Why are gasoline and volatile solvents considered objectionable in a sewer?

Gasoline and volatile solvents are considered objectionable in a sewer primarily because they produce an explosion hazard. When these substances are present in confined spaces, particularly within sewer systems, they can vaporize and create flammable mixtures with air. These vapors are not only dangerous due to their flammability but can also lead to increased risks of fire or explosion if ignited by a spark or other heat source.

While there are concerns related to toxicity to aquatic life and potential changes to the pH balance of water bodies, the immediate danger associated with the accumulation of gasoline and volatile solvents in a sewer is the significant risk of explosion. Additionally, while chemical reactions can occur with some substances, the focus here is on the safety hazards of flammable vapors. Thus, recognizing the explosive risks helps underscore why these materials are regulated and prohibited in sewage systems.