Embryotoxic effects of benzene and its methyl derivatives: toluene, xylene.

CFY rats were exposed to inhalation of 1000 mg/m3 (313ppm) benzene, 1500 mg/m3 (399 ppm) toluene, or 1000 mg/m3 (230 ppm) xylene for 24 h/day from day 9 to day 14 of pregnancy; to that of 1500 mg/m3 (399 ppm) toluene for 24 h/day from day 1 to day 8 of pregnancy, or 1000 mg/m3 (266 ppm) toluene for 8 h/day from day 1 to day 21 of pregnancy,. CFLP mice were exposed to inhalation of 500 mg/m3 (133 ppm) toluene for 24 h/day from day 6 to day 13 of pregnancy. Untreated animals and groups inhaling pure air served as controls. None of the solvents proved to be teratogenic, the incidence of malformations did not change as a result of exposure, though an increase in skeletal anomalies (extra ribs, fused sternebrae) was observed with all 3 solvents. Benzene and toluene also caused considerable retardation of fetal development. The growth retarding effect of toluene on fetal development in early pregnancy is of particular importance from the point of view of occupational hygiene.