The problem is trying to figure out the long-term effects associated with these chemicals. So it's always a good idea to use precautions when working with any kind of chemical, like using protective gloves or glasses, and you should never, ever burn treated wood at home. It's a good idea to find out what your wood has been treated with before using it. Exposure to arsenic can cause, among other things, nausea, diarrhea and headaches. Long-term exposure can damage organs, poison mucous membranes and affect normal heart and liver functions.
Pure arsenic is lethal.
For more information about CCA or pesticides visit the American Wood Preservers Institute or Beyond Pesticides .