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Chemicals and Disease
• Three major types of
toxic agents:
• Mutagens:
–Chemicals or radiation
that produces
mutations in DNA
• Teratogens
–Chemicals, radiation, or
viruses that cause birth
defects during pregnancy
• Carcinogens
–Chemicals, radiation, or
viruses that cause or
promote cancerous cells.
–Environmental and
lifestyle factors account for
up to 80% of all cancers
• Long term exposure to
various toxic chemicals
in the environment can
disrupt the body’s
immune, nervous, and
endocrine systems
–Immune system: cells and
tissues that protect the body
against disease
–Nervous system: brain,
spinal cord, and peripheral
–Endocrine system: releases
hormones into bloodstream
•Hormone disrupters:
chemicals similar to
estrogens (female
•Hormone blockers:
chemicals that prevent
natural (male) hormones
from working correctly
–“Gender benders”
• Thyroid disrupters: affect
growth and weight, may cause
behavioral disorders.
Toxicology and Human Health
• Toxicity: a measure of how
harmful a substance is.
• Depends on:
–Dose: the amount of a
substance ingested, inhaled,
or absorbed through the skin
–Frequency of exposure
–Age/body size
–Body detox
–Genetic make-up
• Harm caused by a toxin
depends on:
•Water: water supply
•Oil/fat: penetrate cell
–Persistence: resistance to
–Bioaccumulation: toxin
absorbed and stored in
organs, muscles, and/or
–Biomagnification: levels of a
toxin are magnified as they
pass through/up food chains
• Response: they type/amount
of health damage
–Acute: immediate
–Chronic: long lasting
Chapter 23
• The IDEAL pesticide would:
–Kill ONLY the target species
• (Harm NO other species)
–Breakdown easily
• (No persistence)
–NOT cause genetic resistance in
target species
The 2 Major Categories:
• Broad Spectrum: kills target
and non-target species (kills
• Narrow Spectrum: (selective)
kills specific group of pests
Specific Categories
• Insecticides
–Chlorinated hydrocarbons
• DDT – banned in 1972
• HIGH persistance
• Herbicides
–Contact (atrazine)
–Soil Sterilants
–AGENT ORANGE: used in the
Vietnam war – cause birth
defects in animals and humans
as well as cancer
• Fungicides
• Fumigants (spays)
–(Carbon tetrachloride: CCl4)
• HIGH persistance…
• Rodenticides
• Nematocides
• Persistent Organic Pollutants:
man-made chemicals that do
NOT break down
–Pesticides (DDT)
–Industrial chemicals
–By-products & contaminants
• Although some pesticides
such as DDT are banned in
the U.S. – companies can still
manufacture and export them
to other countries…
–Note: the U.S. stopped
manufacturing DDT in 1985
• Genetic resistance
–Remember: insects are rstrategists so they reproduce
–Remember: anti-biotic
resistant bacteria… SAME
–Pesticide Treadmill: when
“farmers” increase the
amount of pesticide sprayed
on their crops due to
increased genetic resistance
• Greater amounts have been
shown to be ineffective…
• Broad Spectrum pesticides kill
NON-TARGET species:
natural predators and
parasites that HELP maintain
populations of pest species
–Wiping out natural predators
can unleash new pests whose
populations had previously held
in check
–Pesticides are also killing honey
bees which are a keystone
species because of the vital job
of pollination
• Some pesticides
bioaccumulate leading to
disastrous problems for higher
organisms (biomagnification!)
• Human Health Affects…
–Nervous disorders
–Reproductive disorders
–Immune system disorders
–Birth defects
Pesticide Benefits
• Combat insect-borne diseases
• Increases food supplies
• Lowers food costs (?)
• Faster/Efficient
• Department of Health and
Human Services: FDA
• Pesticide regulations: HANDOUT!!
Reductions in Pesticide Use
• IPM: Integrated Pest
–Goal: NOT to eradicate pest
populations, but to reduce crop
damage at an economically
tolerable level…
–Uses cultivation, biological, and
chemical methods as part of an
overall program.
–Need experts
–Initial costs are higher
–Hindered by subsidies
“Alternative” Methods of
Controlling Pests
• Cultivation Practices:
–Crop rotation
–Intercropping, polyculture,
polyvarietal practices
–Adjust planting times
• Biological pest control:
–Provide habitats for pests’
natural enemies (spiders’ huts
in China)
• Spiders kill more insects than
insecticides do!!!
–Import natural predators (also
bacteria, viruses, parasites)
• Insect birth control
• Sterilize the males
• Lure pests away using
• Disrupt life cycles using
• Hot water
• Organic methods:
–Soap spray
–Tobacco spray
–Alcohol spray
–Bt (Bacillus thurengienses)
–Pyrethrins (from chrysanthemum)
–Cayenne pepper
–Citrus oil
• Create GMO’s (Bt Corn)
• Irradiation