Which of the following is NOT a route of lead exposure?

Lead exposure can occur through several routes, including inhalation, ingestion, and absorption through the skin, but injection is not a common or recognized route of lead exposure.

Inhalation refers to the intake of lead particles or dust that can occur in occupational settings or during activities where lead-based materials are present. Ingestion can happen when lead particles contaminate food, water, or surfaces that are then consumed. Absorption through the skin can occur when lead dust or particles come into contact with the skin, although this route is less significant compared to inhalation and ingestion.

Injection, on the other hand, typically refers to the direct entry of substances into the body via a needle or other device, which is not a typical or recognized method for lead exposure. This means that among the options provided, injection does not represent a standard way through which individuals come into contact with lead, making it the correct answer for identifying which route is NOT associated with lead exposure.