Risk to Pollinators from the Use of Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 227

If the RQ exceeded the level of concern (LOC of 0.4 for acute tests), higher-tier
assessments were needed to obtain a more realistic measure of the risk of CPY to
pollinators. The Tier-2 process involved more elaborate semi-field or field studies
with whole colonies, quantification of residues in pollen and nectar, and modeling.
Risks of exposure to CPY through water on wet soil, such as puddles, and wet foli-
age from rain and dew was assessed by use of simulation models. Tier-3 tests stud-
ies were used to resolve important uncertainties identified in Tier-1 and Tier-2
assessments. Incident reports were also considered in the Tier-3 assessment.
Honey bees have long been included in regulatory test requirements as a surro-
gate for pollinators as well as for terrestrial invertebrates in general (USEPA 1988 ),
and most data on CPY in this risk assessment relate to honey bees. In studies on 21
species of non- Apis bees, LD 50 values for several species are within an order of
magnitude of that of the honey bee (Fischer and Moriarty 2011 ), suggesting A. mel-
lifera can be a good surrogate species for other bees (Porrini et al. 2003 ). Toxicity
data for CPY in non- Apis pollinators were used when available.
In addition, certain non-target arthropods (NTA) such as Aphidius spp.
(Hymenoptera: Braconidae), Typhlodromus spp. (Mesostigmata: Phytoseiidae), and
Aleochara bilineata (Coleoptera: Staphylinidae) can be useful in assessing risks to
non- Apis pollinators (Miles and Alix 2012 ). Therefore, an attempt was made to find
useful toxicity data for CPY with these non-target arthropods and their usefulness
as surrogates for non- Apis bees was evaluated.

3 Characterization of Exposures

3.1 General Physical and Chemical Properties and Fate

The chemical, physical, and environmental profile of CPY (Giesy et al. 1999 ; Racke
1993 ; Solomon et al. 2001 , 2014 ), and its environmental fate on plants, in water and
in soil (Mackay et al. 2014 ; Racke 1993 ; Solomon et al. 2001 ), have been well-
described by others and is not repeated here.

3.2 General Fate in Insects

The metabolism of CPY in animals consists of transformation and conjugation
processes. When not exposed to lethally toxic doses, CPY is readily metabolized
and eliminated by most insects (Racke 1993 ). Activation to CPYO, which is the
toxic form of CPY, and deactivation to form trichloropyridinol (TCP) occur simul-
taneously. Conjugation of the intermediates is a precursor to excretion (Racke
1993 ). In cockroaches ( Leucophaea maderea ), imported fire ants ( Solenopsis