CHAPTER TWO
Evaluating Relationships Between
Hazardous Substances and Health:
Toxicologic Research
A
second major goal of ATSDR is to
evaluate relationships between hazard
ous substances in the environment and
adverse human health outcomes. To help
achieve that goal, ATSDR has a toxicologic
research program that is filling many of the data
gaps about how hazardous substances affect
human health. ATSDR also helps provide
information about the relationship between
hazardous substances and health outcomes by
developing toxicological profiles that summa-
rize information about many of the most hazard-
ous substances found at Superfund sites.
Identification and Ranking of
Asbestos fibers
Hazardous Substances
To ensure that the priority list is current,
The Comprehensive Environmental Response,
ATSDR periodically reexamines its information
Compensation, and Liability Act of 1980
database (HazDat) of all hazardous substances
(CERCLA) Priority List of Hazardous Sub-
known to exist at NPL sites. In early fiscal year
stances contains the names of 275 substances
2000, the 1999 CERCLA Priority List of
found at NPL sites and believed to pose the
Hazardous Substances was published. Its
most significant potential threat to human
availability was announced in the Federal
health. This list helps form ATSDR priorities on
Register on October 21, 1999 (64 FR 56792).
many issues. The Superfund Amendments and
The top substance on the 1999 Priority List of
Reauthorization Act of 1986 (SARA) requires
Hazardous Substances was arsenic, followed by
ATSDR, in cooperation with EPA, to compile
lead and mercury (see Table 1).
this priority list, which is drawn from all
hazardous substances known to exist at NPL
Along with the publication of the revised
sites. The ranking of substances on the priority
priority list in October 1999, ATSDR also
list is based on three criteria: (1) frequency of
published an updated Completed Exposure
occurrence at NPL sites, (2) toxicity, and
Pathway Site Count Report. A completed
(3) potential for human exposure.
exposure pathway (CEP) is an exposure path-
way that links a contaminant source to a recep-
tor population. The CEP ranking is based on a
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