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EC number: 202-049-5
CAS number: 91-20-3
* Dunnett’s or William’ test, p<0.05
§Test for linear Trend, p<0.05
% Fetuses malformed
% Litters with malformed fetuses
% Fetuses with enlarged ventricles (brain)
% Fetuses with variations
% litters with one or more variations
** Fisher’s Exact Test,p<0.05
In this well conducted study, groups of 28 female Sprague-Dawley rats
were treated by gavage with 0, 50, 150 or 450 mg/kg/day naphthalene on
days 6-15 of gestation. Caesarean sections were performed on day 20. The
results from this study indicate that naphthalene administered orally
had minimal effects on fetal development in the presence of significant
Developmental toxicity was expressed only as significant trends toward
decreased fetal weight and increased incidence of visceral malformations
in the naphthalene-treated groups. The dose of naphthalene which caused
the largest developmental changes (450 mg/kg/day) also significantly
reduced maternal corrected weight gain and food consumption.
There was an increase in the incidence of one visceral malformation
(enlarged lateral ventricles of the brain), but only in one replicate in
the 450 mg/kg/day group. It is equivocal whether this represents a
direct effect of naphthalene on fetal development, because there was an
order of magnitude difference in the incidence of these malformations
between replicates in the control group. Additionally, the incidence of
enlarged lateral ventricles of the brain in the background control data
from RTI laboratory has been reported to be highly variable in recent
years. In six NTP-sponsored rat developmental teratology studies
conducted at RTI from January 1989 through December, 1990, the
occurrence of this particular malformation has ranged from 0% to 27%.
developmental toxicity of naphthalene cannot be based solely on an
increase in the incidence of enlarged lateral ventricles in one
replicate of the high dose group. Therefore, it can be concluded a
developmental NOAEL for orally administered naphthalene is closer to 450
mg/kg/day and the developmental LOAEL is probably higher than 450
mg/kg/day naphthalene. In the absence of other data, 150 mg/kg bw/d has
been adopted as unequivocal NOAEL.
Naphthalene caused significant maternal toxicity. Two dams died during
dosing in the 50 mg/kg/day group, but the absence of any deaths in the
higher dose groups does not suggest an association between
naphthalene-treatment and maternal mortality.
More consistent were the significant reductions in maternal body weight
and weight gain in the 150 mg/kg/day and 450 mg/kg/day naphthalene
groups. The effects of these two doses on maternal weight parameters may
be secondary to naphthalene-induced suppression of food and water
consumption on gd 6 to 9. The fact that maternal body weight began to
rise in these two groups at essentially the same rate as controls after
food and water consumption returned to normal, supports this view.
Furthermore, when maternal nutritional status was not affected by
treatment (50 mg/kg/day naphthalene), no effect on maternal weight or
maternal weight gain was observed. The threshold for effects of
naphthalene on respiration and motor activity was lower than that for
weight reduction since 50 mg/kg/day naphthalene was comparable to 450
mg/kg/day naphthalene in producing shallow breathing and lethargy during
the early phases of dosing.
The LOAEL for naphthalene-related maternal toxicity is 50 mg/kg/day.
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