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EC number: 639-566-4
CAS number: 165184-98-5
The toxicity of HCA to various aquatic
organisms has been examined.
For algae, it was not possible to
maintain hexyl cinnamic aldehyde at
the solubility limit of the substance in a 72 hour study as it
photodegraded and hydrolysed (and perhaps biotically degraded) under the
conditions of the study. For this reason, the EC50 cannot be calculated
at the maximum attainable concentration which was attainable in the
For daphnids an acute study was
originally considered invalid due to the use of solvents in a
flow-through study which led to effects above the water solubility of
the test substance as defined in an OECD 105 study. However, futher to
the performance of a new solubility study in both ultra-pure water and
daphnid medium, it was found that the original water solubility study
erroneously provided results around 0.3 mg/L. The true water solubility
in mineral medium is around 1.5 mg/L and therefore the toxicity observed
in the daphnid study is below the solubility limit. substance losses by
protecting the test solutions from light during the study, keeping them
under closed conditions and using a semi-static technique. No
significant effects (5% immobilisation) were observed up to a WSF
loading of 1 mg/L, significantly higher than the maximum water
solubility limit for hexyl cinnamic aldehyde. Effects were observed at
the higher WSF concentrations but these are considered of no
significance as they were hundreds of times higher than the solubility
limit and almost certainly contained micro-droplets of test substance.
For fish in acute, no effects were
observed up to the aqueous solubility limit of the substance. Any
mortality or effects observed were therefore due to physical effects due
to the solvent artificially maintaining the test substance in an
emulsion that was stable under the conditions of the study (flow-through
conditions) but not possible to maintain under environmental conditions.
For chronic effects, a chronic study
was performed on daphnid according to international guidelines but with
the use of solvent. It appears that there were no statistically
significant treatment-related effects on survival, reproduction or
growth at concentrations up to 63 µg a.i./L. Growth, measured as length
and dry weight, and reproduction were the most sensitive biological
endpoints measured in this study. Daphnids exposed to the test substance
at a concentration of 157 µg a.i./L had statistically significant
reductions in growth and reproduction in comparison to the pooled
control. Consequently, the 21-day EC10 value for adult immobility was
107 µg a.i./L and the 21-day EC10 value for reproduction was 69 µg
In the algae study the NOEC is based
on the measured concentration of 0.065 mg/L which relates to the maximum
attainable concentration which was tested in the study for this species
(i.e. not a true NOEC).
Based on biodegradation studies,
micro-organisms are not considered sensitive to the test substance.
In conclusion, for acute data,
toxicity was observed belfor one species, daphnids, at 0.247 mg/L
(meaused concentration). Other studies in which toxicity was found
either found effects at or above the water solubility limit of hexyl
cinnamic aldehyde or no effects at the highest concentration attainable
over the study period.
For chronic data in the pelagic
compartment, a chronic NOEC was determned for Daphnia magna at a
concentration of 63 µg/L.
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