Opinion on the results of the Environmental Risk Assessment of : Decabromodiphenyl ether [CAS N° 1163-19-5] [EINECS N° 214-604-9] - Report version: final draft of August 1999 carried out in the framework of Council Regulation (EEC) 793/93 on the evaluation and control of the risks of existing substances1 - Opinion expressed at the 16th CSTEE plenary meeting, Brussels, 19th of June 2000.
Terms of reference
The CSTEE has been
invited to examine the
Environmental Risk Assessment
Report for Decabromodiphenyl
ether and address the following
issues:
1. Does the CSTEE agree
with the conclusions of the
Risk Assessment Report?
2. If the CSTEE
disagrees with such
conclusions, the CSTEE is
invited to elaborate the
reasons for this divergence of
opinion.
GENERAL
COMMENTS/CONCLUSIONS
DeBDE is an extremely
lipophilic substance, which
makes it difficult to predict
its environmental distribution.
The compound is probably not
dissolved in the polymer matrix
were it is used, but present as
small crystals, which may be
emitted as such to the
environment. Due to low
solubility in water and low
vapour pressure these crystals
will only slowly be
redistributed in the
environment and this will
persist for a very long time.
Data on the effects of
decabromodiphenyl ether on all
environmental compartments are
very scarce, in general not
suitable for a sound assessment
of the effects, even if some
reasonable extrapolation can be
made. Indeed, in the report,
this part is defined as
"provisional".
On the basis of the few
data available, a potential
risk for the environment cannot
be excluded.
The CSTEE agree with the
conclusions of the report on
the need for further
information and testing for the
aquatic compartment (water,
sediment and sewage treatment
processes), for the terrestrial
compartment and for secondary
poisoning in relation to
degradation products. The
Committee also encourages
further studies on the
environmental behaviour of
extremely lipophilic compounds
such as this one, especially
where toxicity and
bioavailability may increase
following degradation. The
CSTEE do not think that the
equilibrium partitioning method
can be applied for these very
adsorptive compounds with low
water solubility, and thus also
further information is needed
for effects on organisms in the
sediment and soil compartments.
The CSTEE has the main
following comments to make on
the chapters indicated.
SPECIFIC COMMENTS
3.1 Exposure
assessment
Bis(pentabromodiphenyl)
ether, probably better known as
decabromodiphenyl ether
(DeBDE), is a very lipophilic
substance with very low vapour
pressure. The logKow value used
in the report (6.27) is
surprisingly low, but seems to
be determined with a reliable
method. Another determination
resulted in a value of 9.97,
which is more in line with what
the CSTEE would have expected.
Both the solubility in water
(< 0.1 microg/L) and the
vapour pressure (4.63x10-6 Pa
at 21° ) are very low and the
Committee expects it to be
difficult to predict the
environmental distribution of
this substance. At least the
levels predicted for air and
root crops are obviously too
high, and (as is pointed out in
the report) some of the
predicted concentrations in
surface and pore water are
greater than the water
solubility. In Appendix E of
the report the assessors have
done a sensitivity analysis of
the environmental modelling for
DeBDE. An increase of Kow is
increasing the human estimates
dramatically.
DeBDE has high bromine
content and is used as a flame
retardant in polymers, which is
the major use, and textiles.
There is only one producer of
the substance in the EU, and
the major part of the used
volume is imported from other
areas.
In the General
information on exposure,
relatively old data on
production and uses are
reported. All references are to
1994 or before. The "worst
case" use volume within the EU
used in the report (8210
tonnes/year) is in agreement
with data from the industry
specifying 8000 tonnes used in
1993 and 7000 tonnes as
estimated use in 1999 (De
Poortere, "Brominated Flame
Retardants", presented at a
Swedish Society of Toxicology
Workshop, 2000).
The CSTEE finds the
statement that "the presence of
DeBDE in fires is unlikely to
significantly affect the total
release of toxic products" (p
11) surprising. The formation
of polybrominated dioxins and
furan has been shown in many
combustion experiments, and
these substances are regarded
as equally toxic as the
chlorinated counterparts. Such
statements need to be supported
by some sort of evidence.
The major release of
DeBDE to the air environment is
expected to be due to
evaporation from flame-retarded
goods (2.55 tonnes/year), and
to water from the washing of
textiles (up to 120
tonnes/year).
The possibilities for
debromination of DeBDE to lower
brominated diphenyl ethers are
discussed in the report. The
CSTEE questions the statement
that "the actual extent of this
reaction in the environment is
likely to be small" (p25). The
argument that formed PBDE will
be further debrominated does
not seem to be true for all
bromination degrees. The study
of Sellström et al, which is
discussed in the report,
indicates formation of hepta-
to nonabromodiphenyl ethers.
There seems to be a
mistake somewhere in the
description of the dietary
uptake study by Kierkegaard et
al (1999). The product given to
the rainbow trout didn't
contain the high levels of
lower brominated congeners
described in the report (p 29).
This may be due to a wrong
product name in the article or
due to an erroneous composition
of the product assumed by the
risk assessor. The
concentrations of the hepta- to
nonabromodiphenyl ethers did
increase in relation to DeBDE
in the fish, although it is not
possible to say if this is due
to metabolism or selective
uptake.
3.2.1 Effects in the aquatic
compartment
Toxicity tests on three
marine algae indicate that
growth inhibition was observed
only at the highest
concentration tested (1 mg/L).
Therefore, a precise EC50
cannot be calculated (EC50>1
mg/L). This concentration is at
least 10000 times higher than
the water solubility of the
chemical and was tested using a
solvent carrier. The CSTEE
doubts the relevance of these
tests, as the substance will
not be in solution at these
levels, but rather in an
emulsion, as solid particles or
adsorbed to the walls.
No data are available on
aquatic invertebrates. For
octabromodiphenyl ether, a NOEL
of 2 microg/L (called
solubility limit in the report,
but it is 4 times the given
water solubility of that
compound) was obtained in a
21-days reproduction test on
Daphnia. This figure has been
assumed as reliable by analogy.
The only available toxicity
test on fish indicate a 48h
LC50>500 mg/L, again far
beyond the solubility of the
substance. In synthesis, the
compound seems to be slightly
harmful at the water solubility
(1 microg/L), but information
is too scarce for a precise
assessment.
Two options are proposed
for calculating a tentative
PNEC:
1. PNECwater> 1
microg/L estimated by applying
a factor of 1000 to the algal
EC50>1 mg/L;
2. PNECwater>0.2
microg/L estimated by applying
a factor of 10 to the long term
NOEC on Daphnia for
octabromodiphenyl ether.
None of these options
are considered valid by the
CSTEE. For the first one, the
EC50 should be expressed as
higher than the solubility
limit (not as higher than the
load concentration) and
therefore be higher than 0.5
microg/l. A factor of 1000
applied on this EC50 produces a
PNECaquatic organisms
>0.0005 microg/l. However,
no toxicity was observed, and
the only possible conclusion is
that chronic toxicity data are
required to establish a PNEC
for aquatic organisms. For the
second, the use of
octabromodiphenyl ether data is
not appropriate because a
significant difference in the
bioavailability is expected and
there is not enough information
to allow a scientifically sound
extrapolation of toxicity data
among the different brominated
derivatives.
No data are available on
sediment dwelling organisms.
According to the equilibrium
partitioning method proposed by
the TGD, PNECs have been
estimated on the basis of the
two options proposed for water.
Calculated PNECsed are >34.5
mg/kg and >6.90 mg/kg
respectively.
However, the validity of
the equilibrium partitioning
method for this chemical is
highly questionable because
pore water is not expected to
be the main exposure route for
sediment dwelling organisms.
3.2.2 Effects in the
terrestrial compartment
No effects data are
available on plants and
terrestrial organisms.
The RAR states that the
use of the equilibrium
partitioning method is not
possible since no effects were
seen in the aquatic toxicity
test. This statement is
considered fully valid by the
CSTEE. However, the RAR
includes a tentative derivation
of the PNEC values using this
method, which is regarded as
non-valid. These PNEC values
are not used in the risk
characterisation and in terms
of transparency the use of a
non-valid method for deriving a
non-valid value which later on
will not be used should be
avoided.
3.3.4 Non compartment
specific effects relevant to
the food chain (secondary
poisoning)
Decabromodiphenyl ether
has a low bioaccumulation
potential. A long term feeding
experiment on trout showed some
effect (increased liver weight)
at high dose (7.5-10 mg/kg body
weight per day) after 120 days
of exposure, but no effects
were observed after 49 days.
Thus, the hypothesis of a low
concern for secondary poisoning
is acceptable.
On the other hand, the
document underlined the
possibility of formation of
more accumulative and toxic
compounds (lower brominated
diphenyl ethers, brominated
dibenzo-p-dioxins and furans)
from degradation or combustion
processes.
The proposed risk
assessment must be re-evaluated
by the CSTEE after the
submission of the mammalian
toxicity data in the human
health RAR for DeBDE.
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1 Regulation 793/93
provides a systematic framework
for the evaluation of the risks
to human health and the
environment of those substances
if they are produced or
imported into the Community in
volumes above 10 tonnes per
year. The methods for carrying
out an in-depth Risk Assessment
at Community level are laid
down in Commission Regulation
(EC) 1488/94, which is
supported by a technical
guidance document.