Traditionally,
health
agencies
determine
potential
adverse
human
health
effects
based
on
results
of
published
animal
studies.
It
is
difficult
for
many
agencies
to
say
for
certain
if
a
chemical
is
dangerous
to
humans
because
there
may
be
no
published
studies
of
human
exposures.
Public
health
agencies
examine
all
available
data
when
evaluating
chemicals.
For
mixtures
of
chemicals
such
as
crude
oil,
agencies
can
examine
studies
on
individual
component
chemicals
to
anticipate
the
toxicity
of
the
mixture.
Agencies
such
as
the
Environmental
Protection
Agency
and
the
Agency
for
Toxic
Substances
and
Disease
Registry
publish
documents
summarizing
the
potential
health
effects
based
upon
current
scientific
knowledge.
.