About Pepper Spray

by Deborah Blum,
Guest Blog - Commentary invited by editors of Scientific
American

Scientific American
November 21, 2011

http://blogs.scientificamerican.com/guest-blog/2011/11/21/about-pepper-spray/

One hundred years ago, an American pharmacist named Wilbur
Scoville developed a scale to measure the intensity of a
pepper's burn. The scale - as you can see on the widely used
chart to the left - puts sweet bell peppers at the zero mark
and the blistering habanero at up to 350,000 Scoville Units.

I checked the Scoville Scale for something else yesterday. I
was looking for a way to measure the intensity of pepper
spray, the kind that police have been using on Occupy
protestors including this week's shocking incident involving
peacefully protesting students at the University of
California-Davis.

As the chart makes clear, commercial grade pepper spray
leaves even the most painful of natural peppers (the
Himalayan ghost pepper) far behind. It's listed at between 2
million and 5.3 million Scoville units. The lower number
refers to the kind of pepper spray that you and I might be
able to purchase for self-protective uses. And the higher
number? It's the kind of spray that police use, the super-
high dose given in the orange-colored spray used at UC-
Davis.

The reason pepper-spray ends up on the Scoville chart is
that - you probably guessed this -  it's literally derived
from pepper chemistry, the compounds that make habaneros so
much more formidable than the comparatively wimpy bells.
Those compounds are called capsaicins and - in fact - pepper
spray is more formally called Oleoresin Capsicum or OC
Spray.

One hundred years ago, an American pharmacist named Wilbur
Scoville developed a scale to measure the intensity of a
pepper's burn. The scale - as you can see on the widely used
chart to the left - puts sweet bell peppers at the zero mark
and the blistering habanero at up to 350,000 Scoville Units.

I checked the Scoville Scale for something else yesterday. I
was looking for a way to measure the intensity of pepper
spray, the kind that police have been using on Occupy
protestors including this week's shocking incident involving
peacefully protesting students at the University of
California-Davis.

As the chart makes clear, commercial grade pepper spray
leaves even the most painful of natural peppers (the
Himalayan ghost pepper) far behind. It's listed at between 2
million and 5.3 million Scoville units. The lower number
refers to the kind of pepper spray that you and I might be
able to purchase for self-protective uses. And the higher
number? It's the kind of spray that police use, the super-
high dose given in the orange-colored spray used at UC-
Davis.

The reason pepper-spray ends up on the Scoville chart is
that - you probably guessed this -  it's literally derived
from pepper chemistry, the compounds that make habaneros so
much more formidable than the comparatively wimpy bells.
Those compounds are called capsaicins and - in fact - pepper
spray is more formally called Oleoresin Capsicum or OC
Spray.

But we've taken to calling it pepper spray, I think, because
that makes it sound so much more benign than it really is,
like something just a grade or so above what we might mix up
in a home kitchen. The description hints maybe at that eye-
stinging effect that the cook occasionally experiences when
making something like a jalapeno-based salsa, a little burn,
nothing too serious.

Until you look it up on the Scoville scale and remember, as
toxicologists love to point out, that the dose makes the
poison.  That we're not talking about cookery but a potent
blast of chemistry.  So that if OC spray is the U.S. police
response of choice  - and certainly, it's been used with
dismaying enthusiasm during the Occupy protests nationwide,
as documented in this excellent Atlantic roundup -  it may
be time to demand a more serious look at the risks involved.

My own purpose here is to focus on the dangers of a high
level of capsaicin exposure. But as pointed out in the 2004
paper, Health Hazards of Pepper Spray, written by health
researchers at the University of North Carolina and Duke
University, the sprays contain other risky materials:

    Depending on brand, an OC spray may contain water,
    alcohols, or organic solvents as liquid carriers; and
    nitrogen, carbon dioxide, or halogenated hydrocarbons
    (such as Freon, tetrachloroethylene, and methylene
    chloride) as propellants to discharge the canister
    contents.(3) Inhalation of high doses of some of these
    chemicals can produce adverse cardiac, respiratory, and
    neurologic effects, including arrhythmias and sudden
    death.

Their paper focuses mostly, though, on the dangerous
associated with pepper-based compounds. In 1997, for
instance, researchers at the University of California-San
Francisco discovered that the "hot" sensation of habaneros
and their ilk was caused by capsaicin binding directly to
proteins in the membranes of pain and heat sensing neurons.
Capsaicins can activate these neurons at below body
temperature, leading to a startling sensation of heat.
Repeated exposure can wear the system down, depleting
neurotransmitters, reducing the sensation of the pain. This
knowledge has led to a number of medical treatments using
capsaicins to manage pain.

Its very mechanism, though, should remind us to be wary. As
the North Carolina researchers point out, any compound that
can influence nerve function is, by definition, risky.
Research tells us that pepper spray acts as a potent
inflammatory agent. It amplifies allergic sensitivities, it
irritates and damages eyes, membranes, bronchial airways,
the stomach lining - basically what it touches. It works by
causing pain - and, as we know, pain is the body warning us
of an injury.

In general, these are short term effects. Pepper spray, for
instance, induces a burning sensation in the eyes in part by
damaging cells in the outer layer of the cornea.  Usually,
the body repairs this kind of injury fairly neatly. But with
repeated exposures, studies find, there can be permanent
damage to the cornea.

The more worrisome effects have to do with inhalation - and
by some reports, California university police officers
deliberately put OC spray down protestors throats.
Capsaicins inflame the airways, causing swelling and
restriction. And this means that pepper sprays pose a
genuine risk  to people with asthma and other respiratory
conditions.

And by genuine risk, I mean a known risk, a no-surprise any
police department should know this risk,  easy enough to
find in the scientific literature. To cite just three
examples here:

1) Pepper Spray Induced Respiratory Failure Treated with
Extracorporeal Membrane Oxygenation

2) Assessing the incapacitative effects of pepper spray
during resistive encounters with the police.

3) The Human Health Effects of Pepper Spray.

That second paper is from a law enforcement journal. And the
summary for that last paper notes: Studies of the effects of
capsaicin on human physiology, anecdotal experience with
field use of pepper spray, and controlled exposure of
correctional officers in training have shown adverse effects
on the lungs, larynx, middle airway, protective reflexes,
and skin. Behavioral and mental health effects also may
occur if pepper spray is used abusively.

Pepper spray use has been suspected of contributing to a
number of deaths that occurred in police custody. In
mid-1990s, the U.S. Department of Justice cited nearly 70
fatalities linked to pepper-spray use, following on a 1995
report compiled by the American Civil Liberties Union of
California. The ACLU report cited 26 suspicious deaths; it's
important to note that most involved pre-existing conditions
such as asthma. But it's also important to note a troubling
pattern.

In fact, in 1999, the ACLU  asked the California appeals
court to declare the use of pepper spray to be dangerous and
cruel. That request followed an action by northern
California police officers against environmental protestors
- the police were accused of dipping Q-tips into OC spray
and applying them directly to the eyes of men and women
engaged in an anti-logging protest.

"The ACLU believes that the use of pepper spray as a kind of
chemical cattle prod on nonviolent demonstrators resisting
arrest constitutes excessive force and violates the
Constitution," wrote association attorneys some 13 years
ago.

Yesterday, the University of California-Davis announced that
it was suspending two of the police officers who pepper-
sprayed protesting students. Eleven of those students were
treated by paramedics on scene and two were sent to a
hospital in Sacramento for more intensive treatment.

Undoubtedly, these injuries will factor into another
scientific study of pepper spray, another acknowledgement
that top of the Scoville scale is dangerous territory. But
my own preference is that we start learning from these
mistakes without waiting another 13 years or more, without
engaging in yet another cycle of abuse and injury.

Now would be good.

[Deborah Blum is a Pulitzer-Prize winning science writer and
the best-selling author of The Poisoner's Handbook: Murder
and the Birth of Forensic Medicine in Jazz Age New York. A
professor of science journalism at the University of
Wisconsin, she blogs about chemistry culture at Speakeasy
Science. http://blogs.plos.org/speakeasyscience ]

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