Final answer:
Injection is the least common method of toxic chemical entry in the workplace as opposed to skin absorption or inhalation, which are more typical exposure routes.
Step-by-step explanation:
The method of toxic chemical entry which is least commonly found at the workplace is injection. This route of exposure happens when chemicals are introduced directly into the bloodstream through a break in the skin, usually by a needle or sharp object. While there are many routes of exposure to chemicals, such as inhalation, skin absorption, and ingestion, injection is much less common in a workplace setting.
Occupational exposures typically occur through skin absorption, especially on exposed areas like the face, hands, forearms, neck, and chest, or through inhalation, particularly in environments with poor ventilation or during specific actions such as spraying operations. However, injection typically happens in more controlled settings, such as medical procedures, rather than through accidental workplace exposure.