Properties and Uses of Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 13

foliage, and food items (Cutler et al. 2014 ; Moore et al. 2014 ), and in surface-water
aquatic systems (Giddings et al. 2014 ; Williams et al. 2014 ). The currently-registered
formulations of chlorpyrifos and their uses in the United States were the basis for the
development of the scenarios of exposure and the conceptual models used in assessing
risks to birds (Moore et al. 2014 ), pollinators (Cutler et al. 2014 ), and aquatic organ-
isms (Williams et al. 2014 ). These data on use are based on the current labels and
reflect changes in labels and use-patterns since the earlier assessments of risks to
aquatic (Giesy et al. 1999 ) and terrestrial organisms (Solomon et al. 2001 ). Physical
and chemical properties of chlorpyrifos were extensively reviewed by Racke ( 1993 )
and, rather than repeat all of this information, relevant values from Racke 1993 are
included in this paper and supplemental material (SI) with updates as appropriate.

2 Physical and Chemical Properties of Chlorpyrifos

Fundamental to assessing and predicting the general fate of chlorpyrifos in the envi-
ronment are having reliable data on physical chemical and reactivity properties that
determine partitioning and persistence in the environment. In the following sec-
tions, some of the key properties are discussed in more detail.

2.1 Properties Affecting Fate in Air

and Long-Range Transport

The fate of CPY and chlorpyrifos-oxon (CPYO; CAS No. 5598-15-2; CPY's biologi-
cally active metabolite, degradate, and minor technical product component) in air, with
respect to short- and long-distance transport are discussed in detail in a companion
paper (Mackay et al. 2014 ). The physical and chemical properties specific to fate in air
are presented in Tables 5 -8 in Mackay et al. ( 2014 ) and are not repeated here except in
the context of biological relevance and fate and movement in other matrices.

2.2 Properties Affecting Fate in Soil, Water, and Sediment

An extensive review of the data on half-lives of CPY in soils and has shown the high
variability attributed to soil organic carbon content, moisture, application rate and
microbial activity (Racke 1993 ). Fewer data are available for water and sediments,
but processes related to soils and sediments have been summarized in a recent
review (Gebremariam et al. 2012 ). The key physical and chemical properties of
CPY are listed in Tables 1 and 2 .
Chlorpyrifos has short to moderate persistence in the environment as a result of
several dissipation pathways that might occur concurrently (Fig. 1 ). Primary mech-
anisms of dissipation include volatilization, photolysis, abiotic hydrolysis, and