A Probabilistic Arsenic Exposure Assessment for Children Who Contact CCA‐Treated Playsets and Decks, Part 1: Model Methodology, Variability Results, and Model Evaluation

Abstract

Concerns have been raised regarding the safety of young children who may contact arsenic residues while playing on and around chromated copper arsenate (CCA)-treated wood playsets and decks. Although CCA registrants voluntarily canceled the production of treated wood for residential use in 2003, the potential for exposure from existing structures and surrounding soil still poses concerns. The EPA's Office of Research and Development developed and applied the probabilistic Stochastic Human Exposure and Dose Simulation model for wood preservatives (SHEDS-Wood) to estimate children's absorbed dose of arsenic from CCA. Skin contact with, and nondietary ingestion of, arsenic in soil and wood residues were considered for the population of children in the United States who frequently contact CCA-treated wood playsets and decks. Model analyses were conducted to assess the range in population estimates and the impact of potential mitigation strategies such as the use of sealants and hand washing after play events. The results show predicted central values for lifetime annual average daily dose values for arsenic ranging from 10(-6) to 10(-5) mg/kg/day, with predicted 95th percentiles on the order of 10(-5) mg/kg/day. There were several orders of magnitude between lower and upper percentiles. Residue ingestion via hand-to-mouth contact was determined to be the most significant exposure route for most scenarios. Results of several alternative scenarios were similar to baseline results, except for the scenario with greatly reduced residue concentrations through hypothetical wood sealant applications; in this scenario, exposures were lower, and the soil ingestion route dominated. SHEDS-Wood estimates are typically consistent with, or within the range of, other CCA exposure models.

Quantified outdoor micro-activity data for children aged 7–12-years old

“…Incidental ingestion is a primary route of exposure for pesticides, metals including lead and arsenic, flame retardants and microbes (Chisolm Jr and Harrison, 1956;Aung et al, 2004;Jones-Otazo et al, 2005;Zartarian et al, 2006;De Miguel et al, 2007;Morgan et al, 2007;Nicas and Best, 2008). Furthermore clean-up decisions and appropriate risk mitigation actions for hazardous waste sites, including Superfund sites, are based on estimates of the incidental ingestion and dermal exposure pathways (US EPA, 2004).…”

“…Non-dietary ingestion exposure has continued to be the primary route for lead and other heavy metal exposure in children (Chisolm Jr and Harrison, 1956;Aung et al, 2004;Zartarian et al, 2006;De Miguel et al, 2007), and is the primary contribution to the polybromindated diphenyl ether body burden of toddlers through adults (Jones-Otazo et al, 2005). Furthermore, non-dietary ingestion exposure is the primary means of transmission for certain infectious diseases like the influenza virus, where exposure occurs through the hand and mouthing contacts with fomites (Nicas and Best, 2008).…”

“…Mouthing and hand contact frequencies are key parameters for estimating non-dietary ingestion and dermal exposure (Zartarian et al, 2006;Nicas and Best, 2008;Stapleton et al, 2008;Julian et al, 2009;Schleier et al, 2009;Macedo et al, 2010;Tulve et al, 2010), as well as soil/dust ingestion rates (Ö zkaynak et al, 2010) critical for most hazardous site clean-up risk assessments including Superfund sites (US EPA, 2004). Several studies have quantified these mouthing and hand contact behaviors in children (Zartarian et al, 1997aBrinkman et al, 1999;Reed et al, 1999;Freeman et al, 2001Freeman et al, , 2005Tulve et al, 2002;AuYeung et al, 2004;Black et al, 2005;Auyeung et al, 2006;Beamer et al, 2008); however, we know of only one other study that has reported any data on children over 6 years of age (Freeman et al, 2001).…”

Biologically based modeling of multimedia, multipathway, multiroute population exposures to arsenic

“…However, (a) chemical form and bioavailability of As in environmental and microenvironmental media, including food (USEPA, 1998), (b) routes and pathways of exposure Zartarian et al, 2006), (c) presence of other contaminants (Hays et al, 2006), and (d) individual variability in metabolism, depending on genetic makeup and developmental stage (Meza et al, 2005;Suzuki, 2005;Valenzuela et al, 2005) are important in determining biologically relevant target tissue dose and health effects.…”

“…The option of estimating contributions from hand-to-mouth pathway is also available within MENTOR-4M, based on the approach described in Zartarian et al (2006). However, due to lack of data for characterizing model inputs, this option was not used in the present study.…”