Biomedical Engineering Reference
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to those observed in rats by Nelson et al. (1985). There was a significant
increase in resorptions at 7500 ppm and above and an increase in fully
resorbed litters at 10,000 and 15,000 ppm. Despite malformations at
lower exposure levels, fetal weight was reduced only at 10,000 and
15,000 ppm. Interestingly, the induction of cleft palate and exencephaly
by methanol were found to be nonindependent events in this study. The
incidence of cleft palate among fetuses without exencephaly was
21.9%, while the incidence of cleft palate among fetuses with exence-
phaly was only 11.1%. Yasuda et al. (1991), studying TCDD, reported a
similar decrease in susceptibility to cleft palate among fetuses with
exencephaly.
The effects of methanol administered by oral gavage during preg-
nancy in CD-1 mice were also studied by Rogers et al. (1993a). Mice
were given twice daily dosages of 2 g/kg methanol, 7 hours apart, on GD
6-15. Effects observed were similar to those observed following
inhalation exposure (cleft palate, exencephaly, skeletal defects, and
resorptions), and quantitatively the peak blood level and incidence of
effects were similar to those observed after an inhalation exposure to
10,000 ppm methanol for 7 hours/day.
The developmental phase specificity for the adverse effects of
exposure to inhaled methanol in pregnant CD-1 mice has been exam-
ined. Bolon et al. (1993) exposed pregnant mice to 10,000 ppm metha-
nol (7 hour/day) for 10 days on GD 6-15; to 5000, 10,000, or
15,000 ppm for 3 days on GD 7-9; or to 10,000 or 15,000 ppm for
3 days on GD 9-11. Gestation day 17 fetuses were examined for
external and visceral anomalies, but skeletal exams were not done.
Exposure to 10,000 or 15,000 ppm on GD 6-15 resulted in cleft palate,
exencephaly, hydronephrosis, tail and digit defects, and increased
resorptions. Exposure to 10,000 or 15,000 ppm on GD 7-9 resulted
in exencephaly, cleft palate, hydronephrosis, and ocular and tail defects.
Exposure to these same concentrations on GD 9-11 resulted in cleft
palate and digit and tail defects. Exposure to 15,000 ppm methanol on
GD 7-8 also caused exencephaly. Single or two-day (7 hours/day)
inhalation exposures of pregnant CD-1 mice to 10,000 ppm methanol
during the period of GD 5-13 were carried out by Rogers and Mole
(1997). Two-day exposures were carried out beginning on each of GD
