> Did I miss it? Has no one remarked that apricot kernels are a source of
> cyanide? It may require digestion within the body to become toxic, but
it's
> cyanide nonetheless.
>
> Ken Bland
Hazmat 101 News - August 2004
Hydrogen Cyanide Clouds from Cacao Beans Fire - an Urban Legend?
By Jetty Middelkoop
In December 2003, after a fire in a cacao beans warehouse in Wormer (a
Province in North Holland, the Netherlands), it happened again. Newspapers
quickly reported that the whole area near the burning warehouse had been
evacuated due to high levels of hydrogen cyanide and carbon monoxide,
causing
serious alert. True, the area had indeed been evacuated as a precaution. But
not due to excessively high amounts of hydrogen cyanide or carbon monoxide,
but because of the expectation of a long time exposure to a smelly gas. Air
monitoring had shown the presence of hydrogen cyanide and carbon monoxide.
Is this is an example where the media disseminated the "urban
legend" that a cacao beans fire produces large clouds of hydrogen cyanide?
In this article, I hope to debunk this misconception.
What is hydrogen cyanide (HCN)?
Where does the name "cyanide" come from? Its name does not
come from its color. Hydrogen cyanide is colorless--not cyan. Nor is it true
that persons exposed to it turn blue. What happens: their lips and nails
may turn a bit blue-ish, but their skin will turn red. These symptoms are
caused
by an excess of oxygen in the blood--and oxygen rich blood is red. The
cyanide
(CN) in the hydrogen cyanide binds to iron, manganese and copper in
important
enzymes in the body to develop "iron blue"- a blue colored bond between
cyanide
and iron, manganese or copper. Hence, the name "cyanide".
Where is cyanide found?
In nature. Cyanide is found in many vegetables. 10% of all the plants on
earth
contain cyanide compounds. I think this may be a bit exaggerated, but an
impressive list of natural products which contain cyanide compounds
includes:
heated spinach, fresh bamboo shoots, cassava, sago, lima beans, line seed,
peanuts, coffee beans, apricot seeds, almond seeds (especially in the bitter
type,
less in the sweet), the seeds of apple, cherry, grape and peach, beech nuts,
walnuts, mountain-ash berry, Yew, bird cherry, rubber tree, eucalyptus leaf,
clover and some mushrooms.
But where in these products is the cyanide located? Well, mostly in certain
sugar compounds, called glycosides, and there are many kinds of these to be
found. Most of them are not harmful or even useful, like saponin in the
Soapwort flower plant (Saponaria officinalis). However, there are three
groups of glycosides which can be very harmful. These are:
the alkaloid glycosides (e.g. in certain parts of plants of the Night
Shade family (Solanaceae>) such as in tomato and potato, the
heart-glycosides
such as in Oleander and Foxglove (Digitalis spp.). the cyanide glycosides.
Plant cells do not contain pure cyanide, but compounds in which cyanide is
incorporated. The cells also contain an enzyme which is capable of
disconnecting
the cyanide from the glycoside. In the intact cell, the cyanide glycoside
and
the enzyme do not come in contact with each other. When plant cells are
damaged,
they can come in contact and the cyanides are then released. Animal enzymes,
too, can release cyanide from the cyanide glycosides. Plants use cyanide
glycosides as protection against gluttony. An animal which starts eating
such a
plant is either deterred by the bitter taste, or eats on and becomes ill
and/or
dies. The amount of cyanide glycosides in a plant depends very strongly on
the
species, age and environmental factors, such as frost or drought.
In non-ruminating mammals like humans who have acid stomach fluid, small
amounts of cyanide that enter the body with food are converted into less
damaging compounds. Ruminators such as cows and sheep hardly have any acids
in
their stomach fluids. As a result, their stomachs cannot break down
cyanides.
For this reason, the amount of cyanide compounds in animal feed is closely
monitored. The liver, too, can turn limited amounts of cyanides into the
less
damaging thiocyanate at low intake rates. All animals get in trouble when
their
intake of cyanide is higher than their break down rate.
In manmade products. Cyanide is used in rodenticides and
insecticides (gassing). It is also used in the production of artificial
materials such as insulation material (polyurethane foam), clothes and home
textiles (polyamides, polyacrylic nitril, acryl). It can be found in
galvanizing
baths and even in certain food additives. High concentrations of cyanides
can be
found in the soil and in cesspools around old gas factories (factories that
make
gas from coal).
How to remove cyanide in food
Cyanide glycosides can be rendered harmless by heating or flushing with
water
for quite some time. Some jungle tribes take the cyanide out of their sago
flour
by treading it for a long time while repeatedly throwing water over it. Most
of
the cyanide will then be flushed away with the "tread-water". Long time
storage
can also reduce the amount of cyanide. This is what happens with walnuts,
beechnuts and peanuts. This explains why one can eat many more dried nuts
than
fresh nuts before getting symptoms of cyanide poisoning. Finally, many
cyanide-containing food products are made safe for eating by boiling them
and
pouring off the water.
The release of hydrogen cyanide in a fire
When products that contain cyanide are burnt, the release of cyanide is
enhanced. If the burning product is of herbal origin, this will not lead to
a
cloud of hydrogen cyanide -- only to traces of hydrogen cyanide in the
smoke.
The reason for this is that plants only contain a limited percentage of
cyanide
glycosides -- plants need to do much more than just frighten off potential
eaters, and for all these other processes the plants need many more other
compounds. For manmade products, it can be quite a different story. These
products normally only serve one goal, and thus they can contain a much
larger
percentage of cyanide compounds than plants can. If polyurethane foam is
burnt
for example, you should certainly reckon with a high concentration of
hydrogen
cyanide in the smoke depending on the temperature of the fire! An example of
this is the fire that broke out several years ago on the airport of
Dusseldorf
(Germany). Sixteen people died then. The high concentration of hydrogen
cyanide
released when the ceiling insulation burned contributed to the death of
several
of these victims.
Conclusion
Finally, not only cyanide glycosides can lead to the production of hydrogen
cyanide when burned. Also other chemical compounds that contain carbon (C)
and
nitrogen (N), can partly be turned into hydrogen cyanide. This is certainly
true for amines and amides. That is why you can get hydrogen cyanide from
the
burning of wool. But this is another subject, which I will not deal with
here,
or my article would grow much too long. And besides, that would also bring
me
too far away from my primary subject: a cacao beans fire.
More info
http://users.rcn.com/prokopis/hydrogen_cyanide.pdf
Emergency Response Card for Hydrogen Cyanide
Jetty Middelkoop is a chemical advisor for the fire department of
Amsterdam, The Netherlands. Part of her spare time she spends as a
volunteer fire fighter in her home town. Before becoming a chemical
advisor, she was head of the Radiological Protection Service of the
Dutch Ministry of Defense for several years. Ever since, Class 7 is
her favorite Dangerous Goods Hazard Class. Dangerous goods not only
are a means to earn a living for her, they are also her hobby. She
likes to spread the knowledge of dangerous goods as wide as possible.
She collects pictures of dangerous goods accidents to use them in her
lectures. She welcomes suggestions for articles and accident pictures.
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