Dislodgeable copper, chromium and arsenic from CCA-treated wood surfaces
Introduction
Due to its excellent fungicidal and insecticidal properties, chromated copper arsenate (CCA) is currently the most widely used wood preservative. Treated wood is used outdoors for both residential and commercial applications. Such uses include decks, picnic tables, landscape timbers, highway sound barriers, telephone poles and docks. Recent concerns that dispersal of these additives from the wood could impact the environment (Weis and Weis, 1996, Weis and Weis, 2002, Stilwell and Gorny, 1997, Stilwell and Graetz, 2001, Lebow et al., 2000, Hingston et al., 2001, Townsend et al., 2001) have resulted in a phase-out of all new uses of this material for residential purposes in the US, effective January 2004 (Federal Register, 2002). Nonetheless, potential environmental impacts, especially with regard to arsenic, still exist since the wood is expected to remain in service for many years (Solo-Gabriele and Townsend, 1999). Various aspects of the environmental and health hazards of arsenic exposure have been extensively covered (Nriagu, 1994, NRC, 1999).
The extent of arsenic exposure to individuals due to physical contact with CCA wood surfaces, including playground equipment, decks and picnic tables built using CCA-treated wood, is of major concern. Because of children's frequent hand-to-mouth activity, they are considered the most vulnerable to this potential risk. In this study, we provide data that will assist in the assessment of this potential risk by analyzing the Cu, Cr and As in wipe samples taken from CCA-treated wood surfaces. These surfaces consisted of test coupons, cut from wood bought at lumber yards, that were placed outside to weather and periodically sampled for up to 2 years. While surface-dislodgeable As in treated wood using wipe samples has been determined in some instances, primarily limited to surveys, there is no information on how its availability varies over time.
Section snippets
Test samples
Six sets of 2.5-m-long CCA pressure-treated pine boards, treated nominally with 6.4 kg/m3 CCA preservative, were purchased from three lumber yards. Each set consisted of three–four boards, and the total number of boards used was 19. Each board was cut into 30- or 60-cm test coupons. Either two or four coupons from the interior portions of each board were tested. The coupons were placed on racks outside, and were periodically tested over 1 (sets 3–6) or 2 (sets 1–2) years. Coupons from set 1
Extraction efficiency of nitric acid solutions
Shown in Fig. 1a are the extraction efficiencies of the various components of CCA in wood powder over time using 20% HNO3 solution at room temperature (approx. 25 °C). These results show that Cu and As are readily extracted within 2 h. The average extraction efficiency for these elements for periods greater than 1 h was 98±3% for Cu and 95±4% for As. The Cr in the CCA wood powder was not completely extracted until the extraction time approached 48 h. However, by raising the extraction
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2016, Science of the Total EnvironmentCitation Excerpt :After sampling, wipes were placed in digestion tubes and 50 mL 10% HNO3 was added. Tubes were placed in a 65 °C water-bath for 16 h prior to filtration using 0.45 μm polyester filters (Environmental Express, South Carolina) (Stilwell et al., 2003; CPSC, 2005). The goal of wipe sampling was to remove dislodgeable As residues that are easily accessible through casual contact (CPSC, 2005; USEPA, 2005a,b).
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2014, Science of the Total EnvironmentCitation Excerpt :Once cool, another 3.0 ml of concentrated HNO3 and 1.0 ml of 30% H2O2 were added and again heated at 95 °C until the volume was reduced to 5 ml, followed by addition of DI water to 50 ml and analysis with ICP-MS (Sigmon and Patch, 2010). The wipes used to sample DA on railings and shoes were digested in 50 ml 10% HNO3 and a 65 °C water bath for 16 h, followed by shaking at 150 rpm for 5 min, filtration and analysis by ICP-MS (Stilwell et al., 2003; CPSC, 2003). Conversion of the amount of DA collected on wet wipes to the amount estimated to accumulate on children's hands after contact was made following Shibata et al. (2006), which conservatively estimates that only 2% of the DA collected on a 100 cm2 wipe surface will be found on children's hands with the same surface area.
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