Principles of Toxicology

Question 1

What do many chemicals require to be harmful

Answer 1

access to the internal environment

Question 2

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

Answer 2

GI tract, respiratory and skin

Question 3

example of two biological targets

Answer 3

enzymes and transport proteins

Question 4

what does carbon monoxide bind with high affinity to

Answer 4

haemoglobin

Question 5

where is paraquat concentrated

Answer 5

in its target cells within the lung

Question 6

what is TD50

Answer 6

the median toxic dose or concentration

Question 7

what is LD50

Answer 7

the median lethal dose or concentration

Question 8

what does NOAEL stand for

Answer 8

no-observed-adverse-effect level

Question 9

what are quantal responses?

Answer 9

all-or-none, they have two outcomes

Question 10

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

Answer 10

yes

Question 11

what is used in the risk assessment of chemicals

Answer 11

threshold of toxicological concern

Question 12

what is the threshold of toxicological concern

Answer 12

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

Question 13

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

Answer 13

divided by 100

Question 14

what aids the determination of NOAEL

Answer 14

exposure-response studies

Question 15

what are the starting points for hazard recognition

Answer 15

data from in silico and in vitro studies

Question 16

what is the EU regulatory framework for chemicals known as

Answer 16

REACH

Question 17

what does REACH stand for

Answer 17

registration, evaluation and authorisation of chemicals

Question 18

what does REACH aim to do?

Answer 18

identify properties and hazards of chemicals before they harm people

Question 19

what are reference doses

Answer 19

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

Question 20

how do you work out the reference dose

Answer 20

NOAEL/ safety factor

Question 21

what may reference doses be used to estimate

Answer 21

threshold of toxicological concern

Question 22

what shape are hormetic exposure-response curves

Answer 22

U or J

Question 23

are hormetic exposure-response curves biphasic?

Answer 23

yes

Question 24

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

Answer 24

negative effects

Question 25

what does biphasic mean

Answer 25

having two phases

Question 26

define hormesis

Answer 26

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

Question 27

what is an example of hormesis

Answer 27

effect of alcoholic beverages

Question 28

what must be considered in risk analysis

Answer 28

socio-economic benefits

Question 29

can absolute safety ever be guarenteed

Answer 29

no

Question 30

how is risk sometimes expressed

Answer 30

hazard x exposure

Question 31

what are the three routes of entry

Answer 31

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

Question 32

define bioavailability

Answer 32

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

Question 33

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

Answer 33

corrosive

Question 34

what makes a substance a toxicological concern

Answer 34

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

Question 35

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

Answer 35

transcellular and lipid soluble

Question 36

what occurs if the toxicant reaches the target, 4 things

Answer 36

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

Question 37

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

Answer 37

stress activated protein kinases

Question 38

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

Answer 38

there is only a limited ability of stress response

Question 39

define hazard

Answer 39

the potential to cause harm

Question 40

define risk

Answer 40

the probability that harm will occur

Question 41

why is risk of toxic exposure high for us

Answer 41

because we do not know enough about chemicals

Question 42

what is a graded response

Answer 42

a response that has varying degrees of damage

Question 43

when was REACH introduced

Answer 43

2007

Question 44

what is the Ames test

Answer 44

test to determine the mutagenic activity of chemicals

Question 45

what are the shapes of most log-dose curves

Answer 45

sigmoidal

Question 46

where in a sigmoidal curve is the NOAEL taken from

Answer 46

threshold region