Risk to Pollinators from the Use of Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 217

There is concern about potential adverse effects of pesticides on pollinators (EFSA
2012 ; NAS 2007 ). Chlorpyrifos (CPY; CAS No. 2921-88-2) is an organophosphorus
insecticide and acaricide that is widely used in agriculture and horticulture in the U.S.
and other countries to control a wide variety of foliage- and soil-borne insect pests on
a variety of food and feed crops (Solomon et al. 2014 ). Many of the agro-ecosystems
where CPY is used contain populations of managed and wild pollinators. In some of
these, such as almonds, citrus fruits, and cranberries, pollinators play a critical role in
the production of the crop being protected with sprays of CPY. Other crops, such as
soybean and corn, which are treated with CPY, do not directly rely on pollinators for
production because they are mainly pollinated by wind, but can nonetheless serve as
a source of forage for multiple species of pollinators during parts of the season. In
addition to food (pollen and/or nectar), pollinators might also obtain nesting materi-
als and occupy nesting sites in habitats exposed to CPY.
In this study, the risk posed by use of CPY to insects that serve as pollinators was
assessed. Patterns of use of CPY that are currently registered in the U.S. and Canada
were the main focus (Solomon et al. 2014 ), but tests with formulations used in other
countries were considered when relevant data from the U.S. were lacking. Because
microencapsulated formulations are not used in the U.S., they were excluded from
the assessment. Bees were the focal taxa but other groups of insects were also con-
sidered when data were relevant and available, particularly where they are used as
surrogate species in regulatory risk assessments. Non-insect pollinators were not
considered. Most studies and scenarios explored for the risk assessment were con-
cerned with agricultural systems, but patterns of use of CPY in horticulture and
landscaping, such as turf were considered.

2 Problem Formulation

The central question considered in the problem formulation was: Is there sufficient
exposure of pollinators to CPY and/or its degradate, chlorpyrifos oxon (CPYO), to
present a risk of widespread and repeated mortality or biological impairment to
individuals or populations of pollinators? This question forms the basis for the
detailed development of the risk assessment in the following sections.

2.1 Use Patterns of Chlorpyrifos: Pollinator Considerations

The uses and properties of CPY are discussed in detail in a companion paper
(Solomon et al. 2014 ). Chlorpyrifos is used to control a wide variety of economically
important insect pests in a large number of agricultural and specialty application
scenarios throughout the U.S. Several granular and sprayable formulations of CPY
are currently marketed in the U.S. and Canada, including Lorsban Advanced ® and
Lorsban ® 15G for agriculture, and Dursban ® 50 W for horticultural uses on trees,