INTRODUCTION - terms of
reference
In the follow-up to its
Recommendation of 1st of July
1998 on phthalates in toys and
childcare articles, the
Commission is, inter alia,
monitoring developments in the
field of phthalate migration
test methods.
The CSTEE, in its
opinion of 27th November 1998
on "Phthalate migration from
soft PVC toys and childcare
articles", has recommended that
"an inter-laboratory comparison
exercise be carried out in
order to document the
reproducibility of the Dutch
laboratory method to measure
phthalate release from PVC
toys".
A report has been
recently published by TNO on
"Validation of the method:
Determination of
Diisononylphthalate in saliva
simulant" - TNO report v99.598
of 27th May 1999
(CSTEE/97/1-Add 149).
Shortly after, in June
1999, the LGC has published a
report (LGC Technical Report n°
LGC/1999/DTI/004 on
Inter-laboratory Validation of
Laboratory-Based Agitation
Methods for Determination of
Phthalate Plasticiser migration
from toys and childcare
articles (CSTEE/97/1-Add 148D).
In relation to the
above-mentioned reports, the
opinion of the CSTEE has been
requested on the questions
presented below (The answers
are in Italics in direct
connection to the individual
questions).
In addition, the CSTEE
has been requested to consider
additional results of in-vivo
tests in the US and the
relation between in-vivo and
in-vitro tests (CSTEE/97/1-Add
163A-D).
TNO report
1. Has the
inter-laboratory comparison in
question been performed using a
target value for DINP release
of 9 µg/10cm2/min, as it was
requested by the CSTEE?
No, the method developed
by TNO is aiming at a migration
of about 1.38 µg/10 cm2/min,
which was the mean release
found in the Dutch in-vivo
study (Könemann, W.H., ed.,
RIVM report 613320 002,
CSTEE/97/1-Add 107).
2. How do the results of
the tests performed with the
method in question compare with
the "in vivo" data available
from the Dutch and other
studies?
The overall mean DINP
migration found by the five
laboratories for the "standard
PVC discs" is somewhat higher
(2.09 µg/10cm2/min) than the
mean value found in the in-vivo
study (1.38 µg/ 10 cm2/min).
The overall mean DINP
migration found by the five
laboratories for "discs from an
unidentified teething ring" is
somewhat higher (2.40 µg/10
cm2/min) than the mean value
found in the in-vivo study
(1.63 µg/10 cm2/min).
3. The variability of
mean values for release of DINP
(table 13 of the report)
obtained for a same product in
the various laboratories goes
from a minimum factor 1.9
(sample 4) to a maximum factor
4.2 (sample 9). What may be the
reasons for such variability
and what are the implications
in terms of possible "false
positive" or "false negative"
when the migration level is
near the limit set for control
purposes?
The large differences in
results, both for the standard
PVC discs and for the discs
from the test samples, reflects
a poor reproducibility among
the laboratories. This will be
a serious problem if the method
is used for legal purposes.
4. Do the results of a
validation study of the TNO
method satisfy the CSTEE that
this method could be used in
routine enforcement to assure
that the guidance value for
DINP set down in their Opinion
can be respected?
The answers given under
questions 1 and 3 explain why
the CSTEE does not accept this
method for testing of
plasticiser migration from
toys.
LGC report
1. How do the "migration
trial results" for commercial
samples obtained in the series
of tests performed at 37°C and
65°C compare with the target
value of 9 µg/10cm2/min and the
in vivo data available from the
Dutch and other studies?
The LGC experiments are
performed using "reference
discs" different from those
used in the Dutch in-vivo
study. It is mentioned in the
text that "the LGC reference
discs have already been shown
to demonstrate similar release
characteristics to the Dutch
standard discs", but this
documentation is not available
to the CSTEE. Bearing this in
mind, it can be said that the
methods LGC have set up give
mean values of DINP migration
from "LGC standard PVC discs"
1.43 µg/10 cm2/min at 37°C,
which is close to the mean
value found in the Dutch
in-vivo study; and 8.83 µg/10
cm2/min at 65°C, which is close
to the highest migration found
in the in- vivo study.
2. Are the samples used
representative of toys and
childcare articles intended to
be mouthed by children under 3
years?
The CSTEE cannot answer
this question because the
report does not contain that
information.
3. The variability of
the mean values for release of
DINP at 65°C (Table 6 of the
report) obtained for a same
product in the various
laboratories goes from a
minimum factor of 1.8 (sample
4) to a maximum factor of 2.8
(sample 3), whereas some
results are apparently missing.
The variability seems to change
unpredictably with the
temperature [e.g. for sample 4:
Lab.1 Õ 2.74 (37°C), 2.86
(65°C); Lab.3 Õ 1.16 (37°C),
5.3 (65°C)]. What may be the
reasons for this variability
and what are the consequences
in terms of possible "false
positive" or "false negative"
when migration level is near
the limit set for control
purposes? How should the fact
that certain results are
missing affect the conclusions?
The CSTEE has also
observed the missing data in
those and other tables but has
no explanation for these
omissions. The variability both
within and between laboratories
is large making it difficult to
use the method for legal
purposes. The present analysis
is obviously a difficult
determination and variability
may be due to a situation where
migration gives phthalate
concentrations in the aqueous
phase which are higher than the
solubility of DINP so that
micelles are probably formed.
4. Do the results of the
validation study of the LGC
"simulated" method satisfy the
CSTEE that this method could be
used in routine enforcement to
assure that the guidance value
for DINP set down in their
Opinion can be respected?
This method is developed
to give migrations close to the
mean value found in the Dutch
in-vivo study and cannot be
used to simulate the maximum
DINP migration (ca. 9 µg/10
cm2/min) found in that study
and which the CSTEE requested
in its Opinion.
5. Do the results of the
validation study of the LGC
"stringent" method satisfy the
CSTEE that this method could be
used in routine enforcement to
assure that the guidance value
for DINP set down in their
Opinion can be respected?
This method is developed
to mimic the worst case
scenario in the in-vivo study
and the mean value of several
tests on standard PVC disc in
five different laboratories
comes close to that. However,
the variations in the results
both within and among the
laboratories are so high that
it is not possible to use the
method for regulatory purposes
in its present status.
Very few data are
available on discs from test
samples. It appears that the
participating laboratories have
analysed only a single disc
from each sample. So, the
repeatability (variation in
test-results within the
laboratories) data on the
samples are not available. The
reproducibility (variation in
test-results among the
laboratories) is also very
high, similar to that for
standard PVC-discs. Therefore,
the method, as reported, is not
suitable for the purpose of
enforcement.
Both in-vitro methods
1. These methods seem
conceived to achieve
predetermined extraction (or
migration) levels. Is it
possible to calibrate and use
these methods in order to
discriminate among commercial
products giving rise "in vivo"
to a migration below/above the
recommended limit value?
a) The TNO method is
validated for average migration
of DINP (approximately 2 m
g/min) found in the in-vivo
study performed by Dutch
Consensus Group. By this method
it may not be possible to
identify commercial products
which may release ³ 6.7 m g/min
DINP corresponding to the TDI
of DINP.
b) The LGC 'stringent
method' did reveal in-vitro
migration of > 6.7 m g/min
DINP from 'LGC standard PVC
disc'. However, there is no
documentation available to
confirm that the 'LGC standard
PVC disc' is equivalent to the
standard PVC disc used in the
Dutch Consensus Study. Finally,
the data produced for the
validation of the test method
is very limited and the
repeatability and the
reproducibility of the test
method are poor. Therefore, the
method in the present state may
not be able to discriminate
among commercial products
giving rise "in- vivo" to a
migration below/above the
recommended limit value.
2. Should these methods
be subjected to a formal ISO
ring test before they can be
considered as validated? Can
otherwise the methods be
considered as validated and if
not, which additional efforts
would be necessary? The
committee is invited to make
specific recommendations, where
relevant, in order to improve
the methods in view of
achieving this.
No, it would be a waste
of resources to set up an ISO
ring test at the present state.
From the studies
reported so far, it appears
that in-vitro migration rate of
phthalates from a PVC product
depends upon two factors, the
matrix and the conditions
employed for the forced
migration. The matrix related
factors - phthalate content,
homogeneity of the phthalate
distribution in the matrix,
other matrix constituents - all
seem to influence migration
rate. The test conditions which
have been shown to influence
in-vitro forced migration of
phthalates from PVC-products
appear to be: mechanical force
applied, temperature and the
saliva composition. Besides the
above mentioned factors, the
physical properties of a
PVC-product, as a result of
'moulding' and 'curing'
processes used for the
manufacture of PVC products,
may also affect the migration
rate of the plasticiser.
It is suggested that for the
validation of a test method for
phthalate migration from
commercial products:
- The target migration
rate for the test method should
be 9m g/min from the reference
discs used in the Dutch
volunteer study. This will
allow to identify the products
which may not comply with the
recommended limit values. The
test method, prior to a
validation exercise using ISO
guidelines, should demonstrate
that products with DINP
migration rates below/above the
recommended limit value can be
discriminated.
- The test samples
should be products of a known
matrix with respect to
manufacturing process and other
matrix factors described above.
Test samples should include
products produced using
different manufacturing process
and with different phthalate
contents. The reference
material should be available
upon request by national
authorities.
- The simulation
conditions used for the test
method for in-vitro migration
should in principle be as close
as possible to in-vivo
conditions. It is possible to
change the extracted amount by
changing at least three
different parameters: the
physical force, the temperature
and the composition of the
saliva simulant. In the LGC
methods the two first were used
to "calibrate" against the
target values, but the
repeatability within a
laboratory and the
reproducibility among
laboratories were poor. It may
be worth to try to use
different saliva simulant
composition to see whether that
gives less variations. To match
the in-vivo studies, an
artificial saliva with some
organic content should be
preferred.
- The metal balls used
as a source of mechanical force
in the LGC study may tear off
the PVC sample. This process
will result in poor
repeatability. In the LGC
report, no mention has been
made concerning the physical
appearance of the test samples
after the completion of the
experiment. Moreover, the
particles release due to
aberration of PVC may also
affect the test results. In the
report from JRC Ispra (CSTEE/
97/1 - Add. 170), a reference
has been made to a home made
'gnawing machine', which may be
a better option as a source of
mechanical force for the
in-vitro test method.
- The phthalate analysis
should be performed by an
analytical technique which can
identify phthalates
unequivocally.
- The variability of the
test method should be as low as
possible, ideally < 20%
(Allowance of 20% tolerance in
the results permits 40%
deflection from the target
value!)
Final recommendation
- For further work with
migration studies, the use of a
standardised reference material
is recommended. Such a material
should be of the same
composition as the one used in
the Dutch in vivo experiment.
The US in-vivo and in-vitro
studies
1. How does the CSTEE
interpret the additional
results of in-vivo tests in the
US (CSTEE/97/1-Add.163/C) and
the relation between in-vivo
and in-vitro tests.
In the US in-vivo test
ten persons chewed/mouthed
discs cut from a toy containing
almost 43% DINP, and the saliva
was collected and analysed for
phthalates. The procedure was
divided in four times fifteen
minutes and the saliva samples
from these periods were
analysed separately. The
results show variations for
each subject between the four
periods (up to a factor of 3)
and a variation between
subjects of almost an order of
magnitude. The average of all
results was 4.3 µg/10 cm2/min
and the maximum value was 9.7
µg/10 cm2/min, with an extreme
for one 15-minute period of
13.4 µg/10 cm2/min. These
results support those obtained
in the Dutch and Austrian
studies used for the earlier
opinion of the CSTEE.
The in-vitro migration
of DINP was also tested in the
US study. Different sizes of
pistons were used to
mechanically treat the test
material in different saliva
simulants. The material used in
the in- vivo test gave a
migration of 3.3 µg/10 cm2/min
with extremes of 2.5 and 4.1,
respectively, in a series of
five determinations. The
in-vitro method produced a mean
close to the mean value from
in-vivo study, but the
repeatability seem to be rather
low (few data points) and it is
not possible to say anything
about the reproducibility among
different laboratories.