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EC number: 201-622-7
CAS number: 85-68-7
Butyl benzyl phthalate showed weak positive responses in two key in vivo
studies (reliability 2) conducted under the auspices of the National
Toxicology Program (NTP, 1997f). Both studies involved a single
intraperitoneal injection of up to 5 g/kg bw in mice. In the chromosome
aberration assay, examination of the bone marrow cells 17 hours later
revealed a weak (but statistically significant) increase in aberrations
at the top dose of 5 g/kg bw, while no such increase was observed at the
delayed 36-hour sampling time. In this assay the mitotic index was not
determined as an indicator of cytotoxicity. In the sister-chromatid
exchange (SCE) assay, in which the bone marrow cells were examined 23 or
42 hours after treatment, there was a weak increase in numbers of SCEs;
this showed a significant trend at 42 hours, and also at 23 hours after
disregarding the top dose level (which had shown a reduced response).
Two other in vivo studies of lower reliability provide no evidence of
genotoxic potential. Thus, in a study available in abstract form only
(reliability 4), butyl benzyl phthalate did not induce dominant lethal
mutations in the foetuses when two strains of male mice were given three
subcutaneous injections of up to 4.6 g/kg bw and mated with untreated
females of the same strain. A slight, dose-related reduction in total
implants was observed after the first mating period, indicating that the
compound was tested at a high enough dose to produce signs of toxicity
(a slight reduction in fertility) (Bishop et al., 1987). Another study
assigned a reliability code of 3 (not reliable) due to the low test dose
used (0.18 mg/kg bw/day) found no evidence of micronucleus induction in
the bone marrow of female rats that were treated via the drinking water
throughout pregnancy and lactation (Ashby et al., 1997).
In two reliable studies, butyl benzyl phthalate did not induce
chromosome aberrations and showed no convincing evidence of
sister-chromatid exchange (SCE) induction when tested in vitro with
Chinese hamster ovary cells, both in the presence and absence of a rat
liver metabolic activation (S9) fraction (NTP, 1997e). Although an
equivocal result was obtained in the first SCE assay in the absence of
S9 (a significant trend (P=0.004) without any significant increase in
SCEs at any of the dose levels), the subsequent study without S9 using a
higher top dose and the assay with S9 were clearly negative.
Butyl benzyl phthalate (or Santicizer 160) also showed no convincing
evidence of mutagenicity at the thymidine kinase locus in two reliable
mouse lymphoma assays, when tested up to a cytotoxic concentration in
the presence and absence of a rodent liver metabolic activation fraction
(Litton Bionetics, 1977; NTP, 1997c). The NTP study reported increased
mutant frequencies in the absence of S9, but only at concentrations that
produced precipitation. No increase in mutant frequency was observed in
the presence of S9 (NTP, 1997c).
When tested at concentrations of 10 mg/plate or higher in the Ames
bacterial test, in the presence and absence of a liver metabolic
activation fraction, butyl benzyl phthalate (or Santicizer 160) has
shown no evidence of mutagenic potential in Salmonella typhimurium
strains TA98, TA100, TA1535, TA1537 and TA1538. Three such studies are
reported, two reliability 2 (Litton Bionetics, 1976; NTP, 1997d) and the
other reliability 4, not assignable (Flowers, 1976).
The available studies on the in vivo and in vitro genotoxicity of butyl
benzyl phthalate are considered adequate for concluding that the
compound does not need to be classified for mutagenicity, under the EU
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