Studies on the embryotoxic effects of ortho-, meta- and para-xylene

Abstract

CFY rats were exposed to inhalation of ortho-, meta-, or para-xylene at 150, 1500, or 3000 mg/m 3 concentration for 24 h/day from day 7 to day 14 of pregnancy. Additional groups of 3 rats were exposed to o-xylene at 150, 1500, or 3000 mg/m 3 concentrations for 2 h only on the 18th day of pregnancy. In this latter group of rats exposed to o-xylene 18th day of pregnancy, the o-xylene concentration in the blood of the rats was proportional to that in the atmosphere. The solvent crossed the placenta; it was present in the fetal blood and amniotic fluid. All the 3 xylene isomers inhaled at the highest concentration brought about toxic effects in the mother animals. All the 3 isomers brought about the retardation of fetal development: a decrease in the weight of the fetuses, an increase in the incidence of the symptoms of skeletal retardation, a decrease in the activity of different enzymes, succinic dehydrogenase, alkaline- and acid phosphatase and glucose 6-phosphatase, characteristic features of the functional maturity of the nephron. Retardation of the fetuses was dose-dependent, but also dependent on the chemical structure of the particular isomer; their effectiveness was para-, ortho- and meta-xylene in the decreasing order of potency. None of the isomers proved to be teratogenic. Meta- and para-xylene inhalation at the highest concentration increased the incidence of extra ribs. Preimplantation fetal loss was increased by meta- and para-xylene, meta-xylene at the highest concentration interfered with the process of implantation, while para-xylene exposure resulted in an increased postimplantation loss of the fetuses. Ortho-xylene inhalation was without effect on the incidence of the extra ribs, either on implantation, or on the pre- and postimplantation fetal losses.