Virtually all wood windows have preservatives, but not all preservatives are the same. If a wood window did not have preservatives, it would disintegrate quickly, due to moisture, rot, and insect infestations.

Manufacturers seem more concerned about the exterior of the window than then interior. Some manufacturers now sell windows that are wood on the interior only (for beauty) and some other material on the exterior (for easy maintenance), so how much you may be exposed to whatever preservative is used is unknown.

There seem to be two methods of application of preservatives:

1. dip -- wood is dipped into preservative solution, applying it in a thin layer on the outside of the wood
2. infusion -- preservative is applied to the wood with pressure so it permeates the wood through and through.

The dip method is less effective as a preservative, as wood in nail and screw holes is left unprotected.

The Window and Door Manufacturers Association gives this list of chemicals in approved preservatives:

Bis (Tri-N-Butyltin) Oxide (TBTO)
"More hazardous than most chemicals."

3-Iodo-2-Propynyl Butyl Carbonate (IPBC)
"Less hazardous than most chemicals in 3 ranking systems."
Suspected Gastrointestinal or Liver Toxicant and Neurotoxicant.

2-(Thiocyanomethylthio) Benzothiazole (TCMTB)
"Less hazardous than most chemicals in 2 ranking systems."
Suspected carcinogen.

Propiconazole
"Less hazardous than most chemicals in 2 ranking systems."
Suspected carcinogen, Gastrointestinal or Liver Toxicant.

Tebuconazole
"Lacks data required for assessment."
Suspected carcinogen.

Imidicloprid
not listed on the Agency for Toxic Substances and Disease Registry.

Zinc Borate
not listed on the Agency for Toxic Substances and Disease Registry.

These preservative treatments when applied to windows are not considered hazardous by any regulating agency that I could find. Any paint or finish applied would further encapsulate them. Here are my recommendations:

• Salvage wood windows would likely have fewer, if any, preservative residues remaining.
• Check with individual manufacturers to find out what type of preservative is used on the windows you are considering purchasing.
• Choose windows with the least hazardous preservatives.
• Apply a nontoxic paint or finish to the wood on the window.
• Explore windows made from different woods. I suspect (though I haven't verified this) that softer woods (such as pine) would require more preservatives than a harder wood (such as mahagony).

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