Notes Pesticides

Pests

Any organism that

interferes in some way

with human welfare or

activities

PESTICIDE

NOTES

PROTECTING FOOD RESOURCES:

PEST MANAGEMENT

• Organisms found in nature (such as spiders) control populations of most pest

species as part of the earth’s free ecological services

• We use chemicals to repel or kill pest organisms as plants have done for millions of years

• Chemists have developed hundreds of chemicals

(pesticides) that can kill or repel pests

▫ Pesticides vary in their persistence

▫ Each year > 250,000 people in the U.S. become ill from household pesticides

Classification of

Pesticides

Specific Types:

A toxic chemical that kills

_______.

Herbicides

Insecticides

Rodenticides

Fungicides

nematodes (roundworms)

Bactericides

Algaecides

Nematicides

Characteristics:

•Composed of compounds that retain their toxicity for long periods of time

•Biomagnification

▫Accumulate in fatty tissues and stay indefinitely

•Chlorinated hydrocarbons (DDT)

•Organophosphates (nerve gases)

•Carbamates

Hard/Persistent Pesticides

Characteristics:

•Don’t harm the environment or humans

•Soaps, oils, plant extracts, baking soda, etc.

Soft Pesticides

Benefits of

Disease Control

•

Save human lives

▫Prevent insect-transmitted diseases  _{Malaria (anapheles mosquito)}

 _{Bubonic plague (rat fleas)}  _{Typhus (body lice & fleas)}  _{Sleeping sickness (tsetse fly)}

•

Increase food supplies

•

Lower food costs

▫About 55% of the world’s food supply is lost to pests before (35%) and after (20%) harvest

• Control most pests quickly and at a reasonable cost

▫When genetic resistance occurs, farmers can use stronger doses or switch pesticides

• Have a long shelf life

• Easily shipped and applied • Safe when handled properly

• Using botanicals to develop pest-resistant crop strains

▫Very expensive to develop

 _{Only working on large-market crops (wheat, corn, soybeans)}

Efficient When Compared to Alternatives

Problems Associated with

Pesticide Usage

Impact on Non-Target Organisms

• Insects breed rapidly

• Within 5-10 years (sooner in tropics), immunity to pesticides can develop

• Cause farmers > $200 million/year in U.S. crop losses

• EX: Silver whitefly (cotton pest)

• Weeds and plant-disease organisms also become resistant • At least 17 insect pest species are resistant to all major

classes of insecticides

Superpests

Are pesti

cides an

d

monocul

tures

responsi

ble for

C

olony

C

ollapse

D

isorder a

nd

why doe

s CCD m

atter?

• USDA says only 2% of insecticides from aerial or ground spraying actually reaches the target pests

• Only 5% of herbicides applied to crops reaches the target weeds

Persistence

•

Stay in the environment for a very long time

▫EX: DDT

•

Increase in the concentration of a chemical in

specific organs or tissues at a level higher than

normal

•

Stored in body fat, passed to offspring

▫A concern to organisms _________ on the food chain

•

Pesticides run off into water

•

Pesticides stay on food

Bioaccumulation

Formation of New Pests

•

Minor pest can become major pests

▫EX: DDT was used to control insect pests on lemon

trees. This caused an outbreak of a scale insect (a sucking insect that attacks plants) that had originally not been a problem.

•

Children are at a greater risk than adults

▫W.H.O. estimates > 3 million people are poisoned by pesticides each year & about 220,000 die

 Short-term exposure to high levels of pesticides can result in harm to organs and even death

 _{National Cancer Institute—Long-term exposure to lower}

levels of pesticides can cause cancer lymphomas, leukemia, brain, lung, and testicular cancers

How Pesticides Function

•

Dosage required to kill one of the targeted organisms

•

Amount of pesticide it takes, in one dose, to kill ½ of

all the target organisms

LD-50 (Median Lethal Dose)

Threshold of Toxicity

•Some pesticides interfere by causing uncontrollable muscle twitching or paralysis

▫EX: Spectracide, Nicotine, DDT

•A lot of these where first used in WWII as nerve agents

•Some pesticides inhibit photosynthesis by preventing chlorophyll formation

•Vapors kill the pest by suffocating the animal

▫EX: Flea collars, pest strip, and soap

Nervous System

Photosynthesis

Smothering

Dehydration

•

Uses the fossilized remains of tiny, one-celled

organisms called diatoms to kills insects by scratching

their wax outer covering and causing them to

dehydrate

•

Often used with rats

The Ideal Pesticide

•

_{The ideal pest-killing chemical has these qualities:}

▫Kill only target pest

▫Doesn’t cause genetic resistance in the target organism

▫Disappears or breaks down into harmless chemicals after doing its job

Pesticides and the Law

The EPA

(US Environmental Protection

Agency)

& FDA

(US Food and Drug

Administration)

are responsible for the

Research

•

Pesticide companies must use 3 methods to

determine pesticides health threats:

▫Case Reports – (made to physicians) about people suffering from adverse health effects

▫Laboratory Investigations – (usually on animals) to determine toxicity, residence time, what parts of the body are affected and how the harm takes place

▫Epidemiology – (in populations of humans

exposed) used to find why some people get sick while others do not

Who is in charge of testing the pesticides?

The chemical

companies d

o their own r

esearch

and are only

required to ru

n certain test

s, but

what about th

ings like syne

Days to Harvest

• Set last day to spray crops before harvesting for human consumption

• Level of toxicity approved for human consumption

▫Federal Food, Drug, and Cosmetic Act (FFDCA)

 _{Est. 1938, revised in 1996}

• Federal Insecticide, Fungicide & Rodenticide Act (FIFRA)

• Est. 1947, revised in 1996

• Regulates pesticide label & requires registration

▫Food Quality Protection Act (FQPA)  Amends both FIFRA and FFDCA

Restrictions on Pesticide Levels

• Gave FDA rights to

oversee safety of food, drugs, and cosmetics

• Federal Environmental Pesticide Control Act (FEPCA)—1972

• Expanded EPA’s

authority to oversee the use and sale of pesticides

• Mandated the standards of pesticides & created incentives to make safer pesticides for kids

Label Requirements

• Brand name

• Ingredient statement

• Percentage or amount of active ingredient(s) by weight

• Net contents of the container

• Name and address of the manufacturer

• Registration and establishment numbers

• Signal words and symbols

• Precautionary statement

• Statement of practical treatment

• Environmental hazard statement

• Classification statement

• Directions for use

• _{Re-entry statement}

• Harvesting and/or grazing restrictions

•

Published her

Silent Spring

in 1962

▫Heightened public awareness and concern about the dangers of uncontrolled use of DDT and other pesticides

 _{“Pesticide sprays, dusts, and aerosols are now applied almost universally to}

farms, gardens, forests, and homes - non selective chemicals that have the power to kill every insect, the good and the bad, to still the song of birds and the leaping of fish in the streams, to coat the leaves with a deadly film and to linger on soil - all this though the intended target may be only a few weeds or insects. Can anyone believe it is possible to lay down such a barrage of poisons on the surface of the earth without making it unfit for life? They should not be called insecticides, but biocides.”

▫Helped lead to the establishment of NEPA (National Environmental Policy Act, 1970)

 The environmental Magna Carta

 _{Requires executive federal agencies prepare environmental impact}

statements and environmental assessments

Rachel Carson

The

DIRTY DOZEN— twelve persistent organic pollutants

Integrated Pest Management (IPM)

•

Definition: A limited use of pesticides along

with other practices

▫Cultivation, biological, and ecological alternatives  _{Crop-rotation (to prevent pest population build up)}  _{Selecting pest-resistant varieties}

 _{Planting pest-free rootstock with}

the grafted in crop

 _{Adjust planting times}

 _{Vacuum up harmful bugs}

 _{Provide homes for the pest enemies}

“Only when the last tree has died and the last river has been poisoned and the last fish has been caught, will we realize that we can not eat money.” –Cree Indian Prophecy

Both plants were exposed to caterpillars—one was

IPM Cont…

 _{Introduce disease organisms}

 _{Use pheromones to lure pests into traps}

 _{Synthesized bug sex attractant}

▫Attracts males away from ready to mate females ▫Captures insects in various traps

 _{Use hormones to disrupt life cycles}

 _{Males can be raised in the lab, sterilized by radiation or chemicals, and}

released into an infested area to mate unsuccessfully with fertile wild females

 _{Add natural repellents (EX: garlic, sulfur)}

 _{Microbials (bacterial disease sold in powder form for soil)}  _{Photodegradable plastics to keep weeds from sprouting}  _{Implant genetic resistance}

 _{Becoming a faster process due the development of}

Increasing efficiency of the enzyme Rubisco

will alter the rate of photosynthesis

TOXICOLOGY

NOTES

Risks or Hazards

•Risk is a measure of the likelihood that you will suffer harm

from a hazard

•We can suffer from:

▫Biological hazards: from more than 1,400 pathogens

 _{Not caused by living organisms, cannot spread from one} person to another (nontransmissible disease)

 _{EX: Asthma}

 _{Caused by living organisms such as bacteria and viruses can} spread from person to person (transmissible or infectious)

▫Chemical hazards: in air, water, soil, and food

▫Physical hazards: such as fire, earthquake, volcanic eruption…

▫Cultural hazards: such as smoking, poor diet, unsafe sex, drugs, unsafe working conditions, and poverty

Transmissible Disease

• WHO estimates the

world’s seven deadliest infections kill 13.6

million people/per year (mainly in developing countries)

• Ecological (or

conservation) medicine

is devoted to tracking down connections

between wildlife and humans to determine ways to slow and

prevent disease spread

Fix the environmen

t and you’ll fix human hea

Bacterial Diseases: TB

•The highly infectious tuberculosis (TB) kills 1.7 million people per year but #s may be on the rise

•Recent increases in TB are due to:

▫Lack of TB screening and control

programs especially in developing countries due to expenses

▫Genetic resistance to the most effective antibiotics

 _{72 cases in the US}  _{64,000 in India}  _{59,000 in China}

Viral Diseases

•Flu, HIV, and hepatitis B viruses infect and kill many more people each year then highly publicized West Nile and SARS (Severe Acute Respiratory Syndrome) viruses

•The influenza virus is the biggest killer virus worldwide

▫Mainly carried by pigs, chickens, ducks, and geese

▫Virus mutates and exchanges genetic material with other viruses as it moves from organism to organism

Viral Diseases: HIV

•

2

biggest killer virus worldwide

•

Five major priorities to slow the

spread of the disease are:

▫Quickly reduce the number of new infections to prevent further spread

▫Concentrate on groups in a society that are likely to spread the disease

▫Provide free HIV testing and pressure people to get tested

▫Implement educational programs

Protozoan Diseases: Malaria

•

Kills about 2 million people

per year

▫Probably has killed more than all of the wars ever fought

•

Spraying insides of homes with

low concentrations of the

pesticide DDT greatly reduces

the number of malaria cases

▫

Under international treaty

enacted in 2002, DDT is

being phased out in

developing countries

Chemical Hazards

•

A toxic chemical can cause temporary or permanent

harm or death

▫Mutagens are chemicals or forms of radiation that cause or increase the frequency of mutations in DNA

▫Teratogens are chemicals that cause harm or birth defects to a fetus or embryo

▫Carcinogens are chemicals or types of radiation that can cause or promote cancer

•

A hazardous chemical can harm humans or other

animals because it:

▫Is flammable or explosive

▫Is an irritant or induces allergic reactions

▫Interferes with oxygen uptake

Assessing the Damage

•

Factors determining the harm caused by exposure to

a chemical include:

▫The amount of exposure (dose)

▫The frequency of exposure

▫The person exposed

• Children are more susceptible to the effects of toxic substances because:

▫ Children breathe more air, drink more water, and eat more food per unit of body weight than adults.

▫ They put their fingers or other objects in their mouths.

▫ Children usually have less well-developed immune systems and detoxification processes than adults.

▫One’s genetic makeup

Case Study: A Black Day

in Bhopal, India

•

1984—World’s worst industrial

accident at a pesticide plant in

Bhopal, India

▫Union Carbide plant released a large quantity of highly toxic

methyl isocyanate (MIC) gas from an underground tank

▫15,000-22,000 people died

▫Indian officials claim simple

upgrades could have prevented the tragedy

Abandoned plant

Perceiving Risk

•

Most individuals evaluate the relative risk they

face based on:

▫Degree of control

▫Fear of unknown

▫Whether we voluntarily take the risk

▫Whether risk is catastrophic

Number of deaths per year in the world from various causes

(Deaths in terms of the number of fully loaded 400-passenger jumbo jets crashing every day of the year with no survivors)

Annual deaths in the U.S. from tobacco use and other causes in 2003

Shortens average life span in the U.S. by Hazard Poverty Born male Smoking Overweight (35%)

Unmarried _{5 years} Overweight (15%) 2 years

Spouse smoking _{1 year} Driving _{7 months} Air pollution 5 months

Alcohol _{5 months} Drug abuse 4 months Flu _{4 months} AIDS 3 months Drowning 1 month Pesticides 1 month Fire 1 month Natural radiation 8 days

Medical X rays 5 days Oral contraceptives 5 days Toxic waste 4 days

Flying 1 day Hurricanes, tornadoes 1 day Lifetime near nuclear plant 10 hours

6 years 6–10 years

7.5 years

7–10 years

Comparisons of risks people face expressed in terms