What does a decrease in air quality potentially indicate?

A decrease in air quality potentially indicates the presence of harmful substances. Poor air quality often results from pollutants that can originate from industrial activities, vehicle emissions, construction, or agricultural practices. These pollutants can include particulate matter, volatile organic compounds (VOCs), and other harmful chemicals that pose risks to both worker health and the environment.

When air quality deteriorates, it's a clear signal that toxic or hazardous substances may be present in the atmosphere, which can lead to serious health issues for those exposed. Recognizing this connection is crucial for workers in hazardous environments, as it underscores the need for proper monitoring, protective measures, and emergency response strategies to ensure safety.

The other options do not align with this understanding. Increased worker productivity is generally associated with good air quality and a healthy work environment, while lower contamination levels suggest a safer environment rather than poor air quality. Similarly, improved environmental conditions would likely correlate with better air quality. Thus, the correct answer reflects the reality that a decrease in air quality is a critical indicator of potential hazards due to harmful substances.