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EC number: 201-052-9
CAS number: 77-73-6
Dicyclopentadiene has been shown to be non-genotoxic both in vitro and in vivo. These observations indicate that dicyclopentadiene is not expected to be a genotoxic carcinogen.Dicyclopentadiene has been examined in repeat dose inhalation and oral studies and shown low levels of toxicity. The liver and adrenals showed limited changes on histopathological examination, and the kidneys in male rats showed changes consistent with the accumulation of alpha-2-microglobulin, a male rat specific protein.It is concluded that there are sufficient data to indicate that dicyclopentadiene does not pose a risk of genotoxic carcinogenicity. There are also data available to understand that the cellular changes arising from repeated administration of dicyclopentadiene to animals are limited and to conclude that dicyclopentadiene is unlikely to be carcinogenic. The changes in the male rat kidney are consistent with a male rat specific mechanism and even if tumours were formed on chronic administration to male rats, these would be considered not relevant to humans. The conduct of animal carcinogenicity studies is therefore considered to be unwarranted.
No classification is warranted under CLP.
There are no lifetime
animal studies available on dicyclopentadiene in order to directly
investigate for possible carcinogenic activity. However,
there is sufficient information available to make an assessment of the
likely carcinogenic potential of the material.
relevant for carcinogenicity
Dicyclopentadiene is a
relatively straightforward chemical structure. It
contains two olefinic centres, but sufficiently distant as to be
essentially two isolated mono-ene groups. These
are potential centres of chemical functional activity and the only alert
for possible genotoxic activity when the structure of dicyclopentadiene
is considered against the criteria established by Ashby and Tennant
data relevant for carcinogenicity
In vitro data
been examined for mutagenicity in a range of recognised core assay types. In
vitro studies include assays for gene mutation in bacteria (the
Salmonella mutation assay) and also for cytogenetic activity. It
has shown negative results for mutagenicity in all these assays. The
above assays would be considered appropriate for evaluating any activity
that might have arisen from the two centres containing double bonds, and
this indicates that the initial theoretical alert from consideration of
the chemical structure is not expressed in reality. It
is concluded that the available data indicate that dicyclopentadiene has
no significant genotoxicity.
A material containing
dicyclopentadiene has been examined for mutagenicity using a bone marrow
cytogenetic assay in the mouse and was found not to be mutagenic. Dicyclopentadiene
has therefore been examined in the key relevant mutagenicity assays both in
vitro and in vivo and found to be non-genotoxic. There
is therefore good evidence for dicyclopentadiene being non-carcinogenic
in animals with respect to a genotoxic mechanism.
The repeat dose
toxicity of dicyclopentadiene was examined in F344 rats and B6C3F1 mice
by the inhalation route for 13 weeks, 5 days/week, 6 hours/day, at doses
of 0, 5.4, 27.5 and 275mg/m3 (Bushy Run, 1982). No
toxicity was reported in the female rats. In
the male rats, histopathological examination of the kidneys revealed
dose-dependent changes consistent with the accumulation of alpha2u-globulin,
a male rat specific protein. The
only significant toxicity reported in the mice was deaths that were seen
at the top dose group, accompanied by congestion of the lungs and kidney
also been examined in SD(Crj:CD) rats in an OECD screening test for
combined repeat dose and reproductive/developmental toxicity.
Doses used were
0, 4, 20, 100 mg/kg/day. In
males, histopathological examination showed hyaline droplets and
basophilic change in the tubular epithelium of the kidneys together with
single cell necrosis in the liver. In
both male and female animals an increase of fatty droplets was observed
in the fascicular zone in the adrenals. No
treatment related haematological changes were observed (JETOC, 1998a).
Similar findings of
limited or no toxicity were reported in a range of other repeat dose
studies, albeit with limited protocol features (e.g. animal numbers) or
duration of exposure (e.g. Kinkead et al, 1971).
Ashby J and Tennant RW
(1988) Chemical structure, Salmonella mutagenicity and extent of carcinogenicity
as indicators of genotoxic carcinogenesis among 222 chemicals tested in
rodents by the U.S.NCI/NTP.
Mutat Res 204: 17-115.
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