Standard Operating Procedures (SOPs) for Residential Exposure Assessments

3.0 GARDEN PLANTS

Prior to the development of an exposure assessment for a garden scenario, the assessor should consult the pesticide label to determine whether the scenario is appropriate based on the usage characteristics of the product. Specific labeling considerations for garden plants are as follows:

Registered for Use on Ornamentals, Fruits, or Vegetables: Determine whether the labeling contains directions for use on "ornamentals," "flowers," "shrubs," "house plants," "fruits," (non-tree), "vegetables," or on specific species of ornamentals, fruits, or vegetables such as "African violets," "strawberries," "sweet corn," etc.

Limitation and Descriptive Statements: Look for statements describing or limiting the use on ornamentals, fruits, or vegetables. These statements may be on the front panel of the label associated with the brand or trade name or in the use-directions section of the labeling. Assume that a product registered for use on ornamentals, fruit, or vegetables is used at residential sites unless a specific labeling statement indicates otherwise. Field crops, such as corn (other than sweet corn), soybeans, alfalfa, or cotton are assumed to not be grown at residential sites. Restricted-Use Pesticide classification and statements such as "For use by commercial or professional applicators only" indicate that the product cannot be bought or applied by homeowners. Therefore, no residential handler exposure/risk assessment is required. Since commercial applicators do not usually apply pesticides to residential gardens, no post-application exposure/risk assessment is required for these restricted use products. Statements such as "Commercial or research greenhouse use only," "For nursery-grown ornamentals," or "For use in commercial plantings only," and the more specific "Not for use on residential site," "Not for use in home gardens, or Not for use in and around homes or dwellings" indicate that the product cannot be used on residential gardens and no residential handler or post-application exposure/risk assessment is required.

3.1 Handler Inhalation and Dermal Potential Dose from Pesticides Applied to the Garden

Introduction

This SOP provides a standard method to be used for estimating potential doses that homeowners may receive during applications of pesticides to the garden when chemical specific data are unavailable. Garden applications include insect and weed treatments around walkways, driveways, and foundations, vegetables, and ornamentals. Garden applications are also made to control plant diseases. This scenario assumes that pesticides are available for inhalation or have the potential to come in contact with the skin of adults and youth during the mixing/loading and application of pesticides used around the garden. The method to determine handler inhalation and dermal exposure to pesticides from garden applications relies on surrogate PHED data. Thus, this method should be used in the absence of actual field data, or as a supplement to estimates based on field data.

Methods for Estimating Potential Dose

Label information is important for selecting appropriate data inputs for the exposure assessment (see Section 3.0). The data required for estimating handler exposures to pesticide when treating the yard and garden are the application method specific data (i.e., use scenario, formulation types, and unit exposures), application rates, and usage data (e.g., acreage or gallons). The maximum application rate specified on the label should be used, except in cancer assessments when the typical application rate should be used. However, it should be noted that the typical residential use rate is often the maximum residential use rate. In the absence of actual data, the following assumptions can be used for estimating daily inhalation and dermal mixer/loader/applicator doses.

Application methods for granulars will include whirly-bird spreaders, shaker cans, and dispersed by hand (spot treatment). Application methods for liquid formulations will include hose-end sprayers, sprinkler/watering can, low pressure handwands, and backpack. Application methods for ready-to-use products will include trigger pump applications. Dermal and inhalation unit exposures and data confidence descriptions are available for all of these application methods in the Appendix B except for shaker cans (refer to Section 9.1.1), sprinkler/watering can, and the trigger pump scenarios. The unit exposures from the hose-end sprayers should be used as an upper-percentile estimate for the sprinkler/watering can scenario. The current version of PHED uses measures of central tendency to estimate the best-fit unit exposures.
The amount handled is based on 10,000 ft² (i.e., 1/4 acre; large garden in a farm-type setting) for treatments based on area, and 5 gallons of spray diluent (i.e., two 2-1/2 gallon handwand treatments) for treatments based on concentrations. These are believed to be upper-percentile assumptions based on the experience and professional judgement of OPP/HED staff.
Adults are assumed to weigh 71.8 kg (use 60 kg for females when the selected endpoint is from a reproductive or developmental study). A body weight of 71.8 kg represents the mean body weight for all adults (i.e., male and female, 18 years and older) and is the value recommended in U.S. EPA (1996). A body weight of 60 kg represents the mean body weight for females between ages 13 and 54 years (U.S. EPA, 1996). The mean body weight for a 10 to 12 year old youth is 39.1 kg. This represents the mean of the median values for males and females at ages 10, 11, and 12 years.
The density of an organic spray solution contained in a single use pressurized can may be assumed to be 0.80 g/mL unless a product-specific value is available. This is based on an informal survey of various organic solvents described in CRC (1981). A value of 0.80 g/mL represents an mean of various organic solvents from this source.

Inhalation and dermal potential dose rates are calculated as follows: PDR = UE * AR * A

where:

PDR = daily potential dose rate (mg/day)
UE = unit exposure (mg/lb ai)
AR = maximum application rate (lb ai/acre, or lbs ai/gal)
A = maximum area treated (acres/day), amount handled (gal/day)

Inhalation and dermal potential dose rates, normalized to body weight, are calculated as: PDR_norm = PDR / BW

where:

PDR_norm = potential dose rate, normalized to body weight (mg/kg/day)
BW = body weight (kg)

The body weight used can be adjusted to fit any specific scenario (for example, exposure to male or female adults).

Example Calculations

The following is an example calculation to determine the inhalation dose to an adult homeowner applying a product to the garden using a liquid formulation in a low pressure handwand at a rate of 1 lb ai/acre. For the purpose of this example, the estimated inhalation dose assuming an application rate of 1 lb ai/acre and using a unit exposure of 0.022 mg/lb ai would be as follows:

PDR = UE * AR * A
PDR = 0.022 mg/lb ai * 1 lb ai/acre * 0.25 acre/day
PDR = 0.0055 mg/day

Finally, the estimated inhalation dose for an adult with a body weight of 71.8 kg would be:

PDR_norm = PDR / BW
PDR_norm = (0.0055 mg/day) / (71.8 kg)
PDR_norm = 0.00008 mg/kg/day

This dose would be used in conjunction with toxicity data to assess risk.

Limitations and Uncertainty

The dose estimates generated using this method are based on a central tendency estimate of unit exposure and an upper-percentile assumption for the application rate, and are assumed to be representative of high-end exposures. The uncertainties associated with this assessment stem from the use of surrogate exposure data (e.g., differences in use scenario and data confidence) and assumptions regarding the amount of chemical handled. The estimated doses are believed to be reasonable high-end estimates based on observations from chemical-specific field studies and professional judgement.

References

U.S. EPA (1996) Exposure Factors Handbook [Draft]. U.S. Environmental Protection Agency, National Center for Environmental Assessment, Washington, D.C. EPA/600/P-95/002Ba.

3.2 Postapplication Dermal Potential Doses from Pesticide Residues On Gardens

Introduction

This SOP provides a standard method for estimating doses among adults and/or toddlers from dermal contact with gardens that have previously been treated with pesticides. Inhalation dose is considered minimal due to the air exchange that occurs in outdoor scenarios. This scenario assumes that pesticide residues are transferred to the skin of adults and youth that enter treated gardens for gardening, or other homeowner activities. The method for estimating postapplication dermal dose from pesticides on gardens is based on assumptions when adequate chemical specific field data are unavailable. Thus, this method should be used in the absence of actual field data.

Methods for Estimating Potential Dose

Label information is important for selecting appropriate data inputs for the exposure assessment. The only datum required for estimating postapplication doses from pesticide residues on gardens is the application rate. The maximum application rate specified on the label should be used as the residential garden rate. One exception is for cancer assessments where the typical application rates should be used. It should be noted that the typical residential use rate is often the maximum residential use rate. In the absence of actual data, the following assumptions can be used for estimating daily pesticide postapplication doses.

On the day of application, it may be assumed that 20 percent of the application rate is available on the foliage as dislodgeable residue. This value is based on the professional judgement and experience of the OPP/HED staff from the review of company-submitted data, and is assumed to represent an upper-percentile value.
Postapplication exposure must be assessed on the same day the pesticide is applied since it is assumed that homeowners could enter the garden immediately after application. For subsequent days after application, an assumed pesticide dissipation rate should be used, based on chemical-specific data.
The assumed mean dermal transfer coefficient is 10,000 cm²/hr for adults and 5,000 cm²/hr for youth (age 10-12 years) (example tomato harvesting). These values are based on the professional judgement and experience of the OPP/HED staff from the reviewed company-submitted data.
Adults are assumed to weigh 71.8 kg (use 60 kg for females when the selected endpoint is from a reproductive or developmental study). A body weight of 71.8 kg represents the mean body weight for all adults (i.e., male and female, ages 18 years and older) and is the value recommended in U.S. EPA (1996). A body weight of 60 kg represents the mean body weight for females between ages 13 and 54 years (U.S. EPA, 1996). The average body weight for a 10 to 12 year old youth is 39.1 kg. This represents the average of the median values for males and females at ages 10, 11, and 12 years.
The duration of exposure is assumed to be 0.33 hours per day for toddlers (age 1-4 years) and 0.67 hours per day for adults (age 18-64 years), based on the 95^th percentile values for time spent working in a garden or other circumstances working with soil (U.S. EPA, 1996).

Dermal potential dose rates are calculated as follows: PDR_t = DFR_t * CF1 * Tc * ET

where:

PDR_t = potential dose rate on day "t" (mg/day)
DFR_t = dislodgeable foliar residue on day "t" (ug/cm²)
CF1 = weight unit conversion factor to convert ug units in the DFR value to mg for the daily exposure (0.001 mg/ug)
Tc = transfer coefficient (cm²/hr)
ET = exposure time (hr/day)

and DFR_t = (AR * F) * (1-D)^t * CF2 * CF3

where:

AR = application rate (lbs ai/ft² or lbs ai/acre)
F = fraction of ai retained on foliage (unitless)
D = fraction of residue that dissipates daily (unitless)
t = postapplication day on which exposure is being assessed
CF2 = conversion factor to convert the lbs ai in the application rate to ug for the DFR value (4.54E8 ug/lb)
CF3 = conversion factor to convert the surface area units (ft²) in the application rate to cm² for the DFR value (1.08E-3 ft²/cm² or 2.47E-8 acre/cm² if the application rate is per acre)

Potential dose rates, normalized to body weight, are calculated as: PDR_t-norm = PDR_t / BW

where:

PDR_t-norm = dose on day "t" (mg/kg/day)
BW = body weight (kg)

The body weight used can be adjusted to fit any specific scenario (for example, exposure to adults or toddlers).

Example Calculations

The following is an example calculation to determine the dose based on an assumed DFR over time. For the purpose of this example, the application rate is assumed to be 2.2E-5 lbs ai/ft²(approximately 1 lb ai/acre). Thus, the dislodgeable foliar residue on day 0 is as follows:

DFR_t = (AR * F) * (1-D)^t * CF2 * CF3

DFR₀ = (2.2E-5 lb ai/ft² * 0.2) * (1-D)⁰ * (4.54E8 ug/lb) * (1.08E-3 ft²/cm²)

DFR₀ = 2.16 ug/cm²

The estimated dose for the day of application would be as follows:

PDR_t = DFR_t * CF1 * Tc * ET

PDR₀ = 2.16 ug/cm² * 0.001 mg/ug * 10,000 cm²/hr * 0.67 hours/day

PDR₀ = 14.5 mg/day

Finally, the estimated dose for an adult with a body weight of 71.8 kg would be:

PDR_t-norm = PDR_t / BW

PDR_0-norm = (14.5 mg/day) / (71.8 kg)

PDR_0-norm = 0.20 mg/kg/day

This dose would be used in conjunction with toxicity data to assess risk.

Limitations and Uncertainty

The dose estimates generated using this method are based on upper-percentile assumptions for transfer coefficients and duration, and central tendency estimates for body weights. They are considered to be representative of high-end exposures. The uncertainties associated with this assessment stem from the use of an assumed amount of pesticide retained on gardens, and assumptions regarding dissipation and transfer of chemical residues. The dose estimates are believed to be reasonable high-end estimates based on observations from chemical-specific field studies and professional judgement.

References

U.S. EPA (1996) Exposure Factors Handbook [Draft]. U.S. Environmental Protection Agency, National Center For Environmental Assessment, Washington D.C. EPA/600/P-95/002Ba.

3.3 Postapplication - Incidental Nondietary Ingestion

3.3.1 Eating Pellets or Granules (refer to 2.3.1)

3.3.2 Hand-to-Mouth Transfer (refer to 2.3.2)

3.3.3 Eating Plant Material ( no SOP - exposure via this route is considered negligible)

3.3.4 Soil Ingestion (refer to 2.3.4)

4.0 TREES (NUT, FRUIT, ORNAMENTAL)

Prior to the development of an exposure assessment for a tree scenario, the assessor should consult the pesticide label to determine whether the scenario is appropriate based on the usage characteristics of the product. Specific labeling considerations for trees are as follows:

Registered for Use on Trees (Ornamentals, Fruits, or Nuts): Determine whether the labeling contains directions for use on "fruit trees," "nut trees," or "ornamental trees," or on specific species of trees, such as "citrus," "pecans," "maples," etc.

Limitation and Descriptive Statements: Look for statements describing or limiting the use on trees. These statements may be on the front panel of the label associated with the brand or trade name or in the use-directions section of the labeling. Assume that a product registered for use on trees is used at residential sites unless a specific labeling statement indicates otherwise. Restricted-Use Pesticide classification and statements such as "For use by commercial or professional applicators only" indicate that the product cannot be bought or applied by homeowners, therefore no residential handler exposure/risk assessment is required. Since commercial applicators do not usually apply pesticides to residential trees, no post-application exposure/risk assessment is required for these restricted-use products. Statements such as "For use in commercial or research forests only," "For nursery-grown trees only,"or "For use on commercial plantings only," and the more specific "Not for use on residential sites," or "Not for use in and around homes or dwellings" indicate that the product cannot be used on residential trees and no residential handler or post-application exposure/risk assessment is required. Assume no residential uses if the directions for use are solely for Christmas-tree farms and/or wide-area (i.e., aerial) uses in forestry settings.

4.1 Handler Inhalation and Dermal Potential Doses from Pesticides Applied to Trees

Introduction

This SOP provides a standard method for estimating potential doses that homeowners may receive during application of pesticides to "backyard" trees (e.g., fruit and nut trees) when chemical specific data are unavailable. This scenario assumes that pesticide are available to be inhaled or have the potential to come in contact with the skin of adults and youth during the mixing/loading and application of pesticides used to treat "backyard" trees. The method to determine handler inhalation and dermal exposure to pesticides during the treatment of trees relies on using PHED surrogate data. Thus, this method should be used in the absence of actual field data, or as a supplement to estimates based on field data.

Methods for Estimating Potential Dose

Label information is important for selecting appropriate data inputs for the exposure assessment (see Section 4.0). The data required for estimating handler doses from pesticide when treating trees are the application method specific data (i.e., use scenario and unit exposures), application rates, and usage data (e.g., gallons). The maximum application rate specified on the label should be used as the residential application rate. One exception is for cancer assessments where the typical application rate should be used. It should be noted that the typical residential use rate is often the maximum residential use rate. In the absence of actual data, the following assumptions can be used for estimating daily inhalation and dermal mixer/loader/applicator doses.

Application methods will include hose-end sprayers, low pressure handwands, backpack sprayers, and potentially brush-type applications. The PHED V1.1 data for "back yard" trees is not representative. Most of the available data are based on applications below the waist which may underestimate exposure for this scenario. Dermal and inhalation unit exposures and data confidence descriptions are available in the Appendix B. The current version of PHED uses measures of central tendency to estimate the best-fit unit exposure.
The amount handled will be based on 5 gallons for runoff treatments (i.e., one 5-gallon backpack sprayer) and 1 gallon for brush-on treatments (i.e., this is believed to be the maximum amount an individual would brush on; at a higher rate, an individual would be likely to use a different application method).
Adults are assumed to weigh 71.8 kg (use 60 kg for females when the selected endpoint is from a reproductive or developmental study). A body weight of 71.8 kg represents the mean body weight for all adults (i.e., male and female, ages 18 years and older) and is the value recommended in U.S. EPA (1996). A body weight of 60 kg represents the mean body weight for females between ages 13 and 54 years (U.S. EPA, 1996). The average body weight for a 10 to 12 year old youth is 39.1 kg. This represents the mean of the median values for males and females at ages 10, 11, and 12 years.

Inhalation and dermal potential dose rates are calculated as follows: PDR = UE * AR * A

where:

PDR = daily potential dose rate (mg/day)
UE = unit exposure (mg/lb ai)
AR = maximum application rate (lb ai/gal)
A = maximum amount handled (gal/day)

Inhalation and/or dermal potential dose rate, normalized to body weight, are calculated as: PDR_norm = PDR / BW

where:

PDR_norm = potential dose rate, normalized to body weight (mg/kg/day)
BW = body weight (kg)

The body weight used can be adjusted to fit any specific scenario (for example, exposure to male or female adults).

Example Calculations

The following is an example calculation to determine the dermal dose based on a homeowner mixing/loading/applying a liquid application using a hose-end sprayer. A complete assessment would also include inhalation and dermal exposure for low pressure handwands, backpack sprayers, and potentially brush-on applications. For the purpose of this example, the application rate is assumed to be 0.5 lb ai/gallon of diluted spray.

The estimated dermal potential dose rate using a hose-end sprayer would be as follows, using a unit exposure value of 30.6 mg/lb ai:

PDR = UE * AR * A

PDR = 30.6 mg/lb ai * 0.5 lb ai/gal * 5 gal/day

PDR = 76.5 mg/day

Finally, the estimated dermal potential dose rate, normalized to body weight, for an adult with a body weight of 71.8 kg would be:

PDR_norm = PDR / BW

PDR_norm = (76.5 mg/day) / (71.8 kg)

PDR_norm = 1.1 mg/kg/day

This dose would be used in conjunction with toxicity data to assess risk.

Limitations and Uncertainty

The dose estimates generated using this method are based on a central tendency to high-end estimate of the unit exposure and an upper-percentile assumption for the application rate, and are assumed to be representative of high-end exposures. The uncertainties associated with this assessment stem from the representativeness of the available surrogate exposure data (e.g., surrogate data available in PHED V1.1 are mostly based on applications below the waist), data confidence and assumptions regarding the amount of chemical handled. These assumptions are believed to be reasonable central tendency to high-end estimates based on observations from chemical-specific field studies and professional judgement.

References

U.S. EPA (1996) Exposure Factors Handbook [Draft]. U.S. Environmental Protection Agency, National Center For Environmental Assessment, Washington D.C. EPA/600/P-95/002Ba.

4.2 Postapplication Dermal Potential Doses from Pesticide Residues While Harvesting Fruit from Trees

Introduction

This SOP provides a standard method for estimating dose to adults and/or children from dermal contact while harvesting fruit from fruit trees that have previously been treated with pesticides. Inhalation dose is considered minimal due to the air exchange rate that occurs in outdoor scenarios. This scenario assumes that pesticide residues are transferred to the skin of adults and youth that come in contact with treated fruit trees while harvesting fruit or during other homeowner activities. The method for estimating postapplication dermal dose from pesticides while harvesting fruit from trees is based on assumptions when adequate site-specific field data are unavailable. Thus, this method should be used in the absence of actual field data.

Methods for Estimating Potential Dose

Label information is important for selecting appropriate data inputs for the exposure assessment (see Section 4.0). The only datum required for estimating postapplication exposures to pesticide residues while harvesting fruit from fruit trees is the application rate. The maximum application rate specified on the label should be used as the residential fruit tree application rate. One exception is for cancer assessments where the typical application rates should be used. It should be noted that the typical residential use rate is often the maximum residential use rate. In the absence of actual data, the following assumptions can be used for estimating daily pesticide postapplication doses.

On the day of application it may be assumed that 20 percent of the application rate is available on the foliage as dislodgeable residue. This value is based on the experience and professional judgement of the OPP staff from the review of company-submitted data and is assumed to be an upper-percentile value.
Postapplication exposure must be assessed on the same day the pesticide is applied since it is assumed that homeowners may harvest fruits immediately after application. For subsequent days after application, an assumed pesticide dissipation rate should be used, based on chemical-specific data.
The assumed mean dermal transfer coefficient is 10,000 cm²/hr for adults and 5,000 cm²/hr for youth (age 10-12 years). This value is based on the experience and professional judgement of the OPP staff from the review of company-submitted data.
Adults are assumed to weigh 71.8 kg (use 60 kg for females when the selected endpoint is from a reproductive or developmental study). A body weight of 71.8 kg represents the mean body weight for all adults (i.e., male and female, ages 18 years and older) and is the value recommended in U.S. EPA (1996). A body weight of 60 kg represents the mean body weight for females between ages 13 and 54 years (U.S. EPA, 1996). The average body weight for a 10 to 12 year old youth is 39.1 kg. This represents the mean of the median values for males and females at ages 10, 11, and 12 years.
The duration of exposure is assumed to be 0.33 hours per day for toddlers (age 1-4 years) and 0.67 hours per day for adults (age 18-64 years), based on the 95^th percentile values for time spent working in a garden or other circumstances working with soil (U.S. EPA, 1996).

Dermal potential dose rates are calculated as follows: PDR_t = DFR_t * CF1 * Tc * ET

where:

and DFR_t = AR * F * (1-D)^t * CF2 * CF3

where:

Potential dose rates, normalized to body weight, are calculated as: PDR_t-norm = PDR_t / BW

where:

PDR_t-norm = potential dose rate, normalized to body weigh, on day "t" (mg/kg/day)
BW = body weight (kg)

The body weight used can be adjusted to fit any specific scenario (for example, exposure to adults or toddlers).

Example Calculations

The following is an example calculation to determine the doses from liquid formulations based on an assumed DFR over time. For the purpose of this example, the application rate is assumed to be 2.2E-5 lbs ai/ft² (approximately 1 lb ai/acre). Thus, the dislodgeable foliar residue on day 0 is as follows:

DFR_t = AR * F * (1-D)^t * CF2 * CF3

DFR₀ = 2.2E-5 lb ai/ft² * 0.2 * (1-D)⁰ * 4.54E8 ug/lb * 1.08E-3 ft²/cm²

DFR₀ = 2.16 ug/cm²

The estimated potential dose rate for the day of application would be as follows:

PDR_t = DFR_t * CF1 * Tc * ET

PDR₀ = 2.16 ug/cm² * 0.001 mg/ug * 10,000 cm²/hr * 0.67 hours/day

PDR₀ = 14.5 mg/day

Finally, the estimated dose for an adult with a body weight of 71.8 kg would be:

PDR_t-norm = PDR_t / BW

PDR_0-norm = (14.5 mg/day) / (71.8 kg)

PDR_0-norm = 0.20 mg/kg/day

This dose would be used in conjunction with toxicity data to assess risk.

Limitations and Uncertainty

The dose estimates generated using this method are based on upper-percentile assumptions for duration of exposure, transfer coefficient, and application rate, and a central tendency estimate of body weight, and are assumed to be representative of high-end exposure. The uncertainties associated with this assessment stem from the use of an assumed amount of pesticide retained in the fruit trees, and assumptions regarding dissipation and transfer of chemical residues. The estimated doses are believed to be reasonable high-end estimates based on observations from chemical-specific field studies and professional judgement.

References

U.S. EPA (1996) Exposure Factors Handbook [Draft]. U.S. Environmental Protection Agency, National Center For Environmental Assessment, Washington D.C. EPA/600/P-95/002Ba.

Standard Operating Procedures (SOPs) for Residential Exposure Assessments

3.3.3 Eating Plant Material ( no SOP - exposure via this route is considered negligible)

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