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Food Toxicology -TOX30306 > Week 1 - Risk assessment 1 + 2 > Flashcards

Week 1 - Risk assessment 1 + 2 Flashcards

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1
Q

What is the definition of a risk ?

A

It is the probability that an adverse effect will occur. So the Risk = Hazard + Exposure

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2
Q

What is the definition of a hazard ?

A

It is the potential danger of a compound or a process

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3
Q

T or F : hazard only becomes a risk at a certain exposure

A

True. Risk = hazard + exposure

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4
Q

In which step of the risk assessement would you get a dose response curve of your compound

A

in the hazard characterisation

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5
Q

What is the first step of the risk assessment of a compound ?

A

to know if the compound is genotoxic or not

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6
Q

What are the in vitro genotoxicity testings seen in class ?

A

1- Bacterial / and or mammalian cell mutation tests (Ames test or Tk-assay)

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7
Q

What are the in vivo genotoxicity testings seen in class ?

A

1- Mammalian erythrocyte or bone marrow micronucleus test 2- Transgenic rodent somatic and germ cell gene mutation assays 3- in vivo comet assay

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8
Q

T or F : when the genotoxicity test are positive in vitro, you will do in vivo testings but if you have a negative in vitro you don’t need the in vivo from the regulatory affairs.

A

True

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9
Q

What is the Ames test ?

A

Test done with Salmnoella typhimurium in which the bacteria can’t biosynthesize histidin unless there is a reversion of the mutation.

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10
Q

T or F : there is a high correlation with a positive Ames test and carcinogenicity

A

true, there is a 22-95% correlation depending on the class of compounds.

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11
Q

What is the mouse lymphoma thymidine kinase (tk) assay

A

it is an assay to know the genotoxicity of a compound in which the cell lines are Tk+/- and mutations make them Tk-/- and enable them to grow in the presence of the toxic thymidine analogue (trifluorothymidine).

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12
Q

What is the advantag of the mouse lymphoma thymidine kinase assay

A

you can know where is the mutation depending on the colonies that have grown.

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13
Q

in the Tk assay, small colonies will form due to ___ dammage

A

chromosomal dammage

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14
Q

in the Tk assay, large colonies will form due to ___ dammage

A

point mutations

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15
Q

What is the micronucleus assay ?

A

It is an assay that quantify the chromosomal damage by the formation of small nucleus in daugther cells

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16
Q

The micronucleus assay will give information on the ___ dammage

A

chromosomal

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17
Q

T or F : the comet assay is an assay done in vitro

A

false, it is done both in vivo and in vitro

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18
Q

What is the process behind the comet assay ?

A

the compound will create some dammage in the DNA and form smaller strand that will migrate faster during electrophoresis (stained with fluorescence). Longer the tail (head) of the comet an the more DNA dammage.

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19
Q

What is the general flow chart of in vitro test for the genotoxicity

A

if both or only one of the Ames (bacterial reverse mutation assay) and in vitro assay of micronucleus test are positive : in vivo follow up
if they are both negative: no further test needed
If negative or inconclusive : further in vitro test

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20
Q

T or F : a safe level of exposure (threshold) can only be defined for non-genotoxic compound

A

true

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21
Q

Why can’t a threshold be established for genotoxoci compounds ?

A

because every molecule raise the risk of cancer

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22
Q

What is the next step of the risk assessment for non-genotoxic compounds ?

A

define the target organ, which is the most sensitive organ which is often the liver

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23
Q

T or F : the NOAEL protects the most sensitive individuals

A

true

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24
Q

What does NOAEL stands for ?

A

no observed adverse effect level

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25
Q

Exam : what is the definition of the NOAEL ?

A

the NOAEL : the concentration at which there is no response/effect on the most sensitive organ. helps define the safe level of exposure for humans.

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26
Q

EXAM : What is the LOAEL ?

A

the lowest concentration at which there is an adverse or toxic effect observed.

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27
Q

From the in vivo dose response relationship, we can get the ___ and the ___

A

The NOAEL and the LOAEL

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28
Q

What are the reasons that the dose response relationship is important for the risk assessment of a compound?

A
  1. you can get the NOAEL and LOAEL of the compound
  2. shows a causality of the chemical, that the observed effects are due to the chemical
  3. The slope give info on the rate at which the adverse effect builds up.
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29
Q

What does ADI stands for ?

A

Acceptable daily intake

30
Q

What does TDI stands for ?

A

tolerable daily intake

31
Q

For unavoidable contaminants, we use the ___ and for avoidable we use the ___

A

Unavoidable : TDI

avoidable : ADI

32
Q

What is the matematical formula of the ADI or TDI

A

TDI / ADI = NOAEL * UF of interspecie of /100 * UF of intraspecie of 1/100 * other UF (for the quality of the data and the type of exposure)

33
Q

What is the MPL ?

A

Maximum permitted use level. It is the maximum amount the industry can put inside a product depending on the mean intake of that product. For example, the cyclamate MPL was reduced when studies showed that children were drinking more than expected, reaching the ADI

34
Q

What are the disadvantages of using the NOAEL to assess the risk of a compound?

A
  1. NOAEL value depends on the sample size, more animals generally results in lower NOAEL so good experimental designs are penalized.
  2. NOAEL depends on the dose given to the animals
  3. NOAEL differs accross the studies
  4. Only one data point is used
35
Q

What is the BMD approach

A

it is an approach that corresponds to the statistical lower confidence limit of the dose corresponding to a small increase in effect over the background level

36
Q

What is the BMDL ?

A

Lower confidence limit of the BMD

37
Q

What is the BMD ?

A

Bench mark dose cuasing the BMR

38
Q

What is the BMR ?

A

Benchmark response pe 5% or 10% effect over background level

39
Q

What are the advantages of using the bench mark dose approach instead of the NOAEL ?

A
  1. Not dependent on the set-up of experiment
  2. Making use of all the toxicity data
  3. BMDL10 has the same level of protection than the NOAEL
  4. Same UF can be used
  5. More animals can be used / better experimental designs without being penalized
40
Q

T or F : BMDL has on average about same level of protection as NOAEL

A

true

41
Q

In the case of the BMD approach, bad study design results in ____ ADI

A

lower ADI because lower BMDL10 since more uncertainty in the data

42
Q

In the case of the NOAEL approach, bad study design results in ____ ADI

A

higher ADI and this is bad because it is less protective and it is because the NOAEL will be higher

43
Q

T or F : The BMDL is preferredover theNOAEL todefine

anADI or TDI

A

true

44
Q

For non-genotoxic compounds a safe level of exposure ___ and ___ can be defined

A

(ADI or TDI)

45
Q

What does ALARA stands for ?

A

As low as reasonably acheivable

46
Q

T or F : we can apply the ALARA for avoidable genotoxic carcinogens

A

false, there is a 0 tolerance for avoidable compounds, for the unavoidable chemical only we apply the ALARA concept

47
Q

What is the problem with the ALARA

A

That the analytical tech becomes more sensitive

48
Q

What does TTC stands for

A

Threshold of toxicological concern

49
Q

What does VSD stands for ?

A

virtual safe dose, it is the dose that is defined to have an acceptable cancer risk

50
Q

What is the VSD ?

A

it is the virtual safe dose ; a dose that would give an acceptable risk set at 1 in a million probability of getting cancer upon life exposure

51
Q

What is the TTC ?

A

it is the threshold of toxicological concern, it is used for compounds that we use only a low level with negligible risk like food flavours that we do not know the toxicity and it is used based on the knowledge of the chemical strucutre.

52
Q

How are the compounds classified in the TTC approach ?

A

classified with a software depending on the structure and they are classified in either 3 of the cramer classes

53
Q

What are the three cramer classes ?

A

Class 1 : TTC 1800 µg/d since low oral toxicity
Class 2 : TTC of 540 µg/d since intermidiate toxicity
Class 3 : TTC 90 µg/d no presumption on safety or toxicity

54
Q

T or F: the TTC is based on the NOEL

A

true, the noel based on he fifth percentile is taken. For example the noel in class one is 3 and 95% of the compounds in that class have a noel higher than this

55
Q

T or F : class III of the cramer class have the highest TTC

A

false, it is class I since for class III there is no presumption on the safety

56
Q

T or F : the TTC can be applied to genotoxic / carcinogenic compounds

A

true, but not for high potency carcinogens like N-nitroso, aflatoxin like and azoxy-compounds

57
Q

What is the TTC for genotoxic / carcinogenic compounds ?

A

0.15 µg / person / day

58
Q

How does the VSD is calculated ?

A

calculated with the linear extrapolation from the experimental data of the TD50 (dose that give 50% incidence of tumors) and 0 risk at 0 dose.

59
Q

What are the drawbacks of using the VSD for carcinogenic compounds

A
  1. Linear extrapolation can be wrong
  2. Outcomes is very uncertain, giving a false sense of accuracy
  3. Taken from rat and so species diff. is not taken into account
  4. Chances of misuse and misinterpretation
60
Q

What is used by EFSA instead of the VSD ?

A

the MOE

61
Q

What is the MOE used for ?

A

used to set the priorities of a compound and if it is of concern

62
Q

T or F : based on the VSD approach, acrylamide was considered safe and based on the MOE it is concidered unsafe by EFSA

A

false, the data used for VSD showed that the risk of tumors was higher than 1 in a million (500 in a million) and so this is higher than the VSD and so actions should be taken (judge unsafe).

63
Q

T or F : MOE is a quantative risk assessement

A

false, it only gives a number that gives a priority for the compound

64
Q

what is the BMDL10 ?

A

Statistical lower confidence limit of the dose giving a 10% increase in effect over background level

65
Q

MOE >10,000 is ____

A

low priority, low concern, low health risk

66
Q

why is the factor 10 000 used in the MOE

A

100 10 and 10 for interspecies and intraspecie differences
10 : for the uncertainty of carcinogenicity
10 : for the BMDL10

67
Q

MOE < 10 000 of concern; ___

A

priority for risk management , high concern

68
Q

what is the mechanism of action of aflatoxin?

A

mutation on the p53 tumor suppressor gene which gives liver cancer

69
Q

For genotoxic carcinogens a safe level of exposure can be defined

A

T or F : True

70
Q
A

Food Toxicology -TOX30306 (9 decks)

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