The Acute Toxicity of Agricultural Surfactants to the Tadpoles of Four Australian and Two Exotic Frogs.

Nonionic surfactants are frequently incorporated into pesticide formulations, and are therefore a group of chemicals to which amphibians may be exposed in agricultural or urban landscapes. However, little is known about the effects of surfactant exposure in amphibians. Feeding stage tadpoles of  Bufo marinus ,  Xenopus laevis  and four species of Australian frogs ( Crinia insignifera ,  Heleioporus eyrei ,  Limnodynastes dorsalis  and  Litoria moorei ) were exposed to nonylphenol ethoxylate (NPE) and alcohol alkoxylate in static-renewal acute toxicity tests. All species exhibited nonspecific narcosis following exposure to both these surfactants. The 48-h EC50 values for NPE ranged between 1.1 mg/l (mild narcosis) and 12.1 mg/l (full narcosis). The 48-h EC50 values for alcohol alkoxylate ranged between 5.3 mg/l (mild narcosis) and 25.4 mg/l (full narcosis). Replicate acute toxicity tests with  B. marinus  exposed to NPE at 30°C over 96 h indicated that the narcotic effects were not particularly time dependant. The mean 24, 48, 72, and 96-h EC50 (mild narcosis) values were 3.6, 3.7, 3.5 and 3.5 mg/l, respectively. The mean 24, 48, 72 and 96-h EC50 (full narcosis) were 4.0, 4.1, 4.2 and 4.0, respectively. Acute toxicity tests with  B. marinus  exposed to NPE at 30°C under conditions of low dissolved oxygen (0.8–2.3 mg/l) produced a two to threefold increase in toxicity.