What advancement in public health came as a result of understanding the germ theory?

The advancement in public health that stemmed from the understanding of germ theory is the improvement of wastewater treatment systems. This theory, which gained prominence through the work of scientists like Louis Pasteur and Robert Koch, established that microorganisms could be the cause of diseases. As a result, public health officials recognized the importance of sanitation in preventing the spread of infections.

With this new understanding, cities began to focus on enhancing their infrastructure to manage waste more effectively. Improved wastewater treatment systems were crucial in reducing the presence of pathogens in water supplies, thus lowering the incidence of waterborne diseases such as cholera and typhoid. This marked a significant shift in public health policy, prioritizing hygiene and sanitation based on scientific evidence.

The other options do not directly relate to advancements prompted by germ theory. Surgical instruments were improved due to various factors including anesthesia and surgical techniques, but not specifically due to germ theory. Homeopathy and psychic medicine emerged from different traditions and were not significantly influenced by the scientific findings related to germs at that time.