I'm doing a little research on Copper sulfate, which I think is what the exterior boards on my house are inundated with. The same boards I planed down to use for the interior. This wasn't a great option by way of low-toxicity. On the other hand, it was free. ...funny how that works. Anyhow, more on that later. For now, I want to note some of my findings from Wikipedia.
Mainly, I leared that copper sulfate is an emetic, a vomit inducer. "An emetic is used medically where a substance has been ingested and must be expelled from the body immediately (for this reason, many toxic and easily digestible products such as rat poison contain an emetic). Inducing vomiting can remove the substance before it is absorbed into the body. Ipecac abuse can cause detrimental health effects.
"Salt water and mustard water have been used since ancient times as emetics. Care must be taken with salt, as excessive intake can potentially be harmful.
"Copper sulfate was also used in the past as an emetic. It is now considered too toxic for this use."
Furthermore, and noteable since I just had a little bout of pink eye, "Eye contact with copper sulfate can cause conjunctivitis."
After reading the following, I can say: luckily, I still need to urinate often. "After 1-12 grams of copper sulfate are swallowed, such poisoning signs may occur as a metallic taste in the mouth, burning pain in the chest, nausea, diarrhea, vomiting, headache, discontinued urination, which leads to yellowing of the skin. In case of copper sulfate poisoning, injury to the brain, stomach, liver, kidneys may also occur."
This makes me very interested in finding a local science student/person who would be interested in taking a little sample of my wood's green dust to determine what it is. Or if someone recoginizes it and knows some context, please leave a comment.
This also makes me realize the care I must take so this material isn't able to reach food sources etc. and even further skin contact.