Source reduction appears at the top of the Environmental Protection Agency's (EPA's) hierarchy because it

According to the EPA’s hierarchy, source reduction is prioritized because it addresses the environmental impacts of materials across their entire life cycle. This includes the extraction of raw materials, manufacturing, distribution, usage, and end-of-life management, including recycling and disposal. By reducing the amount of material used, source reduction minimizes the environmental footprint throughout the entire process.

References: The explanation aligns with the principles outlined in the EPA’s waste management hierarchy, which emphasizes the importance of source reduction as the most preferred approach to managing materials and waste streams12. This is also consistent with the sustainable materials management strategies detailed in the LEED v4 Reference Guide for Interior Design and Construction3.