Treated wood is plainly labeled as such. Look for stamps that show the level of ground contact. It includes arsenic, is meant for direct contact with the ground, and is the most hazardous kind if it is marked L-P22. If it's labeled L-P2, it's less hazardous and not intended for direct contact with the earth. P-L is considered the safest type of treatment. It's also important to know the date that the wood was treated because treated lumber must be replaced after 22 years even if it's not visible damage.
If you want to be safe, don't use any wood that hasn't been labeled for ground contact. The wood will continue to emit toxic chemicals over time so use up all your treated lumber before it starts to deteriorate.
Toxic chemicals are used in the treatment process to prevent insects from attacking the wood. They may cause cancer over a long period of time if they are inhaled or ingested. Skin contact could cause irritation or inflammation. The treated wood isn't going to break down completely but it does release toxins over time.
People who live near old growth forests have protested the clearcutting of trees for timber. Old growth forests develop at a slow rate and contain many large trees which provide habitat for rare species of birds and animals. The land around these forests becomes more unstable due to erosion caused by the removal of all the trees. This leads to problems when heavy rains fall into eroded areas creating flood hazards for homes and businesses.
The US Environmental Protection Agency classifies pressure-treated timber as hazardous waste. The chemical connection that binds the arsenic in the wood is broken when the wood is burned, and just one tablespoon of ash from the burned wood carries a fatal amount of this poison. Arsenic is toxic to humans and animals through skin contact, ingestion, or inhalation. It can cause serious health problems including cancer, heart disease, neurological damage, and internal organ failure.
When wood is burned, it produces carbon dioxide and water vapor. Burning treated wood adds more arsenic to the atmosphere. As with other chemicals, there are regulations on how much arsenic can be released into the air during burning. If you live in an area where burning wood is allowed, then you should find out what the rules are before you start making your own firewood.
Burning wood is one of the most effective ways to remove trees or shrubs that have been sprayed with pesticides. However, burning wood also releases pesticides into the air. Pesticides are toxic chemicals used to kill insects that spread harmful diseases. They can be found in residential areas where people don't want pests around their homes and in agricultural lands where they use pesticides to protect crops.
People who make charcoal by burning wood without first treating the wood with a pesticide may be exposing themselves to dangerous levels of pesticides.
Landscape timbers coated with copper, chromium, and arsenic combinations should not be used near plants intended for human food. On the other hand, as previously said, treated wood is still the preferred timber. This is because most homeowners construct benches, retaining walls, or tables out of treated wood. Even though treated wood may look like standard lumber, it is actually made from trees that have died or been cut down before being treated with chemicals. Homes built before 1994 are likely to contain wood that has contained toxic substances since its installation. These homes need to be inspected by a certified arborist before any hazardous materials can be removed from them.
If you plan to use your landscape timber indefinitely, then it's important to choose healthy trees with strong trunks. The wood will need to be treated regardless of whether it is intended as an outdoor furniture piece or not. Treated wood is less expensive than other options and it's recommended if you plan to use your timber for more than one project. However, if you want to use untreated wood instead, there are many types available for different uses. For example, redwood is heavy and durable but very expensive while pine is relatively inexpensive but weak and prone to disease. You should also consider the location of tree harvesting when choosing your material; if possible, try to source timber from sustainable sources. For example, some forestry departments offer programs where you can exchange old trees for new ones (or cash).