RE: Wood preservatives

Studies conducted over a number of years have indicated that some wood preservatives used on utility poles, play structures and backyard decks may pose significant dangers to public health, particularly that of children. Most of the concern has focused on the chemicals pentachlorophenol and chromium copper arsenate (CCA). Pentachlorophenol use in Canada is now restricted to railway ties, utility poles and pilings, but CCA is quite widely used.

Health Canada and the U.S. Environmental Protection Agency are working together to review these and other heavy duty wood preservatives. However, this review has dragged on for years while evidence mounts of possible harmful effects from these chemicals. At this point, federal regulators aim to finish the review in 2002, but the completion date has already been extended several times.

A list of references on the subject is attached. In brief, when rain falls on wood treated with CCA, it can leach (or release) arsenic, a poisonous chemical that can cause cancer and other health effects. Arsenic is found at elevated levels on the surface of CCA-treated wood and in soil under installations. This is of particular concern around playground equipment, where children can pick up the leached chemical on their skin or clothing, and may even ingest it. Officials at Health Canada say they are still trying to determine whether levels of arsenic found around play structures and decks treated with CCA are above those occurring naturally in the environment. In Florida and Connecticut, where CCA research is well advanced, levels well above state limits have been found.

There is also concern for adults who work with treated wood regularly, or use it to build a backyard deck or play structure. They should take protective measures to avoid inhaling the sawdust or allowing their skin to touch the wood surface.

In the future, I encourage you to consider using alternatives such as recycled steel, concrete, a composite of wood and plastic, or arsenic-free treated wood. You should also consider measures to mitigate potential harm to the public from existing structures and the soil under them. In some cases, painting the surface with a sealant is all that's needed. Please also ensure safe disposal of any poles you decide to discard; the chemicals we're discussing are sometimes classified as hazardous waste.

This letter is simply to inform you about the issue and share my concerns. I encourage you to investigate further and review your own practices. I will keep you up to date on future developments as they become known.


Dr. Rob Cushman

Medical Officer of Health

CC: School Boards in Ottawa

Further information on treated wood:

A research organization that brings together universities and government agencies in Florida, where a lot of the leading work is being done, has posted reports and data online at

A series of investigative reports by the St. Petersburg Times, also in Florida, is on the paper's website at (Do a site search under "The poison in your backyard" which is the name of the series. It began March 11, 2001.)

A Connecticut scientist, David Stilwell, has done soil testing and other research on treated wood. His work can be found at which is the Connecticut Agricultural Experiment Station. Once there, do a site search using his name, for his papers on the subject.

Public health statements and other information about the toxicity of pentachlorophenol and arsenic are available on the ATSDR (Agency for Toxic Substances and Disease Registry), a federal U.S. government agency, at

Fact sheet entitled Pesticides Used in Pressure-Treated Wood is available at

Recent scientific journal articles:

Fields S Caution--children at play: how dangerous is CCA? Environmental Health Perspectives. June 2001;109(6):A262-9.

Hingston JA, Collins CD, Murphy RJ, Lester JN. Leaching of chromated copper arsenate wood preservatives: a review. Environmental Pollution. 2001;Vol. 111(1): pages 53-66.