Which of the following is a major concern related to cross-connections?

Cross-connections pose a significant risk to the safety of potable water supplies because they allow for the unintentional mixing of drinking water with non-potable sources, which can lead to contamination. When a cross-connection occurs, especially during a drop in pressure within the water distribution system, contaminated water from another source can flow into the drinking water supply. This can introduce pathogens, chemicals, and other harmful substances into the water that people consume, leading to health issues and potential outbreaks of waterborne diseases.

The other concerns mentioned in the options are related to different aspects of water systems. Unstable water pressure may affect the reliability of water delivery but is not primarily about contamination. Water loss due to leaks is a significant operational concern but does not directly lead to cross-connection issues. Increased sedimentation pertains to the physical quality of water rather than its potability. Therefore, the primary and major concern inherently linked to cross-connections is the contamination of potable water supplies, making it the correct choice.