Lecture 14 Pesticide Hazards

Define Pesticide

any substance used to control pests

Define Toxicity

capacity to cause injury to a living system

Define Hazard

the potential for injury from the use of a pesticide

Toxicity vs Hazard

Toxicity → the capacity the cause injury → “how poisonous”

Hazard → the risk or potential for injury

Toxicity represents the kind & extent of what?

damage that can be done by a chemical

Hazard is always based on what?

its ability to harm and the ease which a person comes into contact

What is the most important factor the effect of a pesticide is dependent on?

Dose-Time Relationship

Define the Dose-Time Relationship

Dose → quantity of a substance it is exposed to

Time → how often the exposure occurs

What is this describing:

How much of the substance is involved and how often the exposure occurs

Dose-Time Relationship

What does the Dose-Time Relationship determine?

acute and chronic toxicity

Define Acute Toxicity

how poisonous a pesticide is after a single short-term exposure

Define Chronic Toxicity

the delayed poisonous effects from exposure to a substance

Describe High Acute Toxicity

deadly even when a very small amount is absorbed

These are used as a way to assess and compare how poisonous pesticides are

Acute Toxicity Levels

These are used as the basis for label warning statements

Acute Toxicity Levels

What are the 3 ways Acute Toxicity Levels may be measured as?

1. Acute Oral Toxicity

2. Acute Dermal Toxicity

3. Acute Inhalation Toxicity

How is Chronic Toxicity measured?

in experimental conditions after 3 months of either continuous or occasional exposure

True or False:

A material that has high acute toxicity does not necessarily have high chronic toxicity

True

True or False:

A material that has high acute toxicity has high chronic toxicity

False

True or False:

A chemical with low acute toxicity does not necessarily have low chronic toxicity

True

True or False:

A chemical with low acute toxicity has low chronic toxicity

False

Describe:

Hazard = Toxicity x Exposure

the risk of harm from pesticide exposure =

how poisonous the pesticide is (x) route and amount of exposure to the pesticide

What are the 2 types of Pesticide Exposure?

Acute and Chronic

Define Acute Exposure

one-time contact with a pesticide

Define Chronic Exposure

repeated contact with a pesticide

The potential for chronic effect is related to what?

the level and frequency of exposure

What are the 4 Routes of Pesticide Bodily Entry?

1. Dermal

2. Inhalation

3. Eye

4. Oral

Which types of pesticides can be absorbed through the skin?

1. Wet

2. Dry

3. Gaseous

This exposure occurs while mixing or applying, or if pesticide-contaminated clothing is not removed promptly and properly cleaned before being worn again

Dermal Exposure

Which types of pesticides can be drawn into your lungs as you breath?

1. Dusts

2. Spray Mists

3. Fumes

This type of exposure occurs during the mixing of wettable powders, dusts, or granules

Inhalation Exposure

This type of exposure occurs while fumigating or spraying without a:

→ self-contained breathing apparatus

→ proper respirator

in enclosed or poorly ventilated areas

Inhalation Exposure

Inhalation Exposure:

The largest particles that are inhaled stay where?

on the surface of the throat and nasal passages, and do not enter the lungs

Inhalation Exposure:

What is the difference between small and large particles?

Smaller particles can be inhaled directly into the lungs.

Larger particles do not enter the lungs.

This type of exposure occurs when hands are not properly washed before eating or smoking

Oral Exposure

Ingested materials can be absorbed where? What is the major absorption site?

anywhere along the GI tract; small intestine

What are the 6 individual qualities in people that can influence toxicity?

1. Health Conditions

2. Health Behaviors

3. Body Size

4. Age

5. Gender/Sex

6. Environment

Define Local Effects

take place at the site of contact with a material

Define Systemic Effects

take place away from the original point of contact

Define Immediate Toxic Effects

experienced upon or shortly after exposure

Define Delayed Toxic Effects

occur after some time has passed

Define Reversible Effects

not permanent and can be changed or remedied

4 examples of Reversible Effects

1. Dizziness

2. Eye Irritation

3. Nausea

4. Skin Rash

Define Irreversible Effects

permanent and cannot be changed once they have occured

4 examples of Irreversible Effects

1. Birth Defects

2. Cancer

3. Mutations

4. Nervous System Injuries

Define Additive

combined effect of two pesticides = the sum of each

→ 2 + 2 = 4

Define Antagonisitic

combined effect of pesticides = less than what would be predicted

→ 2 + 2 = 3

Define Synergistic

combined toxic effect of two pesticides = much greater than the sum of each

→ 2 + 2 = 5

7 effects of exposure to pesticides

1. Mutagenic

2. Immunosuppression

3. Carcinogenic

4. Reproductive

5. Oncogenic

6. Neurotoxicity

7. Teratogenic

Because you can’t use people to measure toxicity, what is used instead?

animal testing → rats, rabbits, mice, guinea pigs, dogs

Define NOEL

No Observable Effect Level

→ at the stated dose, no effects were observed in test animals

How do scientists figure out how acutely toxic a pesticide is?

they give lab animals short-term exposure to doses

Define LD₅₀

the amount of pesticide that has killed ½ of the animals in a lab test

For example, an acute oral LD₅₀ indicates what?

the amount of pesticide swallowed has killed ½ of the animals tested

Smaller the LD₅₀ value =

less chemical required to kill ½ of the test animals + pesticide is more poisonous

A pesticide with a dermal LD₅₀ of 25 is more / less poisonous than a pesticide with a dermal LD₅₀ of 2000

more poisonous

LD_50’s for different chemicals can only be compared if?

the same test animal was used

Pesticide LD₅₀ are measured in units of weight called?

milligrams per kilogram (mg/kg)

Define LD₅₀ in terms of weight

the number of mg of pesticide needed to kill ½ of the test animals for each kg of body weight

Another way of expressing how much pesticide is involved in toxic doses is referred to as?

PPM

Define PPM

for every million parts of a solution, there is one part of the substance being measured

Define LC₅₀

the concentration of a pesticide in air or water that kills 50% of the test animals.

The lower the LC₅₀ value =

the more poisonous the pesticide is

How is LC₅₀ measured?

mg/L or PPM

How is Chronic Toxicity measured?

there is no standard measure like LD₅₀ for chronic toxicity studies

What are Toxicity Categories based on?

the acute oral, dermal, and inhalation toxicities, as well as eye and skin irritation effects of each pesticide

What must appear on every product label so pesticide users are alerted to the pesticide’s acute toxicity

Signal Word

Based on the LD₅₀ and the results of other acute tests, each pesticide is classified how?

into a toxicity category and given an associated signal word

True or False:

A pesticide is categorized by its lowest level of toxicity

False

True or False:

A pesticide is categorized by its highest level of toxicity

True

True or False:

Highly Concentrated Formulation = More Hazardous

True

True or False:

Low Concentrated Formulation = More Hazardous

False

Categories of Acute Toxicity:

Category I + Signal Word

Highly Toxic + DANGER

Categories of Acute Toxicity:

Category II + Signal Word

Moderately Toxic + WARNING

Categories of Acute Toxicity:

Category III + Signal Word

Slightly Toxic + CAUTION

Categories of Acute Toxicity:

Category IV + Signal Word

Relatively Nontoxic + CAUTION