The effect of exposure to a commercial 2,4-D herbicide formulation during gestation on urethan-induced lung adenoma formation in CD-1 mice

Female CD-1 mice were exposed to a commercial amine Formulation of 2.4-dich lorophenoxyacetic acid (2,4-D) on days 6-16 of gestation in drinking water at concentrations ranging from 0 to 1.0% of the formulated product, equival ent to approximately 0 650 mg/kg/d expressed as the amine derivative. The e ffect of 2,4-D on urethan-induced pulmonary adenoma formation was evaluated in female offspring 19 w after birth. Urethan-induced sleeping times obser ved following ip injection of 1.5 mg urethran/g bw 7 w after birth were not altered by 2,4-D (0 = 0.10), indicating that 2,4-D did not affect the rate of urethan elimination. 2,4-D exposure did not affect the number of tumors produced (0 = 0.58), but did reduce the mean tumor diameter in the highest dose group (p < 0.01). This minor antineoplastic activity of 2,4-D may be related, in part, to inhibitory effects of 2.4-D on various enzymatic or me tabolic pathways, essential for cellular growth and tissue development. Sin ce exposure to 2,4-D during pregnancy had little impact of tumor production , it is unlikely that persistent alteration to developing immune cells invo lved in the cell-mediated immunosurveillance mechanisms occurred. The subtl e alteration in tumor size and the mild impairment of growth in the offspri ng were observed almost exclusively in the highest treatment group. Since t his level of exposure is well in excess of those associated with normal app lication of 2,4-D, the hazard to non-target mammalian populations appears m inimal.