Arsenic on Children’s Hands: Le et al. Respond

after Playing in Playgrounds We commend Kwon et al. (2004) for their very interesting study of arsenic on the hands of children in contact with chromated copper arsenate (CCA)-treated wood structures and soil after playing in playgrounds. We would like to comment on some of their cited references and discuss the implications of the reported arsenic concentrations found in their sand/soil samples. Kwon et al. (2004) accurately stated that previous studies on CCA-treated wood have mostly examined soil and sand samples from playgrounds but have not assessed the amounts of arsenic found on the hands of children playing on the CCA-treated wood structures. However, to justify their statement, they inappropriately cited our previous work that examined arsenic speciation in various synthetic soil samples artificially contaminated with CCA in the laboratory (Balasoiu et al. 2001) and arsenic concentrations in field-collected soils near CCAtreated utility poles (Zagury et al. 2003). Therefore, it is not surprising that the levels of arsenic on the hands of children playing on wood-treated structures were not evaluated during the aforementioned studies. In our field study, arsenic concentrations found in surface soil collected immediately adjacent to CCA-treated utility poles ranged between 153 ± 49 and 410 ± 150 mg/kg (mean ± SD), although they dropped to between 6.3 ± 1.5 and 61 ± 60 mg/kg at 0.1 m from the pole. Therefore, arsenic concentrations found immediately near CCAtreated utility poles are much higher than the values reported by Kwon et al. (2004) in their study using soil/sand samples collected from playgrounds. Moreover, in a recent study conducted near 217 CCA-treated wood play structures in Toronto, Canada (Ursitti et al. 2004), mean arsenic concentrations in soil samples taken from beneath elevated platforms (mean 20.3; range 12.4–47.5 mg/kg) were significantly greater than background soil samples (mean 2.4; range 0.5–13 mg/kg) and soil from within 1 m (mean 2.1; range 0.5–10 mg/kg). Composite soil samples exceeded the Canadian federal soil guideline (Canadian Council of Ministers of the Environment) of 12 mg/kg at 32 CCA-treated wood play structures. Furthermore, Stilwell and Gorny (1997) reported a mean arsenic concentration of 76 mg/kg in soils collected beneath seven decks built with CCA-treated lumber, compared to a mean concentration of 3.7 mg/kg in control soils (collected at a minimum distance of 5 m from the decks). All these studies suggest that the sampling protocol is crucial in order to obtain a representative pattern of the soil contamination and that the closer the sample is to the CCA-treated wood structure, the higher the arsenic concentration is expected to be. Therefore, when Kwon et al. (2004) stated that “it is important to point out to the general public that arsenic is naturally present in the soil and sand regardless of whether the playgrounds contain CCA-treated wood structures,” they do not adequately refer to previously published studies; therefore, their statement might be misleading. We agree with the authors that there is a natural background concentration of arsenic in soils near CCA-treated utility poles (0.5–7.3 mg/kg) (Zagury et al. 2003; Chirenje et al. 2003), near CCA-treated decks (0.4–2.2 mg/kg) (Stilwell and Gorny 1997; Chirenje et al. 2003), and near CCA-treated play structures (0.5–13 mg/kg) (Ursitti et al. 2004). However, published studies all conclude that arsenic concentrations in soil samples taken from beneath or immediately adjacent (within 01–0.3 m) to CCA-treated wood structures are significantly greater than background arsenic concentrations. Nevertheless, as the data of Kwon et al. (2004) show, the amount of total arsenic from hand washing suggests that direct contact with CCA-treated wood is a major contributor to arsenic concentration on children’s hands. Therefore, oral ingestion of dislodgeable arsenic via hand-to-mouth contact appears to be an important exposure pathway, and we agree with the authors when they recommend that children wash their hands after playing in CCA-treated playgrounds. However, potential ingestion of arsenic from soil under CCA-treated structures should not be neglected based on the unusually low arsenic concentrations found in the soil/sand samples in their study. The importance of this additional exposure pathway can be fully assessed when accurate estimates become available for a) soil physicochemical properties and contamination pattern beneath CCA-treated structures, b) children’s daily soil intake values, and c) relative oral bioavailability of arsenic in CCA-contaminated soils. Part of the authors’ work on occurence and toxicity assessment of metals in soil near CCAtreated utility poles is supported by Bell Canada and Hydro-Quebec. Gerald J. Zagury Priscilla Pouschat Department of Civil, Geological and Mining Engineering École Polytechnique de Montréal Montréal, Québec E-mail: [email protected]