Refined Avian Risk Assessment for Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 163

(3) transformation products in the environment; (4) routes of exposure; and (5) mode of
toxic action and thresholds for effects. The information cogent to these topics was
used to create a conceptual model and identify focal avian species for the assessment.
The problem formulation concludes with a list of exposure scenarios that were
included in the refi ned avian risk assessment and an overview of the analysis plan.

2.1 Patterns of Use

Chlorpyrifos is an organophosphate insecticide that provides broad spectrum control of
insects in cereal, oil, forage, nut, and vegetable crops (Solomon et al. 2014 ; USEPA 2011 ).
The focus of this assessment is on representative current use fl owable and granular
formulations of Lorsban, i.e., Lorsban ® Advanced and Lorsban ® 15G, respectively.
Chlorpyrifos is registered for use on a wide variety of crops including Brassica
vegetables, corn, onion, peanut, sugar beet, sunfl ower, and tobacco for the granular
formulation (Lorsban 15G), as well as alfalfa, Brassica vegetables, citrus, corn, cot-
ton, grape, mint, onion, peanut, pome and stone fruits, soybean, sugar beet, sun-
fl ower, sweet potato, tree nuts, and wheat for the fl owable formulations (e.g.,
Lorsban Advanced) (Gomez 2009 ; Solomon et al. 2014 ). The greatest amounts of
CPY used in 2007 were applied to soybean, corn, almond, apple, alfalfa, wheat, and
pecan (Gomez 2009 ; Solomon et al. 2014 ). Chlorpyrifos is widely used in the
Midwest and Plains regions, California, Florida and Georgia because these are the
primary growing areas for many row crops, citrus and tree nuts. For additional
information on CPY use patterns, see Sect. 2.8 and Solomon et al. ( 2014 ).

2.2 Formulations

The focus of this risk assessment is on two formulations, the granular and the fl owable.
Lorsban 15G (Dow AgroSciences 2008 ) is a clay-based (e.g., montmorillonite,
bentonite) granular formulation containing 15% active ingredient. Lorsban
Advanced (Dow AgroSciences 2009 ) is a fl owable formulation, specifi cally an
emulsion in water that contains 40.2% active ingredient.

2.3 Metabolites of CPY in the Environment

The fate and transport of CPY in the environment is reviewed in Mackay et al.
( 2014 ). In this section, we focus on degradates of CPY in the environment that
could be relevant to the avian risk assessment. The major transformation product of
hydrolysis of CPY in alkaline soil is 3,5,6-trichloro-2-pyridinol (TCP) (Solomon
et al. 2014 ). TCP is non-toxic to birds at concentrations greater than what would be
encountered in the environment (acute LD 50 >1,000 mg ai kg −1 bwt, chronic LC 50 s