Measuring Potential Dermal Transfer of a Pesticide to Children in a Child Care Center
Hubal, Elaine A. Cohen, Egeghy, Peter P., Leovic, Kelly W., Akland, Gerry G., Environmental Health Perspectives
Currently, the major determinants of children's exposure to pesticides are not fully understood, and approaches for measuring and assessing dermal exposure in a residential setting have not been sufficiently evaluated. In one approach, dermal exposure is estimated using empirically derived transfer coefficients. To assess the feasibility of using this approach for assessing children's exposure to pesticides, we conducted a study was conducted in a child care center that had a preexisting contract with a pest control service for regular monthly pesticide applications. Children in the selected child care center were monitored using full-body cotton garments to measure dermal loading. Pesticide residues on classroom surfaces were measured in the areas where the children spent time. Measured surface-wipe loadings ranged from 0.47 to 120 ng/[cm.sup.2], and total garment loadings ranged from 0.5 to 660 pg/[cm.sup.2]. The garment and surface loading measurements were used to calculate dermal-transfer coefficients for use in assessing children's residential exposure to pesticides. Dermal-transfer coefficients calculated using these data range from approximately 10 to 6,000 [cm.sup.2]/hr. The wide range in these values demonstrates the importance of developing standard surface-measurement protocols if this approach is to be used to assess dermal exposure in a residential environment. The upper-range values resulting from this study were found to be similar to the default value used by the U.S. Environmental Protection Agency to assess children's dermal exposures resulting from contact with indoor surfaces. Key words: children, dermal exposure assessment, dermal-transfer coefficients, FQPA, pesticide exposure. doi:10.1289/ehp.8283 available via http://dx.doi.org/[Online 20 September 2005]
The Food Quality Protection Act of 1996 requires that children's risks to pesticide exposures from all sources be considered during the tolerance-setting process. An initial assessment of critical exposure pathways for children indicates that dermal contact may result in high residential exposures to pesticides (Cohen Hubal et al. 2000b). Currently, because of insufficient data on children's exposures and activities, quantitative assessments must rely heavily on default assumptions as substitutes for missing information (Cohen Hubal et al. 2000a, 2000b). In addition, the major determinants of children's exposure are not fully understood, and approaches for measuring and assessing dermal exposure in a residential setting have not been sufficiently evaluated.
Currently, the U.S. Environmental Protection Agency (EPA) Office of Pesticide Programs (OPP) uses a transfer-coefficient approach to assess children's residential exposures to pesticides (U.S. EPA 1997, 1999, 2001a). In this type of assessment approach, exposure is estimated using empirically derived dermal-transfer coefficients to aggregate the mass transfer associated with a series of contacts with a contaminated medium. The transfer-coefficient approach was developed to assess occupational exposure in an agricultural setting where workers are engaged in similar activities and are exposed to relatively homogeneous environmental concentrations of pesticides. With this approach, dermal exposure sampling using a surrogate-skin technique such as a patch sampler or a whole-body garment sampler is conducted simultaneously with surface sampling for a specific activity (e.g., harvesting apples). A dermal-transfer coefficient is then calculated for this work activity. In later studies, this transfer coefficient can then be used to estimate exposure for a similar activity by collecting only surface samples (Fenske 1993).
Although pesticide levels in a residential environment are likely to be nonuniform and resident activities varied, this approach has also been used to assess residential exposure to pesticides. Dermal-transfer coefficients for assessing residential exposures to pesticides have been developed previously (Formoli 1996; Ross et al. …