Treated wood contains chemical preservatives or pesticides to protect wood from rotting due to insects, moisture, and fungus. Some of these chemicals may be harmful to people and the environment. To protect your family’s health and the environment, be sure to select, use, and dispose of treated wood carefully.
Chromated Copper arsenate (CCA) was a major source of treated wood since the 40s. Due to health concerns related to arsenic, manufactures discontinued producing CCA-treated wood for residential use. If you have a wood structure built before 2004, and it’s not made of cedar or redwood, it’s most likely made from CCA-treated wood.
Arsenic-free wood preservatives
A range of other less toxic wood preservatives for pressure-treated lumber are available.
- Ammoniacal copper quaternary (ACQ)
- Borate preservatives (Disodium Octoborate Tetrahydrate or DOT)
- Copper azole
Consult with your local home improvement store about the best type of wood and hardware to use for your outdoor construction project.
Recycled plastic and wood-plastic lumber doesn’t leach toxic chemicals into the soil or water and costs less to maintain. Additionally, there are several Minnesota manufactures of plastic lumber, when you buy Minnesota-made products you are helping local businesses.
Redwood, cedar, and cypress are naturally resistant to insects and rot. Be sure to purchase FSC-certified wood. Forest Stewardship Council (FSC) ensures the product comes from responsibly managed forests.
Reclaimed wood is typically recycled from old barn structures, and "sinker" logs from the days of river-based log drives.
Stone or metal. Stone and landscape blocks can be used for gardens and landscaping, while metal can be used in place of some treated wood applications.
Tips for working with treated wood
- Work outdoors and wear a dust mask, goggles, gloves and long sleeves when working with pressure-treated lumber. And always wash your hands after working with the product.
- Avoid using pressure-treated lumber where it may come into contact with drinking water or food (such as cutting boards or for use in beehives).
- Do not use treated wood for animal food storage bins, water trough, and compost bins.
- Remember to “measure twice and cut once” to avoid wasting time and material.
- Never use treated wood for mulch or compost.
Use and care
- No matter what product use for your outdoor project, be sure to follow the manufacturer’s instructions for use and care.
- The US Environmental Protection Agency recommends sealing existing CCA-treated wood annually with an oil- or water-based penetrating sealant or stain.
- Most treated wood can be disposed of with your regular trash. Some haulers have special requirements for pickup, or may not accept it. Contact your county solid waste office for information on how to dispose of treated wood. Disposal in a demolition landfill is prohibited.
- Do not burn treated wood in wood stoves, fireplaces, or recreational or cooking fires. Open burning of treated wood is prohibited by state law (Minn. Stat. § 88.171). The particulate matter and toxic gases released during burning can cause eye and nose irritation, breathing difficulty, coughing, and headaches. People with heart disease, asthma, emphysema, or other respiratory diseases are especially sensitive to air pollutants. The chance of human health impacts depends mostly on the concentration of air pollutants in people’s breathing zone (the air that’s breathed around the nose and mouth).
- Do not bring treated wood to a compost site.
Treated wood to avoid
Creosote, a tar-like substance, is most commonly used for railroad ties, utility poles, and pilings. Due to exposure to skin, inhalation and possible ingestion, the US EPA does not approve creosote-treated wood for residential use.
Pentachlorophenol (PCP or Penta) is commonly used for utility poles and should not be used for residential landscape projects. Pentachlorophenol is extremely toxic to humans from acute (short-term) ingestion and inhalation exposure.