Receptor Types
The human or ecological species that is potentially exposed to contaminants at the source area or other locations where contaminants were transported because of release mechanisms. A receptor may be subject to several exposure pathways. Receptor characterization includes determining locations of potential receptors, activity patterns, and the presence of subpopulations. This characterization is also conducted for future land uses.
Many receptor types or species could be exposed to the hazardous substances or radionuclides released and transported from the source to the exposure media. According to Risk Assessment Guidance for Superfund (RAGS), only significant receptors are to be evaluated for exposure pathway completeness. These receptors should be those who have the highest degree of exposure (high-end exposure), based on consideration of the exposure patterns (frequency, duration, and contact rate). In the case of ecological receptors, any identified threatened or endangered species should also be considered.
These receptors include both free-swimming and benthic organisms. These species could be exposed to contaminated surface water and sediment if such contaminants have been released or transported to the location where these species are located. Groundwater infiltration (intersecting surface water), runoff carrying contaminated soil or sediment, or surface water could cause these species to be exposed. Bottom feeders or prey fish may ingest contaminated benthic invertebrates or other aquatic species if the site contaminants are bioaccumulative and have been transported from the site to surface water bodies.
These receptors include wild, domestic, farm, and game animals. These animals may be subject to exposure from airborne contaminants (gaseous or fugitive dust emissions/ particulates) if the ambient air is contaminated. Moreover, if these receptors use contaminated surface or groundwater or are provided with such water for consumption, they may be exposed. If these species ingest food crops or other species that bioaccumulate site contaminants, these terrestrial species may also be impacted. On-site burrowing animals may be impacted or exposed via incidental soil ingestion and dermal contact routes of exposure.
Trespasser/Non-Residential Visitors
These receptors include humans who live off site and come in contact with the site at a frequency less than on-site workers or residents. They include scholar/student visitors, contract personnel, and delivery personnel. The relevancy of these receptor categories will depend on the exposure area and the anticipated activities of the receptor groups. Depending on their activities and where they trespass or visit the site and the source area, these receptors could be exposed via airborne contaminants (gaseous emissions or fugitive dust emissions/particulates), incidental soil and sediment ingestion, or dermal contact. If they wade or swim, they may be exposed to the contaminants in on-site sediment or surface water. If food chain species have been impacted, these receptors may be impacted if such food/species are collected or hunted and ingested.
Occupational receptors include persons who live or work on site. They may be office workers, groundkeepers, or construction workers. They may also be on-site industrial workers or visitors. Depending on their activities and where they are located relative to the source area, these humans may be exposed via airborne contaminants (gaseous [including indoor air] or fugitive dust emissions/particulates), incidental soil and sediment ingestion, and dermal contact. If they use on-site wells or surface water, they may be exposed to the contaminants if such media have been contaminated. If food chain species have been impacted, these persons may be impacted if such food or species are collected or hunted and ingested, although this is highly unlikely in most occupational settings.
Public receptors include humans who live or work near the site (off-site residents and workers).
Public receptors may be exposed to airborne contaminants (gaseous or fugitive dust emissions/particulates) if they are located downwind from the site; or to contaminants in surface water or groundwater, if these waters are used and if contamination is feasible or has occurred, and if the flow directions are toward these receptors. Public receptors may also be exposed to contaminants via ingestion of contaminated food/species collected or hunted.