Occupational and Environmental Medicine: Exposure, Dose, and Prevention
Core concepts
Occupational medicine frames disease as a function of exposure (agent, route, dose, duration) interacting with host susceptibility. Know the hierarchy of controls: elimination, substitution, engineering controls, administrative controls, then personal protective equipment last. Understand exposure assessment: air sampling, biological monitoring, and the difference between threshold limit values (TLVs) and permissible exposure limits (PELs). Learn classic toxidromes and target organs: lead (anemia, neuropathy, nephropathy), mercury (tremor, erethism), organophosphates (cholinergic crisis), solvents (CNS depression, hepatotoxicity), silica (silicosis), asbestos (mesothelioma, asbestosis), and noise (noise-induced hearing loss, the 4 kHz notch).
Traps in questions
Latency is the favorite trap: asbestos-related mesothelioma appears decades after exposure, and silicosis may present years later. Distinguish acute versus chronic effects and exposure route (inhalation, dermal, ingestion). Questions often test whether a finding is work-related using temporal association and dose-response. Remember that PPE is the least effective control yet the most commonly emphasized in vignettes. Environmental questions test the same dose-response logic for air, water, and soil contaminants, plus susceptible populations (children, pregnant workers, elderly).
Worked example
A worker in a battery plant has microcytic anemia, wrist drop, and a blue line on the gums. The answer is lead toxicity, and the prevention answer is engineering controls (ventilation, enclosure) rather than respirators alone.
Rule of thumb
When a vignette describes a symptom cluster plus a workplace, name the agent from the target organ, then choose the highest-level control that removes the exposure.