What safety hazard is associated with hydrogen sulfide in sewer systems?

Hydrogen sulfide (H2S) is a colorless gas that has a characteristic smell of rotten eggs and is known to be highly toxic. In sewer systems, this gas can accumulate and pose significant health risks to workers and the public. The primary safety hazard posed by hydrogen sulfide is its toxicity; it can cause respiratory distress and can be lethal even in relatively low concentrations due to its ability to affect the central nervous system.

When H2S is present in confined spaces, such as sewers, it may not only lead to immediate health issues but also create conditions where individuals are unable to escape, increasing the danger. Proper monitoring and ventilation are crucial for safety in environments where hydrogen sulfide can be encountered.

The other options do not adequately describe the primary hazard associated with hydrogen sulfide in sewer systems. Flammable liquids, radioactive materials, and corrosive substances are not the main concerns related specifically to hydrogen sulfide in this context, which is why the focus on toxic gases accurately identifies the critical risk involved.