Element 4: Exposure Routes

This section explains the process for evaluating exposure routes, the fourth element in the exposure pathway evaluation.

“Exposure route” refers to how a contaminant enters a person’s body. Keep in mind that possible routes of exposure can change significantly depending on the land use at a site and surrounding areas. In general, individuals may be exposed to contaminants in environmental media in one or more of the following ways:

  • Ingestion: Oral ingestion of chemical and radioactive contaminants in groundwater, surface water, soil, and food.
  • Inhalation: Breathing in chemical and radioactive contaminants in air (dust, vapor, gas), including those volatilized or otherwise emitted from groundwater, surface water, and soil. Communities may also be affected by smelling environmental odors in air.
  • Dermal contact: Skin contact with chemical and radioactive contaminants in sediments, soil, water, and other media, such as exposed wastes or other contaminated material.
  • External exposure to radioactive materials: Radiation exposure is unique compared to chemical contaminants. Radiation exposure can occur without direct contact with the body. Of the three major types of radiation (alpha, beta, and gamma), alpha particles do not travel very far in air and do not penetrate the upper levels of intact skin. Materials emitting alpha particles can enter the body through wounds or other damaged areas of the skin. The other types of radiation, beta particles and gamma radiation, can travel several meters or more in air and can easily penetrate the skin, depending on their energies. Once these radiations penetrate the skin, the beta radiation and gamma radiation can then interact with cells, tissues, and organs.

It is important to critically evaluate whether an exposure route is viable for each possible exposure point and potentially exposed population.

Examples: How Exposure Points Can Affect Exposure Routes

Person washing produce in the sink

CDC; photographer: Amanda Mills

Example 1:
If contaminated groundwater is being supplied to a household, residents might be exposed via ingestion (e.g., by drinking the water, using it to wash and cook vegetables, using it to brush their teeth), inhalation (e.g., from volatilization of the contaminants during a shower), and dermal contact (e.g., when taking a shower or bath).

Person in workout clothes drinking from water bottle

CDC; photographer: Amanda Mills

Example 2:
If residents use bottled water for drinking, cooking, and brushing their teeth, and use groundwater only for non-potable purposes, they will not be significantly exposed to the contaminated groundwater through ingestion. But, if children use the water for bathing or swimming, they could be exposed by incidental ingestion, dermal contact, and inhalation.

Page last reviewed: April 14, 2022