Which of the following is NOT a recognized route of entry for hazardous chemicals?

The route of entry that is not typically recognized for hazardous chemicals is digestion. This refers to the process of breaking down food and absorbing nutrients in the gastrointestinal tract. While it is true that ingesting certain hazardous materials can lead to poisoning or toxic effects, digestion itself as a defined biological process is not a deliberate or recognized pathway for the entry of hazardous chemicals into the body in the context of chemical exposure.

Inhalation involves breathing in vapors or particles that can be harmful, absorption refers to the uptake of substances through the skin, and injection signifies the introduction of chemicals directly into the bloodstream, all of which are common methods through which hazardous substances can affect human health. Hence, while ingestion can occur, it is not categorized alongside the more direct and recognized routes such as inhalation, absorption, and injection when strictly considering the defined routes of chemical entry in safety contexts.