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Standard Operating Procedures (SOPs) for Residential Exposure Assessments

11.0 IMPREGNATED MATERIALS

Prior to the development of an exposure assessment for an impregnated material 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 impregnated materials are as follows:

Impregnated Materials with Pesticidal Claims. Some impregnated materials (e.g., pet collars, "no-pest strips") that contain pesticides have a pesticide label on their container. The labels of such products make claims about pest control, such as "kills fleas and ticks" or "kills flying insects." These labels will contain an active ingredient statement indicating the amount of active ingredient in the container.

Impregnated Materials with No Pesticidal Claims. Some impregnated materials (e.g., mattress covers, shower curtains, paper, adhesives) that contain pesticides do not have a pesticide label and their labels do not make claims about pest control. The pesticide in these products is present as a biocide added during the manufacture of the product. Persons using these household products are considered "secondary handlers," since they are not handling the pesticide itself -- they are handling products that contain pesticide. The SOP for exposure/risk assessments for such secondary handlers (and secondary post-application exposures) is in the biocide SOP under secondary exposures. In order to determine the amount of pesticide in these products, the pesticide label for the biocide product must be obtained and the use-rate for the household product must be calculated.

Limitation and Descriptive Statements: Look for statements describing or limiting the use of impregnated materials that have pesticide labels on their containers. 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 such products are used at residential sites unless a specific labeling statement indicates otherwise. Statements such as "For use on commercial livestock only," "Not for sale or use at residential sites," or "Not for homeowner use" indicate that the product cannot be bought or applied by homeowners. Therefore, no residential handler exposure/risk assessment is required.

11.1 Handler - Dermal and Inhalation (no SOP - pesticides added in manufacturing setting)

11.2 Postapplication Pesticide Residue Dermal and Inhalation Dose from Materials Impregnated with Pesticides

Introduction

This SOP provides a standard method for estimating postapplication dose from dermal contact with materials impregnated with pesticides when adequate chemical-specific field data are unavailable. Inhalation dose is not a concern due to several factors including (1) the pesticide is generally contained within the matrix (i.e. vinyl mattress or shower curtain), (2) pesticides usually have low vapor pressures, and (3) the concentrations used are typically low. This method should be used in the absence of actual field data.

Methods for Estimating Dose

Label information is important for selecting appropriate data inputs for the exposure assessment (see Section 10.0). The only datum required for estimating postapplication exposures to materials impregnated with pesticides is the percent ai content of the material in question. In the absence of actual data, the following assumptions can be used for estimating daily pesticide postapplication doses.

- 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). Toddlers (3 years old), used to represent the 1 to 6 year old age group, are assumed to weigh 15 kg. This is the mean of the median values for male and female toddlers (U.S. EPA, 1996).

- Dose should be based on a duration of exposure that is relevant to the impregnated material being assessed. For example, 8 hours per day of contact would be reasonable for vinyl mattresses based on the median value for the amount of time sleeping (U.S. EPA, 1996). Materials such as shower curtains would have shorter contact periods (e.g., 0.5 hours).

Dermal potential dose rates are calculated as follows: PDR = FR * SA * ET * CF1

where:

PDR = potential dose rate (mg/day)
FR = flux rate for pesticide of concern (mg/m2/day)
SA = body surface area (m2)
ET = exposure time (hours/day)
CF1 = time unit conversion factor (day/24 hours)

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)

Example Calculations

The following is an example calculation to determine the dose based on an assumed flux rate of 15 mg/m2/day in the impregnated materials. The estimated dose from dermal contact with impregnated materials would be as follows:

PDR = FR * SA * ET * CF1

PDR = 15 mg/m2/day * 1 m2 * 8 hours/day * day/24 hours

PDR = 5.0 mg/day

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

PDRnorm = PDR / BW

PDRnorm = (5.0 mg/day) / (71.8 kg)

PDRnorm = 0.070 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 central tendency assumptions. The uncertainties associated with this assessment stem from the potential use of a model for predicting flux rates from impregnated materials. The dose estimates are considered to be reasonable central tendency estimates based on professional judgement.

References

AMEM: Polymer Migration Estimation Model, Arthur D. Little.

U.S. EPA (1992) Methods for Assessing Exposure to Chemical Substances, Volume 11, Methodology for Estimating the Migration of Additives and Impurities from Polymeric Materials. U.S. Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington, D.C. EPA/560/5-85-015.

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.

11.3 Postapplication Doses Among Toddlers From Incidental Non-dietary Ingestion of Pesticide Residues Contained In Materials Impregnated With Pesticides

Introduction

This SOP provides a standard method for estimating incidental dose among toddlers from ingesting pesticide residues that have been transferred from the surfaces of impregnated materials (e.g., toys). This scenario assumes that pesticide residues are transferred to the mouth from mouthing impregnated materials. This method for estimating non-dietary ingestion doses from pesticide residues on impregnated materials is based on assumptions and should be used in the absence of field data. The exposures estimated using this method may be combined with toxicity data to estimate the risks to toddlers from non-dietary ingestion of pesticide residues from impregnated materials.

Methods for Estimating Dose

Label information is important for selecting appropriate data inputs for the exposure assessment (see Section 11.0). The data required for estimating non-dietary ingestion doses from impregnated pesticide residues includes the solubility factor (i.e., ppm in the finished impregnated material) and the concentration of the active ingredient in the formulation (i.e., chemical-specific concentration factor). The maximum solubility factor specified on the label should be used, except in cancer assessments when the typical factors should be used. In the absence of actual data, the following assumptions can be used for estimating daily pesticide non-dietary ingestion doses.

- Toddlers (3 years old), used to represent the 1 to 6 year old age group, are assumed to weigh 15 kg. This is the mean of the median values for male and female toddlers (U.S.EPA, 1996).

- The total surface area of the impregnated material is assumed to be 500 cm2 (e.g., the surface area of an impregnated toy) (Dang, 1997).

- It is assumed that the entire surface of the impregnated material is mouthed once per day. This value is based on the professional judgement and experience of the OPP staff from the review of company-submitted data.

Potential dose rates from incidental non-dietary ingestion are calculated as follows: PDR = FR * SA

where:

PDR = potential dose rate (mg/day)
FR = flux rate for the pesticide of concern (mg/cm2/day)
SA = surface area of impregnated material mouthed per day (assumed to be 500 cm2)

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 assumed chemical-specific solubility and concentration factors. For the purposes of this example, the chemical-specific flux rate is assumed to be 15 mg/m2/day. Thus, the potential dose rate from incidental non-dietary ingestion is calculated as follows:

PDR = FR * SA

PDR = 0.0015 mg/cm2/day * 500 cm2

PDR = 0.75 mg/day

Finally, the estimated potential dose rate, normalized to body weight, for a toddler with a body weight of 15 kg would be:

PDRnorm = PDR/BW

PDRnorm = (0.75 mg/day)/(15 kg)

norm = 0.05 mg/kg/day

Limitations and Uncertainty

The dose estimates generated using this method are considered to be based on some central tendency (e.g., surface area of the impregnated material mouthed and body weight) and some upper-percentile assumptions (e.g., 100 percent of chemical flux transferred and entire surface of an impregnated object mouthed on a daily basis). The uncertainties associated with this assessment stem from the potential use of a model for predicting flux rates from impregnated materials. Uncertainties also occur from assumptions regarding the impregnated material surface area entering the mouth and the frequency and duration of exposure. For example, it is assumed that toddlers consume all of the pesticide residues that are transferred to the surface area of the impregnated material and that the material is placed in the mouth, in its entirety, over the course of a day. The dose estimates are believed to be reasonable high-end estimates based on observations from limited study of chemical flux from impregnated materials.

References

AMEM: Polymer Migration Estimation Model, Arthur D. Little.

Dang (1997) Risk Analysis for microban Additive "B" (Triclosan or Irgasan DP300) Treated Toys For Infants, Memo From Winston Dang (Antimicrobial Division) to Frank Sanders and William Jordan (Antimicrobial Division) Dated February 24, 1997.

U.S. EPA (1992) Methods for Assessing Exposure to Chemical Substances, Volume II, Methodology for Estimating the Migration of Additives and Impurities from Polymeric Materials. U.S. Environmental Protection Agency, Office of Pollution Prevention and Toxics, Washington, D.C. EPA/560/5-85-015.

U.S.EPA (1996) Exposure Factors Handbook. [Draft]. U.S. Environmental Protection Agency, Office of Health and Environmental Assessment, Washington, DC. EPA/600/P-95/002Ba.

12.0 TERMITICIDES

Prior to the development of an exposure assessment for termiticides, 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 termiticides are as follows:

Registered for Use as a Termiticide: Determine whether the labeling contains directions for use as a termiticide.

Limitation and Descriptive Statements: Look for statements describing or limiting the use of the termiticide. 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 as a termiticide is used at residential sites unless a specific labeling statement indicates otherwise. Assume that all termiticides are applied by commercial applications. Therefore, no residential handler exposure/risk assessment is required. Since termiticides are applied to residences, a post-application exposure/risk assessment is required. Statements such as "For use on commercial buildings only," and the more specific "Not for use at residential sites," or "Not for use in and around homes or dwellings" indicate that the product cannot be used at residential sites and no residential handler or post-application exposure/risk assessment is required.

12.1 Handler - Dermal and Inhalation (no SOP - pesticides are applied by commercial handlers only)

12.2 Postapplication - Dermal and Inhalation (no SOP for dermal because of limited exposure potential; refer to 13.2 for inhalation exposure)


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