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Steps and Components of the PHA Process
This section provides an overview of the steps involved in the PHA process. It also discusses the five main components associated with the process: triggers, data and information, scientific evaluations, products, and outcomes.
The PHA process helps ATSDR find out:
- Whether people living near a hazardous waste site are being exposed to toxic substances.
- Whether that exposure is harmful.
- What must be done to stop or reduce exposure.
During the PHA process, ATSDR:
- Evaluates site conditions and determines the nature and extent of environmental contamination.
- Engages communities at the beginning of site activities and involves them throughout the process to respond to their health concerns.
- Defines potential human exposure pathways related to site-specific environmental contaminants.
- Identifies who may be or may have been exposed to environmental contamination associated with a site (past, current, and future).
- Evaluates sampling data, screens detected contaminants to identify those that require further examination, and if appropriate, defines exposure units for completed and potential exposure pathways before or after the screening analysis.
- Estimates the exposure point concentrations and performs exposure calculations to evaluate non-cancer and cancer effects to assess potential human exposures to site-specific contaminants.
- Examines the public health implications of site-related exposures through the examination of environmental and health effects data.
- Clearly communicates the findings of its evaluations, while acknowledging the impact of uncertainties and limitations.
- Provides recommendations to site-related entities, partner agencies, and communities to prevent and minimize harmful exposures.
Keep track of the key action items you are responsible for at every step of the PHA process with these checklists [PDF – 858 KB].
The PHA process helps identify appropriate public health actions and respond to community health concerns related to hazardous waste sites. There are five basic components of the process: triggers, data and information, scientific evaluations, products, and outcomes. Once the first component—triggers—is initiated, ATSDR uses the Steps in the PHA Process to address and fulfill the needs of the next three PHA process components: data and information, scientific evaluations, and products. The recommendations that come out of ATSDR’s PHA process lead to the fifth component: outcomes.
PHA Process Basic Components
The PHA process is triggered when an individual, a community group, or other parties submit a petition to ATSDR to investigate a specific site or facility; when a site is proposed or listed on the National Priorities List (NPL); or when other federal, state, or local agencies or tribal health departments ask ATSDR for technical assistance
There are different meanings of the word “trigger.” In this e-manual, ATSDR uses the word trigger to refer to the different types of events that initiate the PHA process.
Triggers that Initiate the PHA Process
Trigger
Trigger
Trigger
Why Done?
Why Done?
Why Done?
How Used?
How Used?
How Used?
A site is listed or proposed for placement on EPA’s National Priorities List (NPL).
Trigger
A site is listed or proposed for placement on EPA’s National Priorities List (NPL).
ATSDR is required by law to conduct a PHA at all sites proposed for or listed on EPA’s NPL.
Why Done?
ATSDR is required by law to conduct a PHA at all sites proposed for or listed on EPA’s NPL.
ATSDR evaluates health implications of exposures to environmental contamination and identifies appropriate public health actions for affected communities.
How Used?
ATSDR evaluates health implications of exposures to environmental contamination and identifies appropriate public health actions for affected communities.
An individual or concerned party petitions ATSDR to evaluate a waste site, facility, or release.
Trigger
An individual or concerned party petitions ATSDR to evaluate a waste site, facility, or release.
ATSDR established a “Petition Program” as part of its mandate to allow any concerned person or entity to petition ATSDR to investigate a waste site, facility, or release.
Why Done?
ATSDR established a “Petition Program” as part of its mandate to allow any concerned person or entity to petition ATSDR to investigate a waste site, facility, or release.
ATSDR determines whether to perform the PHA process at a site.
How Used?
ATSDR determines whether to perform the PHA process at a site.
ATSDR receives a request from another agency (e.g., state and federal regulatory agency or a state, local, or tribal environmental/health departments).
Trigger
ATSDR receives a request from another agency (e.g., state and federal regulatory agency or a state, local, or tribal environmental/health departments).
ATSDR evaluates data when requested by other entities (e.g., to determine if a remediation alternative is protective of public health).
Why Done?
ATSDR evaluates data when requested by other entities (e.g., to determine if a remediation alternative is protective of public health).
ATSDR evaluates and provides scientific expert input regarding a proposed or completed action.
How Used?
ATSDR evaluates and provides scientific expert input regarding a proposed or completed action.
Under CERCLA, ATSDR must collect information about the hazardous waste site, site-related contaminants, communities potentially affected by the site (e.g., demographics), possible exposures to site-related contaminants, community health concerns, and health outcome data.
ATSDR performs different types of scientific evaluations during the PHA process (see table). After examining the available information and data, health assessors conduct an exposure pathways evaluation. For completed and potential exposure pathways, health assessors will perform a screening evaluation using the available sampling data. Based on the screening results, you may need to conduct an evaluation of exposure point concentrations (EPCs) and exposure calculations (exposure doses, hazard quotients, and cancer risks). Then, if necessary, you would perform an in-depth toxicological effects evaluation. The sequence of steps can differ based on site-specific factors. For instance, health assessors might define an exposure unit before or after the screening analysis.
Evaluation Type
Evaluation Type
Evaluation Type
Description
Description
Description
Exposure pathways
Evaluation Type
Exposure pathways
This involves studying the available environmental and biological data and developing a conceptual model of the site to determine the specific ways in which people might contact site-related contamination.
Exposure units also can be defined during this step.
Description
This involves studying the available environmental and biological data and developing a conceptual model of the site to determine the specific ways in which people might contact site-related contamination.
Exposure units also can be defined during this step.
Screening analysis
Evaluation Type
Screening analysis
This involves comparing contaminant concentrations to media-specific screening levels (ATSDR comparison values and non-ATSDR screening levels) to identify those that meet or exceed screening levels. It also involves pinpointing contaminants with no available screening levels and evaluating other factors (e.g., a community concern) that warrant closer examination in the EPC and exposure calculation evaluation.
Exposure units can be determined after performing the screening evaluation and before calculating EPCs.
Description
This involves comparing contaminant concentrations to media-specific screening levels (ATSDR comparison values and non-ATSDR screening levels) to identify those that meet or exceed screening levels. It also involves pinpointing contaminants with no available screening levels and evaluating other factors (e.g., a community concern) that warrant closer examination in the EPC and exposure calculation evaluation.
Exposure units can be determined after performing the screening evaluation and before calculating EPCs.
EPCs and exposure calculations
Evaluation Type
EPCs and exposure calculations
This involves calculating EPCs for each contaminant in each completed and potential exposure pathway (by exposure unit, if appropriate). These calculations use default or site-specific exposure conditions to estimate exposure doses, adjusted air concentrations, hazard quotients, and cancer risks. This includes identifying contaminants that exceed acceptable non-cancer and cancer levels, have no health guidelines or cancer risk values, or pose other issues (e.g., a community concern) and need an in-depth analysis of toxicological effects.
Description
This involves calculating EPCs for each contaminant in each completed and potential exposure pathway (by exposure unit, if appropriate). These calculations use default or site-specific exposure conditions to estimate exposure doses, adjusted air concentrations, hazard quotients, and cancer risks. This includes identifying contaminants that exceed acceptable non-cancer and cancer levels, have no health guidelines or cancer risk values, or pose other issues (e.g., a community concern) and need an in-depth analysis of toxicological effects.
In-depth toxicological effects analysis
Evaluation Type
In-depth toxicological effects analysis
This involves closely analyzing toxicological information for contaminants to determine whether people could possibly have health problems from their exposure. Contaminants examined during this analysis are those that exceeded acceptable non-cancer and cancer levels, had no available health guidelines or cancer risk levels, represented contaminants of community concern, or had other factors (e.g., multiple contaminant exposures) that warranted evaluation.
Description
This involves closely analyzing toxicological information for contaminants to determine whether people could possibly have health problems from their exposure. Contaminants examined during this analysis are those that exceeded acceptable non-cancer and cancer levels, had no available health guidelines or cancer risk levels, represented contaminants of community concern, or had other factors (e.g., multiple contaminant exposures) that warranted evaluation.
At the end of the PHA process, you will develop a document that includes various types of information collected during the PHA process, such as the site’s hazardous substances and responses to community concerns. The report will include findings about whether people could be harmed by coming into contact with the contaminants and provide recommendations to protect public health. ATSDR uses different types of products to communicate the PHA process findings (see table). These products serve as an aid for developing public health actions. The audience for such products often includes environmental and public health agencies, communities, and ATSDR itself.
You may develop various types of outreach, such as fact sheets or other materials, to communicate information related to the PHA process activities for your site. Whether and when to produce these materials and in what format is up to the health assessor, others involved in the PHA process at a site, and their management.
Product
Product
Product
Description
Description
Description
Public Health Assessment (PHA)
Product
Public Health Assessment (PHA)
Documents the results of ATSDR’s evaluation of all available information about a site and the potentially affected communities.
Addresses various exposure situations and/or community health concerns considered in the evaluation.
May address multiple-contaminant, multiple-pathway exposures or a single exposure pathway.
May result when an assessment of a single issue at a petitioned site evolves into a more multifaceted assessment.
Is released for public comment.
Description
Documents the results of ATSDR’s evaluation of all available information about a site and the potentially affected communities.
Addresses various exposure situations and/or community health concerns considered in the evaluation.
May address multiple-contaminant, multiple-pathway exposures or a single exposure pathway.
May result when an assessment of a single issue at a petitioned site evolves into a more multifaceted assessment.
Is released for public comment.
Health Consultation (HC)
Product
Health Consultation (HC)
Focuses, in general, on one public health issue or question, contaminant, health condition, or technical interpretation.
Might be released for public comment, depending upon public interest and who requested ATSDR’s involvement.
Description
Focuses, in general, on one public health issue or question, contaminant, health condition, or technical interpretation.
Might be released for public comment, depending upon public interest and who requested ATSDR’s involvement.
Letter Health Consultation (LHC)
Product
Letter Health Consultation (LHC)
Responds to a specific public health issue or question (like HCs) but provides a much more focused response.
Is sent in the form of a letter to a specific requestor (e.g., environmental agency or health department).
Uses an abbreviated format to address a specialized target audience, such as EPA site managers.
Can be time-critical, necessitating a more rapid and therefore limited response than evaluations that result in a PHA.
Is not released for public comment.
Description
Responds to a specific public health issue or question (like HCs) but provides a much more focused response.
Is sent in the form of a letter to a specific requestor (e.g., environmental agency or health department).
Uses an abbreviated format to address a specialized target audience, such as EPA site managers.
Can be time-critical, necessitating a more rapid and therefore limited response than evaluations that result in a PHA.
Is not released for public comment.
Exposure Investigation-Health Consultation (EI-HC)
Product
Exposure Investigation-Health Consultation (EI-HC)
Might be deemed necessary to assess possible impacts to public health when complete environmental or biological data are lacking.
Can be a follow-up to an ATSDR document or conducted as an initial evaluation when data gaps are identified.
Documents results in a combined product (Exposure Investigation-Health Consultation).
Description
Might be deemed necessary to assess possible impacts to public health when complete environmental or biological data are lacking.
Can be a follow-up to an ATSDR document or conducted as an initial evaluation when data gaps are identified.
Documents results in a combined product (Exposure Investigation-Health Consultation).
Health Advisory (HA)
Product
Health Advisory (HA)
Alerts the public and officials to a public health threat.
May be issued if imminent health hazards are identified during the PHA processexternal icon.
Is not released for public comment (due to its time critical nature).
Description
Alerts the public and officials to a public health threat.
May be issued if imminent health hazards are identified during the PHA processexternal icon.
Is not released for public comment (due to its time critical nature).
Technical Assist (TA)
Product
Technical Assist (TA)
Is a written response to external requests for environmental public health technical and/or educational information.
Does not draw a public health conclusion or comment on another entity’s conclusion but provides information to help the requester make informed decisions.
Is not released for public comment.
Description
Is a written response to external requests for environmental public health technical and/or educational information.
Does not draw a public health conclusion or comment on another entity’s conclusion but provides information to help the requester make informed decisions.
Is not released for public comment.
The PHA process produces several possible outcomes, such as the need to better define exposures or to prevent illnesses in a community. In response, ATSDR might recommend follow-up health actions, such as initiating an exposure investigation (to better define site exposures), conducting a health study (to identify elevated illness or disease rates in a site community), working with the community to implement a health education program for the community and health professionals, or providing technical assistance to other agencies (such as local health departments) in response to their requests. ATSDR’s health recommendations can also support site investigations conducted by other programs (within ATSDR and by external agencies), such as by helping fill data gaps.
The PHA process enables ATSDR to prioritize and identify additional steps needed to answer public health questions. Some recommended actions may be initiated before the completion of your site document, such as certain health education activities or efforts to obtain additional exposure data. Other actions may begin during the PHA process but end after the release of a document (e.g., PHA, HC). For instance, a health assessor may recommend continued maintenance and monitoring of engineering controls at a site, noting in the document that attention to ongoing institutional controls are vital to continued protection of public health into the future.
The type and number of outcomes will depend upon site-specific factors and actions deemed appropriate by the health assessor, others involved in the PHA process at a site, and their management. Some possible outcomes from the PHA process are in the table below.
Possible Outcomes from the PHA Process
Outcome
Outcome
Outcome
Description
Description
Description
Actions to reduce, prevent, and stop exposures
Outcome
Actions to reduce, prevent, and stop exposures
If you identify harmful exposures, you may recommend public health measures to reduce, prevent, or stop exposures. You may make recommendations to the appropriate federal, state, local, or tribal agencies.
Description
If you identify harmful exposures, you may recommend public health measures to reduce, prevent, or stop exposures. You may make recommendations to the appropriate federal, state, local, or tribal agencies.
Address site-specific issues and concerns
Outcome
Address site-specific issues and concerns
Some communities will have specific issues that are necessary to address. For instance, legitimizing and helping address stress in communities potentially affected by environmental contamination is an example of an important outcome of the PHA process.
Description
Some communities will have specific issues that are necessary to address. For instance, legitimizing and helping address stress in communities potentially affected by environmental contamination is an example of an important outcome of the PHA process.
Exposure investigations
Outcome
Exposure investigations
When critical data are missing, environmental or biological sampling may be necessary to better define the extent, if any, of harmful exposures.
Description
When critical data are missing, environmental or biological sampling may be necessary to better define the extent, if any, of harmful exposures.
Health advisory
Outcome
Health advisory
ATSDR may issue an advisory when immediate measures or actions are necessary to eliminate a health threat. Notify your management as soon as you identify an urgent hazard and an immediate action is necessary.
Description
ATSDR may issue an advisory when immediate measures or actions are necessary to eliminate a health threat. Notify your management as soon as you identify an urgent hazard and an immediate action is necessary.
Health education
Outcome
Health education
Throughout the PHA process, you may identify the need for education within a community, such as educating health professionals about identified site-related issues.
Description
Throughout the PHA process, you may identify the need for education within a community, such as educating health professionals about identified site-related issues.
Health services
Outcome
Health services
Site conditions may warrant community health interventions, such as medical monitoring. ATSDR does not have the legal authority to provide medical care or treatment but can work with health care agencies to address community health care needs or make referrals to health care providers. For more information, refer to ATSDR’s Final Criteria for Determining the Appropriateness of a Medical Monitoring Program Under CERCLAexternal icon [PDF – 187 KB].
Description
Site conditions may warrant community health interventions, such as medical monitoring. ATSDR does not have the legal authority to provide medical care or treatment but can work with health care agencies to address community health care needs or make referrals to health care providers. For more information, refer to ATSDR’s Final Criteria for Determining the Appropriateness of a Medical Monitoring Program Under CERCLAexternal icon [PDF – 187 KB].
Health studies/health surveillance
Outcome
Health studies/health surveillance
You may identify an exposed population for whom a site-specific epidemiologic or health study would be appropriate for consideration. An epidemiologist will need to evaluate the need and feasibility of any such study.
Description
You may identify an exposed population for whom a site-specific epidemiologic or health study would be appropriate for consideration. An epidemiologist will need to evaluate the need and feasibility of any such study.
Provide resources
Outcome
Provide resources
You may find some communities with particular issues that are looking for resources to help guide them through environmental contamination and other concerns. An example is for sites with environmental justice issues, health assessors will make efforts to connect those communities with related resources.
Description
You may find some communities with particular issues that are looking for resources to help guide them through environmental contamination and other concerns. An example is for sites with environmental justice issues, health assessors will make efforts to connect those communities with related resources.
Research
Outcome
Research
Knowledge gaps identified at a site may trigger contaminant-specific research, computational toxicology, or expanded efforts in developing ATSDR toxicological profiles.
Description
Knowledge gaps identified at a site may trigger contaminant-specific research, computational toxicology, or expanded efforts in developing ATSDR toxicological profiles.