Public Health Assessment Public Comment Release
EPA Action Levels (ALs) are the estimated contaminant concentrations in water at which
additional evaluation is needed to determine whether action is required to eliminate or reduce
exposure. Action levels can be based on mathematical models.
EPA Soil Screening Levels (SSLs) are estimated contaminant concentrations in soil at which
additional evaluation is needed to determine if action is required to eliminate or reduce exposure.
World Health Organization guidelines (WHO) are guidelines published by the World Health
Organization for drinking water quality.
Some CVs may be based on different durations of exposure. Acute duration is defined as
exposure lasting 14 days or less. Intermediate duration exposure lasts between 15 and 364 days,
and chronic exposures last one year or more. Comparison values based on chronic exposure
studies are used whenever available. If an intermediate or acute comparison value is used, it is
denoted with a small i or a before the CV (e.g., iEMEG refers to the intermediate duration
Determination of Exposure Pathways
ATSDR identifies human exposure pathways by examining environmental and human
components that might lead to contact with COCs. A pathway analysis considers five principal
of contamination, transport through
an environmental medium,
exposure, a route of human exposure, and an exposed population. Completed exposure pathways
are those for which the five elements are evident, and indicate that exposure to a contaminant has
occurred in the past, is now occurring, or will occur in the future. Potential exposure pathways
are those for which exposure seems possible, but one or more of the elements is not clearly
defined. Potential pathways indicate that exposure to a contaminant could have occurred in the
past, could be occurring now, or could occur in the future. It should be noted that the
identification of an exposure pathway does not imply that health effects will occur. Exposures
might be, or might not be, substantive. Therefore, even if exposure has occurred, is now
occurring, or is likely to occur in the future, human health effects might not result.
ATSDR reviewed site history, information on site activities, and the available sampling data. On
the basis of this review, ATSDR identified numerous exposure pathways that warranted
Evaluation of Public Health Implications
The next step
is to take those contaminants present
at levels above the CVs and further
which chemicals and exposure situations are likely to be a health hazard. Child and adult
exposure doses are calculated for the site-specific exposure scenario, using our assumptions of
on the site and how often they contact the site contaminants. The exposure dose
amount of a contaminant that gets into a person=s body. Following is a brief explanation of how
we calculated the estimated exposure doses for the site.