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EC number: 246-690-9
CAS number: 25167-70-8
Adequate information is available to characterise the hazards of this substance following repeated exposure, with a NOEL of 300mg/kg/day.
The administration of 2,4,4-trimethylpentene
to CD rats at a dosage of 1000 mg/kg/day was generally well tolerated.
The liver and kidneys were identified as target organs. The liver
weights of animals given 1000 mg/kg/day were raised compared to controls
but there was no associated histopathological change. The increase in
liver weight is considered to represent an adaptive response to the
administration of a xenobiotic. Variations in plasma protein, glucose
and, possibly, urea concentrations may be due to an alteration in liver
metabolism following treatment.
Males receiving 1000 mg/kg/day had increased
kidney weights compared to controls but there was no associated
histopathological change. The increased urea concentration may be
related to a minor alteration in renal function.
No significant findings were observed among
animals receiving 100 or 300 mg/kg/day and the NOAEL is considered to be
300 mg/kg/day in this study. In addition, as there were no adverse signs
or responses in the battery of neurological tests on this study, it is
considered that 2,4,4-trimethylpentene did not cause any change to
normal nervous system function when administered by gavage at dosages up
to 1000 mg/kg/day.
Groups of five male and five female CD rats
received 2,4,4-trimethylpentene orally, by gavage, at dosages of 100,
300 or 1000 mg/kg/day for four weeks. A similarly constituted control
group received the vehicle (maize oil) at the same volume-dosage. The
administration of 2,4,4-trimethylpentene to CD rats at a dosage of 1000
mg/kg/day was generally well tolerated. The liver and kidneys were
identified as target organs; organ weights were increased but there were no
histopathological changes. The NOAEL is considered to be 300 mg/kg/day
in this study. In addition, as there were no adverse signs or responses
in the battery of neurological tests on this study, it is considered
that 2,4,4-trimethylpentene did not cause any change to normal nervous
system function when administered by gavage at dosages up to 1000
There are 2 keys studies investigating
repeat-dose toxicity following oral administration of 2,4,4
-trimethylpentene (HLS, 1997b; HLS, 1997c).
In the first study (HLS, 1997b) male and
female CD rats received 2,4,4 -trimethylpentene, by gavage, at 0, 100,
300 or 1000 mg/kg/day for four weeks. The administration of 2,4,4
-trimethylpentene to CD rats was generally well tolerated. The liver and
kidneys were identified as target organs with organ weight increases
although this was in the absence of histopathological change. There were
no adverse signs or responses in the battery of neurological tests on
this study. The NOAEL was 300 mg/kg/day (based on organ weight changes
In a second guideline study (HLS, 1997c)
male and female CD rats 2,4,4 -trimethylpentene was administered by
gavage at dose levels of 0, 100, 300 or 1000 mg/kg/day in a combined
reproductive toxicity / developmental toxicity screening test without
adverse effect on the general condition of male and female rats.
Treatment-related findings were confined to the kidneys of males;
basophilic cortical tubules were seen in all treated groups and a
no-observed-effect level (NOEL) was not demonstrated as part of this
study. However in subsequent investigations (Swenberg and Schoonhoven,
2004) on kidney samples from this study, including immunohistochemical
investigations of alpha-2u-Globulin and comparison with prior research
on alpha-2u-globulin nephropathy, the renal lesions were attributed to
alpha-2u-globulin nephropathy and thus considered not to be relevant for
human risk assessment.
In conclusion 2,4,4 -trimethylpentene, like
other structural analogues, produced alpha-2u-globulin nephropathy in
male rats - an effect that is not relevant for human risk assessment.
Neurological tests were negative and only liver and kidney weight
increases, in the absence of histopathological change, were reported at
the highest dose level (1000mg/kg/day). Therefore excluding the male
rat-specific alpha-2u-globulin nephropathy, 2,4,4 -trimethylpentene is
generally well tolerated in the studies available. The overall NOEL,
appropriate for human risk assessment, was 300mg/kg/day.
The results of repeat-dose oral studies on
2,4,4 -trimethylpentene in rats do not warrant classification under DSD
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