Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
nomogram indicates incidental soil ingestion will not likely increase dietary exposure to
pesticides. Inclusion of soil into the diet would effectively reduce the overall dietary
concentration compared to the present assumption that the entire diet consists a contaminated
food source (Fletcher et al. 1994). An exception to this may be soil-applied pesticides in which
exposure from incidental ingestion of soil may increase. Potential for pesticide exposure under
this assumption may be underestimated for soil-applied pesticides and overestimated for foliarapplied
pesticides. The concentration of a pesticide in soil would likely be less than predicted on
food items.
• Exposure through inhalation of pesticides is not considered in the USEPA risk assessment
protocols. Such exposure may occur through three potential sources: spray material in droplet
form at time of application, vapor phase with the pesticide volatilizing from treated surfaces, and
airborne particulates (soil, vegetative matter, and pesticide dusts). The USEPA (1990) reported
exposure from inhaling spray droplets at the time of application is not an appreciable route of
exposure for birds. According to research on mallards and bobwhite quail, respirable particle size
(particles reaching the lung) in birds is limited to maximum diameter of 2 to 5 microns. The
spray droplet spectra covering the majority of pesticide application scenarios indicate that less
than 1% of the applied material is within the respirable particle size. This route of exposure is
further limited because the permissible spray drop size distribution for ground pesticide
applications is restricted to ASAE medium or coarser drop size distribution.
• Inhalation of a pesticide in the vapor phase may be another source of exposure for some
pesticides under certain conditions. This mechanism of exposure to pesticides occurs post
application and it would pertain to those pesticides with a high vapor pressure. The USEPA is
currently evaluating protocols for modeling inhalation exposure from pesticides including nearfield
and near-ground air concentrations based upon equilibrium and kinetics-based models. Risk
characterization for exposure with this mechanism is unavailable.
• The effect from exposure to dusts contaminated with the pesticide cannot be assessed generically
as partitioning issues related to application site soils and chemical properties of the applied
pesticides render the exposure potential from this route highly situation specific.
• Dermal exposure may occur through three potential sources: direct application of spray to
terrestrial wildlife in the treated area or within the drift footprint, incidental contact with
contaminated vegetation, or contact with contaminated water or soil. Interception of spray and
incidental contact with treated substrates may pose risk to avian wildlife (Driver et al. 1991).
However, available research related to wildlife dermal contact with pesticides is extremely
limited, except dermal toxicity values are common for some mammals used as human surrogates
(rats and mice). The USEPA is currently evaluating protocols for modeling dermal exposure.
Risk characterization may be underestimated for this route of exposure, particularly with high
risk pesticides such as some organophosphates or carbamate insecticides. If protocols are
established by the USEPA for assessing dermal exposure to pesticides, they will be considered
for incorporation into pesticide assessment protocols.
• Exposure to a pesticide may occur from consuming surface water, dew or other water on treated
surfaces. Water soluble pesticides have potential to dissolve in surface runoff and puddles in a
treated area may contain pesticide residues. Similarly, pesticides with lower organic carbon
partitioning characteristics and higher solubility in water have a greater potential to dissolve in
dew and other water associated with plant surfaces. Estimating the extent to which such
pesticide loadings to drinking water occurs is complex and would depend upon the partitioning
characteristics of the active ingredient, soils types in the treatment area, and the meteorology of
the treatment area. In addition, the use of various water sources by wildlife is highly species-
G-26 Appendix G. Integrated Pest Management