A whiff of putrefaction, a savour of rot, and the smell of post-mortem decay was in the air this past week as folks awaited the culmination of an eagerly-anticipated event of international significance.
I
refer, of course, to the extremely rare blossoming of Amorphophallus Titanum
– the infamous ‘corpse flower.’
This
sort of thing doesn’t happen very often. Native to Indonesia
(specifically, western Sumatra), the corpse flower, which is also known as Titan
Arum, derives its popular moniker from its name in the working Malay
tongue: bunga (“flower”) bangkai (“cadaver”). The name was
awarded in recognition of the colossal reek that the thing emanates as part of
its reproductive strategy; you might call it the ‘Drakkar Noir’ of the
plant kingdom. It has been cultivated worldwide, especially in tropical
botanical gardens, but there have only been about 135 flowering events outside
of Sumatra in the past century. This makes the opening of the horrid,
two-metre-tall blossom an event of some significance. Last weekend, for
example, saw crowds flock in their thousands to gardens as far apart as Hawaii
(note A) and Switzerland (note B) to witness the opening of the gargantuan
flowers. You can even view the events via time-lapse photography on the
internet.(note C) Perry the Corpse Flower, which resides at Gustavus
Adolphus College in Minnesota, even has his own Facebook page.
Figure
1 - an Amorphophallus
Titanum in all its blooming glory. Note the erect spadix, centre
of the flower’s olfactory puissance
What
does all this have to do with Defence, you ask? Well, the search for
stench-inducing compounds – putrescent chemical agents, or ‘malodorants’ as
they’re commonly known – is pretty much as old as warfare. There are
sound evolutionary reasons for this. Most things that smell bad, after
all, are generally also bad for you to eat, or to otherwise introduce into your
body (e.g. via a puncture wound). Animals tend to shy away from the smell
of rotting flesh, as this usually indicates a kill site. The purpose of
malodorants is to capitalize upon ingrained responses to bad smells to convince
people to voluntarily cease what they’re doing and/or leave an area, generally
for riot control purposes (I mentioned this tangentially in a post last
August). It also, of course, attracts creatures that prefer dead
prey over live (vultures, for example). In the case of Amorphophallus,
the stench serves to entice the insects that pollinate it: carrion-eating
beetles and flesh flies of the family sarcophagidae (literally, “corpse-eaters”).
Insect pollination, incidentally, is necessary because while both male and
female flowers grow within the same inflorescence, they bloom a few days apart,
preventing the thing from self-pollinating.
For
humans, there is an additional layer of complexity to the problem of
designing chemicals to cause aversion. Natural biological olfactory
revulsion is overlain both by a significant socio-cultural matrix, and by large
variances in individual responses to given odours. This makes figuring
out a broad-spectrum malodorant that will be effective against everyone in a
given group a challenging proposition. Researchers investigating
potential candidate compounds in the US, for example, have documented widely
varying responses among US test subjects from different ethnic
backgrounds. Americans of recent Japanese descent, for example, appear
more tolerant of human fecal odours than the average US citizen, due possibly
to the centuries-old widespread use of night soil as fertilizer in a country
that has traditionally had a very low domestic ovine population. At the
same time, test subjects of Japanese descent seemed to be less tolerant than
the average US citizen of the smell of rotting meat. This, it has been
postulated, may be due to the much greater historical prevalence of meat in
American than in Japanese diets.
Within
such broad cultural generalizations, of course, individual preference may skew
results with even greater margins of error. We all know people, for
example, who are repulsed by different odours, or who seem to be more sensitive
to certain smells than other people are (one explanation for the increasing
prevalence of workplace posters asking folks to use sense when applying scents).
Given such variation on the individual level, how is it possible to find
something that, not to put too fine a point on it, is likely to make everyone
sick? Well, one way is to go to the chemicals that lie at the source of
the smells. Lest we imagine that this is a simple prospect, here’s a list
of some of the floral volatiles that have been detected emanating from a
blossoming Amorphophallus: ketones, hydroxides, nitrophenols, anisoles,
acetic acid, acetophenones, pinenes, terpinolenes, benzaldehyde, beta-pinene,
bicyclogermacrene, citronellol, dimethyloctadiene, E,E-alpha-farnesene,
estragole, ethyl acetate, ethyl alcohol, geranial, geraniol, isohexanoic acid,
limonene, methyl-butanoate, -benzoate, -butyrate and –isobutyrate, myrcene,
cresols, phenylmethanol, sabinene, skatole, sulcatone, sulfanes and
trimehtylheptadiene.
The
flower is a literal cornucopia of complex organic compounds, some of the latter
of which are the truly interesting ones. Organic sulphur compounds and
skatoles have played key roles in the development of malodorant
chemicals. The Israeli Defence Forces, for example, reportedly developed
a riot-control mixture known as “skunk.” Based on common organic products
(including yeast and baking soda), “skunk,” which replicates the odour produced
by the eponymous beastie, may be dispersed as a liquid or mist, leaving rioters
smelling “less than fresh.” According to at least one news article, the stench
of the compound can linger in clothing for up to five years.(note D) The
organic compounds in question – methyl and butyl thiols (sulphur compounds)
commonly known as “mercaptans” – are also found in rotten eggs and garlic,
and are produced when vulcanized rubber (which contains sulphur) is
burnt. Mercaptans are some of the most potent odorants in existence,
detectable by the human nose in concentrations as low as 10 parts-per-billion
(ppb). For this reason, certain of these compounds (originally
ethanethiol, now t-butyl mercaptan) are added to natural gas, which is
naturally odourless, in order to make leaks detectable. Mercaptans are
preferred for these applications because they are less dangerously reactive
than other very smelly compounds, such as ammonia and hydrogen sulphide.
High-grade
malodorants may have reached their zenith in two compounds produced for the US
military: “US Government Bathroom Malodor”, which smells exactly like the name
implies; and “Who, me?” a compound developed during the Second World War that
was intended for use by resistance forces to demoralize occupying German
troops, but which was allegedly discontinued because of the difficulty of
dispersal (the disperser often ended up smelling as bad as the target.
Self-contamination is not an unusual problem when dealing with chemicals
potent in ppb concentrations). The “Bathroom Malodor” mixture actually
contains some of the same volatile organic compounds given off by the corpse
flower, including skatole, hexanoic acid, and various thiols. Other
compounds have been tried as well.(note E) Unfortunately, a lot of the
original archived documentation on malodorants once held by cbwtransparency.org
is no longer available. The website closed down some years ago, and the
URL has been camped by a site offering dog training tips.
The
question has been raised whether malodorants constitute “chemical weapons”
under the Chemical Weapons Convention. Those who argue that they
do base their position on the Article II definition of “toxic chemical” as “any
chemical which through its action on life processes can cause death, temporary
incapacitation or permanent harm to humans or animals.” The argument
hinges on whether malodorants impact “life processes”, i.e. whether the
physical revulsion resulting from exposure is a biological/physiological
reaction or a purely psychological one – i.e., are you fleeing and/or vomiting
not merely because you’re grossed out, but rather because the chemicals are
interacting with your body chemistry? There are, after all, chemicals
that will force you to vomit; they’re called “sternutators”, and have
been in use since the First World War (Adamsite, aka diphenylaminechlorarsine
or DM, is one example); but there is no experimental evidence to suggest that
malodorant compounds actually induce a physiological reaction.
Beyond
the variance in responses, perhaps the most significant complicating factor in
trying to design an effective malodorant is not the legal status of the
compounds, but rather the fact that personnel can become inured even to
horrific smells through long exposure to the individual odorous compounds used
in formulating the mixtures. This is not an uncommon animal response when
acute irritants become chronic; we are adaptive creatures by nature, and
can learn to put up with a surprising amount of discomfort and
annoyance in order to avoid facing up to unpalatable alternatives.
All
of which to say that, while our friend Amorphophallus may smell truly
awful, it at least has the virtue of not lasting very long; the magnificent
spadix droops, and the colossal blossom collapses and dies only 24 hours
after blooming into its full, reeking majesty. Would
that all irritants were as transitory.
Cheers,
//Don//
Notes
A)
[http://www.staradvertiser.com/news/hawaiinews/20110425_Crowd_swarms_to_sniff_stinky_
corpse_flower.html]
B)
[http://cnews.canoe.ca/CNEWS/WeirdNews/2011/04/23/18057936.html]
C)
[http://www.bigislandvideonews.com/2011/04/26/video-corpse-flower-blooms-in-hilo-hawaii-on-easter/]
D)
[http://www.haaretz.com/news/israel-develops-skunk-bomb-for-riot-control-situations-1.135003]
E)
[http://news.nationalgeographic.com/news/2002/01/0107_020107TVstinkbomb.html]
