The U.S. EPA announced this week a two-year phase out of an arsenic-based preservative used to pressure-treat lumber against rot and insect damage. The treated wood is popular for use in fences, decks, and playground equipment, and its manufacturers and vendors — including Home Depot and other building-supply stores — currently face a class-action suit for an alleged failure to adequately warn consumers of its potential danger. Arsenic is a known human carcinogen, and some environmental and consumer groups claim that children exposed to the treated wood face a higher risk of developing cancer. Under pressure from such groups, the vendors voluntarily negotiated the current phase-out with the EPA; environmentalists generally praised the action, but some said it failed to address the continued presence of arsenic-treated wood products in homes and public recreation areas.