Routes of Chemical Exposure | How do Chemicals Enter the Body?

Chemicals can produce beneficial or harmful health effects, but exposure must occur before any chemical-induced health effects occur. Exposure to chemicals at work might occur through several possible pathways. These pathways are also called routes of exposure. For a given chemical, the route of exposure will depend on the use of the chemical as well as the nature of the chemical. For example, if used in a poorly ventilated area, a chemical in gas form might pose a hazard because of exposure by inhalation. A liquid material, on the other hand, might present a higher risk of exposure to the skin or eyes. All chemicals can be handled safely if exposure is kept to appropriate, low levels. Understanding the routes of chemical exposure is a fundamental part of managing chemical hazards to reduce or eliminate the potential for exposure.

Routes of Chemical Exposure – What Are They?

Although there are a variety of possible routes by which chemical substances may enter or affect the body, the most common routes are:
  • Breathing or Inhalation 
  • Contact with Skin or Eyes
  • Ingestion or eating
  • Injection
routes of chemical exposure


The most common route of chemical exposure at work is to inhale them. Inhalation is the act of breathing through the nose or mouth and occurs regularly and rhythmically throughout the day and night. The rate and depth of inhalation vary with cycles of work and rest. The internal surface of the human lungs would cover an area about the size of a tennis court. So there is a great deal of surface area upon which chemicals may deposit and from which they might be absorbed. Thus, the entry of chemicals into the lungs constitutes a significant route for distribution in the whole body. 
The respiratory tract can filter out some aerosols and particles during inhalation. Many coarse particles deposit in the airway passages and are carried to the throat, where they can be ingested. However, vapors, gases, fine particles, and aerosols taken in by breathing reach the deep portions of the lungs where absorption can occur. Some inert materials in finely divided form deposit in the deep portion of the lungs and reside there without absorption. These can contribute to mechanical obstruction.
Several unwanted hazards may occur depending on the nature of the chemical materials inhaled. These include direct chemical damage to the lungs with scarring. Also, raising allergic symptoms (asthma), constriction of the elastic tubes (bronchioles), mechanical obstruction of lung function, and distribution of chemicals to different organs where unwanted effects might occur.

Contact with Skin or Eyes

The skin is one of the largest human organs. It covers a surface area of about 2 m3 and forms a relatively tough covering for the body. Because of the large surface area, skin is one of the primary routes of exposure to chemicals. 
Contact of chemicals with skin can give rise to various local effects at the site of contact. These local effects can include chemical burns, corrosive effects, irritation, allergic symptoms (allergic dermatitis), acne or acne-like eruptions, and in rare cases, skin cancer. The specific effects that may occur will depend on the nature of the chemical contacting the skin and other factors such as duration and frequency of exposure. 
Although relatively impermeable to particles and water-soluble chemicals, certain fat-soluble materials and solvents can pass easily through the skin. In cases where chemicals pass through the skin and enter the blood, exposure by the skin can be a significant source of chemical distribution to the whole body. This type of exposure is known as systemic exposure. The barrier function of the skin is dependent on the skin being intact. Cuts, abrasions, blisters, and skin damage can enhance the absorption of chemicals through the skin.
The eyes are usually considered vulnerable to the direct effects of chemicals (such as irritation or burns). However, the membranes surrounding the eyes can absorb certain chemicals quite readily and contribute to systemic exposure.


Ingestion is the act of consuming something by mouth. Exposure to chemicals by ingestion is a preferred method for intentional exposure to medicines. However, in occupational circumstances, unintentional ingestion of chemicals might occur. For example, licking a fingertip with chemical substances on it could contribute to unintentional ingestion. In addition, chemical materials could be deposited on or absorbed by foods stored in work areas. For this reason, workers should avoid drinking, eating, and smoking in locations where chemicals may be present.


The injection is generally an intentional act and is not usually related to the occupational use of chemicals. Therefore, it is rarely a common route of workplace chemical exposure. However, if you work in an environment where sharp objects are common, take precautions to avoid needles and sharp objects that could introduce materials directly through the skin or into the bloodstream.

How to Avoid Chemical Exposure?

Considering the potential for chemical exposure via the routes of exposure mentioned above, the following are recommended safe working practices:
  • Consult safety data sheets of the chemicals to know their hazards and possible routes of exposure.
  • Conduct chemical risk assessments of all workplace activities to determine whether and where chemical exposure might occur.
  • Use engineering controls such as filters, vacuum exhausts, down-draft booths, and ventilated weighing enclosures to control and suppress dust, vapors, and gases.
  • Use appropriate respiratory equipment, considering the nature of chemicals and required protection levels.
  • Pay attention to compliance with safety rules and guidelines regarding respirator fit testing and maintenance.
  • Use appropriate chemically resistant gloves, considering the chemical compatibility.
  • Use safety glasses or goggles as appropriate to the physical nature of chemicals and the possibility of direct exposure to the eye.
  • Pay continuous attention to proper technique when donning and removing gloves and other skin and eye protection to avoid contamination of skin or eyes with chemicals deposited on the exterior of gloves, glasses, or goggles.
  • Avoid touching the mouth, tongue, or face with gloved or ungloved hands when working with chemicals.
  • Ensure ready access to eye-wash stations and emergency showers.
  • Thorough washing of hands, wrists, and forearms with warm water and soap following work with chemicals and before handling food items.
  • Ensure that eating is confined to canteens, cafeterias, or other areas in which workplace chemicals are not used.
For more information on chemical safety, toxicology, and occupational hygiene, please take a look at this free online course, Introduction to Occupational Hygiene.

Jawad Chand

Jawad Chand is an occupational health & safety practitioner and trainer with extensive experience in oil & gas safety management, process safety, pharmaceuticals hazard control, and health & safety management systems. He is a highly qualified professional with the most prestigious degrees in Business Administration, Chemical Engineering, and Occupational Health & Safety.

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