Environmental Engineering Reference
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of 500-5,600 mg ai kg −1 in the diet) (Campbell et al. 1990 ; Long et al. 1990 ;
Miyazaki and Hodgson 1972 ). Transformation products of TCP are also not toxic to
birds at concentrations observed in the environment (Racke 1993 ). The oxon of
CPY (CYPO; O -ethyl O -(3,5,6-trichloro-2-pyridinol) phosphorothionate) is formed
in vivo in birds by oxidative desulfuration (Testai et al. 2010 ). This metabolite is
shorter lived in the environment than CPY and is rapidly degraded via hydrolysis
to TCP and diethylphosphate (Mackay et al. 2014 ). The oxon of CPY is toxic to
non-target organisms, including birds, but poses little risk because it is formed in
very small quantities in the terrestrial environment and is rapidly degraded (Bidlack
1979 ; Chapman and Harris 1980 ; de Vette and Schoonmade 2001 ). The Pesticide
Management Regulatory Agency of Canada (PMRA) ( 2007 ) did not consider
CPYO to pose a risk to birds. Another transformation product, 3,5,6-trichloro-2-
methoxypyridine (TMP) has also been reported in aerobic biodegradation studies
(Bidlack 1979 ; Racke 1993 ). The half-life of TMP is similar to that of TCP and is
not toxic to birds at concentrations observed in the environment (Racke 1993 ;
Reeves 2008 ). For the reasons cited above, TCP, CPYO, and TMP were not consid-
ered in this refi ned assessment of risks of CPY to birds.
2.4
Routes of Exposure for Birds in Terrestrial Environments
Based on the physical and chemical properties of CPY (Solomon et al. 2014 ),
bioaccumulation of CPY could occur. It is not likely, however, to be a signifi cant
pathway of exposure for birds because CPY is rapidly metabolized with a half-life
of approximately 1-d (Barron and Woodburn 1995 ; Mackay et al. 2014 ; Racke
1993 ; Smith et al. 1967 ). Because CPY has a half-life of 2-5-d on foliage under
fi eld conditions (Williams et al. 2014 ), acute exposure is the primary concern.
Although not persistent in the fi eld, there is the potential for chronic exposure
because fl owable CPY may be applied up to four times per season with intervals as
short as 10-d. Therefore, for fl owable CPY, both acute and chronic risks to birds
were estimated. Because granular CPY can only be applied once per season
(Solomon et al. 2014 ), only acute risks were estimated for this formulation.
Whether applied as a granular or fl owable formulation, wind and rain cause pen-
etration of CPY into soil (Solomon et al. 2001 ), and volatilization from moist soil
surfaces is rapid (HSDB 2013 ; Mackay et al. 2014 ). Once below the soil surface,
CPY is much less available to birds. The most likely routes of exposure of birds to
CPY following application of the fl owable formulation are through the ingestion of
residues on plants and prey and in drinking water. Exposure to CPY through inhala-
tion, dermal contact, and preening are also routes of exposure for birds following
application of fl owable CPY. However, the results of several studies conducted with
turkeys ( Meleagris gallopavo ) (Kunz and Radeleff 1972 ; McGregor and Swart
1968 , 1969 ) indicate that uptake from dermal exposure directly from soil and
vegetation sprayed at maximum allowable rates on the Lorsban Advanced label, and
any subsequent preening would not cause adverse effects (Solomon et al. 2001 ).
By performing an analysis with the USEPA ( 2010 ) Screening Tool for Inhalation
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