What harmful effect do pesticides and herbicides have on water sources?

Pesticides and herbicides pose significant risks to water sources primarily because they can wash into rivers and other bodies of water, leading to contamination of drinking water supplies. When these chemicals are applied to agricultural lands, they can be carried away by rainfall or irrigation runoff, entering nearby waterways. This runoff can result in elevated concentrations of harmful chemicals in both surface and groundwater, which can pose serious health risks to humans and aquatic life.

When contaminated water is consumed, it can lead to a variety of health issues, including neurological problems, reproductive issues, and other long-term chronic conditions. The contamination can also disrupt ecosystems, affecting the health of fish and other aquatic organisms.

Thus, the correct response emphasizes the hazardous nature of pesticides and herbicides and their potential to negatively impact water quality and public health.