Until 2004, most preservative-treated wood was pressure-treated with CCA (chromated copper arsenate). Concerns about arsenic and chromium leaching from decks and fences led to the removal of CCA-treated lumber from the residential market. Today, direct substitutes include such less toxic products as ACQ (ammoniacal copper quaternary) and CBA (copper boron azole). Naturally rot-resistant wood species, including redwood and cedar, are only a small segment of the market, but are increasingly being offered from certified, well-managed forests. There are also green alternatives to traditional decking that are easy to maintain, including wood-plastic composite lumber that incorporates some of the characteristics of wood with those of plastic lumber.