ATSDR -- FY 1999 AGENCY PROFILE AND ANNUAL REPORT
Table 1.
Top 10 Substances on the 1999 Priority List of Hazardous Substances
Rank
Name
1
Arsenic
2
Lead
3
Mercury
4
Vinyl chloride
5
Benzene
6
Polychlorinated biphenyls (PCBs)
7
Cadmium
8
Benzo(a)pyrene
9
Polycyclic aromatic hydrocarbons (PAHs)
10
Benzo(b)fluoranthene
In June 1999, Congressman John Dingell's office contacted ATSDR to
request that the agency provide information on adverse effects associated with
the top 50 substances on the Priority List that have latency periods of 6 years or
greater. In response, the Division of Toxicology reviewed and compiled the
information available in the existing toxicological profiles. The report noted
that vinyl chloride, benzene, PCBs, trichloroethylene, hexavalent chromium,
lead, arsenic, creosote, and benzidine are classified as "known to cause cancer
in humans" or "probable human carcinogens," and they have a latency period
of at least 6 years. In addition, a number of other substances on the list are
classified as "reasonably anticipated to cause cancer in humans" because of
limited evidence in humans, but sufficient evidence in animals. These
substances include cadmium, chlordane, beryllium, carbon tetrachloride, and
cobalt. The consultation also summarized the potential for developmental or
neurologic effects with a latency of 6 years. This information was subsequently
published as a scientific manuscript, "ATSDR's 1997 Priority List of
Hazardous Substances: Latent effects--Carcinogenicity, Neurotoxicology, and
Developmental Deficits in Humans and Animals" (Toxicology and Industrial
Health 1999; 15:143).
Along with the priority list, ATSDR developed a Completed Exposure
Pathway Site Count Report. A completed exposure pathway is an exposure
pathway that links a contaminant source to a receptor population. The
completed exposure pathway ranking is based on a site frequency count, and
thus lists the number of sites at which a substance has been found in a
completed exposure pathway. In late FY 1999, most of the development of the
completed exposure pathway report was completed. Lead was the substance
found most frequently in completed exposure pathways, followed by
trichlorethylene and arsenic. The top 10 substances are shown in Table 2.
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