What must be done to protect water sources during pesticide handling?

To protect water sources during pesticide handling, it is essential to never rinse containers in open water sources. This practice is crucial because rinsing containers can lead to the introduction of pesticide residues directly into the water, potentially harming aquatic life and contaminating drinking water supplies.

Proper rinsing should always be conducted in a manner that prevents any chemical substances from entering water bodies. This includes using designated rinse areas or containers that will be properly disposed of or managed, far away from any water source.

The other choices involve practices that could directly or indirectly lead to contamination of water sources and are therefore not suitable safeguards against pesticide runoff and chemical introduction into aquatic environments.