Staying Safe around Treated Wood
Some pesticides are used as preservatives to extend the service life of wood. They provide long-term protection of wood against fungi, insects and marine borers. When treated wood is going to be used on a flat surface that will be exposed to water, a water-repellent treatment may also be applied.
On this page
- Types of chemicals used to treat wood in Canada
- Treated wood risks
- General safety tips
- Safety tips for handling older treated wood
Types of chemicals used to treat wood in Canada
Treated wood used in home building projects tends to have little or no odour. Aged treated wood and untreated wood can look the same colour.
For residential building projects, the wood may have been treated with:
- Alkaline Copper Quaternary (ACQ) or Copper Azole (CA-B), which is available in various shades of brown
- Chromated Copper Arsenate (CCA), which is no longer available for residential construction projects
- CCA-treated wood is a light green colour when it is new, but can look like untreated wood when it has aged
- Residential decks, fences or playground structures built before 2004 are likely to have been made from CCA-treated lumber
- Chromium, copper and arsenic are a natural part of the environment. However, since damaged wood can release small amounts of arsenic, it is a good practice to monitor older CCA-treated wood regularly for signs of damage, like rot or scraped surfaces. Although the released amount of arsenic is generally not of concern, extended exposure can pose risks to health. Exposure to CCA should be minimized.
People may also come in contact with ‘industrial use’ wood that has been treated with:
- Creosote, used for railroad crossties, which has a distinct, petroleum-based odour
- Pentachlorophenol, used for utility poles
- CCA used for utility poles, marine timbers and pilings, highway construction, and many other industrial uses
Treated wood risks
While wood treatment products are designed to bind to the wood, small amounts of the chemicals can slowly leach out of the wood. Over time, or from damage, small amounts of treated wood chemicals may escape as wood dust or splinters from the surface of the wood. How much and how fast this can happen depends on:
- the type of wood
- the amount of rainfall
- the acidity of the rain and soil coming into contact with the wood
- the age of the structure
The amount of leached chemicals generally drops quickly within a short distance from where soil is in contact with the treated wood.
If you follow safety precautions around treated wood, you should not have any health effects as a result. However, you should avoid exposure to the smoke or ash from burning treated wood. If you suspect poisoning, seek medical attention immediately.
General safety tips
Follow these general safety tips to stay safe around treated wood:
- Wash children’s hands after they have been in contact with treated wood.
- Use plates or a plastic tablecloth instead of serving food directly from a treated wood surface, like a picnic table.
- Never burn treated wood - indoors or outdoors. Burning this type of wood releases chemicals in the ash and smoke.
- Do not use treated wood where it may come into direct contact with food, such as cutting boards, counter tops, beehives, animal feed storage, silos, water troughs, compost bins, mulch, or as an edging for an edible garden.
- Do not use treated wood near livestock, feed, or food-producing animals. This could transfer chemicals into animal products, such as meat, milk and eggs.
- Do not use treated wood where it may come into contact with drinking water, like wells, and water reservoirs and covers.
- Do not place treated wood or sawdust in a compost bin, and do not use it as mulch.
- Do not use bleaching or cleaning agents such as sodium hypochlorite, sodium hydroxide, sodium percarbonate, citric acid or oxalic acid on treated wood. These can cause the wood to release chemicals that may be inhaled or come in contact with skin.
Safety tips for handling older treated wood
If you have CCA-treated wood structures on your property such as a deck or fence, monitor regularly for signs of damage. Replace the wood if it shows signs of damage like rot or scraped surfaces, to avoid the release of arsenic.
Consider applying a sealant to the wood annually. This can reduce the likelihood of exposure to arsenic leaching from treated wood. Use an oil- or water-based stain. Paints and other film-formers are not recommended. These can chip or flake over time, requiring scraping or sanding, which increases the potential for exposure to the arsenic in the wood.
For home projects such as removal or construction of a deck or fencing with treated wood:
- Wear gloves and long sleeves when handling treated wood.
- Wear a dust mask, eye protection, gloves and long sleeves when sawing, sanding, shaping or otherwise machining treated wood to avoid skin contact or inhaling sawdust.
- Only work with treated wood outdoors.
- Wash hands and other exposed skin after working with the wood, and before eating, drinking, or smoking.
- Launder clothing worn to work with treated wood after each use, separately from other clothing.
- After construction, clean up and dispose of all cut ends, sawdust and construction debris in accordance with local regulations.
All wood waste must be disposed of in accordance with the manufacturer's guidelines and local and provincial regulations.
For more Information
- About the Pest Management Regulatory Agency
- How to Report a Pesticide Incident
- Environment and Climate Change Canada - Wood Preservation
- Natural Resources Canada - Treated Wood
- Precautions for Using Pressure-Treated Wood Products
Contact Canada's Pest Management Information Service
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