Which of the following can lead to the build-up of contaminants in pool water?

Inadequate filtration is a significant factor that can lead to the build-up of contaminants in pool water. A pool's filtration system plays a critical role in maintaining water quality by removing debris, organic material, and microorganisms. When filtration is inadequate, it fails to effectively capture and eliminate these contaminants, which can cause cloudy water, unpleasant odors, and health risks associated with pathogens thriving in unclean conditions. This emphasizes the importance of regular maintenance and proper functioning of the filtration system to ensure that contaminants are adequately removed from the water, thus promoting a safe swimming environment.

Other factors like overusing chlorine can momentarily sanitize the water but will not remove debris or solids. Low water temperatures do not directly contribute to the build-up of contaminants, and while high pH levels can disrupt chlorine's effectiveness, they do not inherently lead to contaminant accumulation in the absence of proper filtration.