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Toxicology > Principles of Toxicology > Flashcards

Principles of Toxicology Flashcards

1
Q

What do many chemicals require to be harmful

A

access to the internal environment

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2
Q

what are the main routes of toxicant entry into the body?(3)

A

GI tract, respiratory and skin

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3
Q

example of two biological targets

A

enzymes and transport proteins

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4
Q

what does carbon monoxide bind with high affinity to

A

haemoglobin

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5
Q

where is paraquat concentrated

A

in its target cells within the lung

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6
Q

what is TD50

A

the median toxic dose or concentration

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7
Q

what is LD50

A

the median lethal dose or concentration

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8
Q

what does NOAEL stand for

A

no-observed-adverse-effect level

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9
Q

what are quantal responses?

A

all-or-none, they have two outcomes

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10
Q

can you define a threshold dose or concentration below which there is no detectable biological response?

A

yes

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11
Q

what is used in the risk assessment of chemicals

A

threshold of toxicological concern

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12
Q

what is the threshold of toxicological concern

A

a level of exposure to chemicals below which there would be negligible risk to human health

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13
Q

how can NOAEL be used to determine the reference dose/exposure

A

divided by 100

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14
Q

what aids the determination of NOAEL

A

exposure-response studies

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15
Q

what are the starting points for hazard recognition

A

data from in silico and in vitro studies

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16
Q

what is the EU regulatory framework for chemicals known as

A

REACH

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17
Q

what does REACH stand for

A

registration, evaluation and authorisation of chemicals

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18
Q

what does REACH aim to do?

A

identify properties and hazards of chemicals before they harm people

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19
Q

what are reference doses

A

estimates of the daily exposure to an agent that is assumed to not cause adverse effects on human health

20
Q

how do you work out the reference dose

A

NOAEL/ safety factor

21
Q

what may reference doses be used to estimate

A

threshold of toxicological concern

22
Q

what shape are hormetic exposure-response curves

A

U or J

23
Q

are hormetic exposure-response curves biphasic?

A

yes

24
Q

what may be experienced at high levels of exposure in hormetic curves

A

negative effects

25
Q

what does biphasic mean

A

having two phases

26
Q

define hormesis

A

biphasic dose response to an environmental agent characterised by low dose stimulation and high dose inhibitory effect

27
Q

what is an example of hormesis

A

effect of alcoholic beverages

28
Q

what must be considered in risk analysis

A

socio-economic benefits

29
Q

can absolute safety ever be guarenteed

A

no

30
Q

how is risk sometimes expressed

A

hazard x exposure

31
Q

what are the three routes of entry

A

ingestion through GI
inhalation and absorption through lungs
tropical and absorption through skin

32
Q

define bioavailability

A

the proportion of a drug or other substance which enters the circulation when introduced into the body and so is able to have an active effect

33
Q

if a chemical is poisonous at point of contact it is known to be

A

corrosive

34
Q

what makes a substance a toxicological concern

A

if it is highly lipid soluble and if exposure to that substance is significant

35
Q

what two factors for diffusion in the gut, small intestine and lungs

A

transcellular and lipid soluble

36
Q

what occurs if the toxicant reaches the target, 4 things

A
  1. disruption of homeostasis
  2. cell death
  3. organ/tissue dysfunction
  4. irreversible changes to DNA/chromosomes
37
Q

what happens to try and stop the effects when a toxicant reaches its target

A

stress activated protein kinases

38
Q

what is the down side of stress activated protein kinases that respond to toxicant reaching its target

A

there is only a limited ability of stress response

39
Q

define hazard

A

the potential to cause harm

40
Q

define risk

A

the probability that harm will occur

41
Q

why is risk of toxic exposure high for us

A

because we do not know enough about chemicals

42
Q

what is a graded response

A

a response that has varying degrees of damage

43
Q

when was REACH introduced

A

2007

44
Q

what is the Ames test

A

test to determine the mutagenic activity of chemicals

45
Q

what are the shapes of most log-dose curves

A

sigmoidal

46
Q

where in a sigmoidal curve is the NOAEL taken from

A

threshold region

Toxicology (9 decks)

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