The wave of public concern about the safety of CCA-treated lumber (see “New Arsenic Scare Puts Spotlight on PT Lumber,” Notebook, 6/01) was ratcheted up a notch last fall with the appearance of a controversial report from a Washington, D.C.-based environmental organization. The Environmental Working Group tested samples of new pressure-treated lumber at Home Depot and Lowe’s lumberyards in 13 metropolitan areas by passing a moistened swab over a 100-square-centimeter surface — an area it compared to the size of a fouryear- old child’s handprint — and sending the swabs to a government-certified lab for analysis. Each swab was found to have picked up an average of nearly 250 micrograms of arsenic. Based on the residue levels measured, the group