APPENDIX XVII: METHODOLOGY AND PRINCIPLES FOR EXPOSURE ASSESSMENT IN THE CODEX GENERAL STANDARD FOR CONTAMINANTS AND TOXINS IN FOODS

1. The methodology set out in this document is an elaboration of the principles for the establishment of Maximum Limits (MLs) for contaminants in food in Annex 1 of the GSC. This methodology enables MLs to be set for chemical contaminants in primary, unprocessed food commodities in international trade, but does not address the management of genotoxic chemicals for which no safe dose can be assigned and where even very low concentrations may present a health risk. In such cases, it may be helpful to develop specific quantitative risk assessments in order to assist appropriate risk management decisions. This paper also does not consider exposure from air or water when developing the MLs, as these sources are expected to make only minor contributions to the overall exposure for most consumers.

2. The exposure assessment comprises four steps with each step considering a number of criteria. Figure 1 illustrates the overall methodology.

• The first step considers whether the dietary exposure to a contaminant requires the development of MLs to protect public health. If elevated levels of a contaminant are possible, with the potential for high level consumers or vulnerable subgroups of the population to exceed the safe/tolerable dietary exposure level, then MLs may be required. If so, it then identifies foods for which limits should be set.
• The second step assesses the data available on concentrations of the contaminant occurring in these food commodities in order to propose draft MLs.
• The third step then assesses the total exposure from food containing the contaminant at the draft MLs. This is done for each of the thirteen FAO/WHO regional diets, proposed in "Progress Report by WHO on the Revision of GEMS/Food Regional Diets" (CX/PR 99/3), to assess if the draft MLs provide sufficient protection for consumers in each regional/cultural group. If the exposure from any diet is higher than the relevant safe/tolerable dietary exposure level for that contaminant, then a further stage is required to revise the draft MLs. In this stage, an assessment is made of whether any of the draft MLs are a cause for toxicological concern. Revised final MLs can then be set if necessary.
• The fourth step considers the practical implications of setting the MLs with particular attention to possible effects on trade.

Table 1: General Procedure for Establishing Maximum Levels (MLs) for Contaminants in Individual Foods

STEP 1: IDENTIFICATION OF HEALTH RISK AND IDENTIFICATION OF FOODS FOR WHICH MAXIMUM LEVELS ARE REQUIRED

i) Is dietary exposure to contaminant by consumers likely to exceed the safe/tolerable dietary exposure level?

3. One of the aims of setting standards is to reduce the levels of contaminants to the lowest reasonably achievable. However, the dietary exposure to a contaminant by consumers should not exceed the safe/tolerable dietary exposure level established on the basis of expert toxicological advice. Recommendations from the Joint FAO/WHO Expert Committee on Food Additives (JECFA), based on a full evaluation of an adequate toxicological data base, is the main basis for decisions on specific contaminants by CCFAC. If there are concerns about a contaminant for which no safe/tolerable dietary exposure level has been established, such as a Provisional Tolerable Weekly Intake (PTWI) or Tolerable Daily Intake (TDI), then advice should be obtained from JECFA.

ii) Identification of foods for which Maximum Levels are required.

4. International limits established to facilitate trade should also serve to protect consumers on a global basis. However, this does not imply that exceeding these limits will necessarily constitute a health risk.

5. Where a contaminant has acute toxicity, limits on the maximum concentrations of that contaminant in food are necessary to protect consumers. However, for most contaminants it is the long-term or chronic toxicity effects that are of concern. For such contaminants, limits are only necessary for those foods or food groups that are significant for the total dietary exposure of consumers to the contaminant and preferably where the limits could be achieved by Good Manufacturing Practice or the use of measures directed at the source(s) of the contaminants. This stage identifies the foods most likely to present a hazard and thus emphasises the value of MLs as measures to decrease overall dietary exposure of the contaminant world-wide. This stage also enables national resources to focus on those foods where significant reductions in concentrations of contaminants could be achieved.

6. In addition to the criteria given in Annex I of the GSC, four specific criteria are used to identify foods for which limits for contaminants should be set.

Criterion 1: The application of source-directed measures would ensure that the ML could be achieved in all foods.

7. To fulfil this criterion, actions to, i) eliminate or control the source of the contamination and, ii) to identify and separate contaminated items/lots/consignments of food from food fit for human consumption, have the potential to reduce the concentrations of the contaminant in food. As it may take some time for the actions to be effective, it may be necessary to agree a timescale within which the ML is phased in.

Criterion 2: The food or food group contributes more than 10% of the total dietary exposure in at least one regional diet or of specific population groups.

8. This figure has been chosen to ensure that all foods that provide a significant contribution to dietary exposures are considered. The food groups should be those currently broadly defined in CX/PR 99/3. However, individual foods or small food groups can be listed separately and can be assigned a different ML (or be exempted) when there are inherent differences in levels of contamination and adequate risk management requires a more specific approach. Other non-food sources of contaminants, for example water, are best managed at a national or regional level according to any national controls.

Criterion 3: The food commodity for which a specific ML is to be set is traded internationally and contributes to a significantly higher dietary exposure in at least 2 regions, i.e. the potential contribution is more than 5% of the total dietary exposure of more than one region.

9. To fulfil this criterion the food must be traded from one country to another country where there may be very different dietary patterns. There must be evidence that the food would directly increase the dietary exposure by consumers in the importing country beyond what would be considered safe, due to their high consumption of the food. Evidence must show that dietary patterns in importing countries will cause consumers to exceed safety levels.

Criterion 4: Although the dietary exposure from a food commodity is lower than 5%, a ML would have an important role in the management of food contamination and environmental monitoring.

10. This allows MLs to be set for food groups that can have elevated levels of contaminants, although their contribution to the overall dietary exposure to those contaminants is low.

STEP 2: SETTING THE MAXIMUM LEVEL

11. In this step, draft MLs can be formulated at the upper end of the range of contaminant concentrations normally found in those foods selected by Step 1. These data should be evaluated carefully to ensure that they are as representative as possible of current values for the contaminant in those foods and have been measured using reliable and sensitive analytical methodology.

STEP 3: ESTIMATING THE DIETARY EXPOSURE FROM FOODS WITH MAXIMUM LEVELS

12. The third, and most important, step assesses the potential total dietary exposure from foods containing the contaminant at the draft MLs to ensure that these provide sufficient protection for most consumers. In order to determine the acceptability of the draft MLs, the total dietary exposure from foods assigned MLs can be calculated using the consumption data in Table 1. It is desirable that above-average food consumption figures are used in the calculation of potential dietary exposure to contaminants when setting MLs, to ensure that even high level consumers are protected. The availability of reliable global consumption data is still a problem however.

13. It is therefore recommended that the thirteen proposed FAO/WHO regional/cultural diets are used in the process of setting MLs for contaminants in traded foods in order to reflect dietary and cultural diversity. (Any future development of these diets can be incorporated in this Step.) The FAO/WHO regional diets, currently used to make estimates of dietary exposure of pesticides are based on FAO Food Balance Sheet (FBS) data. The FBS data probably reflect above-average consumption for consumers for most foods, as food wastage is not taken into account, but may underestimate the consumption of home-grown or minor foods. Details of the countries assigned to the regional/cultural diets (from CX/PR 99/3) are given at the Appendix to this document.

Table 2: Average Consumption in Regional Dietary Groups
(weighted averages - g/person/day)

Food Group	A	B	C	D	E	F	G	H	I	J	K	L	M
Apples and products	1.3	66.0	17.4	39.1	64.2	59.6	8.9	12.5	3.8	0.8	8.5	21.4	43.5
Bananas	34.5	17.5	11.0	3.0	25.4	30.2	15.5	42.6	18.5	3.6	78.7	32.2	30.6
Citrus fruit	4.7	79.5	56.5	17.8	54.7	57.6	10.1	60.4	8.5	1.0	66.1	37.7	104.0
Other fruits	20.2	163.5	95.4	68.5	83.3	58.6	55.7	81.0	23.4	40.0	58.8	73.2	65.2
Fruit (total)	183.5	403.1	246.8	154.9	263.2	228.3	98.9	258.2	101.5	106.9	276.9	192.4	310.2
Potatoes	16.4	186.4	60.3	250.4	243.9	230.6	31.2	48.0	27.5	2.1	50.8	49.0	157.9
Roots and tubers (total)	392.1	187.2	65.1	250.4	244.3	230.6	111.8	93.4	356.1	344.4	172.1	110.0	165.8
All cucurbits	5.0	30.9	26.2	21.7	14.3	13.6	14.7	5.7	4.2	1.4	6.1	16.0	14.3
Tomatoes and products	11.8	164.8	121.1	59.6	43.1	31.4	14.7	27.5	12.3	11.9	34.5	12.8	98.5
Onions	4.2	55.3	33.1	24.0	26.4	14.9	17.7	11.1	6.4	8.6	11.7	34.6	27.9
Other fresh vegetables	23.5	97.2	48.3	43.4	55.8	24.2	125.0	18.8	38.5	57.1	20.4	114.1	24.5
Dried or dehydrated vegetables	0.2	0.5	0.5	0.1	0.5	0.5	0.2	0.0	0.1	0.1	0.0	1.7	0.2
Vegetables (total)	59.6	451.2	270.5	223.6	261.2	172.7	209.8	92.0	77.5	89.3	85.8	276.7	277.4
Maize	65.6	17.0	62.0	13.0	16.8	2.2	31.1	247.8	241.3	55.3	67.3	55.1	31.7
Wheat	67.1	406.3	436.4	405.5	238.2	228.4	170.3	111.5	66.3	45.0	118.3	106.9	241.8
Rice, husked equivalent	47.4	22.9	62.4	27.8	8.9	10.5	307.5	44.3	27.6	56.8	119.5	246.9	22.2
other cereals	25.3	0.2	1.1	0.2	1.3	8.5	1.3	6.9	2.1	3.9	0.8	1.4	0.2
Cereals (total)	255.3	448.1	602.8	482.5	295.0	324.5	492.2	410.6	359.8	409.7	292.8	379.3	310.3
Soyabean oil	1.1	9.3	6.4	3.9	9.2	9.3	2.3	11.8	1.5	0.9	26.6	8.3	41.6
Vegetable oils (total)	14.2	62.6	36.6	22.6	41.7	31.6	16.1	24.6	19.0	26.8	37.9	29.2	59.5
Sugar, refined	17.0	75.8	74.0	71.6	96.4	98.4	24.9	106.0	43.6	23.1	116.2	54.7	84.8
Sweeteners (total)	19.2	85.3	82.1	80.0	112.3	111.8	37.6	120.8	48.6	25.8	137.1	80.2	166.1
Meat products, other	5.3	7.1	3.2	2.8	5.3	6.1	1.0	3.0	4.8	4.5	0.8	1.3	2.2
Sheep	6.8	13.6	12.0	9.7	7.4	4.8	2.9	3.1	5.3	8.2	1.9	1.6	6.1
Bovine	14.4	42.6	15.3	50.9	53.5	55.7	6.7	37.1	22.7	13.3	62.9	21.0	118.9
Pork	6.9	68.3	0.1	39.0	120.4	77.1	32.3	24.2	3.8	3.3	19.4	46.1	71.4
Poultry	7.3	46.7	25.1	22.8	44.4	17.6	8.7	37.5	11.2	5.2	46.9	39.2	101.5
Meat (total)	33.4	131.6	30.6	102.4	186.6	143.7	42.9	67.4	36.6	29.3	85.0	70.0	198.6
Fish	18.6	61.0	15.1	22.1	41.4	86.6	25.2	29.5	23.8	21.4	20.0	137.6	56.0
Pulses	31.0	23.7	17.9	9.6	7.5	3.2	16.3	31.9	17.6	24.1	36.3	8.9	10.4
Brassica	2.4	33.1	11.4	54.7	45.0	39.0	22.2	6.2	5.5	0.1	4.4	55.2	15.8
Oil crops	13.4	12.0	10.4	4.8	7.6	3.6	23.9	8.9	9.5	16.0	14.2	25.1	12.6
Cocoa, coffee, tea	2.7	13.0	5.9	4.5	22.4	25.0	1.4	7.2	2.0	4.4	8.3	8.7	18.2
Spices	2.8	1.3	2.9	0.4	1.4	0.8	2.5	1.0	1.5	2.0	0.5	1.9	1.6
Eggs	3.3	31.1	11.4	27.4	33.8	30.6	14.2	24.3	5.7	5.5	19.2	34.5	32.6
Milk	44.9	274.8	113.9	317.0	344.8	472.5	73.0	177.2	91.5	104.7	250.6	102.1	379.1
Alcohol, including beer and wine	90.9	176.1	6.8	70.5	339.1	184.4	24.0	102.4	109.2	109.5	100.8	138.7	272.4

(Data from CX/PR 99/3)

15. While these assumptions will produce an overestimate of dietary exposure, if this estimate is still below the PTWI/TDI then the MLs can be accepted with confidence. If the calculated total dietary exposures are higher than the PTWI/TDI, then one or more of the proposed MLs may be too high. To check this, an assessment is made of whether any of the MLs is a cause for toxicological concern.

16. A Calculated Tolerable Concentration (CTC) is estimated as in (1) below for each food commodity for which a draft ML has been set and for each regional/cultural diet in turn to take account of the differences in food consumption and patterns of food contamination. The consumption data used to calculate the dietary exposures for the ML foods are in all cases taken from Table 2.

17. The CTC is an assessment of the highest level of a contaminant that could be present in a food without an average consumer of the contaminated food exceeding the Provisional Tolerable Weekly Intake (PTWI) or Tolerable Daily Intake (TDI) for the contaminant established by JECFA, after allowing for exposure from the rest of the diet. This exposure is accounted for by adding the exposure from the other foods with MLs to a proportion of the total exposure from all food in that dietary group. Annex I of the GSC specifies that foods with proposed MLs should account for 80% of total dietary exposure from a contaminant. Thus, a figure of 20% of the exposure from all foods is added. This overestimate of exposure from the average diet is likely to take account of the low exposure from air and water for most consumers.

18. The next stage enables a revised ML to be proposed by comparing the lowest CTC from the regional diets for each food commodity with the draft ML selected in Step 2. These final MLs are selected from the geometric scale recommended in Annex I of the GSC. The aim here is to propose a ML that is as low as reasonably achievable, but is unlikely to cause serious economic impact. There are two possible outcomes:

• the CTC is higher than the draft ML - an ML based on the draft ML may be established which does not raise concern for human health. As the draft ML takes account of the normal distribution of the contaminant, it is unlikely to cause serious economic impact.
• the CTC is lower than the draft ML - the resulting ML should be as low as reasonably achievable. This means that the CCFAC will need to discuss the likely economic consequences and review the health aspects of the proposed ML(s). It may be necessary to set a higher ML in foods that contain inherently elevated concentrations of certain contaminants.

19. In all cases, MLs should not be lower than a level that can be analysed with methods of analysis that can be readily applied in normal product control laboratories. However, health considerations may necessitate a lower detection limit that can only be achieved by means of a more elaborate method of analysis.

STEP 4: CONSIDERING THE PRACTICAL IMPLICATIONS OF SETTING THE MAXIMUM LEVELS

20. There are two issues to consider. Firstly, what economic impacts are the proposed MLs likely to have in practice? Secondly, how do countries ensure that foods where MLs have not been established are safe for consumption by their own population?

i) What economic impacts are the proposed MLs likely to have in practice?

21. The likely costs to business of complying with the proposed MLs should be assessed to ensure that the MLs do not pose unnecessary burdens on business or the economies of members of the World Trade Organization. A trade issue may arise owing to health concerns involving a contaminant in food commodities for which no ML has been proposed because of its low average contribution to the total dietary exposure of the contaminant. In such a case, the countries involved should provide information on the health risks involved to JECFA for its view, followed by an assessment by CCFAC.

ii) How does a country ensure that foods where MLs have not been established are safe for consumption by their own population?

22. National authorities should be encouraged to monitor the foods with MLs as they, in effect, act as indicators of how well source-control measures are implemented. National authorities should also be encouraged to monitor the foods without MLs particularly where local problems have been identified. For quality control purpose it is advisable to analyse raw or primary products but in order to estimate dietary exposure it is more useful to determine the residue concentrations in foods as consumed. Total diet (market basket) surveys should be used to determine the overall trend of dietary exposure within the population as a whole or in specific groups of concern. It may be appropriate to establish a specific Codex ML when there is evidence that the health of specific consumers may be at stake.

References

Codex General Standard for Contaminants and Toxins in Food

Methodology and principles for exposure assessment in the Codex General Standard for Contaminants (CX/FAC 99/13)

Progress Report by WHO on the Revision of GEMS/Food Regional Diets (CX/PR 99/3)

Appendix: Country Assignments to the 13 Proposed WHO Regional/Cultural diets

Dietary group	Country
A	Angola
A	Burundi
A	Cameroon
A	Central African Republic
A	Comoros
A	Congo, Democratic Republic of
A	Côte d'Ivoire
A	Djibouti
A	Eritrea
A	Ethiopia
A	Gabon
A	Guinea
A	Guinea Bissau
A	Liberia
A	Madagascar
A	Mauritius
A	Rwanda
A	Sao Tome & Principe
A	Seychelles
A	Sierra Leone
A	Somalia
A	Uganda
A	Yemen
B	Cyprus
B	Greece
B	Israel
B	Italy
B	Lebanon
B	Portugal
B	Spain
B	Turkey
B	United Arab Emirates
C	Algeria
C	Egypt
C	Iraq
C	Jordan
C	Kuwait
C	Libya Arab Jamahiriya
C	Morocco
C	Saudi Arabia
C	Syrian Arab Republic
C	Tunisia
D	Albania
D	Armenia
D	Azerbaijan
D	Belarus
D	Bosnia and Herzegovina
D	Bulgaria
D	Georgia
D	Iran, Islamic Rep of
D	Kazakhstan
D	Kyrgyzstan
D	Moldova, Republic of
D	Romania
D	Russian Federation
D	Tajikistan
D	The former Yugoslav Republic of Macedonia
D	Turkmenistan
D	Ukraine
D	Uzbekistan
E	Austria
E	Belgium
E	Croatia
E	Czech Republic
E	Denmark
E	France
E	Germany
E	Hungary
E	Ireland
E	Malta
E	Netherlands
E	Poland
E	Slovakia
E	Slovenia
E	Switzerland
E	United Kingdom
E	Yugoslavia
F	Estonia
F	Finland
F	Iceland
F	Latvia
F	Lithuania
F	Norway
F	Sweden
G	Afghanistan
G	Bangladesh
G	Cambodia
G	China
G	India
G	Indonesia
G	Laos
G	Mongolia
G	Myanmar
G	Nepal
G	Pakistan
G	Sri Lanka
G	Thailand
G	Vietnam
H	Bolivia
H	El Salvador
H	Fiji
H	Guatemala
H	Haiti
H	Honduras
H	Mexico
H	Nicaragua
H	Panama
H	Paraguay
H	Peru
H	Saint Kitts & Nevis
H	St. Vincent & Grenadine
I	Botswana
I	Cape Verde
I	Ghana
I	Kenya
I	Lesotho
I	Malawi
I	Mozambique
I	Namibia
I	Reunion
I	South Africa
I	Swaziland
I	Togo
I	United Republic of Tanzania
I	Zambia
I	Zimbabwe
J	Burkina Faso
J	Chad
J	Congo, Republic of
J	Gambia
J	Mali
J	Mauritania
J	Niger
J	Nigeria
J	Senegal
J	Sudan
K	Antigua & Barbuda
K	Aruba (Netherlands)
K	Bahamas
K	Barbados
K	Belize
K	Bermuda
K	Brazil
K	Colombia
K	Costa Rica
K	Cuba
K	Dominica
K	Dominican Republic
K	Ecuador
K	French Guyana
K	Grenada
K	Guadeloupe
K	Guyana
K	Jamaica
K	Martinique
K	Saint Lucia
K	Suriname
K	Trinidad and Tobago
K	Venezuela
L	Brunei Darussalam
L	French Polynesia
L	China, Hong Kong
L	Japan
L	Kiribati
L	Democratic People's Republic of Korea
L	Republic of Korea
L	Madagascar
L	Malaysia
L	Maldives
L	New Caledonia
L	Papua New Guinea
L	Philippines
L	Solomon Islands
L	China (Taiwan Province)
L	Vanuatu
M	Argentina
M	Australia
M	Canada
M	Chile
M	New Zealand
M	United States
M	Uruguay