What is a potential risk of collecting lake water without treatment?

Collecting lake water without treatment poses a potential risk due to the presence of harmful microorganisms. Lakes can harbor various pathogens, including bacteria, viruses, and parasites that can lead to waterborne diseases. These microorganisms may originate from various sources, such as agricultural runoff, animal waste, or even natural occurrences in the environment. Consuming or using untreated lake water contaminated with these pathogens can result in serious health issues, including gastrointestinal illnesses and other infections.

While the other options present possibilities that could occur in different contexts, they do not directly address the most critical health risk associated with using untreated water. For instance, overly treated water is not a concern in this context, as the issue revolves around the lack of treatment. Similarly, water temperature might vary for different reasons but does not inherently pose a health risk. Lastly, the efficiency of collection time can be a logistical concern but does not relate to the immediate dangers of waterborne diseases. Thus, the significant health risk of harmful microorganisms makes it essential to treat lake water before use.