Surfactant Effects on Environmental Behavior of Pesticides - Reviews of Environmental Contamination and Toxicology - page 155

for a hydrophobic chemical with log P greater than 3 and most studies have been
conducted in the presence of some solvents or dispersants, information on the effect
of adjuvants on the bioconcentration of a chemical are very limited. Kaka and
Hayton (1978) studied the effect of 0.01% polysorbate 80 on the bioaccumulation of
4-aminoantipyrine and ethanol in goldfish at 10°-35°C and reported increase of
uptake rate, especially for the former compound, presumably from enhanced diffu-
sion through the gill. In contrast, any significant effect of nonionic surfactant at the
concentrations less than cmc was not observed in a recent study.
The bioconcentrations of seven hydrophobic chemicals (log P = 4.2-6.9) includ-
ing DDT (1) to carp have been investigated in the presence and absence of castor
oil HCO surfactants having the polyethyleneglycol substructure in accordance with
OECD 305, and almost similar bioconcentration factors were obtained irrespective
of the nonionic surfactants (Yakata et al. 2006). Alternatively, Park et al. (2002)
demonstrated the significantly reduced bioconcentration of three PAHs to freshwa-
ter mussels in the presence of 0.02% Tween 80 above cmc. They assumed the parti-
tion of PAH to the micelles and obtained micelle partition coefficients of 5-6 × 10 3
(L/kg) by analyzing the time-dependent uptake profiles in the presence of the
surfactant.
Effects of the dispersant Corexit 9527 including ethoxylated sorbitans, anionic
surfactant, and hydrocarbon solvent on the bioconcentration of PAH in a few
aquatic species have been investigated extensively as well as its trophic transfer.
Wolfe et al. (1998a,b) reported not only increased bioaccumulation of naphthalene
to marine algae at 20°C but also increased trophic transfer to the rotifer by the dis-
persant at 20 ppm. The dispersant-induced leakiness and lysis of algal cells resulted
in the increased depuration of naphthalene as a result of the increased cell permea-
bility. Similar effects of this dispersant were also reported for phenanthrene (Wolfe
et al. 1999). By using these PAHs in the presence of Corexit 9527, their uptake and
trophic transfer in the model aquatic system including algae (primary producer),
rotifer (primary consumer), and laval topsmelt (higher consumer) were observed
(Wolfe et al. 2001; Mielbrecht et al. 2005). The dispersant increased the uptake and
trophic transfer of less hydrophobic naphthalene, but the bioconcentration of phen-
anthrene in topsmelt decreased, probably from more solubilization of the PAH in
the micelles. Although available information on the effect of adjuvants and sur-
factants is limited, not only their concentration above or below cmc but also the
hydrophobicity of a chemical are the controlling factors for bioconcentration in
aquatic species.
Summary
The potential effects of adjuvants, including surfactants used in pesticide formula-
tion, have been extensively studied for many small organic chemicals, but similar
investigation on pesticides is limited in most cases. Solubilizing effects leading to
the apparently increased water solubility of a pesticide are commonly known