Ecological Risk Assessment of the Uses of the Organophosphorus Insecticide Chlorpyrifos, in the United States - Reviews of Environmental Contamination and Toxicology - page 2

soil, or dormant trees (Solomon et al. 2014 ). CPY can be applied by use of aerial
spraying, chemigation, ground boom or air-blast sprayers, tractor-drawn spreaders,
or hand-held equipment.
Since the registration of CPY was last re-evaluated (USEPA 2004 , 2008 ), there
have been changes in how assessments of risks of chemicals used to protect agri-
cultural crops are conducted. The amount of data available on mobility, persistence,
and concentrations in the environment and toxicity of CPY to animals has increased.
Most importantly, many methods and models for estimating concentrations in the
environment and exposures to wildlife have improved signifi cantly since the results
of the last assessments were published (Giesy et al. 1999 ; Solomon et al. 2001 ).
Also, patterns of use have changed in response to changes in cropping, pest pres-
sure, introduction of genetically modifi ed crop (GMO) technology, and competing
pesticides. Uses of CPY are the primary determinants of the entry of CPY into the
environment and its subsequent fate in the regions of use and beyond. The purpose
of this paper is to provide a synopsis of uses and properties of CPY and the results
risk assessments conducted for aquatic life and terrestrial biota. Mammals were not
addressed in any of these risk assessments because they are less sensitive to CPY
and do not have as large a potential for exposure as do birds. It was previously
concluded that, if birds are not affected by a particular pattern of use, then mam-
mals occurring in the same environment would also not be adversely affected
(Solomon et al. 2001 ).

2 Uses and Properties of Chlorpyrifos

The second paper in the series reviews the current uses permitted under the current
label and patterns of use in various crops (Solomon et al. 2014 ). The data on physi-
cal and chemical properties were reviewed and a set of consensus values were
selected for use in the environmental fate assessments, which included modeling of
long-range transport and assessment of bioaccumulation (Mackay et al. 2014 ), char-
acterizing routes of exposure to CPY through soil, foliage, and food items in ter-
restrial systems (Cutler et al. 2014 ; Moore et al. 2014 ), and in surface-water aquatic
systems (Giddings et al. 2014 ; Williams et al. 2014 ). Currently-registered formula-
tions of CPY and their uses in the U.S. were the basis for the development of the
exposure scenarios and the conceptual models used in assessing risks to aquatic
organisms (Giddings et al. 2014 ; Williams et al. 2014 ), birds (Moore et al. 2014 ),
and pollinators (Cutler et al. 2014 ). These data on use were based on the current
labels and refl ect changes in labels and use-patterns that have occurred since 2000.
Important changes included removal of all residential and termiticide uses and
changes in buffers. CPY is now registered only for use in agriculture in the U.S. but
is an important tool in management of a large number of pests, mainly insects and
mites. CPY is used on a wide range of crops, although applications to corn and
soybeans account for 46-50% of annual use in the U.S. Estimates of total annual
use in the U.S. from 2008 to 2012 range from 3.2 to 4.1 M kg y −1 , which is about
50% less than the annual use prior to 2000.