Two less-toxic alternatives are ACQ Preserve with UltraWood water repellent and Kodiak lumber. Both are preserved without arsenate, and are backed for life against termites, decay and fungi. Quality grades run in descending order. Choose grade No. 1 for railings and benches, and grade No. 2 or BTR for decking. Redwood and cedar heartwood has glowing color, handsome straight grains and natural resistance to rot and insects.
Boards are easy to cut and can be left untreated to weather naturally.
Life span is easily more than 20 years. Both are expensive. Cedar sapwood breaks down quickly in moist conditions. Redwood and cedar are sold in all standard dimensions. Redwood can take a few days for special orders.