From 1952 to 1953, Sydney
detectives investigated
a staggering number of murder
and attempted murder cases
that were unrelated yet shared
a common element:
thallium poisoning.
The secret to thallium toxicity lies in
its structural similarity to potassium—
an element that helps regulate
the body's fluids,
initiate muscle contraction,
and transmit nerve signals.
If even a small amount of thallium
sneaks its way into the body—
for example, through a tainted tea
or a slice of cake—
it easily supplants potassium,
causing the body to slowly
and painfully shut down.
At the time, thallium's
risks were well known,
so how were the perpetrators able to get
their hands on such a lethal element?
And thallium isn't the only dangerous
element on the periodic table.
Within this tabular array loom
several potential threats,
each with their own unique method
of imposing destruction.
Some elements, like thallium,
are dangerous due to their toxicity.
Once they enter the body,
they wreak havoc on the biological systems
that keep us alive.
Lead, for example, switches places with
the body's essential metals like calcium,
in turn disrupting neuronal communication
in the brain.
Traveling through the bloodstream, it also
generates toxic levels of molecules
known as reactive oxygen species,
which over time can stress and kill cells.
Mercury's toxicity was made famous
in the 19th century
due to its widespread use
in felt hat production.
Prolonged exposure made hat makers ill
with what was later known
as "Mad Hatter" disease,
with symptoms that included
personality changes,
emotional disturbances, and tremors.
Mercury is quick to react
with certain parts of proteins
found throughout the body.
And upon binding, mercury twists
the proteins into different shapes,
rendering them useless.
Some elements are dangerous because of
how they respond, react, or even explode
in the outside environment.
Top reactive elements reside in the
first column of the periodic table
and are known as alkali metals.
They're rarely found in their
pure elemental form,
as alkalis readily donate the single
electron in their outer shell
to whatever's around to form more
stable ionic compounds.
This can lead to violent results—
pure cesium, for example, bursts
into flames when exposed to air,
and explodes when dropped in water.
Francium is likely the
most reactive alkali
based on its position
in the periodic table,
but we don't know for sure.
With a half-life of 22 minutes at most,
it's thought that less than an ounce
exists on Earth at any one time.
But perhaps the most threatening elements
are those that silently emit.
Known as radioactive elements,
the substances readily release energy,
or decay,
due to their highly unstable
nuclear composition.
This reactive nature is what's
harnessed to create
some of the world's most dangerous
nuclear weapons.
Radioactive elements typically emit energy
in the form of alpha particles,
beta particles, neutrons,
or electromagnetic radiation.
While all dangerous,
alpha particles, which consist
of two neutrons and protons
bound tightly together,
can be particularly hazardous.
Heavy and positively charged,
if alpha particles find their
way into the body,
they can easily bombard and kill
any cell in their path.
In fact, it's theorized that a single
gram of one alpha emitter, polonium,
could kill upwards of 50 million people.
Polonium was first discovered
by Marie Curie,
and tragically her daughter,
researcher Irene Joliot-Curie,
may have been one of its first victims
after she was exposed in a lab accident.
Polonium is rare in nature
with few commercial uses,
so only a small amount is
synthesized each year.
Thallium, on the other hand,
wasn't so difficult to find
in the early 1950s in Austalia.
At the time, Sydney was plagued
with chronic rat infestations.
And thallium was the main ingredient
in the popular and cheap
rat poison called Thall-Rat.
Thankfully, detectives were
able to connect the dots,
and in 1953 Australian Parliament
effectively banned all sale of thallium.