Toxicity of 19 adjuvants to juvenile Lepomis macrochirus (bluegill sunfish)

Abstract

Nineteen adjuvants, many used as surfactants for aquatic herbicide applications, were applied in static bioassay to bluegill sunfish (Lepomis macrochirus) for 96 h to determine median lethal concentrations (LC50). Surfactants are added to the tank mix as a percentage (v/v) of the total volume, in contrast to herbicide application rates, which are usually expressed in kilograms per hectare. Two ethoxylated tallow amine products were the most toxic, having LC50 values of 1.6 and 2.9 ppm (all values v/v). Seven alcohol/glycol-based surfactants had 96-h LC50 values of 4.0 to 11.6 ppm (mean = 7.9 ppm). The polysiloxane- or silicone-based surfactants had toxicities of 18.1 to 29.7 ppm (mean = 24.7). Two limonene-based products had LC50 values of 10.2 and 30.2 ppm. A methylated seed oil with emulsifier had a LC50 of 53.1 ppm. Two acid/buffer utility adjuvants had LC50 values of 60.8 and 221 ppm. To compare the relative safety of the tested surfactants, we assumed maximum label rate applications to 1 m deep water with uniform mixing. This comparison of relative safety is based on mortality to 50% of the test organisms and does not imply application rates that would not result in any mortality. The two ethoxylated tallow amines, neither used or recommended for aquatic applications, had a relative safety factor of 12.6 or less. Relative safety factor varied from 6.2 to 20.4 for the seven alcohol/glycol surfactants, 38.4 to 63.2 for silicone-based products, 5.5 to 16.1 for limonene products, 113 for methylated seed oil, and 132.2 to 315.7 for acid/buffer utility adjuvants. When used according to label recommendations under normal use conditions, these adjuvants should not be present in acutely toxic concentrations; however, the most toxic adjuvants in very shallow water (< 10 cm) would be toxic to bluegill sunfish that did not move to deeper water to avoid lethal concentrations.

Toxicological Risks of Agrochemical Spray Adjuvants: Organosilicone Surfactants May Not Be Safe

“…The non-ionic spray adjuvant R-11 synergized the acute toxicity of the insecticides spinosad ( 19 ) and imidacloprid ( 20 ) on aquatic crustaceans and, in the absence of an insecticide, reduced the growth rate of Daphnia pulex at relevant field concentrations found after application near aquatic systems ( 21 ). Aquatic organisms are particularly vulnerable to the general ecotoxicity of adjuvant surfactants ranging from invertebrates ( 22 , 23 ) to fish ( 19 , 24 , 25 ) and amphibians ( 26 ). Terrestrial insects, in turn, have long been shown susceptible to insecticide synergisms associated with spray adjuvants ( 27 , 28 ).…”

Cetyl Alcohol Polyethoxylates Disrupt Metabolic Health in Developmentally Exposed Zebrafish

“…Studies examining commercial AEO mixtures in Xenopus reported 72 h LC 50 values of ~5 mg/L, various malformations (edema, loss of pigmentation, and microcephaly), and the collapse of the mitochondrial electrochemical gradient [ 63 ]. Various alcohol-based surfactants induced 96 h LC 50 values of ~8 mg/L in bluegill sunfish [ 64 ] and ~3.0 mg/L 28-day toxicity in fathead minnows [ 65 ] (with more sensitive effects on growth than survival). A variety of AEOs induced no observed effect concentrations on survival and reproduction from 0.8 to 2.8 mg/L with varying carbon chain lengths of 10–14.5 (cetyl alcohol, examined here, has a backbone of 14 carbons) and average ethoxylate chains of ~6.5 in Daphnia [ 66 ]; 21-day LC50s were 1.2–5.9 mg/L for these surfactants [ 66 ].…”

Acute toxicity of three herbicide formulations in Astyanax altiparanae (Characiformes, Characidae), an emerging Neotropical fish model species

“…The observed LC 50 value for pure glyphosate ranged from 10 to 97 times higher than the LC 50 for surfactants in studies with adults and early embryonic developmental stages. The toxicities of 19 adjuvants, commonly used as surfactants in aquatic herbicide applications, were evaluated in juveniles of Lepomis macrochirus (Haller and Stocker, 2003). Two surfactants, classi ed as members of the ethoxylated tallow amine group, are found in some formulations of glyphosate-based herbicides and are highly toxic with LC 50 values of 1.6-2.9 ppm.…”