Four Routes of Chemical Exposure
Hazardous substances can enter the body through several routes of exposure. This toxicology visualization illustrates four important routes— inhalation, absorption, ingestion, and injection—and shows how workplace chemicals can gain access to the body.
About This Video
This OSHACode® visualization illustrates four routes by which hazardous substances can enter the human body: inhalation, absorption, ingestion, and injection.
The route of exposure can influence how a substance enters the body, how quickly it may be absorbed, and which tissues or organs are initially affected. Understanding these exposure pathways is an important part of recognizing chemical hazards and selecting appropriate workplace controls and personal protective equipment.
Preventing exposure begins with identifying the hazardous substance, understanding how workers could come into contact with it, and applying appropriate controls to interrupt the exposure pathway.
This video is part of the OSHACode® HAZWOPER Visual Library, a collection of technical safety, environmental, and scientific visualizations designed to make complex concepts easier to understand.
What Are the Four Routes of Chemical Exposure?
Inhalation
Inhalation occurs when airborne gases, vapors, dusts, fumes, mists, aerosols, or other contaminants are breathed into the respiratory system. In occupational environments, inhalation can be a significant route of exposure because contaminants may reach the lungs and, depending on their properties, enter the bloodstream or produce effects within the respiratory tract.
Absorption
Absorption can occur when a chemical passes through the skin or other biological membranes. The ability of a substance to penetrate the skin depends on factors including its chemical properties, concentration, duration of contact, condition of the skin, and area exposed.
Ingestion
Ingestion occurs when a hazardous substance enters the gastrointestinal tract. Workplace ingestion can result from contaminated hands, food, beverages, cigarettes or other objects contacting the mouth.
Injection
Injection occurs when a hazardous substance enters the body through a puncture, cut, abrasion, or other break in the skin. Needles, sharp contaminated objects, high-pressure equipment, and certain workplace injuries can provide a direct pathway into tissue or the bloodstream.
Why Does the Route of Exposure Matter?
The same hazardous substance can produce different exposure patterns depending on how it enters the body. Route of entry can influence the amount absorbed, the rate of absorption, the tissues initially exposed, and ultimately the potential health effects.
Recognizing the likely routes of exposure helps employers select effective controls. Depending on the hazard, these may include substitution, engineering controls, ventilation, safe work practices, respiratory protection, chemical-resistant clothing, gloves, eye and face protection, hygiene practices, and other exposure-control measures.
Exposure Does Not Automatically Mean Dose
Exposure and dose are related, but they are not the same thing. Exposure describes contact with a hazardous agent, while dose refers to the amount that actually enters or is delivered to the body or a target tissue.
The resulting dose can depend on the route of exposure, concentration, duration and frequency of exposure, absorption characteristics, and other biological and chemical factors.
