Medical surveillance (or medical monitoring) is a systematic approach to tracking worker health through periodic medical examinations, biological monitoring, and health assessments. OSHA requires medical surveillance under over 20 substance-specific standards including lead (29 CFR 1910.1025), asbestos (1910.1001), benzene (1910.1028), cadmium (1910.1027), and noise (1910.95). Programs typically include: baseline exams before initial exposure, periodic exams at defined intervals, additional exams triggered by overexposure events, and exit exams upon termination. Results are used to detect early signs of occupational disease, evaluate the effectiveness of engineering controls, and determine fitness for continued work. All costs are borne by the employer.