Wood - Treated
Treated wood is wood treated with a chemical for the purpose of resisting decay. Examples include pressure-treated dimensional lumber, creosote-treated railroad ties, and telephone poles.
Pressure treated, preserved wood, or treated wood waste (including the sawdust), referred to as TWW, has preserving chemicals like arsenic. Common uses of TWW are fence posts, sill plates, landscape timbers, pilings, guardrails, decking, and railroad ties.
TWWDisposal.org has fact sheets and outreach materials on the appropriate handing, disposal, and other management of TWW for facilities that may receive or handle treated wood waste.
Painted, engineered, stained, laquered, plywood/composite, and wood painted with "copper green" wood may go in the garbage.