CHAPTER TWO:
TOXICOLOGIC RESEARCH AND
INFORMATION DISSEMINATION
T
he Division of Toxicology is composed of three branches under the Office
of the Division Director: the Emergency Response and Scientific
Assessment Branch, the Research Implementation Branch, and the Toxicology
Information Branch. The division is responsible for substance-specific research
and technical assistance; dissemination of technical information; and
emergency technical support to industry, local first responders, other
government agencies, and the public.
IDENTIFICATION AND RANKING OF HAZARDOUS
SUBSTANCES
The Comprehensive Environmental Response, Compensation, and Liability
Act of 1980 (CERCLA, or Superfund) Priority List of Hazardous Substances
contains the names of 275 substances found at NPL sites and that are believed
to pose the most significant potential threat to human health. This list helps
form ATSDR priorities on many issues. The Superfund Amendments and
Reauthorization Act of 1986 (SARA) requires ATSDR to compile this priority
list, which is drawn from the universe of hazardous substances known to exist
at NPL sites. The ranking of substances on the list is based on three criteria: (1)
frequency of occurrence at NPL sites, (2) toxicity, and (3) potential for human
exposure.
To ensure that the most hazardous substances are on the priority list,
ATSDR periodically reexamines its information database (HazDat) of
hazardous substances known to exist at NPL sites. The list is updated annually
and published biennially because EPA routinely adds new sites to the NPL,
new data about how people might be exposed becomes available as public
health assessments are completed, and important new toxicity information
about substances is discovered. Each substance on the list may become the
subject of an ATSDR toxicological profile and subsequently a candidate for the
identification of priority data needs.
In late FY 1999, the preparatory work and most of the development of the
1999 CERCLA Priority List of Hazardous Substances was completed. The final
1999 list was published and its availability announced in the Federal Register
during the first quarter of FY 2000. Arsenic was at the top of the 1999 list,
followed by lead and mercury. The top 10 substances are shown in Table 1.
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