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Is your tuna safe?
by Likha C. Cuevas |
January-March
2004
|
 We
have lead and cadmium in our food?
Yes, and our food like canned tuna that we
export and rice must be analyzed to determine if they contain
these contaminants. Dr. Evangeline C. Santiago of the Natural
Sciences Research Institute (NSRI) at the University of the
Philippines Diliman (UPD) has discussed this topic in the
seminar on, "Identification and Initial Validation of
an Analytical Method for the Determination of Lead and Cadmium
in Fish (Canned Tuna) and Rice Samples to be used for Monitoring
and Regulatory Purposes," on August 6, 2003 at the Bureau
of Agricultural Research (BAR) CERDAF Conference Room. This
seminar was organized by the Product Quality Systems Network
(PQSN) and co-sponsored by BAR.
According to Dr. Santiago, cadmium and lead
are metals with no known role in metabolism but have been
involved in historic poisoning episodes of human populations
and wildlife resulting from contaminated food and prey. They
are introduced to the environment by human activities usually
from mining and metal industries and from leaded gasoline.
These metals that are released into the atmosphere may settle
with dust particles on plants and crops or may find their
way to the soil and coastal and river waters and sediments.
Cadmium may be present in elevated amounts
in soil treated with sewage sludge as fertilizer. The toxicity
of cadmium includes the direct binding of this contaminant
with the negative groups of DNA to produce precursors of tumors.
Lead, on the other hand, is deposited on and retained by crops,
particularly leafy vegetables and fruits. Shellfish and fish
are also contaminated by lead that range from 0.1 ppm up to
0.8 ppm for shellfish. Canned goods are also contaminated
from leaching of lead solder in cans and others get contaminated
from lead glazes in pottery and ceramic ware. Lead accumulates
in the body over a lifetime and the body releases it slowly,
so over time even in small doses, this can cause lead poisoning
and one of its effects is the impairment of the nervous system.
To prevent these things from happening to consumers, monitoring
contaminants in food for trade and regulatory purposes has
to satisfy the criteria for data quality set by CODEX. CODEX
specifies a set of criteria for acceptability of the method
in analyzing a specific contaminant in a particular matrix.
The study that Santiago and her team of experts
regarding lead and cadmium contamination analysis validated
an analytical method that meets the CODEX criteria for analysis
of lead and fish and cadmium in rice in three selected local
laboratories under a supervised inter-laboratory analysis
program. The supervised laboratory program would then use
a set of documented test procedures and test materials to
eliminate as much variability between laboratories.
The study showed that the analysis of cadmium
in rice using the standard AOAC procedure involving dry ashing
and direct aspiration in Atomic Absorption Spectrophotometry
(AAS) for monitoring and regulatory purposes can be done at
the Institute of Chemistry (IC) at UP Los Baños (UPLB),
Philippine Institute of Pure and Applied Chemistry (PIPAC)
in Ateneo de Manila University, and the Research and Analytical
Services Laboratory (RASL) of NSRI. However, Santiago's research
team concluded, the analysis of lead in canned fish in these
local laboratories using standard AOAC method does not satisfy
the requirements of CODEX/EU for the detection limits and
precision of the analytical method for the specified regulation
level of 0.5 mg/kg lead. On the other hand, Santiago said,
"the laboratory at NSRI showed that modification of the
method by chelation (the process of forming a ring by forming
one or more hydrogen bonds with the use of organic chemical
that bonds with and removes free metal ions from solutions)
of the digests before AAS analysis can satisfy the requirements
on the detection limit and precision. Full validation of the
modified method is recommended before it can be used to analyze
lead in tuna."
The full validation of the modified method
is recommended before it can be used to analyze lead in tuna.
"It will all depend on the funds given by the Department
of Agriculture. Since AAS is a common instrument and is available
on laboratories, BFAR is already training their analysts on
this method," Santiago added. There is no reference laboratory
yet for this method. Can local laboratories comply with the
requirements for trade exports? For the meantime, Santiago
explained, local laboratories are using the AOAC method. When
questioned, their methods will not be acceptable (in international
standards) since unspiked tuna samples analyzed would have
no lead detected because AOAC has a low od detection level.
Tuna industries do not support the analysis
of lead and rather they proposed the removal of the regulation
level but they cannot do that since it is required in the
international trade, Santiago said. Since CODEX wanted to
lower the regulation level of lead in tuna (2 ppm for trace
metals), the formation of a reference laboratory for trade
export is subject to the technical capabilities of analysts.
Source: “Identification and initial
validation of an analytical method for the determination of
lead and cadmium in fish (Canned Tuna) and rice samples to
be used for monitoring and regulatory purposes” 2002
by E.C. Santiago of the Research and Analytical Service Laboratory,
Natural Sciences Research Institute (NSRI), University of
the Philippines, Diliman, Quezon city, email: ecs@nsri@upd.edu.ph
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