What is a key concern when applying pesticides near water sources?

When applying pesticides near water sources, a primary consideration is the risk of runoff and contamination. Pesticides can easily wash off treated areas during rain or irrigation events, leading to these chemicals entering nearby water bodies. This contamination poses significant environmental hazards, including harmful effects on aquatic life and the potential for water supply pollution.

Regulatory agencies are particularly concerned about protecting water quality, as pesticides may disrupt ecosystems and harm organisms living in or around water. Additionally, once pesticides enter a water source, they can be difficult to remove and may persist for long periods, emphasizing the need for cautious application practices near these critical areas.

Other options, while relevant to pesticide application generally, do not address the specific environmental aspect that makes proximity to water sources particularly sensitive. Evaporation, drift, and loss of effectiveness due to dilution are important factors to consider in different contexts, but the potential for runoff and long-lasting contamination is the most critical concern in this case.