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Scientific Advisory Panel
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- SOPS for Residential Exposure Assessments: Swimming Pools
Scientific Advisory Panel
Prior to the development of an exposure assessment for a swimming pool 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 swimming pools are as follows:
Registered for Use in Swimming Pool Water: Determine whether the labeling contains directions for use in swimming pool water.
Limitation and Descriptive Statements: Look for statements describing or limiting the use in swimming pools. 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 in swimming pools 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 swimming pools, these restricted-use pesticides would be unlikely to be in residential pools; thus no post-application exposure/risk assessment would be required for these types of pesticides.
5.1 Handler Inhalation and Dermal Potential Doses from Pesticides Applied to Swimming Pools
Introduction
This SOP provides a standard method to be used for estimating potential doses that homeowners may receive during pesticide applications to swimming pools from inhalation and dermal contact when chemical specific data are unavailable. This scenario assumes that pesticides are available to be inhaled or have the potential to come in contact with the skin of adults and youth during the loading and application of pesticides. The method to determine handler inhalation and dermal exposure to pesticide 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 5.0). The data required for estimating handler exposures to biocides for swimming pools are the application method specific data (i.e., open pour liquids, place solid, etc. and unit exposures), application rates (e.g., amount of ai per 1,000 gallons of pool water), and usage data (e.g., typical pool size in gallons). The maximum application rate specified on the label should be used. 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. The following assumptions are also needed for estimating daily inhalation and dermal applicator doses.
Inhalation and/or dermal potential dose rates are calculated as follows: PDR = UE * AR * V
where:
PDR = potential dose rate (mg/day)
UE = unit exposure (mg/lb ai)
AR = maximum application rate (lb ai/gal)
V = maximum volume treated (gals/day)
Inhalation and/or dermal potential dose rates, normalized to body weight, are calculated as: PDRnorm = PDR / BW
where:
PDRnorm = 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 for a homeowner pouring a ready-to-use liquid formulation into a swimming pool. For the purpose of this example, the application rate is assumed to be 1 lb ai/20,000 gallons of pool water or 5E-5 lb ai/gallon.
The estimated dermal dose for a homeowner pouring a ready-to-use liquid formulation into a swimming pool assuming a unit exposure of 2.9 mg/lb ai would be as follows:
PDR = UE * AR * V
PDR = 2.9 mg/lb ai * 5E-5 lb ai/gallon * 20,000 gallons/day
PDR = 2.9 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:
PDRnorm = PDR / BW
PDRnorm = 2.9 mg/day / 71.8 kg
PDRnorm = 0.04 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 assumption for unit exposure and pool size treated, and an upper-percentile application rate, and are assumed to be representative of central tendency exposures. The uncertainties associated with this assessment stem from the use of surrogate exposure data (e.g., differences in the use scenarios and data confidence) and assumptions regarding amount of chemical handled. The estimated doses are believed to be reasonable central tendency estimates based on professional judgement.
References
Kirk-Othmer (1984) Encyclopedia of Chemical Technology, 3rd Edition. Vol. 24, p. 427.
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.
Introduction
5.2.1 Postapplication Potential Doses from Incidental Nondietary Ingestion of Pesticide Residues While Swimming
This SOP provides a standard method to be used for estimating postapplication incidental ingestion dose from pesticides in previously treated residential swimming pools when chemical specific data are unavailable. This scenario assumes that swimmers ingest pool water that enters their mouth during swimming or playing in the pool. This method should be used in the absence of actual field data. Methods for estimating doses from pesticides in swimming pool water via other routes of exposure (i.e., buccal/sublingual, orbital/nasal, aural, and sexual organs) are described by Dang (1996).
Methods for Estimating Potential Dose
Label information is important for selecting appropriate data inputs for the exposure assessment (see Section 5.0). The data required for estimating postapplication doses from pesticides in swimming pools is the use rate. The maximum use rate specified on the label should be used, except in cancer assessments when the typical application rates should be used. It should be noted, however, that the typical residential use rate is often the same as the maximum rate. The following assumptions are also needed for estimating daily pesticide postapplication doses.
Potential dose rates from ingestion are calculated as follows: PDR = CW * IgR * ET
where:
PDR = potential dose rate (mg/day)
CW = concentration of ai in pool water (mg/L)
IgR = ingestion rate of pool water (L/hour)
ET = exposure time (hours/day)
and CW = AR * CF1 * CF2
where:
AR = application rate (lbs ai/gal)
CF1 = weight unit conversion factor (4.54E5 mg/lb)
CF2 = volume unit conversion factor (2.64E-1 gal/L)
Potential dose rates, normalized to body weight, are calculated as: PDRnorm = PDR / BW
where:
PDRnorm = potential dose rate, normalized to
body weight (mg/kg/day)
BW = body weight (kg)
Example Calculations
The following is an example calculation to determine the dose based on ingestion of pool water. For the purpose of this example, the application rate is assumed to be 5E-5 lbs ai/ gal (approximately 1 lb ai/20,000 gal or 5E-5 lb ai/gal). Thus, the concentration of ai in the pool water is as follows:
CW = AR * CF1 * CF2
CW = (5E-5 lb ai/gal) * (4.54E5 mg/lb) * (2.64E-1 gal/L)
Cw = 6.0 mg/L
The estimated incidental ingestion potential dose rate among children would be as follows:
PDR = Cw * IgR * ET
PDR = 6.0 mg/L * 0.05 L/hr * 5 hr/day
PDR = 1.5 mg/day
Finally, the estimated potential dose rate, normalized to body weight, for a child with a body weight of 22 kg would be:
PDRnorm = PDR / BW
PDRnorm = (1.5 mg/day) / (22 kg)
PDRnorm = 0.07 mg/kg/day
This dose would be used in conjunction with toxicity data to assess risk.
Limitations and Uncertainty
The exposure dose generated using this method are based on some central tendency (i.e., ingestion rate, body weight) and some upper-percentile assumptions (i.e., exposure, duration, application rate for acute assessments), and are assumed to be representative of high-end exposures. The uncertainties associated with this assessment stem from the assumptions regarding dissipation of chemical residues in the water. The dose estimates are considered to be reasonable high-end estimates based on observations from chemical-specific field studies and professional judgement.
References
Dang, W. (1996) The swimmer exposure assessment model (SWIMODEL) and its use in estimating risks of chemical use in swimming pools. EPA internal guidance document.
U.S. EPA (1989) Risk Assessment Guidance for Superfund. U.S. Environmental Protection Agency, Office of Emergency and Remedial Response, Washington, DC. EPA/540/1-89/002
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.
Introduction
This SOP provides a standard method to be used for estimating postapplication dermally absorbed dose from pesticides in previously treated residential swimming pools when chemical specific data are unavailable. This scenario assumes that swimmers are exposed to pesticides in pool water as a result of dermal contact with the water and subsequent absorption of the chemical through the skin while swimming or playing in the pool. 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 dose from pesticides in swimming pool water via other routes of exposure (i.e., buccal/sublingual, orbital/nasal, aural, and sexual organs) are described by Dang (1996).
Methods for Estimating Absorbed Dose
Label information is important for selecting appropriate data inputs for the exposure assessment (see Section 5.0). The data required for estimating postapplication dermally absorbed dose from pesticides in swimming pools is the use rate and the skin permeability of the pesticide. The maximum use rate specified on the label should be used, except in cancer assessments when the typical application rates should be used. It should be noted, however, that the typical residential use rate is often the same as the maximum rate. The following assumptions are also needed for estimating daily pesticide postapplication dermally absorbed doses.
- It may be assumed that 100 percent of the application concentration is available in the pool water for dermal contact. This is believed to be a reasonable assumption because biocides are typically maintained in pool water at specified levels.
- For subsequent days after application, it may be assumed that the pesticide will not dissipate because it is usually desirable to maintain a specified level of biocide in the water.
- The assumed surface area is 20,900 cm2 for adults and 9,000 cm2 for children (age 6 years) ( U.S. EPA, 1996). These are the means of the 90th percentile values for females and males in these age groups (U.S. EPA, 1996).
- The duration of exposure is assumed to be 5 hours a day for children (age 6 years) and 6 hours per day for adults (18-64 years). This is the 90th percentile value for the time spent at home in a pool or spa (U.S. EPA, 1996).
- The permeability coefficient (Kp) is a chemical specific value (cm/hr). (U.S. EPA, 1992 provides measured or predicted Kp values for various chemicals and equations for estimating Kp from octanol-water partition coefficient (Kow) values and molecular weight.)
- 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). Children (age 6) are assumed to weigh 22 kg. This is the mean of the median value for male and female children (age 6 years) (U.S. EPA, 1996).
Dermally absorbed dose rates are calculated as follows: ADR = CW * SA * ET * Kp * CF1
where:
ADR = absorbed dose rate (mg/day)
CW = concentration of ai in pool water (mg/L)
SA = surface area exposed (cm2)
ET = exposure time (hours/day)
Kp = permeability coefficient (cm/hr)
CF1 = volume unit conversion factor (L/1,000 cm3)
and CW = AR * CF2 * CF3
where:
AR = application rate (lbs ai/gal)
CF2 = weight unit conversion factor (4.54E5 mg/lb)
CF3 = volume unit conversion factor (2.64E-1 gal/L)
Dermally absorbed dose rate, normalized to body weight, is calculated as: ADRnorm = ADR / BW
where:
ADRnorm = absorbed dose rate, normalized to body
weight (mg/kg/day)
BW = body weight (kg)
Example Calculations
The following is an example calculation to determine the dermally absorbed dose of a pesticide used in swimming pool water. For the purpose of this example, the application rate is assumed to be 5E-5 lbs ai/gal (approximately 1 lb ai/20,000 gal). The assumed permeability coefficient is 0.001 cm/hr. Thus, the concentration of ai in the pool water is as follows:
CW = AR * CF2 * CF3
CW = (5E-5 lb ai/gal) * (4.54E5 mg/lb) * (2.64E-1 gal/L)
CW = 6.0 mg/L
The estimated dermally absorbed dose among 6 year old children would be as follows:
ADR = CW * SA * ET * Kp * CF1
ADR = 6.0 mg/L * 9,000 cm2 * 5 hr/day * 0.001 cm/hr * L/1,000 cm3
ADR = 0.27 mg/day
Finally, the estimated dermally absorbed dose, normalized to body weight, for a child with a body weight of 22 kg would be:
ADRnorm = ADR / BW
ADRnorm = (0.27 mg/day) / (22 kg)
ADRnorm = 0.012 mg/kg/day
This dose would be used in conjunction with toxicity data to assess risk.
Limitations and Uncertainty
The exposure dose generated using this method are based on some central tendency (i.e., body weight) and some upper-percentile assumptions (i.e., surface area, exposure duration, application rate), and are assumed to be representative of high-end exposures. The uncertainties associated with this assessment stem from the use of an assumed permeability coefficient, and assumptions regarding dissipation of chemical residues in the water. The estimated doses are considered to be reasonable high-end estimates based on observations from chemical-specific field studies and professional judgement.
References
Dang, W. (1996) The swimmer exposure assessment model (SWIMODEL) and its use in estimating risks of chemical use in swimming pools. EPA internal guidance document.
U.S. EPA (1992) Dermal Exposure Assessment: Principles and Applications, Office of Health and Environmental Assessment, Washington, DC. EPA/600/8-90/011F.
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.
Introduction
This SOP provides a standard method to be used for estimating postapplication inhalation dose from pesticides in previously treated residential swimming pools when chemical specific data are unavailable. This scenario assumes that swimmers inhale pesticides that offgas from the pool water. 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 exposure to pesticides in swimming pool water via other routes of exposure (i.e., buccal/sublingual, orbital/nasal, aural, sexual organs are described by Dang (1996)).
Methods for Estimating Potential Dose
Label information is important for selecting appropriate data inputs for the exposure assessment (see Section 5.0). The data required for estimating postapplication doses from pesticides in swimming pools is the application rate (i.e., the target concentration of the pesticide active ingredient in the pool water), and the pesticide's vapor pressure. The maximum application rate specified on the label should be used, except in cancer assessments when the typical application rates should be used. It should be noted, however, that the typical residential use rate is often the same as the maximum rate. The following assumptions are also needed for estimating daily pesticide postapplication doses.
- It may be assumed that 100 percent of the application rate is available in the pool water for inhalation. This is believed to be a reasonable assumption because biocides are typically maintained in pool water at specified levels.
- For subsequent days after application, it may be assumed that the pesticide will not dissipate because it is usually desirable to maintain a specified level of biocide in the water.
- The assumed mean inhalation rate is 1.7 m3/hour for adults (i.e., over 18 years) and 1.2 m3/hour for children (i.e., under 18 years), based on a moderate activity level (U.S. EPA, 1996).
- The duration of exposure is assumed to be 5 hours a day for children (age 6 years) and adults (18-64 years). These are 90th percentile values for the time spent at home in a pool or spa (U.S. EPA, 1996).
- 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). Children (age 6) are assumed to weigh 22 kg. This is the mean of the median values for male and female children (age 6 years). (U.S. EPA, 1996).
- Gas phase concentrations are based on an ideal gas model and Raoult's Law (Dang, 1996).
Inhalation potential dose rates are calculated as follows: PDR = Cvp * IR * ET
where:
PDR = potential dose rate (mg/day)
Cvp = vapor concentration of ai in air (mg/m3)
IR = inhalation rate (m3/hour)
ET = exposure time (hours/day)
Cvp is calculated as follows (Dang, 1996):
Cvp = (Cw * VP * 273 K * MW * 1,000 L/m3 * L/1,000 g) / (760 mm Hg * T * 22.4 L/mole)
where:
Cw = concentration of ai in water (mg/L)
VP = vapor pressure (mm Hg or Torr) at the pool water temperature
T = Kelvin temperature (K)
MW = molecular weight of water (18 g/mole)
and Cw = AR * CF1 * CF2
where:
AR = application rate (lbs ai/gal)
CF1 = weight unit conversion factor (4.54E5 mg/lb)
CF2 = volume unit conversion factor (2.64E-1 gal/L)
Inhalation potential dose rates, normalized to body weight, are calculated as: PDRnorm = PDR / BW
where:
PDRnorm = potential dose rate, normalized to
body weight (mg/kg/day)
BW = body weight (kg)
Example Calculations
The following is an example calculation to determine the dose based on an assumed pool water vapor inhalation rate. For the purpose of this example, the application rate is assumed to be 5E-5 lbs ai/gal (approximately 1 lb ai/20,000 gal). Thus, the concentration of ai in the pool water is as follows:
Cw = AR * CF1 * CF2
Cw = (5E-5 lb ai/gal) * (4.54E5 mg/lb) * (2.64E-1 gal/L)
Cw = 6.0 mg/L
The vapor concentration (Cvp) for a chemical with a vapor pressure of 200 mm Hg at 298 K would be:
Cvp = (Cw * VP * 273 K * MW * 1,000 L/m3 * L/1,000 g) / (760 mm Hg * T * 22.4 L/mole)
Cvp = (6.0 mg/L * 200 mm Hg * 273 K * 18 g/mole * 1,000 L/m3 * L/1,000 g) /
(760 mm Hg * 298 K * 22.4 L/mole)
Cvp = 1.16 mg/m3
The estimated inhalation potential dose rate among children would be as follows:
PDR = Cvp * IR * ET
PDR = 1.16 mg/m3 * 1.2 m3/hr * 5 hr/day
PDR = 6.96 mg/day
Finally, the estimated potential dose rate, normalized to body weight, for a child with a body weight of 22 kg would be:
PDRnorm = PDR / BW
PDRnorm = (6.96 mg/day) / (22 kg)
PDRnorm = 0.32 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 some central tendency (i.e., inhalation rate, body weight) and some upper-percentile (i.e., exposure, duration, and application rate for acute assessments) assumptions and are considered to be representative of high-end exposures. The uncertainties associated with this assessment stem from the use of assumptions regarding dissipation of chemical residues in pool water. The estimated doses are considered to be reasonable high-end estimates based on observations from chemical-specific field studies and professional judgement.
References
Dang, W. (1996) The swimmer exposure assessment model (SWIMODEL) and its use in estimating risks of chemical use in swimming pools. EPA internal guidance document.
U.S. EPA (1996) Exposure Factors Handbook, [Draft]. U.S. Environmental Protection Agency, National Center for Environmental Assessment, Washington, DC. EPA/600/P-95/002Ba.