Opinion on the results of the Environmental Risk Assessment (Report version: final draft of August 1999) of : Octabromodiphenyl ether [CAS N° 32536-52-0] [EINECS N° 251-087-9] 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 Octabromodiphenyl
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
Commercial
octabromodiphenyl ether is a
mixture containing congeners
with varying bromine content.
These congeners have different
properties and will behave
differently in the environment.
An option to handle this would
be to make separate risk
assessments for at least the
different homologue groups, but
the scarce amount of data
available makes this
impossible. These compounds are
very lipophilic and organisms
absorb at least some of them
slowly, which makes acute
effect data less relevant.
While some of these compounds
are predicted to bioaccumulate
and degrade slowly in the
environment, available data
suggests limited
bioaccumulation.
On the basis of the few
data available, a potential
risk for the environment cannot
be excluded. The conclusions of
the report suggest the need for
further information and testing
for: The aquatic compartment to
assess the effects on sediment
from local sources and to
assess the risk to waste water
treatment processes; The
terrestrial compartment to
assess effects on soil
organisms from local sources;
The secondary poisoning in
relation to degradation
products. The CSTEE agrees with
these conclusions. In addition
some more precise information
to quantify the effects on
water organisms at local level
is needed. The CSTEE do not
think that the equilibrium
partitioning method can be
applied for these very
adsorptive compounds with very
low water solubility, and thus
also further information is
needed of 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
Octabromodiphenyl ether
is used as technical mixtures
(31-35% OBDE) containing large
amounts of other congeners, in
particular hexabromo- (10-12%),
heptabromo- (44%) and
nonabromodiphenyl ethers
(10-11%). In a recent thesis
(Andreas Sjödin, "Occupational
and Dietary Exposure to
Organohalogen Substances, with
Special Emphasis on
Polybrominated Diphenyl
Ethers", Stockholm University,
2000), which was not available
to the assessors, the
composition of one OBDE product
is shown to have higher
concentrations of the higher
brominated groups. Most of the
few toxicity data available
refer to commercial mixtures
and it is not possible to
assess the effects of different
congeners.
In the General
information on exposure,
relatively old data on
production and uses are
reported and all references are
to 1994 or before. The
anticipated "worst case" use
(2550 tonnes/year) seems to be
verified by data from the
industry saying that 2500
tonnes were used 1993 (De
Poortere, "Brominated Flame
Retardants", presented at a
Swedish Society of Toxicology
Workshop, 2000). The use of
OBDE products was estimated to
have decreased since that time
and for 1999 about 400 tonnes
were expected to be used in the
EU.
There are only few
measurements of OBDE
concentrations in the
environment reported, and most
of these are from
industrialised areas. There is
a reasonable agreement between
those data and the EUSES
predicted values. The CSTEE
have earlier pointed at the
problems with predictions of
root crop concentrations, and
also for OBDE the levels
predicted there are probably
far too high.
The exposure to possible
transformation products of OBDE
has to be taken into account,
and the CSTEE does not agree
with the statement "the
presence of octabromodiphenyl
(ether) in fires is unlikely to
significantly affect the total
release of toxic products" (p
12).
3.2.1 Effects in the aquatic
compartment
No data on toxicity to
algae are available for
commercial OBDE. An EC50>1
mg/L (high above the
solubility) was obtained for
decabromodiphenyl ether. For
pentabromodiphenyl ether a 96h
NOEC = 26 microg/L was
observed, but growth inhibition
was present at lower
concentrations in shorter time
(24 h EC10=2.7-3.3 microg/L).
A NOEL > 2 microg/L
was obtained in a 21-days
reproduction test on Daphnia
for the commercial OBDE
mixture. QSAR data seem not to
be in disagreement with this
result.
The only available
toxicity test on fish indicate
a 48h LC50>500 mg/L for the
technical mixture, a
concentration far above the
solubility of these substances.
At least some of the components
in the commercial mixtures are
absorbed slowly and therefore
short-term tests are less
relevant.
A PNECwater>0.2
microg/L has been estimated by
applying a factor of 10 to the
21-days reproduction NOEC on
Daphnia.
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
PNECwater. A calculated PNECsed
is >5.93 mg/kg but the use
of this method for the highly
adsorptive OBDE is
questionable.
For hexabromodiphenyl
ether components, a reasonable
worst case has been assumed to
calculate a PNECwater = 0.11
microg/L.
3.2.2 Effects in the
terrestrial compartment
No effect data for OBDE are available on terrestrial organisms. The PNEC has been derived according to the TGD rules, but this approach is not considered valid for this particular chemical. The derivation of a PNECsoil using the partitioning equilibrium method for a chemical which does not show toxicity for aquatic organisms at the solubility limit is not scientifically valid. The basis for the equilibrium partitioning method is that pore water represents the main (or even the only) exposure route, and this assumption is clearly not valid for chemicals which water solubility is so low that toxicity is not observed at this level. The RAR properly applies and additional safety factor of 10 to consider food exposure, but even under these circumstances the method is not valid, because the lack of toxicity for water exposures is related to the unavailability of the substance to enter into the organisms, and not to lack of toxicity if the substance is able to enter in the organisms by any other route. A basic rule for the application of the partitioning equilibrium method is to observe toxicity or to confirm that the chemical has had the opportunity to reach the target organ.
Therefore although the
CSTEE recognised that the RAR
has followed the TGD, the
suggested PNEC for terrestrial
organisms is not considered
valid.
3.2.4 Non compartment
specific effects relevant to
the food chain (secondary
poisoning)
Available data indicate
that OBDE has a low
bioaccumulation potential, but
it is higher for lower
brominated homologues present
in the products. A PNEC = 6.7
mg/kg food has been calculated
for secondary poisoning.
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 CSTEE also
underlines the possibility for
formation of lower brominated
diphenyl ethers that are more
rapidly absorbed by organisms.
The proposed risk
assessment must be re-evaluated
by the CSTEE after the
submission of the mammalian
toxicity data.
3.3 Risk characterisation
3.3.1.1 Water
Calculated local
PEC/PNEC ratio for surface
water is close to 1, thus, the
risk for water is low but
cannot completely excluded from
available data.
3.3.1.2 Sediments
As for sediments, low
PEC/PNEC ratios have been
calculated for OBDE, but a
local value >1 has been
calculated for
hexabromodiphenyl ether
components. However, the
validity of 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.
3.3.2 Risk characterisation
for the terrestrial
compartment
For the soil
compartment, a relatively high
local PEC/PNEC ratio has been
observed for octabromodiphenyl
ether. However, a PNEC value
cannot be derived with the
available information and
therefore conclusion (i) -
there is a need for further
information - is the only
acceptable conclusion.
The RAR suggests the refinement of the risk characterisation after the submission of the toxicity tests currently ongoing for other brominated homologues. However, the CSTEE considers that the extrapolation from one homologue to the other will only be possible if the produced information allows a clear understanding of the relationships between the toxicity and the bioavailability of each substance. A low level or lack of toxicity for any substance cannot be extrapolated to other homologues and/or exposure routes if it is related to a reduced bioavailability for that particular exposure route. Therefore the assumption of lack of toxicity for any non-tested homologues can only be accepted if there is clear evidence that the tested substance has been able to reach the target organ, or if the bioavailability for the non-tested homologue or exposure route is equal to or lower than the tested homologue and route.
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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.