TERATOGENIC POTENTIAL OF ATRAZINE AND 2,4-D USING FETAX

The teratogenic potential of commercial formulations of atrazine (40.8 %) and 2,4-D was evaluated using FETAX (frog embryo teratogenic assay- Xenopus). Because these herbicides have been detected in ground and su rface water, this study was designed to determine the adverse effects in buffer and natural water for both herbicides. All treatments showed a significant concentration-response effect on exposed embryos, excep t for the 2,4-D natural water sample. Atrazine (solubility of the comm ercial formula used 70 mg/L at 20 degrees C), compared to 2,4-D (solub ility = 311 mg/L at pH = 1 and 25 degrees C), had a significantly grea ter teratogenic effect in both the buffer (atrazine EC50 = 33 mg/L, LC 50 = 100 mg/L, Tl = 3.03; 2,4-D EC50 = 245 mg/L, LC50 = 254 mg/L, Tl = 1.04) and natural water samples (atrazine EC50 < 8 mg/L, LC50 = 126 m g/L; 2,4-D EC50 and LC50 > 270 mg/L). The 2,4-D EC50 and LC50 values f or the buffer were similar at 245 mg/L and 254 mg/L. These similar val ues and the teratogenic index (Tl) of 1.04 suggested that 2,4-D was mo re embryotoxic than teratogenic to frog embryos at high concentrations . Atrazine in natural water demonstrated a significantly greater EC50 (100% abnormality at 8 mg/L, the lowest test concentration) to frog em bryos than the buffer experiment (EC50 = 33 mg/L). The extrapolated lo west observable adverse effect concentration (LOAEC) for the natural w ater experiment was 1.1 mg/L. These results suggest that atrazine toxi city is enhanced by the synergistic or additive effects of some compon ent of the water or atrazine was already present in the sample. In con trast to atrazine, 2,4-D was less toxic in natural water than buffer. These results suggest that both atrazine and 2,4-D pose little threat, since their embryotoxicity and teratogenicity to frog embryos occur a t high concentrations approaching their maximum solubility levels in w ater.