useful stain but also a
dangerous compound capable of producing mutations in human DNA. Gloves
should be worn when handling Et Br solutions and solutions containing the
dye must be decontaminated before disposal. Below we describe some methods
for decontaminating Et Br solutions.
Decontamination of Et Br
Et Br decomposes at 262 C and is not supposed to be hazardous after
incineration. Concentrated solutions of Et Br should be diluted with water
before decontaminated with one of the following procedures.
Diluted solutions (equal or less than 0.5 ug/ml) can be treated
with Amberlite XAD-16 each 100 ml of solution and then filtrated with a
Whaltman No. 1 filter for further disposal. Another treatment implies the
use of powdered activated charcoal each 100 ml of solution, storage at
room temperature with intermittent shaking, further filtration (Whaltman
No. 1) and disposal.
Treatment with sodium hypochlorite (bleach) is not recommended because
it turns Et Br into another compound that has been proved to be mutagenic
in some bacteria. Contaminated surfaces can be cleaned with slurries of
Amberlite XAD-16 or activated charcoal.
