The Planetary Benefit of Suspending USMLE Step 2 CS: Estimating Carbon Emissions Associated with US Medical Students' Travel to Testing Centers.

Background: The discontinuation of the Step 2 Clinical Skills Exam (CS) by the United States Medical Licensing Examination (USMLE) eliminated the need for personal travel to testing centers. The carbon emissions associated with CS have not been previously quantified. Objective: To estimate the annual carbon emissions generated by travel to CS Testing Centers (CSTCs) and to explore differences across geographic regions. Methods: We conducted a cross-sectional, observational study by geocoding medical schools and CSTCs to calculate the distance between them. We obtained data from the 2017 matriculant databases of the Association of American Medical Colleges (AAMC) and the American Association of Colleges of Osteopathic Medicine (AACOM). The independent variable was the location as defined by USMLE geographic regions. The dependent variables were distance traveled to CSTCs and estimated carbon emissions in metric tons CO₂ (mtCO2) calculated using three models. In model 1 all students used single occupancy vehicles; in model 2, all carpooled; and in model 3, half traveled by train and half by single occupancy vehicle. Results: Our analysis included 197 medical schools. The mean out-of-town travel distance was 280.67 miles (IQR: 97.49-383.42). The mtCO2 associated with travel was 2,807.46 for model 1; 3,135.55 for model 2; and 635.34 for model 3. The Western region traveled the farthest, while the Northeast traveled significantly less than other regions. Conclusion: The annual estimated carbon emissions from travel to CSTCs was approximately 3,000 mtCO2. Northeastern students traveled the shortest distances; the average US medical student expended 0.13 mtCO2. Medical leaders must consider the environmental impact of medical curricula and pursue accordant reforms.