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Chemistry for
Changing Times,
Thirteenth Edition
Lecture Outlines
Chapter 22
Poisons
John Singer,
Jackson Community College
© 2013 Pearson Education, Inc.
Chemical Toxicology
Poison
A poison is a substance that causes injury,
illness, or death of a living organism.
“The dose makes the poison.” All substances
can be poisonous, depending on the amount.
Toxicology is the study of poisons, their effects,
detection, identification, and antidotes.
© 2013 Pearson Education, Inc.
Chapter 22
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Natural Poisons
Many natural substances are acutely toxic.
Socrates was put to death by drinking a cup of
hemlock. Hemlock contains coniine, which is
an alkaloid.
© 2013 Pearson Education, Inc.
Chapter 22
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Natural Poisons
Poisons in the Garden and on the Farm
Many of the berries, flowers, and leaves found in
a common garden are toxic. Oleander is one
such plant.
© 2013 Pearson Education, Inc.
Chapter 22
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Corrosive Poisons: A Closer
Look
Acids and bases can catalyze the hydrolysis of
amides. The peptide bond of proteins is an
amide linkage. Exposure to acids and bases can
denature proteins by hydrolyzing the peptide
bonds. If the protein is an enzyme, it can be
deactivated by hydrolysis.
© 2013 Pearson Education, Inc.
Chapter 22
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Corrosive Poisons: A Closer
Look
Oxidizing Agents
Many airborne pollutants are damaging to living
tissue. Ozone, peroxyacetyl nitrate (PAN), and
other oxidizing agents found in photochemical
smog can cause the deactivation of enzymes.
© 2013 Pearson Education, Inc.
Chapter 22
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Metabolic Poisons
Blood Agents
Carbon monoxide (CO) binds tightly to the iron
in hemoglobin preventing the transport of oxygen.
© 2013 Pearson Education, Inc.
Chapter 22
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Metabolic Poisons
Blood Agents
Nitrate ions (NO3-) found in some foods and in
drinking water in some areas can be converted
to nitrite ions (NO2-) in the body. Nitrite ions
oxidize Fe2+ in hemoglobin to Fe3+, forming
methemoglobin, which is incapable of carrying
oxygen. The result is a condition known as
methemoglobinemia or “blue-baby syndrome.”
© 2013 Pearson Education, Inc.
Chapter 22
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Metabolic Poisons
Blood Agents
Cyanide ions (CN-) bind to the iron(III) ions in
oxidative enzymes known as cytochrome
oxidases. This puts an end to cellular
respiration and brings near immediate death.
© 2013 Pearson Education, Inc.
Chapter 22
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Metabolic Poisons
Antidotes for cyanide poisoning must be
administered quickly. One such antidote is
sodium nitrite followed by sodium thiosulfate.
Thiosulfate reacts with cyanide ions forming
thiocyanate ions.
© 2013 Pearson Education, Inc.
Chapter 22
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Make Your Own Poison:
Fluoroacetic Acid
When fluoroacetic acid is introduced
into the body, it can replace citric
acid, which is normally broken down
in the citric acid cycle to produce
energy. Thus fluoroacetic acid can
shut down the citric acid cycle, which
makes the acid an effective poison.
Natives in South Africa used a
substance containing fluoroacetic
acid from the gifblaar plant to poison
the tips of their arrows.
© 2013 Pearson Education, Inc.
Chapter 22
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Heavy Metal Poisons
Many metals are toxic. Heavy
metals with densities at least five
times greater than water are
especially so.
Most heavy metals display their
toxicity by reacting with sulfhydryl
groups (-SH), which can
deactivate enzymes.
© 2013 Pearson Education, Inc.
Chapter 22
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Heavy Metal Poisons
Mercury
Mercury is used in many places. Many people
have dental amalgams containing mercury. It is
used in thermostatic switches in homes and
some thermometers. It is used as fungicide on
seeds. Mercury vapor is toxic when inhaled. The
body converts the mercury to Hg2+.
© 2013 Pearson Education, Inc.
Chapter 22
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Heavy Metal Poisons
Lead
Lead too has many uses and is found in the
environment. It was once widely used in
household paints and in gasoline. Lead can
cause brain, liver, and kidney damage.
Treatment for lead and mercury poisoning can
involve the use of chelating agents.
© 2013 Pearson Education, Inc.
Chapter 22
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Heavy Metal Poisons
Cadmium
Cadmium is used in alloys, electronics, and
rechargeable batteries. Cd2+ ions lead to the
loss of Ca2+ ions in bones. They also cause
severe abdominal pain, vomiting, and diarrhea.
© 2013 Pearson Education, Inc.
Chapter 22
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Heavy Metal Poisons
Arsenic Poisoning
Although arsenic is not a metal, it exhibits some
metallic properties. Arsenic is toxic because it
inactivates enzymes by binding with sulfhydryl
groups.
© 2013 Pearson Education, Inc.
Chapter 22
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More Chemistry of the Nervous
System
Acetylcholine (ACh) is a neurotransmitter. ACh
carries a nerve impulse across a synapse. It is
then hydrolyzed to acetic acid and choline by the
enzyme acetylcholinesterase. The receptor
releases these products, which are then
converted back to ACh by other enzymes.
© 2013 Pearson Education, Inc.
Chapter 22
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More Chemistry of the Nervous
System
Nerve Poisons and the ACh Cycle
The following nerve poisons affect the ACh cycle:
Botulin is a powerful ACh antagonist. It blocks
the synthesis of ACh.
Curare, atropine, and some local anesthetics act
by blocking receptor sites.
Anticholinesterase poisons inhibit the enzyme
cholinesterase.
© 2013 Pearson Education, Inc.
Chapter 22
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More Chemistry of the Nervous
System
Organophosphorus
insecticides inhibit
the enzyme
acetylcholinesterase.
ACh builds up,
causing
overstimulation of
muscles, glands, and
organs.
© 2013 Pearson Education, Inc.
Chapter 22
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More Chemistry of the Nervous
System
Research on
organophosphorus
insecticides has
allowed for the
development of
powerful chemical
warfare nerve
poisons, such as
tabun, sarin, and
soman.
© 2013 Pearson Education, Inc.
Chapter 22
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The Lethal Dose
The toxicity of substances is often quantified by
the LD50. LD50 stands for a lethal dose for 50%
of the exposed population.
© 2013 Pearson Education, Inc.
Chapter 22
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The Liver as a Detox Facility
Through the use of enzymes, the liver is able to
detoxify many compounds through oxidation,
reduction, or coupling.
Highly toxic nicotine is detoxified by oxidation to
cotinine.
© 2013 Pearson Education, Inc.
Chapter 22
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Carcinogens
A carcinogen is a substance that causes the
growth of tumors. Tumors can be either benign
or malignant. Benign tumors grow slowly and
do not invade surrounding tissue. Malignant
tumors (cancers) grow rapidly and invade and
destroy neighboring tissue.
© 2013 Pearson Education, Inc.
Chapter 22
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Carcinogens
What Causes Cancer?
The U.S. Occupational Safety and Health
Administration (OSHA) has a National
Toxicology Program (NTP). NTP lists two
categories of carcinogens: known human
carcinogens and reasonably anticipated to
be human carcinogens. The latter compounds
are structurally similar to known carcinogens.
The vast majority of carcinogens are naturally
occurring substances.
© 2013 Pearson Education, Inc.
Chapter 22
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Chemical Carcinogens
What Causes Cancer?
© 2013 Pearson Education, Inc.
Chapter 22
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Carcinogens
How Do Cancers Develop?
Genetics plays a role.
Some carcinogens modify DNA, scrambling the
code for replication and protein synthesis.
Oncogenes seem to cause certain normal cells
to become cancerous cells.
Suppressor genes prevent the development of
cancers.
© 2013 Pearson Education, Inc.
Chapter 22
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Carcinogens
Chemical Carcinogens
A variety of natural and synthetic chemical
substances are carcinogenic, including polycyclic
aromatic compounds, aromatic amines,
nitrosoamines, vinyl chlorides, heterocyclic
compounds, and epoxides.
© 2013 Pearson Education, Inc.
Chapter 22
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Carcinogens
Anticarcinogens
Some substances in our food appear to act as
anticarcinogens including the food additive
butylated hydroxytoluene (BHT) and antioxidant
vitamins A, C, and E. Diets rich in cruciferous
vegetables (cabbage, broccoli, Brussels sprouts,
kale, and cauliflower) have been shown to
reduce the risk of cancer.
© 2013 Pearson Education, Inc.
Chapter 22
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Three Ways to Test for
Carcinogens
The Ames test assumes
that most carcinogens are
also mutagens. It uses a
special strain of bacteria
that requires histidine. The
bacteria are incubated in a
medium with the suspected
carcinogen and without
histidine. If they mutate and
grow, the substance is likely
a carcinogen.
© 2013 Pearson Education, Inc.
Chapter 22
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Three Ways to Test for
Carcinogens
Animal testing
Suspected carcinogens can be tested on animal
populations such as rats or mice. Such tests are
expensive, and there may not be a strong
correlation to humans.
© 2013 Pearson Education, Inc.
Chapter 22
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Three Ways to Test for
Carcinogens
Epidemiological Studies
Epidemiological studies involve studying a
population of humans that show more than a
normal rate of cancer. The population is studied
to see if there are common factors that could
lead to cancers. Epidemiological studies have
concluded that cigarette smoking, asbestos
exposure, and exposure to vinyl chloride cause
cancer.
© 2013 Pearson Education, Inc.
Chapter 22
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Birth Defects: Teratogens
Teratogens are substances that cause birth
defects. Epidemiological studies have shown
that a number of substances are teratogens,
including thalidomide, isotretinoin (Accutane®
and anti-acne medication), and ethyl alcohol.
Ethyl alcohol is by far the most hazardous
teratogen in terms of the number of children
affected.
© 2013 Pearson Education, Inc.
Chapter 22
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Hazardous Wastes
Hazardous wastes are substances that cause or
contribute to death or illness or environmental damage
when improperly managed.
© 2013 Pearson Education, Inc.
Chapter 22
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Hazardous Wastes
Hazardous wastes can be divided into four
categories:
1.Reactive wastes
2.Flammable wastes
3.Toxic wastes
4.Corrosive wastes
© 2013 Pearson Education, Inc.
Chapter 22
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Hazardous Wastes
Hazardous wastes can be dealt with by
recycling, treatments to render them less
hazardous, incineration, or storage in a landfill.
© 2013 Pearson Education, Inc.
Chapter 22
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What Price Poisons?
The use of any substance includes potential
risks and benefits. Generally, it is the misuse of
chemical substances that leads to tragedy.
© 2013 Pearson Education, Inc.
Chapter 22
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