Which of the following is an example of a pollutant?

The choice highlighting a waste byproduct that clouds a water source is indeed an example of a pollutant. Pollutants are substances that contaminate the environment and can harm living organisms. When waste byproducts enter a water source, they can decrease water quality and pose health risks to both aquatic life and humans.

In contrast, a chemical that improves crop yield may be beneficial for agriculture but could potentially be harmful if it leaches into water supplies; however, it doesn't fit the definition of a pollutant on its own. Similarly, a naturally occurring mineral found in soil can signify a healthy ecosystem and does not inherently act as a pollutant unless present in excessive amounts. Lastly, a safety measure in waste management is designed to prevent pollution rather than being a pollutant itself. Therefore, the option regarding the waste byproduct aptly fits the definition of a pollutant due to its capacity to degrade water quality and impact health negatively.