CHAPTER ONE: CONDUCTING HEALTH ASSESSMENTS AND CONSULTATIONS
Who was exposed?
How were they exposed?
What were they exposed to and to how much?
When were they exposed and for how long?
ATSDR uses geographic information systems, exposure investigations,
fate and transport models, and exposure dose reconstruction to answer
exposure-related questions. Although the merits and key features of each
method and approach are described separately here, they are often used
together in a comprehensive integrated approach to assess exposure.
Geographic Information Systems
The use of geographic information systems (GIS) technology has become
an integral part of the public health assessment process. GIS is a computer
software application that compiles multiple data layers (e.g., environmental,
contaminant, outcomes, and demographic) and then relates these layers to one
another in a geographic area. It helps answer questions about who lives around
sites (that is, the demographic data) and where they live. Maps can help
communities and those involved with assessing hazards associated with the
site to better visualize where things are and how people might be exposed.
Knowing the demographics of surrounding populations could be critically
important, and GIS helps provide initial information to health assessors before
they ever visit the site.
GIS is used to put a demographic face on the populations living within 1
mile of the sites on the National Priorities List (NPL) of Superfund sites. Staff
members use site boundaries, data from the 1990 U.S. census, and an area
proportion technique to identify the number of people living within a mile of
these sites. To date, this technique has been used at approximately 1,600 sites.
ATSDR estimates that almost 15.5 million people live within a mile of a
hazardous waste site. Of those, nearly 4 million (25%) are nonwhite. Hispanics
are the largest ethnic group in the site population, with more than 2 million
people (14%).
GIS and census data are also used to identify the size of potentially
sensitive subpopulations (e.g., the young, the elderly, and women of
childbearing age) around the sites. One example is the number of children less
than 6 years of age. There are more than 1.5 million (11%) children less than 6
years old in the site populations. ATSDR's Child Health Initiative is concerned
with children and teenagers less than 18 years of age. Using GIS, it is estimated
that there are almost 3 million (19%) children and teenagers in the site
populations. To further enhance our understanding of the site populations, in
1999 ATSDR began to incorporate into its site analyses neighborhood
segmentation data from PRIZM, a database containing up-to-date population
estimates and socioeconomic information for census block groups. This
information gives added depth to the analysis of site populations.
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