Assessing and managing exposure from arsenic in CCA-treated wood play structures

Background: Chromated copper arsenate (CCA)-treated wood has been widely used for outdoor play structures. There is a growing scientific concern about children's exposure to the arsenic that leaches from these structures. The purpose of this study was to measure arsenic from CCA-treated wood play structures owned by the City of Toronto to guide an appropriate exposure reduction strategy. Methods: In the fall of 2002, 4 soil and 2 wood surface samples (dislodgeable arsenic) were collected from 217 play structures and analyzed for total arsenic content. Soil arsenic concentrations were compared to the federal soil guideline of 12 mug/g. Dislodgeable arsenic concentrations were compared to a Toronto Public Health-derived interim action level of 100 mug/100 cm(2). Results: Soil arsenic levels in samples taken from within one metre of CCA-treated wood were low (mean 2.1; range 0.5-10 mug/g). However, the means of the arsenic level in the composite soil samples taken from beneath an elevated platform were significantly greater (p<0.01) than the background soil sample and soil from within one metre of the CCA-treated wood (mean 20.3; range 12.4-47.5 mug/g). Composite soil samples exceeded the federal soil guideline of 12 mug/g at 32 play structures. Dislodgeable arsenic values varied widely (mean 41.9 mug/1 00 cm(2); non-detectable to 521.5 mug/1 00 cm(2)). 32 play structures had dislodgeable arsenic levels that exceeded the interim action level. Mean arsenic concentrations on vertical surfaces were significantly higher than on horizontal surfaces (P<0.01). Discussion: Our soil analysis indicates that arsenic does not migrate laterally but accumulates under elevated platforms at levels that can exceed the soil guideline. Dislodgeable arsenic values varied greatly and were not a useful predictor of soil arsenic (R-2 = 0.0015).