Wood, although not tasty, isn't usually toxic, with the exception of pressure treated wood which contains poisonous chemicals that could kill.
Most woods cut directly from a tree could be eaten in small amounts, under the condition that they aren't already infected with bacteria, fungi and insects. Pressure-treated lumber, however, is wood that has been dipped into a liquid preservative then placed in a pressure chamber. The chamber propels the chemical into the fibers of the wood. The pressurized treatment assures that the chemical reaches the core of each piece of wood and is much more effective than soaking the wood in the chemical.
The most common chemical combination used to treat lumber is called chromated copper arsenate, or CCA. These chemicals, chromium, copper and arsenic, are found in small amounts in the human body, but are dangerous or even lethal in large doses. Chromium, copper and arsenic are poisonous to various organisms which attack wood, but are also life-threatening to humans if consumed, particularly arsenic. The risk of illness from mere exposure to chemicals leaking from CCA-treated wood is low. Upon ingestion, though, these chemicals can cause health problems such as diarrhea, vomiting, fatigue, depression, damage to major body organs and certain types of cancer. And, you might not have to actually eat the wood to be effected. Children who are playing on and around pressure treated wood often touch the wood then put their fingers in their mouths. Also, kids are known to play in dirt, which might contain lethal chemicals that have leached from the wood to the soil. Studies prove that arsenic, copper and chromium from pressure treated wood soak into the surrounding ground area. Although somewhat dangerous, the amounts of arsenic and other lethal chemicals measured on CCA-treated wood are a thousand times less than a lethal dose. Still, it is best to avoid unnecessary consumption of arsenic since it is known to be a carcinogen.
While small amounts of arsenic may not be harmful to health in short term exposures, studies aren't clear about just how much handling of toxic chemicals can result in later cancer discovery. To avoid accidental ingestion of arsenic or other toxins, coat the structure with an oil based wood-finishing sealant to reduce any leaching chemicals. Re-apply sealant every one or two years, depending on wear and weather. Wash hands after contact with CCA-treated wood. This is most important for young children. Spread a tablecloth while eating on a picnic table made of CCA-treated wood. For fruit or vegetable gardens made from CCA-treated wood, separate the wood from the dirt with a plastic lining on the base and sides of the box. Never burn CCA-treated wood or use it as compost or mulch. Burning CCA-treated wood is a serious health concern since it releases toxic amounts of chemicals into the air. In addition, fence or screen off areas underneath decks to prevent access by children and pets. Plant a thick ground cover to provide a barrier between the soil and human contact.
Since chemicals in treated wood are generally not safe for humans, wear gloves when handling, and avoid breathing the sawdust. And, if working with pressure treated wood, never peel off a strip and put it in your mouth for chewing, or use a piece of the wood for a toothpick.
