The 'new' improved treated lumber we've used for our raised bed frames does NOT contain chromium or arsenic as the older treated lumber had.
Micronized Copper Azole (MCA) is the latest generation wood preservative systems in which very small (sub-micron) particles of solid copper are suspended in a liquid carrier
and pressure injected into wood, thereby eliminating the need to dissolve the copper as is done in traditional copper-based preservatives. The use of solid copper particles, rather than dissolved
copper, results in a number of improved characteristics of the treated wood. These wood preservatives are designed for long-term performance in both indoor and outdoor applications. MCA treated
lumber is clean, odorless, and non-irritating to humans, animals and plants and is frequently used for decks, playground equipment, picnic tables, etc.