6 ‘Undetectable’ Poisons (and How to Detect Them)

[♩INTRO] Poison. From ancient times through the Cold War and
even up to today, it’s always been a popular method of offing one’s enemies. Depending on the toxin you go with, you can
kill someone slowly and quietly, or abruptly and dramatically — although, to be clear,
we do not recommend any of this… Murder is bad. But is there really such a thing as a “perfect,”
undetectable poison? Well, probably not — but some are definitely
more challenging than others to identify and treat because of how they interact with the
body. Here are six poisons that, at various times
throughout history, have confounded doctors and medical examiners. We’ll start with one you’ve probably heard
of: arsenic. This poison has been around for a long time,
and mixtures of it were known and used going all the way back to the Roman Empire. Arsenic is a type of element called a metalloid
— one whose traits put it in a fuzzy gray area between metals and nonmetals — and it’s
actually pretty common in the Earth’s crust. When it’s mixed into food or drink, it’s
odorless, colorless, and tasteless, and the symptoms of a single large dose resemble those
of bad, fatal food poisoning. Which can seem pretty sneaky if you don’t
know you’ve been poisoned. Arsenic can also be given in smaller doses
over a longer period of time. That produces subtler, slowly progressing
symptoms, including weakness, confusion, paralysis, and, yes, eventually death. Which is even sneakier. Arsenic is absorbed through the small intestine,
and once it gets into the bloodstream, the body mistakenly substitutes them for phosphate. This wreaks havoc on around 200 enzyme-based
systems necessary for a functioning metabolism. Arsenic was a popular murder weapon for much
of modern human history, but it’s a lot less common these days, because it’s easier
to detect. A chemical test for confirming the presence
of arsenic in bodily fluids was perfected back in the early 19th century. Around that time, it had been discovered that
when zinc is added to arsenic dissolved in sulfuric acid, a colorless, smelly gas — called
arsine — will form, along with hydrogen. Marsh used this to develop his test. He suspended a piece of zinc in one arm of
a closed, U-shaped glass tube, which was filled with sulfuric acid. Then, when a sample — a bit of the victim’s
blood, for example — was added to the opposite arm of the U, hydrogen and arsine would form
if there was any arsenic in the sample. After that, the tube was opened, and the escaping
gas was lit on fire. If you held a piece of glass over the flame,
it would show a characteristic brownish spot if arsine was there, proving that a victim
had indeed been murdered. Once it could be reliably detected, arsenic’s
popularity began to wane, and today, murder by arsenic is mostly found in old detective
stories. Another classic, cyanide was supposedly used
in an attempt to murder the famously hard-to-kill Russian mystic Rasputin back in 1916. And it’s still used for the occasional murder
today. Cyanide is made of a carbon atom stuck to
a nitrogen atom, and it has several forms. Hydrogen cyanide is a pale blue or colorless
liquid at room temperature, while sodium cyanide and potassium cyanide are white powders. All of them may smell like bitter almonds. Once someone ingests some cyanide, it quickly
enters their bloodstream. But it might not always be deadly. In small doses, the body can get rid of cyanide
by tacking on a sulfur ion onto it. That converts the poison into a different
chemical called thiocyanate, which can leave the body through urine. But with larger doses, the body gets overwhelmed,
and it can’t turn all the poison into thiocyanate. At that point, the cyanide starts preventing
cells from using oxygen, and eventually, cells start dying off. And a lack of oxygen is not good news for
the heart, respiratory system, or central nervous system. Because all of these essential systems are
affected, there’s a pretty long list of symptoms for cyanide poisoning, including
weakness, nausea, difficulty breathing, seizures, or cardiac arrest. But what makes cyanide especially tricky for
doctors, even today, is that it’s so fast-acting. Depending on the form of cyanide and the dose,
it can kill in hours or even minutes. It can be detected in blood, but a patient
would probably be dead before the lab results came back — the commonly used test takes
about a day. Still, there are some secondary indicators
doctors can check for. One is extra oxygen in the blood, which happens because cells can’t use all the oxygen someone’s breathing. Unfortunately, some of those indicators can
actually show up with other poisons as well. Ultimately, a patient’s best chance for
survival is for doctors to make a careful, educated guess based on the symptoms and circumstances,
and to start treatment right away. So cyanide poisoning may be detectable — but
by the time doctors know for sure, it’ll probably be too late. Thallium is a heavy metal with multiple radioactive
isotopes. It was discovered in 1861, and it’s been
implicated in murders worldwide ever since. Although today, it’s also used in some types
of medical imaging. As a poison, thallium is tasteless, odorless,
and very deadly — ingesting as little as a single gram of the stuff can kill you, and
it can also be inhaled or absorbed through the skin. Once it gets into the body, it corrodes the
lining of the digestive tract, which leads to abdominal pain, diarrhea, and vomiting. It also replaces potassium in certain enzyme
systems throughout the body — like how arsenic replaces phosphate. That impairs the production of proteins. Still, thallium is at least pretty slow-acting
compared to some other poisons. The gastrointestinal symptoms last from 12
to 96 hours. Then, 1 to 5 days after the poisoning, neurological, cardiac, liver, and kidney symptoms can kick in. Patients also eventually lose all their hair
— if they live long enough. Now, even though thallium is slow-acting,
that doesn’t necessarily mean it’s easy to detect — at least, not at first. Which is partly why it’s such a popular
choice. Thallium can be detected in blood and urine,
but the slow progression of symptoms may not be caught right away. And it’s uncommon enough that doctors don’t
necessarily think to test for it. So by the time doctors figure out what’s
going on or the victim dies… the poisoner might have already fled the country. Polonium-210 is a metal found in uranium ore,
which often shows up as a byproduct of nuclear reactors. It can be processed into a tasteless, odorless
compound that dissolves in water, which makes it a good candidate as far as undetectable
poisons go. This stuff is also many times more deadly
than even cyanide: The lethal dose is as little as a few milligrams. And if you don’t know exactly what you’re
looking for, it’s really hard to pin down. Thankfully, as far as anyone knows, this has only ever happened once. In 2006, a former Russian spy named Alexander Litvinenko was assassinated in London, likely
with tea laced with polonium-210. Litvinenko was taken to the hospital that
afternoon, feeling ill. Then, he died three weeks later after experiencing multiple organ failures. Doctors first thought our friend thallium
might be to blame Then, they eventually figured out that Litvinenko
had some sort of radiation poisoning, thanks to his hair loss and immune system failure. But they didn’t ID the culprit as polonium
until just a few hours before his death. What makes polonium-210 so dangerous is that,
as the molecules break down, they emit alpha radiation, positively charged particles made
of two protons and two neutrons. Outside the body, alpha particles can be blocked
with a sheet of paper. But inside the body, the radiation breaks
apart oxygen molecules to create dangerous, highly reactive free radicals, which damage
DNA and kill cells. In this case, those alpha particles also helped
doctors figured out what poisoned Litvinenko. See, the ones emitted by polonium-210 have
a characteristic energy of around 5.3 mega-electronvolts — which is a unit of momentum used in high-energy
physics. And when doctors found particles with that
exact, unique trait in Litvinenko’s urine, they finally identified the element that killed
the spy. As far as we know, this is the only case where
polonium-210 was used as a poison. But it was definitely a tricky one and, if
it turns up again, we’ll hopefully have a better idea how to identify it. Ethylene glycol is the base for a lot of common
antifreeze you use in your car. It tastes sweet, and it’s readily available,
making it a popular choice for murder by poison in the U.S. But to be clear, no matter how it good it
tastes, you should not drink it. After someone ingests it, they’ll seem fine
for a few hours — but their body is actually busy breaking down the poison into other,
toxic substances. Eventually someone will start to feel groggy,
experience abdominal distress, and then go into a coma. [acid-osis — like it looks]
One of the byproducts ethylene glycol breaks down into is glycolic acid, which causes a
dangerous condition called metabolic acidosis. This is when someone’s blood becomes too
acidic, keeping all the chemical reactions that make up their metabolism from functioning
properly. The poison also creates calcium oxalate crystals in the kidneys, which physically tear up kidney tissue. Sounds…not fun. Ethylene glycol can be definitively detected
in the blood, but for most hospitals, it’ll require sending a sample to an outside lab
and waiting days for results. So, kind of like with cyanide, doctors generally
have to diagnose ethylene glycol poisoning indirectly, using tests for things like the
presence of osmotically active substances in the body. These are substances that can’t move across
cell membranes, like ethylene glycol. But also like with cyanide, the results of
these tests aren’t really conclusive, making it hard to ID this type of poisoning fast
enough to treat it effectively. The moral of this story? Don’t drink antifreeze, and also, prevent
other people from drinking antifreeze. No matter how delicious it tastes. California mortician Timothy Waters died in
1985 of what was originally believed to be a heart attack. At first, no one suspected that the culprit
might be a poisonous plant called oleander. Until his alleged murderer started bragging
about the crime. The name “oleander” refers to several
small, shrubby trees in the genus Nerium, which have attractive pink or purple flowers
and are commonly used in gardens. What makes oleander toxic are two potent cardiac
glycosides, oleandrin and neriine, which are found in every part of the plant. These molecules are similar to digitalis,
which you may have heard of because it’s sometimes used as a heart medication. Cardiac glycosides work by manipulating the
ion pump that powers heart muscle cells, which increases the force of heart muscle contraction. This makes them useful for treating some heart
conditions in small, controlled doses — but they’re not so good if you ingest a whole
lot at once, as they can totally mess up your heart rhythm. In addition to cardiac symptoms, oleander
poisoning also causes nausea, vomiting, cramps, and diarrhea, usually about four hours after
ingestion. Waters spent two days vomiting before he died. But oleander isn’t a common poison, and
medical examiners had no reason to test for it at first. Only when a rival funeral home owner supposedly
bragged to an informant about poisoning Waters did investigators expand their search. During an autopsy where the cause of death
isn’t certain, medical examiners typically check for about 100 compounds, including alcohol,
common illicit drugs, and common poisons. If those tests all come back negative, then
the examiner might order detailed tests to check for less-common toxins. In Waters’s case, it took analysis by two
outside labs to finally isolate oleander compounds in samples of his blood. But even then, the murder charges were ultimately
dismissed when a toxicologist hired by the defense couldn’t confirm the results. So either this wasn’t a case of death-by-oleander
after all… or oleander really is the perfect poison. It should go without saying that we here at
SciShow do not condone poisoning your enemies. Or your friends. But the chemistry and medicine behind a lot
of these compounds and how they’re used is undeniably cool. And if this wasn’t enough poison for you and
you’d like to learn even more, you can also watch our episode about 10 plants that could
kill you. [♩OUTRO]

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