Tens of thousands of American families may be living in buildings once used as methamphetamine labs - most of them oblivious to the fact. Some who have learned of their home's history similarly attribute mysterious ailments to the toxic legacy of illicit drug manufacture, but like Katrina Evans they are finding that there is precious little firm knowledge about what risks they are running. Only now is a new federal law authorising more research into the problem, and promising to fill in some gaps.