Styrenated phenol belongs to a group of phenols which are used as antioxidants. These chemicals are of potential because they have widespread use, and cam ne highly toxic to aquatic organisms. In addition, styrenated phenol may be used as replacement for substances of concern such as nonylphenol for some uses, for example as an intermediate for surfactants. Styrenated phenol is used as an antioxidant in rubber, and as an intermediate in the production of surfactants (ethoxylates). These are used largely in the formulation of crop protection products. With minor uses as anti-static agents for wool and stabilizer's for polyurethane foams.
Information for this assessment was collected through an online literature search
(Chemical Abstracts) and through web searches. Further information was provided by
manufacturers and users of the substance during consultation on drafts of the report in
2006, 2007 and 2008.
Styrenated phenol is made up of three main components; mono-, di- and tristyrenated
phenol. The relative amounts of each component differ depending on the use of the
substance. Styrenated phenol used to make surfactants has a typical tristyrenated
component content of 70 per cent, with 23 per cent distyrenated and two per cent
monostyrenated. Styrenated phenol used as an antioxidant has typically 43 per cent diand tristyrenated phenol, with 11 per cent of the monostyrenated component.
The components have notably different properties. For this assessment, the predicted
environmental concentrations (PECs) of each component were calculated individually,
and compared with predicted no-effect concentrations (PNECs) for each component.
Styrenated phenol is not readily biodegradable according to standard tests. There are
some indications of degradation from related substances, and the substance would be
expected to react with oxidants in the environment in view of its intended function; as a
result, inherent degradability in the environment was assumed in the assessment.
Styrenated phenol is expected to partition mainly to soil and sediment in the
environment. Based on the predicted log Kow value, monostyrenated phenol has a
moderate bioaccumulation potential. A dietary fish bioaccumulation study has shown
that tristyrenated phenol accumulates significantly, but that distyrenated phenol is not
accumulative. Emission estimates are largely based on generic industry information
and default values, with limited substance-specific information (relating to production
and rubber production).
There is limited information on aquatic toxicity; short-term studies with fish and Daphnia
where the exposure concentrations were above the solubility, and one valid long-term
study on Daphnia for each of di- and tristyrenated phenol. Quantitative structure-activity
relationship (QSAR) predictions of long-term toxicity were used with the measured data
to derive aquatic fresh water PNEC values for each component: 21 µg/l for
monostyrenated, 4.5 µg/l for distyrenated and 0.42 µg/l for tristyrenated. There are no
toxicity data for sediment or soil organisms, so PNEC values for these were calculated
from the PNEC for water. Worst case PNEC values for secondary poisoning were
derived: 1.2 mg/kg for monostyrenated, and 4.8 mg/kg for di- and tristyrenated. A
PNEC of 11.11 mg/kg is also used for a commercial product.
Based on available information and screening data, styrenated phenol meets the
criteria for very bioaccumulative (vB), persistent (P) and possibly very persistent (vP) in
the environment. It is not currently clear if styrenated phenol meets toxicity criteria due
to lack of data. No risks are identified for production of styrenated phenol. Potential risks are identified
for the freshwater aquatic, marine aquatic and terrestrial environment for a number of
life-cycle stages. These risks are largely due to the tristyrenated component. There are
risks for all relevant stages for freshwater and marine sediments, and for the terrestrial
food chain. There is a risk for marine predators in one scenario. There are no risks for
wastewater treatment or for marine top predators. Risks to humans were not assessed.
Styrenated phenol is not produced in the United Kingdom (UK). It is supplied to the UK
for use in the production of surfactants, and use in the UK in rubber is assumed. The
priority for further investigation is the PBT (persistent, bioaccumulative and toxic) and
vPvB (very persistent and very bioaccumulative) assessment. Testing on persistence is
recommended; long-term testing on fish could be considered if persistence testing
shows that the substance meets the persistent (P) but not vP criteria. As the predicted
environmental concentrations rely heavily on generic or default values, specific data on
actual emissions are needed, preferably based on measurements. For the sediment
and soil assessments, toxicity testing on organisms may also be needed, but this will
depend on the provision of better exposure information.
