Communicating uncertainty - Illustrated by the new approach for risk assessment (Margin of Exposure)

Transcription

1 FAO RAP, Bangkok, Thailand TECHNICAL TRAINING ON RISK ANALYSIS FOR SAARC COUNTRIES Delhi, India, June 17-21, 2013 Quality Council of India Communicating uncertainty - Illustrated by the new approach for risk assessment (Margin of Exposure) John LUM Scientific Officer Centre for Food Safety Hong Kong 1 1

2 Content Dose Response Assessment Health-based Guidance Values Margin of Exposure (MOE) Example of Risk Assessment using MOE Acrylamide 2

3 Dose-response Assessment (1) All substances are poisons; there is none which is not a poison. The right dose differentiates a poison and a remedy. Paracelsus, 1538 Aspirin taken for a headache: - one lick of a pill won t have desired effect - two pills should relieve pain - the entire packet could poison 3

4 Dose-response Assessment (2) The determination of the relationship between magnitude of exposure (dose) to an agent and the severity and/or frequency of the adverse health effects (response) By toxicological tests / experimental data To derive health-based guidance values 4

5 Response A typical dose-response curve NOAEL Dose 5

6 Dose-response Assessment (3) NOAEL (No-observed-adverse-effect level) Greatest concentration or amount of a substance, found by experiment or observation, that causes no adverse alteration of morphology, functional capacity, growth, development or lifespan of the target organism distinguishable from those observed in normal (control) organisms of the same species and strain under the same defined conditions of exposure 6

7 Dose-response Assessment (4) Uncertainties of NOAEL From animal to human Interspecies difference Difference among individuals in human population Genetics, genders, diseases status 7

8 Adapted from Andrew G Renwick, Pest Manag Sci 58:

9 Health-based Guidance Values (1) NOAEL Acceptable Daily Intake (ADI) Estimate of the amount of a substance in food and/or drinking water, expressed on a body weight basis that can be ingested daily over a lifetime WITHOUT appreciable health risk 9

10 Response Use of dose-response curve to derive ADI Toxic effect Test species 60 Average human Sensitive human 40 ADI 20 UF NOAEL Dose For average human to sensitive human For animal to average human 10

11 Health-based Guidance Values (2) In general, toxic effect is assumed to have a threshold A quantitative expression of exposure Deterministic values Exposure of substances below the health-based guidance value without appreciable health risk 11

12 Health-based Guidance Values (3) Additives, pesticide/veterinary drug residues Intentionally added Acceptable Daily Intake (ADI) Contaminants Tolerable Intakes Permissible levels of intake of contaminants unavoidably associated with the consumption of otherwise wholesome and nutritious food Provisional Maximum Tolerable Daily Intake (PMTDI) or Provisional Tolerable Weekly Intake (PTWI) 12

13 Health-based Guidance Values for Genotoxic Carcinogen? Genotoxic carcinogens Any level can potentially cause adverse effect No threshold for toxic effect health-based guidance values CAN NOT be set Alternative approach for risk assessment Margin of Exposure (MOE) approach: A qualitative description for a possible prioritisation of risks Base on the benchmark dose derived from dose response modelling E.g. acrylamide 13

14 Margin of exposure (MOE) (1) Benchmark dose (BMD) Dose corresponding to a specified change in effect over background, e.g. tumour formation Modelling based on sufficient experimental data Mathematical model is selected, based on the data that are being analysed and the characteristics of the response Databases with larger numbers of dose groups and a greater experimental complexity will be better suited for more complex models 14

15 Margin of exposure (MOE) (2) BMDL (Benchmark dose lower confidence limit) The lower confidence limit (lower bound 95% confidence limit) of a point on the dose-response curve that characterises adverse effect, to account for uncertainty in the data BMDL 5 or BMDL 10 - BMDL give rise to 5% or 10% of effect level The BMDL can NOT be regarded as a safety reference value when dietary exposure below the BMDL, it does not mean that there is no health risk 15

16 BMD & BMDL Adopted from Anne Constable and Susan Barlow - Application of the Margin of Exposure Approach to Compounds in Food which are both Genotoxic and Carcinogenic, ILSI 16

17 Margin of exposure (MOE) (4) = BMDL 10 / Estimated Dietary Exposure Provide an indication of the level of health concern without actually quantifying the risk The higher the MOE the lower the health concern Use for priority setting for risk management actions Genotoxic carcinogens: a MOE of 10,000 (based on a BMDL 10 from animal study) low public health concern 17

18 Example of RA using MOE - Acrylamide A food processing contaminant First reported by the Swedish researchers in 2002 High levels were formed in food during frying or baking An industrial chemical that has been used since the mid 1950s in the production of polyacrylamide Also a component of tobacco smoke 18

19 Formation of acrylamide in food Form where foods are cooked or processing in high temperature (usually > 120 o C), mainly via Maillard reactions HC COOH NH 2 O CH 2 C NH 2 asparagine Sugar * Other formation mechanisms, e.g pyrolysis of the wheat protein gluten may be of minor importance Only trace amounts can be formed by boiling * Glucose, fructose, decomposition products of sucrose and other sugars as well as other suitable intermediates (e.g. aldehydes) H 2 C 19 O CH C NH 2 acrylamide

20 Toxicity Toxic to the nervous system of both animals and human Reproductive and developmental effects in animals Genotoxic A multi-site carcinogen in rodents Group 2A agent (IARC) Probably carcinogenic to humans 20

21 BMDL for acrylamide JECFA (2010) BMDL 10 A 10% extra risk of tumours in animals For Harderian gland tumours in male mice: 0.18 mg/kg bw/day For mammary tumours in female rats: 0.31 mg/kg bw/day Epidemiological studies do not provide any consistent evidence that occupational exposure or dietary exposure to acrylamide is associated with cancer in humans 21

22 RA study on acrylamide in food in Hong Kong Study conducted in 2010 Determine the acrylamide levels in local food Estimate the dietary exposure of the local population 22

23 Dietary exposure estimation Dietary exposure ( g/kg bw /day) [MOE] Average High consumer 2010 study 0.13 [1385*] 0.69 [261*] (P97.5) MOE > 10,000 low concern Suggest that there is health concern among the local population because of the relatively low MOE values * MOEs were calculated based on the BMDL 10 for Harderian gland tumours in male mice (0.18 mg/kg bw/day) 23

24 Limitations Limited sample size Only focuses on foods which may have higher risk (in terms of the acrylamide level); Uncertainties in the exposure estimation Large variations between brands of the same product and between batches of the same brand, thus making direct comparison difficult 24

25 Advice to Public and Trade Public Do not over-heat food but ensure the food is cooked thoroughly Maintain a balanced diet i.e. eat more fruits and vegetables and to moderate the consumption of fried and fatty foods Trade To seek ways to reduce the level of acrylamide in food, while not compromising the safety and nutrition value of the products Make reference to the guidelines on reduction in acrylamide level to be published by CFS 25

26 26

27 MOE of various chemicals Malachite green 133,000 1,3-Dichloro-2-propanol 65,000 Polycyclic aromatic hydrocarbons Acrylamide ,000 Ethyl carbamate 19,000 10,

28 Conclusion RA based on Health-based Guidance Values Deterministic RA based on MOE A relative indication of the level of health concern without actually quantifying the risk 28

29 Conclusion (2) The MOE approach is both a prioritisation tool and a risk assessment tool, which gives a relative indication of the level of health concern without actually quantifying the risk In general, small MOEs indicate high concern, and large MOEs low concern The MOE should always be accompanied by a narrative to explain the background and the uncertainties in the reference point and exposure estimates 29

30 Conclusion (3) Uncertainty communication between risk assessors and risk managers communication between risk managers and consumers Risk Assessors moderate their certainty Risk Managers hoping for the most certain statements Consumers perceiving the risk as a function of non scientific criteria i.e. "outrage factors" Risk Analysis Risk Assessment * Science based Risk Management * Policy based Risk Communication * Interactive exchange of information and opinions concerning risks 30

31 Conclusion (4) Need for more formalisation in order to help risk managers in dealing with unknowns and uncertainties Systematic expression of types of uncertainty Transparency of the level of agreement among experts Characterization of the level of confidence of experts Need for improved communication to consumer Simple language Clear graphic representation Assess risk perception 31

32 Conclusion (5) Better communication tools on the concept of the MOE approach and resulting levels of concern need to be developed needs cooperation between risk assessors, risk managers and risk communicators consumer perceptions about these tools have not yet been addressed adequately 32

33 Reference Guidance for Risk Management Options in Light of Different Risk Assessment Outcomes Report of the Sixth Session of the Codex Committee on Contaminants in Foods Application of the Margin of Exposure (MOE) Approach to Substances in Food that are Genotoxic and Carcinogenic Food and Chemical Toxicology. Vol 48, Suppl. 1, Jan 2010 Application of the Margin of Exposure Approach to Compounds in Food which are both Genotoxic and Carcinogenic ILSI Europe Report Series Risk assessment Studies reports of the Centre for Food Safety 33

34 Thank you!