Risks to Aquatic Organisms from Use of Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 119

Fig. 1 The conceptual model for exposures of aquatic organisms to chlorpyrifos in surface waters.
The weights of the arrows indicate importance of the pathway of exposure
(Banks et al. 2005 ; Phillips et al. 2007 ) and sediments (Ding et al. 2010 ) until label
changes occurred in 2001. All current labeled uses of CPY are in agriculture, thus
sources from urban uses were omitted from the conceptual model. As is discussed
in more detail in Williams et al. ( 2014 ), CPY can enter surface waters via several
routes (Fig. 1 ), although some are of lesser importance. CPY is not registered for
direct application to surface waters and the relatively large K OC (973-31,000 mL g −1
Solomon et al. 2014 ) mitigates against leaching and movement via groundwater.
Spills might occur but, because they are episodic and cannot be predicted, the cur-
rent labeled uses were the focus of this review. The major potential sources for
exposures of aquatic organisms are run-off, erosion, and tail waters with lesser
inputs via drift of sprays and deposition from the atmosphere (Williams et al. 2014 ) .
CPY adsorbs to surfi cial sediments in water-bodies, and residues of CPY have
been detected in surfi cial sediments in streams and creeks in areas of use. In a few
cases, observed toxicity in sediments collected from agricultural drains, creeks, and
rivers in California was linked to the presence of CPY (Phillips et al. 2012 ; Weston
et al. 2012 ). However, in most locations CPY contributed less to toxicity of sedi-
ments than other pesticides such as pyrethroids (Amweg et al. 2006 ; Ding et al.
2010 ; Ensminger et al. 2011 ; Phillips et al. 2006 ).
CPY is bioconcentrated and/or bioaccumulated into aquatic organisms to a lim-
ited extent. Measures of bioconcentration factors (BCFs), bioaccumulation factors
(BAFs), and biota-sediment accumulation factors (BSAFs) are relatively small
(Mackay et al. 2014 ). One literature report gave a biomagnifi cation factor (BMF) in