Data for dioxins analyzed by a
screenings method, like DR CALUX^{® }are expressed in CALUXTEQs, while
data for dioxins analyzed by HRGCHRMS are expressed in WHOTEQs. Is there a
difference? Are these different expressions comparable? This
question is raised frequently, and rightly so, because these different
expressions may suggest apparent differences, which creates some level of confusion.
These different expressions of data originate from the scientific discussions
on an international level. Momentarily the consensus opinion is that WHOTEQ should
only be used for data that are generated by making use of the WHOconsensus
list of TEF values for calculating
the WHOTEQ of a sample. This is the case for all analyticalchemical methods,
like HRGCHRMS, which actually measure concentrations of individual congeners
on a, e.g. pg/g lipid basis. These concentrations are consecutively converted
into calculated total toxic potencies (WHOTEQ). In fact, in this calculation
step concentration data are converted into total toxic potencies, using the
WHOlist of TEF values.
Since WHO has reassessed the WHOTEF
numbers for individual congeners several times, it is also required to indicate
which list is used (i.e., 1989 (ITEQ); 1998, or 2006 WHOTEQ).
The EU accepted screenings methods for dioxins, like DR CALUX^{®}, directly
measure the total toxic potency of dioxins and therefore do not require a
conversion step of the data, using a WHOTEF
list. Therefore, CALUX derived data should not be expressed as WHOTEQ but
rather as CALUXTEQ which is equivalent to WHOTEQ. The equivalency of
CALUXTEQ to WHOTEQ is based on the following arguments and observations:
1)
The consensus values by WHO for toxic equivalent potencies (TEF values) for the various congeners is mostly
based on their equivalent liver toxicity data, which also forms the basis for
the DR CALUX^{®}, since this screenings method uses enzyme induction as
a measure of liver toxicity using the H4IIe cell line, which has also been used
by Safe et al., 1989 for the development of the whole TEF
concept. 2)
The TEF values for individual
dioxin congeners measured by DR CALUX^{®} are highly comparable to
the consensus TEF values determined
by the WHO for the same congeners;
3)
The CALUXTEQ values for samples are comparable to WHOTEQ values determined
and calculated by HRGCHRMS for the same samples
In conclusion, the only real difference between CALUXTEQ and WHOTEQ concerns
a difference in the method of determination and/or calculation. CALUX directly
measures the total toxic potency, while HRGCHRMS firstly determines the
concentration for each individual congener (pg/g) which are consecutively
converted into toxic potencies which are added up to a total toxic potency, expressed
as WHOTEQ, using the WHOTEF list
for the calculations. Therefore the numbers generated by both methods are not
equal, but are equivalent to each other. In addition, EU guidelines demand a
reconfirmation by HRGCHRMS of each analysis result by DR CALUX that exceeds
the EU maximum limit value. Therefore, in the end, all final product
evaluations are based on WHOTEQ regarding the question whether, or not the
maximum limit values are exceeded.
