We have a rental property in which a tenant was arrested for having a meth lab in the house. There are no unusual odors in the house. Only one area of the house....the attic tested positive and that was at .1 micrograms/100cm2. Are there any serious reasons for concern ?
What a terrible thing to have to discover. I think you should talk to your local/state health department about this. I don't know that there are set standards for health regarding chemical levels from meth labs.
Here's a link to some information on cleaning up former sites. I would just try to get as complete an understanding of this issue as possible. Good luck!