Proceedings of the International Cyanide Detection Testing Workshop

ainbow trout exposed to 40 mg SCN - /L.
Using depuration rate constants (k 2 ) ranging
from 0.29-0.34 day -1 , a depuration half-life
of about 4 days was estimated. Signifi cant
levels of SCN - were detectable at 8 days and
declined to below detection limits by 16 days.
The determination of plasma SCN - levels may
be a useful biomarker of cyanide exposure.
The studies by Brown, Lanno, and Dixon cited
in the previous paragraphs generally involved
exposing rainbow trout to low levels of either
CN - or SCN - for long time periods (chronic
exposures). Research is needed in which fi shes
are pulse-dosed with higher concentrations
of cyanide over short (acute) time periods
(less than 90 seconds) to simulate exposures
similar to those used during cyanide fi shing.
The conversion rate of CN - to SCN - facilitated
by the enzyme rhodanese is not simply a
function of enzyme kinetics (Leduc 1984).
The conversion rate appears to be limited
by the availability of sulfur present in the
fi sh. Likewise, the metabolism and excretion
of SCN - from the fi sh may be related more
to osmoregulation than to temperaturemediated
enzyme kinetics. Freshwater fi sh
have a higher blood ion concentration (hyperosmotic)
in relation to the surrounding water;
while marine fi sh have a lower blood ion
concentration (hypo-osmotic) in relation to
seawater. Hence, freshwater fi sh have a high
rate of urinary excretion and marine fi sh have
a low rate of urinary excretion; which helps
the fi sh to maintain osmotic equilibrium with
surrounding aquatic environments (Smith
1982).
Since the physiology of freshwater and
marine fi sh is drastically different with regard
to the maintenance of osmotic balance (Smith
1982), it stands to reason that the regulation
of plasma anions may also differ. It is believed
that marine fi sh retain SCN - for a longer
45
time period than freshwater fi sh because of
the lower rate of urinary excretion. Hence,
the interpretation of results from cyanide
exposure studies conducted with freshwater
fi sh to the toxicity and kinetics of cyanide in
marine fi sh should be conducted with caution.
Scientifi c studies are needed concerning the
physiology and pharmaco-kinetics of CN -
and SCN - with marine fi sh.
The committee agreed that there was an urgent
need for research to determine the pharmacokinetics
of cyanide and its metabolites in
MAF. Without this knowledge, it is diffi cult to
predict whether or not various cyanide testing
methods can be applied associated with the
chain-of-custody from collectors to export
companies situated the Philippines, Indonesia,
and Vietnam to importers, wholesalers, and
retailers situated in importing countries like
the U.S.A.
Field Test In Exporting Countries
In response to threats from terrorism, a
number of fi eld tests for cyanide have
been developed and evaluated for the US-
Environmental Protection Agency (US-EPA)
by Battelle. Most of these are either lowcost
colorimetric kits (dependent on color
changes) or based on ion selective electrodes
(ISE) linked to portable ISE meters. These
kits mostly detect cyanide in water. One
colorimetric test kit discussed by Dr. Rubec
is sold by Industrial Test Systems (ITS) and
is called the Cyanide ReagentStrip TM Test Kit
(Batelle 2005). Thermo-Fisher markets the
Thermo Orion 9606 portable ISE equipment.
There are other companies with similar
products that also were evaluated by Batelle
for US-EPA over the past fi ve years.
Mr. Gil Adora (Deputy Director of BFAR
within the Philippines Department of
Agriculture) and Mr. Agus Dermawan (Deputy
Director of the Division of Small Islands