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mbbs 3: community health > Toxicology > Flashcards

Toxicology Flashcards

1
Q

What is toxicology?

A

The study of the negative effects of chemicals on living things

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2
Q

A chemical is considered toxic depending on?

A
  1. How much of it is necessary to cause harm
  2. How easily it can enter the body
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3
Q

What are the routes of exposure to toxins?

A

In order for a chemical to cause injury, it must enter the body
1. Inhalation
2. Ingestion
3. Absorption through the skin
4. Injection

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4
Q

What is distribution?

A

spread throughout the body

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5
Q

What is metabolism?

A

broken into smaller chemical compounds

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6
Q

What is storage?

A

kept in the body for a long time

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7
Q

What is excretion?

A

passed out through urine, faeces, exhaled air or sweat

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7
Q

Describe the effects of toxic chemicals?

A

disrupt the normal functions of the body
Effects can be:
1. Local - at the site of exposure
2. Systemic - affecting the entire body

target organs - organs or systems where symptoms of exposure appear

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8
Q

Describe the relationship between toxicity and dose?

A

Toxicity (poisonous nature) of any substance is Inversely related to the amount (dose) required to cause harm

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9
Q

What is high toxicity?

A

Substances which can cause harm following exposure to very small amounts

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10
Q

What is low toxicity?

A

Substances which require exposure to many grams before harm results

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11
Q

Describe the dose and toxicity of essential nutrients?

A

Even essential nutrients become toxic if the amount ingested is above a certain acceptable dose

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12
Q

What is Paracelsus’s fundamental rule of toxicology?

A

Only the dose required makes the difference between a cure and a poison

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13
Q

Describe the relationship between dose and response?

A

The reaction is dependent on the amount of the chemical received
- Some doses are so small they produce no response
- Once the maximum reaction has occurred, increasing the dose doesn’t change the reaction

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14
Q

Give examples of when dose determines whether a chemical will be beneficial or poisonouus?

A
  1. aspirin
    - beneficial = 300-1000 mg
    - toxic = 1000-3000 mg
  2. vitamin A
    - beneficial = 5000 units/day
    - toxic = 50,000 units/day
  3. oxygen
    - beneficial = 20% (air)
    - toxic = 50-80% (air)
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14
Q

What is an acute and chronic exposure?

A
  1. acute - sudden, brief
    - A bee sting
  2. chronic - repeated small doses over time
    - Smoking cigarettes for years
15
Q

What is acute toxicity?

A

Toxicity resulting from short exposure
- from a few minutes up to 96 hours

16
Q

What are acute and chronic effects?

A
  1. Acute - lasting hours
  2. Chronic - lasting a long time - possibly years
17
Q

What is chronic toxicity?

A

Long term exposure
- repeated or continuous for a period of more than 3 months
- may be a lifetime of about 70 years

18
Q

What is LD50 and LC50?

A

These terms derive from laboratory tests on animals
1. LD50 is the dose which when swallowed, injected, or applied directly, kills half the test subjects
2. LC50 is the concentration of a chemical in a test atmosphere that kills half the test subjects within one hour when inhaled

19
Q

Name 3 exposure limits?

A
  1. PEL
  2. STEL
  3. IDLH
20
Q

What is PEL?

A

permissible exposure limit
- airborne concentration enforced by OSHA

21
Q

What is STEL?

A

short-term exposure limit
-15 minutes four times a day, with l hour free of exposure between each 15 minute exposure

22
Q

What is IDLH?

A

immediately dangerous to life and health
- maximum airborne concentration which would not interfere with ability to escape

23
Q

Detoxification organs?

A
  1. kidney
    - urine
  2. liver
    - bile
  3. lung
    - expired air
24
Q

What is metabolism?

A

major mechanism for terminating the biological activity of chemicals
Note: the liver is the primary site of metabolism

25
Q

What is biotransformation?

A

occurs in the
Liver, kidney, lung, gastrointestinal tract

26
Q

What are the phases of poisoning?

A
  1. chemical exposure phase
  2. toxicokinetic phase
  3. toxicodynamic phase
27
Q

Describe water-soluble substances?

A
  • excreted from the body more easily than fat soluble substances
  • usually less toxic than fat soluble substance
  • Readily transported to the kidneys
    > excreted in the urine
28
Q

Describe fat soluble substances?

A
  1. DDT, DDE (the main natural decomposition product of DDT), or
  2. dioxin (TCDD),
    - Accumulate in the fatty (adipose) tissues of the body
    - accumulate to harmful levels even if daily exposure is low
    - Called persistent organic pollutants (POPs)
    - banned in many countries

mbbs 3: community health (28 decks)

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