I.D.
Have you had the soil in your yard tested? Lead can stay in the first 3 inches. Planting sunflowers is a way to absorb the lead (but don't eat the seeds, since they'll have the lead). Also contact a local lead-safe group. They have much more experience with this kind of issues and can find were the lead has been "hiding" in your house. In Springfield, this is the link: http://www.ci.springfield.oh.us/depts/hr/leadsafe.htm
One more thing, Mexican candy (the spicy kind) contains lead levels that could be harmful children (not enough for adults). So there might be other things you are consuming that could contain lead without knowing!