an international review panel of outside expert
As a result of mothers'
scientists to review three draft documents. The
2-day discussions focused on ATSDR's Guid-
exposure to methylmercury, the
ance Manual for the Assessment of Joint Toxic
type of mercury that
Action of Chemical Mixtures, its Guidance for
Preparation of Interaction Profiles, and the
accumulates in fish, as many as
Interaction Profile for Chlorinated Dibenzo-p-
Dioxins, Hexachlorobenzene, p,p'-DDT, and
60,000 children are born every
Methylmercury. Overall, the panel was very
year in the United States with
supportive of the mixtures program and com-
mended ATSDR scientists for their work to
neurological problems that
address and characterize the health effects of
could lead to poor school
chemical mixtures.
performance.
Also during fiscal year 2000, ATSDR continued
its support of experimental research to enhance
--Toxicological Effects of Methylmercury,
the understanding of the underlying mechanisms
National Research Council, 2000
of toxicity following exposure to chemical
mixtures. Many of
the key research findings
during the year were presented in seven separate
Mixtures Assessment and
presentations at national and international
Research Program
toxicology meetings. One of the papers was
recognized as the best paper presented in the
Superfund sites rarely contain only one hazard-
Risk Assessment speciality section at the annual
ous substance. Frequently, multiple chemicals
meeting of the Society of Toxicology held in
are found at NPL sites. Therefore people who
Philadelphia, Pennsylvania, March 1923, 2000.
are often exposed to mixtures of hazardous
substances.
Computational Toxicology
The principal aim of ATSDR's Mixtures Assess-
Program
ment and Research Program is to develop
As a part of the development of the SSARP,
methods for assessing the joint toxicity of
ATSDR has incorporated the use of state-of-the-
exposure to multiple chemicals that are most
art computational toxicology methods such as
frequently found at hazardous waste sites. The
physiologically based pharmacokinetic (PBPK)
program seeks to identify pertinent mixtures,
modeling, structure-activity-relationship (SAR)
assess joint toxicity, and conduct experimental
techniques, and benchmark dose (BMD) models
testing to fill research needs.
to aid in interpreting and assessing short,
intermediate, and long-term health effects
During fiscal year 2000, identification and
associated with exposure to hazardous sub-
ranking of chemical mixtures that are found in
stances. PBPK, BMD, and SAR are computer-
completed exposure pathways has progressed. A
based mathematical models used to predict the
list of binary mixtures has been identified, and
action of chemicals on the body in the absence
work is being conducted to identify higher order
of little or no experimental data. The alternative
mixtures (such as 3- and 5-component mix-
tures). On May 3031, 2000, ATSDR convened
36 chapter 2