Proceedings of the International Cyanide Detection Testing Workshop

Goal 2: Provide recommendations on the most practical, reliable, and user-friendly tests
that could be used in marine fi sh.
The Working Group discussed the practicality of each test, including the cost and equipment
needs, level of expertise necessary, time required to analyze samples, reliability and reproducibility
of different tests, and feasibility of implementing testing in either an exporting or importing
country. Other considerations included factors that may affect the results, such as cellular
absorption and detoxifi cation kinetics, sampling and analysis time, sample storage time and
conditions, and the sample matrix.
Participants also discussed the need for the development of new methodologies or modifi cations
that could be made to existing tests that would be necessary under different scenarios to
address 1) testing of small fi sh (fi sh tissues) instead of blood; 2) testing of cyanide versus
thiocyanate and ACTA; and 3) benefi ts and limitations of rapid tests that could be used to
detect the presence of cyanide or cyanide metabolites instead of the actual concentration.
Timing of testing
The working group members could not come to consensus on the amount of time cyanide
remains detectable in fi shes. Several participants suggested that cyanide is quickly metabolized
and excreted in a matter of hours, while others maintained that cyanide is retained for longer
time periods.
At present, there is considerable information on metabolism of cyanide in blood. When
analyzing cyanide from blood (the preferred method for determination of cyanide exposure in
larger species), analysis must occur as soon as possible after exposure since the concentration
of cyanide in the blood decays within minutes to hours. However, this may not be the case
for fi sh tissue, as there is evidence that cyanide is concentrated in several organs and tissues,
where it is slowly converted to SCN. There are also reports of rapid excretion of cyanide and
SCN in urine. It is important to note that most work done with fi sh has been on freshwater
species, and the rate of excretion in saltwater fi sh is likely to differ since, being hypo-osmotic
in relation to seawater, they have a lower rate of urine production.
The concentration of cyanide present in fi sh over time is dependent on the concentration of
the cyanide solution used during exposure, the length of time of the exposure, time for holding
and duration of transport, post-collection treatment, as well as other factors. Considerable
work has been done on cytokinetics of cyanide in the rainbow trout (a freshwater fi sh) and
linkages between cyanide exposure and conversion to SCN, but most of this work involved
chronic exposure to low levels of cyanide instead of a single or pulse-dose of a much higher
concentration as would be the case with marine fi shes.
In general, all researchers found a progressive increase in SCN- in plasma over multiple days,
followed by a decline until a period where it was no longer detectable (from 16 days to 16
weeks or more). In addition, at least one study reported detectable levels of HCN in plasma
after 20 days. According to one participant (Rubec), cyanide remained detectable in marine
fi sh tissue up to 5-14 days after exposure when using the ISE method.
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