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EC number: 200-753-7
CAS number: 71-43-2
Female Sprague-Dawley rats were exposed to
dose levels of 1, 10, 30 or 300 ppm benzene (6 h/day, 5 d/week) during
10 weeks pre-mating, mating, gestation and lactation periods up to p.n.
day 21. Five groups of 26 females and 13 proven fertile males were used.
To determine if oestrous was affected by treatment, daily vaginal smears
were made and evaluated for each female beginning 2 weeks prior to
initiation of mating. Observations of females for mortality and clinical
signs were made twice daily. Detailed physical examinations were
performed weekly throughout the study. Body weights were recorded once
weekly through completion of the mating period. Mated females were
weighed on days 0, 7, 14, and 21 of gestation and on days 0, 4, 14, and
21 of lactation. Pups were counted, weighed, and sexed on days 0, 4, 14,
and 21 of lactation. Litters were observed twice daily. On day 4 of
lactation, litters of more than 10 pups were randomly culled to 10 with
equal number per gender where possible. Pups that died were weighed and
sexed by internal examination. All dams were given a gross post mortem
examination. Uteri were examined for the presence and number of
implantation sites, and along with ovaries, were fixed and saved. Gross
post mortem examinations, including internal gender determinations, were
performed on all pups sacrificed on day 21 of lactation and on pups
found dead during lactation. The latter were also checked for the
presence or absence of milk in the stomach. Liver, kidney, and in males,
testes weights were recorded for each pup. Thirty-three organs and
tissues along with any abnormal lesions were fixed in 10% neutral
buffered formalin from two pups per sex per litter and saved for future
There were no effects on maternal body
weight and body weight gain nor were there adverse effects on fertility
as measured by percentage pregnant animals, mean gestational length,
number of litters, litter size, and viability of the pups and the
weanlings at any dose tested. The only statistically significant
differences for offspring were lower female pup body weight on day 21
and lower liver weight at the 300 ppm exposure level. These differences
were small and considered not to be adverse. No treatment related
effects were seen in pup survival or at gross post mortem on post natal
An exposure concentration of 300ppm (960 mg/m3)
is a NOAEC for both adult and offspring toxicity and female fertility.
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