A Public Health Assessment or "PHA" reviews available information about hazardous substances at a site and evaluates whether exposure to them might cause harm to people. A Health Consultation is generally a document that addresses a particular concern or an exposure scenario that is more limited in scope. Public Health Assessments and Health Consultations present conclusions about whether exposures are occurring, whether a health threat is present, and whether adverse health effects from the exposures are possible. In some cases, it is possible to determine whether exposures occurred in the past. If a threat to public health is found at a site, recommendations are made to stop or reduce it. Through a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR), the Health Assessment and Toxicology (HAT) Program prepares a Public Health Assessment for every site on or proposed for listing onto the National Priorities List (NPL) Superfund sites.
If you would like to provide a comment on a Public Health Assessment as part of a Public Comment period, you may use our Response Form or contact us at the address at the bottom of this page.
What type of information is used in a Public Health Assessment (PHA)?
Public Health Assessments consider:
- environmental data – information about chemicals in the air, water, or soil at the site and how people could come into contact with them
- health outcome data – available information on community wide rates of illness, disease, and death
- community health concerns – reports from the public about how the site affects their health or quality of life
How does the Health Assessment and Toxicology (HAT) Program use this information to determine if there is a public health threat?
In order to evaluate the threat to public health from contaminants at an NPL site, the PHA focuses on determining whether:
- there are harmful chemicals at the site
- there are chemicals in places where people could come into contact with them, and
- whether people could come into contact with enough of the contamination to affect their health
In addition, HAT also considers whether there are:
- unusual documented rates of illness or disease in a community
- consistent reports of illness by people in the community
How does HAT determine if people could come into contact with chemicals at the site?
To make the above determinations, HAT first considers each of the potential pathways through which people could come into contact with contaminants. An environmental exposure pathway can be described as the route the chemical follows from a source to people who may come into contact with it. Exposure pathways are have five (5) principal elements. These include:
- media through which the chemicals may travel (like air, water, soil, or food)
- point or location where people may come into contact with the chemicals
- route or manner in which the chemicals can get into people
- population that is exposed
Exposure pathways can be considered completed, potential, or eliminated. An exposure pathway is considered completed if there is sufficient evidence to indicated that all five elements are present and that people were/are/will be exposed to site chemicals. An exposure pathway is considered potential if one or more of the elements is missing due to insufficient information and that obtaining more information could indicated those elements are present. Exposure pathways are eliminated if based on available evidence it appears that one or more of the following elements is missing.
1. People can come into contact with chemicals in:
- food (fish, game, fruits and vegetables)
- surface water (creeks, lakes)
- air (indoor and outdoor)
- groundwater (well water)
2. To pose a possible health threat, chemicals would have to get from the environmental media into peoples bodies. This can happen through:
- inhalation (breathing contaminants in)
- ingestion (eating or drinking)
- dermal contact (absorption through the skin)
How does HAT determine if the chemicals that people come into contact with can harm them?
To determine whether chemicals that people are exposed to can cause harm, HAT first tries to determine:
- how often people come into contact with the chemicals
- how long the contact has been occurring and
- how much they are coming into contact each time that contact occurs
HAT then reviews whatever information is available on the known toxic effects of the chemicals that people are or may be exposed to. HAT reviews toxicological information obtained from:
- studies of workers exposed to chemicals and/or harmful physical agents
- studies of occupational disease
- investigations of people exposed to chemicals in their community
- case reports of accidental or intentional exposures to chemicals
- studies of people exposed to chemicals natural to the environment
- controlled animal experiments
Why does HAT collect community health concerns?
People who live near hazardous waste sites are often concerned that living near the site might affect their health. HAT contacts community members so that their health concerns about the site can be addressed in the PHA. HAT uses several different methods to collect community health concerns; these include:
- community questionnaires
- door-to-door surveys
- talking to people at public meetings or public availability sessions
- talking with community leaders
Why and when does HAT collect health outcome data?
Health outcome data are rates of diseases or illnesses in an area. HAT may try to obtain health outcome data if it appears that exposures at the site could have made people sick, and if data on the rates of those illnesses are available. HAT also may try to obtain health outcome data if community members have specific concerns about high rates of a specific disease in the community and data on the rates of that disease in the community are available.
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