Opinion on the results of the Risk Assessment of: ACRYLONITRILE - CAS N°: 107-13-1 - EINECS N°: 203-466-5. Report version : Final Version, June 2000 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 22nd CSTEE plenary meeting, Brussels, 6/7 March 2001.
Terms of reference
In the context of
Regulation 793/93 (Existing
Substances Regulation), and on
the basis of the examination of
the Risk Assessment Report, the
CSTEE is invited to examine 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 on the
reasons for this divergence of
opinion.
Introduction
Acrylonitrile is a clear
colourless liquid with a
characteristic, slightly
pungent odour. The largest use
of acrylonitrile is the
production of acrylic and
modacrylic textile fibres.
Current production volume in
the EU is in excess of
1,250,000 tonnes per annum and
the EU imports a further
100,000-300,000 tonnes per
annum from outside Europe.
General Comments
The RAR is of good
quality and presents a good
documentation of the
toxicological and
ecotoxicological database.
Especially, the possible
mechanisms of genotoxicity are
extensively and well described.
The CSTEE agrees with the
general conclusions of the RAR
and supports the conclusion
that there is a need for
limiting the risk to workers in
companies that produce monomer
and use of the monomer to
produce acrylonitrile polymers.
The environment part is
using, as much as possible,
realistic information on
emissions of the chemical and
the characteristics of the
receiving environment. However,
the CSTEE considers that
conclusion ii) is not
acceptable for the atmosphere
and additional information
should be requested.
Human Health
The overall risk
assessment is supported.
However, the CSTEE disagrees
with several details of the
report as discussed
subsequently.
Specific comments
1. The CSTEE agrees with
the evaluation of the
mutagenicity of acrylonitrile.
Discussion of the epigenetic
effects about formation of
oxygen radicals, possibly by
induced lipid peroxidation, as
a result of cyanide release or
other mechanism might explain
brain tumours. DNA-adducts
after exposure to the
metabolite 2-cyanoethylene
oxide are low. Smokers and
passive smokers have higher
adduct levels than workers. The
CSTEE supports the
classification in Category 2
carcinogen and it is not
possible to derive a threshold
and a safe exposure level for
this endpoint given the
genotoxic potential of
acrylonitrile.
2. The CSTEE does not
support the derivation of a No
Adverse Effect Level of 4 ppm
for the inhalation route by
application of a safety factor
of 5. The lowest tested
concentration of 20 ppm (45
mg/m3) caused not only
irritative effects, but also
systemic effects like liver
necrosis and increased
haematopoesis, which has been
documented by Quast et al.
(1988a). Due to this limited
database it is not possible to
derive a NOAEL for inhalation
exposure to acrylonitrile.
3. In the RAR it is
summarised that animal data
provide clear evidence of skin
sensitisation following
exposure to acrylonitrile.
There is also some evidence of
skin sensitisation in humans
following skin contact. In view
of these findings and the fact
that inhalation is a primary
route of exposure and
acrylonitrile shows reactivity
for proteins, the possibility
of inhalatory sensitisation
should be investigated. Thus,
the CSTEE does not agree with
the conclusion in 4.1.3.1.3
that acrylonitrile is of no
concern for workers in relation
to respiratory sensitisation.
Risk Characterisation
The estimated risks for
workers and man exposed
indirectly via the environment
are uncertain, because
differences in metabolic
pathways between rodents and
humans exist (page 131). The
RAR could have discussed how
the possible additional
non-genotoxic mechanisms in
tumour development would have
influenced the risk
calculations (page 129).
Conclusion iii) states
that there is a need for
limiting the risks; risk
reduction measures which are
already applied shall be taken
into account The CSTEE supports
this conclusion.
Different statements on
the carcinogenic risks of
workers´ exposure given on page
244 (8,2 x 10-6-1,1 x 10-5) and
page 252 (1,1 x 10-5-8,2 x
10-5) should be clarified
whether these simply are typing
mistakes or not.
ENVIRONMENT
General Comments
The report is, in
general, of very good quality,
trying to use, as much as
possible, realistic information
on emissions of the chemical
and the characteristics of the
receiving environment. However,
the CSTEE considers that
conclusion ii) is not
acceptable for the terrestrial
environment through air
exposure and additional
information should be
requested.
Specific Comments
1. Risk assessment
The CSTEE recognises the
difficulties of assessment on a
weak database and encourages
the use of real information as
much as possible. However, when
real information is used in the
assessment, and large
differences versus modelling
approaches observed, it is
essential to establish if these
differences are related to:
- overestimation from
the models (for example
realistic emissions under
normal production and
formulation much lower than
those use as default values),
- due to the
implementation of specific risk
reduction measures (for example
specific wastewater treatment),
or
- to particular
characteristics of the assessed
site which may differ from
other equivalent facilities
(for example large dilution
factors due to effluent
emissions into very big
rivers).
This distinction is
highly relevant because the
first group is likely expected
to cover all facilities (and
therefore can be included in
the general assessment), the
second group is expected to
cover all facilities only when
the risk reduction measure is
forced by law, and the third
group is very specific and
cannot be extrapolated from one
installation to the other.
The report indicates
that the low risk for the
aquatic environment observed
for the studied sites is
obtained due to the combination
of specific treatments in some
sites, and/or high dilution
factors (up to four orders of
magnitude larger than the
default). In general, the risk
assessment under ESR should be
based, in the first instance,
on realistic worst-case
conditions. Yet at least one of
the sites referred to in the
report diverges from the
specific conditions that lead
to the conclusion of low risk.
Hence this conclusion [i.e.
conclusion ii)] cannot be
extrapolated generally for the
aquatic environment. This
should be clarified in the
overall risk assessment.
Similarly, soil
contamination is expected to be
unlikely only when it is
assumed that sludge from the
WWTP is not applied. This
condition should be included in
the conclusion.
2. Exposure assessment.
In addition to the
general comments, in order to
get the required transparency
the validation of the dilution
factors provided by the
industry should be included.
This is particularly important
for emissions to estuaries and
the sea, where the estimation
of the dilution factor cannot
be based on the direct
comparison of effluent versus
river flow. The available
information, size of the mixing
zone (when the concentration is
expected to be higher than the
estimation) and the likelihood
and relevance of local effects
due to daily and seasonal
reductions in the expected
dilution should be included for
each site.
3. Effect assessment
3.1.- Aquatic organisms.
According to the report of
cumene previously evaluated by
the CSTEE, the very low LC50
values reported by Erben and
Beader for several aquatic
invertebrates seem to be an
error in the units, the
concentrations in the original
paper are expressed as %, but
have been assumed to be, by
error, in mg/l. This point
should be checked and the LC50
values, expressed as mg/l,
estimated and amended if
required. After correction, the
values reported by Erben and
Beader are expected to be in
the same range than those
reported by other authors.
The PNEC derivation for
aquatic organisms is considered
acceptable.
Considering the
toxicological profile and the
physical-chemical properties of
the chemical, the use of the
equilibrium partitioning method
for the derivation of the PNEC
for sediment organisms, in the
absence of toxicity data, is
acceptable.
3.2.- Terrestrial
environment. The report clearly
identifies the atmosphere as
the major compartment for the
distribution of acrylonitrile.
No information on the toxicity
to plants exposed through air
is available and preliminary
PNEC derivations based on acute
data on a number of insect
species suggests a potential
risk when compared to the
estimated PEC local air. The
CSTEE recognises that the
toxicity figures are
questionable but considers that
additional information should
be required before reaching
conclusion ii).
The derivation of a PNEC
soil organisms following the
partitioning equilibrium method
is expected to be protective
enough, as confirmed by
in-vitro data on terrestrial
plants and data on soil
micro-organisms.
4. Risk characterisation
As mentioned above, the
risk assessed for the studied
sites is mostly acceptable
(with the exception of the
atmosphere compartment) but
does not necessarily cover the
unstudied sites.
The report should
clearly mention that the
conditions for the unstudied
sites should be checked before
reaching a general conclusion
on the lack of environmental
risk.
----------------------------------------
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.