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Guidance for Reporting on the Environmental Fate and Transport of the Stressors of Concern in Problem Formulations

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Memorandum

January 25, 2010

SUBJECT: Guidance for Reporting on the Environmental Fate and Transport of the Stressors of Concern in Problem Formulations for Registration Review, Registration Review Risk Assessments, Listed Species Litigation Assessments, New Chemical Risk Assessments, and Other Relevant Risk Assessments

FROM: Donald J. Brady, Director, Environmental Fate and Effects Division, Office of Pesticide Programs

TO: Environmental Fate and Effects Division Scientists

The Environmental Fate and Effects Division's (EFED) Endangered Species Registration Review Workgroup, Office of Pesticide Programs, US Environmental Protection Agency, has developed guidance (attached) for reporting on the environmental fate and transport of the stressors of concern in problem formulations for Registration Review, Registration Review risk assessments, listed species litigation assessments, new chemical risk assessments, and other relevant risk assessments. The purpose of this guidance is to improve the quality, consistency and completeness of the information reported on the environmental fate and transport of the stressors of concern.

Any questions should be directed to Katrina White or other members of the Workgroup.

Endangered Species Registration Review Workgroup

Mark Corbin, EFED
Kevin Costello, PRD
William Eckel, EFED
Stephanie Irene, EFED
Edward Odenkirchen, EFED (Co-Chair)
Melissa Panger, EFED
Anita Pease, EFED
Mohammed Ruhman, EFED
Dana Spatz, EFED
Thomas Steeger, EFED
Ingrid Sunzenauer, EFED (Co-Chair)
Michelle Thawley, EFED
Katrina White, EFED

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Guidance for Reporting on the Environmental Fate and Transport of the Stressors of Concern in Problem Formulations for Registration Review, Registration Review Risk Assessments, Listed Species Litigation Assessments, New Chemical Risk Assessments, and Other Relevant Risk Assessments

December 14, 2009

Katrina White, Ph.D.
Environmental Fate and Effects Division
Office of Pesticide Programs
US Environmental Protection Agency

ACKNOWLEDGEMENTS

This document was prepared by Katrina White with the assistance of the Endangered Species Registration Review Workgroup, which includes the scientists listed below. All scientists are in the Environmental Fate and Effects Division unless noted otherwise.

Mark Corbin, M.S.
Kevin Costello, M.S., Pesticide Re-Evaluation Division
William Eckel, Ph.D .
Stephanie Irene, Ph.D.
Edward Odenkirchen, Ph.D. (Co-Chair)
Melissa Panger, Ph.D.
Anita Pease, M.S.
Mohammed Ruhman, Ph.D.
Dana Spatz, M.S.
Thomas Steeger, Ph.D.
Ingrid Sunzenauer, M.S. (Co-Chair)
Michelle Thawley, M.S.
Katrina White, Ph.D .

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  1. Physical-Chemical Properties

    Physical and chemical properties can be used to identify a priori the potential behavior of a chemical in the environment. The key physical-chemical properties to report in a Problem Formulation for Registration Review and other relevant risk assessments completed in the Environmental Fate and Effects Division (EFED) include:

    • molecular weight,
    • density1,
    • solubility in water,
    • vapor pressure,
    • n-octanol-water partition coefficient (KOW),
    • Henry's Law Constant, and
    • dissociation constant in water (pKa or pKb).2.3

    Other properties that are relevant but may not be available include:

    • the air-water partition coefficient (KAW),
    • n-octanol-air partition coefficient (KOA),
    • and UV/visible light absorption4.

    Make sure the units are reported along with each property provided. At a minimum, report the values in the units reported in the citation and in units needed for modeling. Report the temperature and pH for values for properties that are dependent on temperature and/or pH.5, 6 For chemicals that dissociate, report the pH of the test system when available for physical/chemical and environmental fate studies.

    Use the environmental fate properties for the Pure Active Ingredient (PAI) when available. Values measured on the Technical Grade Active Ingredient (TGAI) may be used when data on the PAI are not available. When more than one value is available for a PAI or TGAI, report all the values, unless one value is more reliable than another. Do not use values measured for end-use products. Some of these data can be found in the Office of Pesticide Programs (OPP) Chem docs database (an IBM Lotus Notes Database) by searching by Pesticide Chemical (PC) Code or Master Record Identification (MRID) number. When data are not available from the database ask the Chemical Review Manager (CRM) in Pesticide Re-Evaluation Division (PRD) to request the information from the Product Chemistry Branch. When the water solubility, KOW, vapor pressure, pKa/pKb, UV/visible light absorption, and density are not available from a submitted study and data are needed for estimating exposure, identify this as a data gap and request that the CRM request the data through a Data Call-In Notice under FIFRA (3)(c)(2)(B).

    Use Good Laboratory Practice (GLP) and Office of Prevention, Pesticides, and Toxic Substances (OPPTS) Guideline compliant data when available. In the absence of these data, or when data are not as sensitive as needed, open literature sources may be used. For example, when the only available submitted water solubility value is a less than or greater than value, a value from the open literature may be used. Make sure that the source of the information is provided. If measured values are not available, values may be estimated. Identify all estimates along with the method used to estimate the value.

    1. Common Calculations

      Henry's Law Constant and the KOA are physical-chemical properties that are often not measured but are needed to understand the environmental fate and transport of chemicals. Equations to calculate these values are provided in this Section. Use these equations when measured values are not available and/or when long range transport or terrestrial bioaccumulation is of concern.

      1. Calculating the Henry's Law Constant

        Henry's Law Constant is the air-water partition coefficient or an expression of the ratio of vapor pressure to solubility in water (Mackay et al., 1999). It is commonly reported with units of atm-m3/mole or as a unitless value (KAW) . The equations for calculating both are shown in equations 1 and 2.

        Equation 1
        • Conventional Henry's Law Constant = (Vapor Pressure x Molecular Weight) / (760 x Water Solubility)

        Where vapor pressure is expressed as torr,
        molecular weight is expressed in g/mole,
        760 is a conversion factor (1 atm = 760 torr),
        and water solubility is expressed in mg/L.

        The resulting units from equation 1 are in atm-m3/mole. The units of mg and liter (L) are cancelled out as there are 1000 mg in one gram and 0.001 m3 in one liter.

        Equation 2
        • KAW (Unitless Henry's Law Constant) = Cair / Cwater = Henry's Law Constant / RT

        Where R is the ideal gas constant of 8.205746 x 10-5 atm-m3/K-mole,
        T is absolute temperature expressed in Kelvin (K), and
        Henry's Law Constant is expressed in atm-m3/mole.

        Use parameters measured or calculated for the same temperature (e.g., 25° C).

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      2. Calculating the Octanol-Air Partition Coefficient

        If there is a potential for long range transport or terrestrial bioaccumulation, calculate and report the KOA for your chemical. 7 The KOA is the ratio of the concentration of a compound in an organic phase (n-octanol) and air at equilibrium (KOA = Coctanol / Cair, where Coctanol and Cair represent equilibrium concentrations in air and n-octanol with the same units). It has been used to describe partitioning between air and aerosol particles, air and foliage, and air and soil (Harner and Shoeib, 2002; Mackay et al., 1999). As measured KOAvalues may be substantially different than calculated values, 8 use measured values when available (Halsall, 2007; Shoeib and Harner, 2002). In the absence of data, calculate KOA values using equation 3 and EPI SuiteTM as discussed below.9 Specify the version of EPI SuiteTM used in your calculations.

        1. Ratio of KOW to KAW: Use when measured values for KOW and/or vapor pressure or Henry's Law Constant are available (Halsall, 2007)

          Equation 3
          • KOA = KOW / KAW = (KOWRT) / Henry's Law Constant

          Where KOW is the n-octanol-water partition coefficient and is unitless10,
          KAW is the air-water partition coefficient and is unitless,
          R is the ideal gas constant of 8.205746 x 10-5 atm-m3/K-mole,
          T is absolute temperature expressed in Kelvin (K), and
          Henry's Law Constant is expressed in atm-m3/mole.

          Use parameters measured or calculated for the same temperature (e.g., 25° C). Use measured values when available, as this method has been shown to have higher accuracy than when estimating both the KOW and Henry's Law Constant (Meylan and Howard, 2005). However, this accuracy is not dramatically different than when only based on estimated values (Meylan and Howard, 2005).11 Use estimated values when measured values are not available.

        2. EPI SuiteTM(USEPA, 2009a): Use when a measured KOW or vapor pressure is not available.

          The Simplified Molecular Input Line Entry System (SMILES) structure is the only required input parameter for EPI SuiteTM. The output is available in KOAWIN.

        The accuracy of the ratio of KOW to KAW and using EPI SuiteTM in estimating KOW and Henry's Law Constants in the calculation of the KOA values have been evaluated (Meylan and Howard, 2005; Shoeib and Harner, 2002; USEPA, 2009a). The difference in measured versus calculated values using equation 1 ranged from 0.01 - 4330 for 19 organochlorine pesticides (Shoeib and Harner, 2002). The error in the two methods of estimating KOA varies for different classes of compounds. For example, the absolute mean deviation is 0.25 for polychlorinated naphthalenes and 0.50 for polychlorinated biphenyls (Meylan and Howard, 2005). When a measured KOA is not available and long range transport or terrestrial bioaccumulation may be a concern, calculate the KOA using the following methods:

        1. use equation 1 when measured KOW and vapor pressure or Henry's Law Constant are available; or

        2. use EPI SuiteTM when a measured KOW or vapor pressure is not available.

        When using EPI SuiteTM, place output files in an appendix and refer to the appendix with the reported value. The estimated value will not replace the need to have a measured value; however, in the absence of a measured value, an estimated value is useful in understanding the environmental fate of a chemical for the development of the conceptual model.

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    2. Classification Systems for Volatility

      The OPPTS 835.6100 Guideline on Terrestrial Field Dissipation provides some calculations and classification systems for examining volatility of chemicals from dry non-adsorbing surfaces, from water, and from moist soil. For consistency, use these classification systems and calculations when volatility is a concern. Make sure the classification system used is cited.

      1. Volatility from Dry Non-adsorbing Surfaces

        Vapor pressure is one factor that may be considered when predicting whether volatility is likely. Use the vapor pressure to predict volatility from dry non-adsorbing surfaces using the classification system provided in Table 1 (USEPA, 2008).12

        Table 1
        Volatility Class from Dry Non-adsorbing Surfaces Based on Vapor Pressure*
        Vapor pressure at 25° C Volatility Class from Dry Non-Adsorbing Surfaces
        TorratmPamPa
        ≤ 9.98 x 10-7≤ 1.32 x 10-9 ≤ 1.33 x 10-4≤ 0.133 Non-volatile under field conditions**
        ≥ 3.90 x 10-5≥ 5.13 x 10-8 ≥ 5.20 X 10-3≥ 5.20 Intermediate to high volatility under field conditions

        * If the vapor pressure is between the two classifications report that it falls between the two classifications.

        **Note that all chemicals may volatilize to some extent; this classification simply indicates that the volatility potential is very low.

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      2. Volatility from Water

        The OPPTS 835.6100 Guideline also has a volatility classification to characterize potential volatilization from water using the unitless water/air distribution ratio (Cwater/Cair) and is shown in Table 2 (USEPA, 2008). Calculate the unitless water/air distribution ratio when a measured value is not available using equation 4 or as the reciprocal of KAW.13

        Equation 4
        • Cwater / Cair = (S x T x R x 760) / ( P x GMW x 106)

        Where Cwater is the concentration of the compound in water in µg/mL,
        Cair is the concentration of the compound in air in µg/mL,
        S is the solubility of the compound in water in µg/mL,
        T is absolute temperature in K [°K = °C + 273.15],
        R is the ideal gas constant of 82.08 mL-atm/K-mole,
        760 is a conversion factor to convert mmHg or torr to atm [760 mmHg = 1 atm],
        P is vapor pressure in torr or mmHg, and
        GMW = gram molecular weight in g/mole.

        Table 2
        Volatility Class from Water
        Based on the Cwater/Cair and KAW(Cair/Cwater)
        Cwater / Cair* KAWVolatility Class from Water
        < 102> 10-2Rapidly lost from a water surface
        102 - 10310-2 - 10-3 Volatile from a water surface
        103 - 10510-3 - 10-5 Slightly volatile from a water surface
        > 105< 10-5Non-volatile**

        * This value is the inverse of the commonly reported air-water distribution coefficient (KAW). The original document reported the classification as Cwater/Cair.

        **Note that all chemicals may volatilize to some extent; this classification simply indicates that the volatility potential is very low.

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      3. Volatility from Moist Soil

        Finally, a volatility classification from moist soil is also available in the OPPTS 835.6100 Guideline and is shown in Table 3 (USEPA, 2008). This classification accounts for sorption of the compound to soil that could reduce subsequent volatilization and is based on a distribution ratio between wet soil and air as shown in equation 5 (USEPA, 2008).14 The classifications in Table 3 assume that the soil contains 2% organic carbon, that the soil/water weight ratio (r) is 6, and that the soil water/soil air volume ratio is 1.

        Equation 5
        • Cwater + soil / Cair = (Cwater / Cair) ((1/r) + Kd)

        Where Cwater+soil is the concentration of the compound in wet soil (w/w on a dry weight basis),
        Cwater is the concentration of the compound in water (w/v),
        Cair is the concentration of the compound in air (w/v),
        r is the ratio of weight of soil/weight of water, and
        Kd is the soil-water distribution coefficient.

        Table 3
        Volatility Classification from Moist Soil
        Based on Cwater+soil/Cair
        Cwater+soil / Cair Volatility Class from Moist Soil*
        < 1 x 103Rapidly lost from moist soil
        1 x 103 - 1.5 x 104Volatile from moist soil
        1.5 x 104 - 105Intermediately volatile from moist soil
        105 - 2 x 106Slightly volatile to non-volatile from moist soil
        > 2 x 106Non-volatile from moist soil**

        *Assuming 2% organic carbon, soil to soil water (w/w) =6, and soil water to soil air (v/v) = 1.

        **Note that all chemicals may volatilize to some extent; this classification simply indicates that the volatility potential is very low.

        Based on this classification system, volatilization of chemicals from soil under laboratory or field conditions is important for chemicals with a Csoil+water/Cair value ≤ 106 (USEPA, 2008). For these chemicals, discuss this classification in the environmental fate discussion.

        Many chemicals that are predicted to be non-volatile (e.g., to have a very low potential for volatilization) based on the vapor pressure alone are shown to be volatile or semi-volatile in the field or to undergo long range transport. If open literature data indicate that volatilization or long range transport is commonly observed, include this in your environmental fate characterization.

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    3. Example Table for Reporting Physical-Chemical Properties

      Table 4 is an example table that may be used to report physical-chemical properties. Physical-chemical properties on degradates/transformation products may be reported on a case by case basis. For example, if the degradate is the main active ingredient of concern, report the physical-chemical properties for that degradate. Also, when a transformation product is identified to be of toxicological concern and exposure to the transformation products will be estimated separately from the parent compound, report the physical-chemical properties. Report the properties in a separate table or in the table for the parent compound. For chemicals that dissociate, report the pH of the test system when available.

      Table 4
      Physical-chemical Properties of XXXXX
      Property Parent Compound Transformation Product
      Value and unitsMRID or Source Value and unitsMRID or Source
      Molecular Weight g/moleMRID xxxxxx  
      Chemical Formula     
      Density / Relative Density/ Bulk Density g/cm3   
      Vapor Pressure Torr @ XX° C
      [Also include value with units from the study if other than Torr]
         
      Henry's Law Constant atm-m3/mole @ XX° C Estimated from water solubility and vapor pressure  
      Water Solubility mg/L @ XX° C   
      Octanol - water partition coefficient
      (KOW)
      @ 25° C   
      Dissociation Constant
      (pKa and/or pKb)
          
      Air-water partition coefficient
      (KAW)
          
      Octanol-air partition coefficient
      (KOA)
          
      UV/visible light absorption [specify wavelength or frequency]   
      Volatilization Flux µg/m2/second   
      Cwater + soil/Cair     

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    4. Sources of Physical-chemical Properties

      When physical-chemical properties are not available from submitted studies, the following sources of information are commonly used.

      Also print sources such as Merck Index, CRC Handbook of Chemistry & Physics, and Herbicide Handbook (WSSA) may be used.

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  2. Other Environmental Fate Properties: Degradation, Dissipation; Bioconcentration, and Sorption

    A chemical's abiotic degradation, biotic degradation, sorption, and bioconcentration depend on the characteristics of the environment or media the chemical is in. Factors such as sunlight intensity, pH, hydroxyl radical concentration, microbial community, components of soil, type of organic carbon present, and the species all influence these measured values. The key environmental fate studies include

    • abiotic degradation (hydrolysis and photolysis),

    • biotic degradation (aerobic and anaerobic) in soil and water,

    • bioconcentration,

    • sorption, and

    • field dissipation studies.

    These properties provide information on the

    1. persistence,

    2. potential transport pathways, and

    3. bioavailability of chemicals in the environment.

    Include the following key information for the environmental fate studies listed below. In all results, report the units of the values and, when relevant, discuss the influence of pH in the studies.

    1. Abiotic Degradation

      Summarize the results from the hydrolysis and photolysis (air, water, and soil) studies. Provide the range of half-lives measured and indicate whether abiotic degradation is an important degradation pathway. Report the atmospheric degradation half-life or measured photolysis in air. When a measured value is not available, calculate this value using EPI SuiteTM and AOPwin. The light absorption maximum wavelength provides information on whether the chemical is likely to undergo direct photolysis and may be included in all environmental fate sections; however, it is not required that you include this information if data on photolysis are available. If data on photolysis are not available include the light absorption maximum wavelength in this section and comment on whether photolysis is likely.15

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    2. Biotic Degradation

      Summarize the results from the biotic degradation studies. Provide the range of half-lives measured, the number of soils or sediments that half-lives were measured in, and indicate whether biotic degradation is an important degradation pathway for the chemical. When important, provide information about the medium/media that the values were measured in.

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    3. Sorption

      Provide the range of solid-water distribution coefficients (Kd)16; Freundlich solid-water distribution coefficients (KF) and Freundlich exponents (1/n) when available; and number of soils/sediments that sorption was measured in. It may be simpler to report these values in a separate table. Freundlich exponents can indicate whether sorption is concentration dependent when the sorption isotherm was measured over a sufficient range of concentrations. Additionally, the sorption coefficients are only valid over the range of concentrations for which they were measured. State whether sorption appears to be concentration dependent based on the information available. Give the range of corresponding organic-carbon normalized Freundlich distribution coefficients (KFOC) or organic-carbon normalized distribution coefficients (KOC). If the average KOC or KFOC is reported instead of the range, provide some indication of the variability in the value such as the coefficient of variation (standard deviation/mean), standard deviation, or confidence interval. Give the coefficient of variation (CV) for Kd, or KF and KFOC or KOC values and state whether the KOC value is appropriate for describing the chemical's sorption. Provide a mobility classification for the pesticide. The mobility classification in Table 5 was developed by FAO and recommended for use in EFED when it is appropriate to describe the compound's sorption using KOC values (FAO, 2000; USEPA, 2006).

      Table 5
      FAO Mobility Classification
      based on KOC
      KOC
      (mL/g or L/kg)
      Log KOC
      (mL/g or L/kg)
      Mobility Class
      < 10< 1Highly Mobile
      10-1001 - 2Mobile
      100-1,0002 - 3Moderately Mobile
      1,000 - 10,0003 - 4Slightly Mobile
      10,000 - 100,0004 - 5Hardly Mobile
      > 100 ,000> 5Immobile

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    4. Soil Column Leaching

      Summarize the results from submitted soil column leaching studies including information on the percent of compound applied in leachate, distance moved by the compound, and the distance moved by the reference compound.

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    5. Field Dissipation

      Summarize the field dissipation studies. Provide the range of measured dissipation half-lives, maximum depth that the parent and analyzed degradates were measured, and whether there was carry over of the pesticide from application to application or year to year. Evaluate whether the dissipation of the pesticide in the field was less than or more than what would be expected based on laboratory studies. When relevant, indicate whether formulations of the pesticide influenced field dissipation.

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    6. Transformation Products and/or Degradates

      Transformation is defined as, "any change in the molecular structure of the substance" (Connell et al., 1997). Transformation may include additions, rearrangements, and degradation of a substance. Degradation refers to, "breakdown of the original molecule by the loss of the various component parts or by the fragmentation of the molecule into smaller substances" (Connell et al., 1997). Discuss degradates and other transformation products under their own heading or under the sections delineated for the parent compound. Summarize the information available on transformation products. For transformation products of toxicological concern, indicate under what transformation/degradation pathways degradates formed and whether they were likely to persist.

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    7. Bioconcentration (BCF)

      Summarize the results of bioconcentration studies. Provide the species and steady state and/or kinetic bioconcentration factors measured in bioconcentration studies for different tissues (e.g., whole fish, edible, and nonedible) on a whole weight basis and lipid weight basis, when available. Explanations of these values are available in the OPPTS 850.1730 Guideline and more information on bioconcentration and bioaccumulation is available in a recent review by Arnot and Gobas (Arnot and Gobas, 2006). State the amount of depuration over a specific time frame. Indicate whether metabolites of the chemical were observed.

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    8. Example Table for Environmental Fate Properties

      Table 6 is an example table for reporting environmental fate properties for the parent compound.

      Table 6
      Environmental Fate Properties of Parent Compound
      StudyValue and unit MRID # or Citation Study Classification, Comment
      Abiotic Hydrolysis Half-life1 =
      XX days, pH 5
      XX days, pH 7
      XX days, pH 9
        
      Air Photolysis Half-life1 = XX days   
      Atmospheric Degradation [Include when an air photolysis study is not available]
      Half-life1 = XX days, estimated
        
      Direct Aqueous Photolysis Half-life1 = XX days, pH   
      Soil Photolysis Half-life1 = XX days, soil texture   
      Aerobic Soil Metabolism Half-life1 =
      XX days, soil texture
      XX days, soil texture
        
      Anaerobic Soil Metabolism Half-life1 =
      XX days, soil texture
      XX days, soil texture
        
      Aerobic Aquatic Metabolism Half-life1 = Source of sediment (e.g., rice paddy, pond, lake):
      XX days in water2
      XX days in sediment2
      XX days in total system
        
      Anaerobic Aquatic Metabolism Half-life1 = Source of sediment:
      XX days in water2
      XX days in sediment2
      XX days in total system
        
      Solid-water distribution coefficient
      (Kd)
      Kd =
      XX L/kg, soil texture
      XX L/kg, sediment source (e.g., pond, sediment)
        
      Freundlich solid-water distribution coefficient
      (KF)
      KF, 1/n
      XXX L/kg, XX, soil texture
      XX L/kg, sediment source (e.g., pond, sediment)
        
      Organic-carbon normalized distribution coefficient
      (KOC)
      KOC =
      XXX L/kg, soil texture
      XX L/kg, sediment source (e.g., pond sediment)
        
      Soil Column Leaching Leaching distance of test compound
      Leaching distance of reference compound
      Percent compound recovered in leachate
        
      Volatility from Soil
      (Laboratory)
      XX % volatilized by XX days, soil texture   
      Volatility from Soil
      (Field)
      Flux = XX µg/m2-s, soil texture   
      Terrestrial Field Dissipation Dissipation Half-life1, 2 = XX days, crop, State   
      Aquatic Field Dissipation Dissipation Half-life1, 2 = XX water body type, State   
      Bioconcentration Factor (BCF)-
      Species Name
      Steady State BCF =
      XXX L/kg wet wt whole fish
      XXX L/kg wet wt edible tissue
      XXXX L/kg wet wt nonedible tissue
      XXX L/kg wet wt lipid
      [Report kinetic BCF when available]
        

      Abbreviations: wt = weight

      1 Half-lives were calculated using the single-first order equation and nonlinear regression, unless otherwise specified.

      2 The value may reflect both dissipation and degradation processes.

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  3. Environmental Transport and Fate Characterization

    Briefly summarize how the chemical will enter the environment, the pathways of transport and dissipation, and the relevant exposure media. State what dissipation pathways are the most important and which environmental compartments will have the highest portion of the chemical applied. Note that all chemicals may be transported via air, water runoff, and soil runoff as some of the chemical will be present in all forms. Whether a transport pathway or media of exposure is important is determined by environmental fate properties, toxicological endpoints, environment characteristics, and the amount of chemical used. The OPPTS 835.6100 Guideline on Terrestrial Field Dissipation gives a good analysis on the development of the conceptual model for terrestrial field dissipation studies that is a good reference for determining whether a particular pathway is likely (USEPA, 2008). Additionally, the recent SAP for persistent, bioaccumulative, and toxic compounds has some useful analysis of considerations that should be included in EFED risk assessments (USEPA, 2009b). Make sure the summary is consistent with the conceptual model.

    Example language is provided below. It is provided to show the type of information to include/consider in the environmental fate and transport characterization.

    Pesticide X will enter the environment via spray directly onto soil or foliage. It may move off-site via spray drift, volatilization, leaching, and runoff. During rainfall or other precipitation events it may move off the field via water runoff, soil erosion, or leaching. Because of its long half-lives in soil, Pesticide X does have the potential to reach surface water through run-off and soil erosion. Pesticide X is classified as [provide mobility classification]. It has the potential/is unlikely to reach ground water except/especially in vulnerable soils with low organic-carbon content and/or the presence of shallow ground water. In water and sediment, it will be present in both the water column and bound to materials in sediments; however, based on measured KOCs a higher concentration will be present in soils/sediments than in the water column. Terrestrial field dissipation studies and Pesticide X's half-lives indicate it may accumulate in soil with successive applications. Based on a relatively low Henry's Law Constant (XXX atm-m3/mol) and moderately to relatively high soil/water partitioning, Pesticide X does not appear to have a high volatilization potential from soil (USEPA, 2008). However, several published studies have shown that Pesticide X is volatile, especially from moist or wet soil (Glotfelty et al., 1984; Majewski et al., 1991; Nash and Gish, 1989; Ross et al., 1989). The atmospheric degradation half-life estimated using EPI Suite was 10 days (results shown in Appendix X) and therefore, once it volatilizes it is likely to be transported over long distances.17 Estimated KOA values range from XX to XX suggesting it has/does not have the potential to accumulate in terrestrial organisms. 18

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  4. Questions

    Any questions should be directed to Katrina White or other members of the Workgroup.

    Endangered Species Registration Review Workgroup

    Mark Corbin, EFED
    Kevin Costello, PRD
    William Eckel, EFED
    Stephanie Irene, EFED
    Edward Odenkirchen, EFED (Co-Chair)
    Melissa Panger, EFED
    Anita Pease, EFED
    Mohammed Ruhman, EFED
    Dana Spatz, EFED
    Thomas Steeger, EFED
    Ingrid Sunzenauer, EFED (Co-Chair)
    Michelle Thawley, EFED
    Katrina White, EFED

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  5. Literature Cited

    • AERU. 2009. Exit EPA Disclaimer The FOOTPRINT Pesticide Properties Database. Agriculture & Environment Research Unit (AERU). (Accessed July 9, 2009).

    • Armitage, J. M., & Gobas, F. A. P. C. 2007. A terrestrial food-chain bioaccumulation model for POPs. Environmental Science and Technology, 41, 4019-4025.

    • Arnot, J. A., & Gobas, F. A. P. C. 2006. A review of bioconcentration factor (BCF) and bioaccumulation factor (BAF) assessments for organic chemicals in aquatic organisms. Environmental Reviews, 14, 257-297.

    • Boethling, R. S., & Mackay, D. 2000. Handbook of Property Estimation Methods for Chemicals. Boca Raton, FL: CRC Press LLC.

    • Connell, D. W., Hawker, D. W., Warne, M. S. J., & Vowles, P. P. 1997. Chapter 3. Environmental Transformation and Degradation Processes. In K. McCombs, A. W. Starkweather Jr. & D. Boyd (Eds.), Basic Concepts of Environmental Chemistry. Boca Raton: CRC Press LLC.

    • FAO. 2000. Exit EPA Disclaimer Appendix 2. Parameters of pesticides that influence processes in the soil. In FAO Information Division Editorial Group (Ed.), Pesticide Disposal Series 8. Assessing Soil Contamination. A Reference Manual. Rome: Food & Agriculture Organization of the United Nations (FAO). (Accessed July 10, 2009).

    • Glotfelty, D. E., Taylor, A. W., Turner, B. C., & Zoller, W. H. 1984. Volatilization of surface-applied pesticides from fallow soil. Journal of Agricultural and Food Chemistry, 32, 638-643.

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Footnotes

1 Density information may be available as density, relative density, or bulk density under OPPTS Guideline 830.7300. When reporting density, specify the type of density reported.

2When the pKa and pKb are not relevant or not available, report that they are not available or not relevant.

3 The identity of the compound is also important and a separate guidance document will address reporting of the structure and identity of stressors of concern.

4 This is a standard data requirement for all use patterns for the PAI or TGAI under Guideline 830.7050 (USEPA, 2007).

5When the pH or temperature are not available, report "not available".

6All partitioning properties change with temperature including KOW, vapor pressure, KAW, KOA and solubility.

7A recent scientific advisory panel (SAP) stated, "Gobas et al (2003) concluded that chemicals with a log KOA > 5 can biomagnify in terrestrial food chains if log KOW > 2 and the rate of chemical transformation is low. However, further proof is needed before accepting these limits without reservations." (Gobas et al., 2003; USEPA, 2009b). This was also supported by Armitage and Gobas's work completed in 2007 (Armitage and Gobas, 2007).

8 Calculated and measured values differed by a factor of 1000 for organochlorine pesticides (Shoeib and Harner, 2002).

9 Octanol-air partition coefficients may also be calculated as the solubility in octanol divided by the solubility in air; however, this calculation is more complicated and is not as commonly used (Mackay et al., 1999; Sepassi and Yalkowsky, 2006, 2007).

10 Make sure to use the KOW and KAW and not the log KOW or log KAW in this calculation.

11 The correlation coefficient and mean deviation were 0.98 and 0.29 using measured values and 0.96 and 0.48 using all estimated values (Meylan and Howard, 2005).

12 This classification system is reported on Page 25 of Guideline 835.6100.

13 This equation and classification Table is reported on Page 26 of Guideline 835.6100.

14 This equation and classification is reported on Page 27 of Guideline 835.6100.

15 Natural sunlight has significant photon fluxes only above 295 nm. When chemicals absorb light at 290 nm and above direct photolysis may be a degradation pathway (Boethling and Mackay, 2000).

16 The solid may be soil or sediment.

17 The minutes of the SAP examining issues related to persistent, bioaccumulative, and toxics states, "To protect against long range transport, a two-day degradation half life in air is used internationally in regulations that identify persistent chemicals." (USEPA, 2009b)

18 A recent scientific advisory panel (SAP) reported, "Gobas et al (2003) concluded that chemicals with a log KOA > 5 can biomagnify in terrestrial food chains if log KOW > 2 and the rate of chemical transformation is low. However, further proof is needed before accepting these limits without reservations" (USEPA, 2009b). This was also supported by Armitage and Gobas's work completed in 2007 (Armitage and Gobas, 2007).

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