Risk to Pollinators from the Use of Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 219

(Michener 2007 ) and it was not possible to obtain data for all species. Searches of
databases incorporated 'chlorpyrifos' with the words such as 'pollinator', 'bee',
' Apis ', ' Bombus ', ' Megachile ', and ' Osmia '. The later four are major bee genera
that exist in the wild and are managed by humans in agricultural settings, and thus
are most likely to have associated data on toxicity of CPY to bees. Family names of
major bee families, such as 'Apidae', 'Megachilidae', Andrenidae', 'Halictidae',
and 'Colletidae' were used. Other potentially important pollinators include the dip-
teran families Bombyliidae (bee flies) and Syrphidae (hover flies), but no reports
examining effects of CPY on these taxa were found. Other insect taxa can pollinate,
but generally do so adventitiously, less frequently, and are generally not considered
important pollinators of crops in the U.S. to which CPY is applied. For estimates of
exposure, data from semi-field or field experiments with leaf-dwelling species was
considered a potential source from which to develop point estimates of contact
exposure for foliar-applied products (Fischer and Moriarty 2011 ), since these spe-
cies may be considered surrogates for bees. Because data on toxicity of CPY to
non- Apis pollinators were rare, studies were considered that assessed effects of
CPY on certain other arthropod taxa that have also been shown to be suitable sur-
rogate species for non- Apis bees (Candolfi et al. 2001 ; Miles and Alix 2012 ).
Data were collected from sources listing 'chlorpyrifos' or 'chlorpyrifos-ethyl' as
the active substance; both are common names of O , O -diethyl O -3,5,6-trichloropyridin-
2-yl phosphorothioate. The insecticidal degradate chlorpyrifos-oxon (CPYO) was
also considered. Exposure and effects data for 'chlorpyrifos-methyl' ( O , O -dimethyl
O -3,5,6-trichloro-2-pyridinyl phosphorothioate)—a different compound—were not
included in the risk assessment. The assessment of risk was primarily focused on
evaluating potential impacts of typical CPY formulations currently registered for
crop production in North America on bee pollinators.

2.3 Conceptual Model

Adverse effects on ecosystems result from the interaction of a stressor, in this case
CPY and its degradation products, with receptors of concern, such as individual
pollinators, hives, nests, or populations. The degradation product of concern for
CPY is CPYO, which is also the activated biologically-active product of CPY
(Solomon et al. 2014 ). Other degradates of CPY are of minimal risk to pollinators.
A conceptual model can be constructed to illustrate potential routes of exposure
during agricultural use, and the taxa and life stages potentially affected (Fig. 1 ). The
conceptual model shows the scope of the risk assessment, guides its development,
and illustrates the relationships among the potential exposure pathways. Previous
conceptual models for assessments of effects of agricultural chemicals on pollina-
tors have noted the need to quantify exposure within and outside the treated area and
to consider the behavioral and biological traits of pollinators (Barmaz et al. 2010 ).
The conceptual model was developed for foliar spray or granular soil-applied
treatments of CPY. For pollinators, exposure is primary if it is to the initial exposed