If transfiguration can only result in non-magical substances, then science would help to transfigure to CBW agents - ending up too close for comfort. Wards cast in transfiguration classrooms and dormitories to detect intent to violate transfiguration rules would catch those, a wise expansive interpretation would catch the worst I can think of (critical mass of fissile material => will generate gas). The Hogwarts House system should force conformity and channel risk-taking into known paths. If failing to attempt homework would lose points, depression and mental illness could be caught early. Would the wizarding world have something of the culture of manners of the Diamond Ages's Victorians, with wards and parlours working as firewalls and time for threat assessment/decontamination?