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Toxicology Letters 149 (2004) 223234

Toxicology databases and the concept of thresholdsof toxicological concern as used by the JECFAfor the safety evaluation of flavouring agents

A.G. Renwick

Clinical Pharmacology Group, Allergy and Inflammatory Sciences Research Division, School of Medicine,University of Southampton, Biomedical Sciences Building, Bassett Crescent East, Southampton SO16 7PX, UK

Abstract

Since 1996 the FAO/WHOJoint Expert Committee on Food Additives (JECFA) has evaluated the safety of 1259flavouring sub-

stances, based on a decision tree that incorporates a series of thresholds of toxicological concern. Safety conclusions are based on

the predicted consequences of metabolism andwhether the estimatedintake is above or belowa threshold of toxicological concern

that is relevantto that compound. Compounds areallocated toone of three structural classes, andthe intake compared with a thresh-

old of toxicological concern derived using data from chronic andsub-chronic toxicitystudies on compounds in thesame structural

class. If the substance is predicted to be metabolised to innocuous products there is no safety concern if the intake is below the

threshold, but suitable toxicity data on the compoundor structural analogues are required if the intake exceeds the threshold. If thesubstance is notpredicted to be metabolised to innocuous products,and the intakeis below the appropriate threshold, safetyevalu-

ation is based on data on thecompoundor structural analogues. An additional thresholdof 1.5g perday, derived from doses of in-

vestigated chemicals giving a calculated cancer risk of one in a million, is applied when appropriate toxicity data are not available.

2004 Elsevier Ireland Ltd. All rights reserved.

Keywords: Flavouring agent; Safety; Metabolism; Intake; Toxicity

1. Introduction

The term threshold can be confusing because ithas two different uses in toxicology and risk assess-

ment:

(i) a dose within the doseresponse curve below

which an adverse effect would not be produced,

because of homeostatic processes and

Tel.: +44-23-8059-4261; fax: +44-23-8059-4262.

E-mail address: [email protected] (A.G. Renwick).

(ii) a level of exposure so low that risk assessment can

be based on the activities of structural analogues,

i.e. a threshold of toxicological concern.

A search of the WHO website for JECFA (Joint

FAO/WHO Expert Committee on Food Additives)

and threshold yields a large number of citations,

but in nearly all cases these refer to the presence

or absence of a threshold within the doseresponse

relationship. In recent years the JECFA has used the

concept of a threshold of toxicological concern for

the safety assessment of flavouring agents, and this

will be the basis of this paper.

0378-4274/$ see front matter 2004 Elsevier Ireland Ltd. All rights reserved.doi:10.1016/j.toxlet.2003.12.034


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224 A.G. Renwick / Toxicology Letters 149 (2004) 223234

An extensive toxicological database is required

for compounds present in the food supply in signif-

icant amounts (Renwick, 1999), but it is generally

recognised that the extent of exposure is an importantdeterminant of the amount of data that is considered

necessary to undertake risk assessment (WHO, 1987).

The draft FDA Redbook II (FDA, 1993) proposed

database requirements for three levels of concern,

with each concern level based on a combination of

chemical structure and predicted intake. The concept

of a threshold of toxicological concern takes this re-

lationship to the point where risk assessment can be

undertaken in absence of toxicity data on the com-

pound under evaluation, providing that the intake is

sufficiently low. What represents sufficiently low

depends on the chemical structure of the compound

and the available toxicity data on structural analogues

that have been subjected to toxicological evaluation.

The threshold of toxicological concern represents an

important and pragmatic approach to risk assessment,

and can make a significant contribution to optimising

the use of toxicological resources. The threshold of

toxicological concern is used in situations where there

are limited or no data on the compound, but the human

exposure is so low that undertaking toxicity studies

is not warranted, because of the costs incurred in the

use of animals, manpower and laboratory resources.The threshold of toxicological concern does not

provide the surety of risk assessment based on

compound-specific data because it is based on as-

sessing the probability of whether or not adverse

effects would occur at the estimated level of exposure.

However, this apparent difference is not black and

white because there are always uncertainties in risk

assessment, even when there is a comprehensive and

complete toxicity database. The use of threshold of

toxicological concern can be thought of as trading-off

increased uncertainty against very low exposure.A threshold of toxicological concern was initially

applied to migrants from food contact materials and

was used as the basis of the US Food and Drug Ad-

ministration Threshold of Regulation for indirect food

additives (Federal Register, 1993, 1995). Initially,

the threshold of toxicological concern was based on

defining a level of exposure that would give a low

risk, even if the compound were to be a carcinogen.

A level in food of 0.5 ppb (parts per billion or g/kg)

was selected because most known carcinogens pose

less than one in a million lifetime risk if present in

the diet at 0.5 ppb, and it was a level 2000 times

lower than the dietary concentration at which the vast

majority of studied compounds are likely to causenon-carcinogenic toxic effect (Federal Register,

1993). Although the value would give a de minimis

risk even if the compound were a genotoxic carcino-

gen, the Threshold of Regulation would not apply

to known carcinogens or substances whose chemical

structures provide reason to suspect that they may be

carcinogens, because that would contravene US food

law. Subsequent refinements to the use of the thresh-

old of toxicological concern concept for food contact

materials are discussed in Cheeseman et al. (1999)

and Munro et al. (2003).

The threshold of toxicological concern principle

was developed significantly by the work of Dr. I.C.

Munro, who analysed available chronic toxicity data

and developed a decision tree based on chemical struc-

ture and intake. The following text analyses the dif-

ferent thresholds of toxicological concern developed

by Munro, and their use by the JECFA in the risk as-

sessment of flavouring agents.

2. The JECFA decision tree for the safety

evaluation of flavouring agents

Flavouring agents represent an enormous challenge

to risk assessors because there are over 3000 sub-

stances, with toxicity data available on only a few

of these. The intakes of flavouring agents are consid-

ered to be self-limiting because of their taste prop-

erties. Flavouring agents have been evaluated by the

JECFA for many years, but it was only with the in-

troduction of a safety evaluation procedure based on

the Munro analyses and decision tree (JECFA, 1997)

that consideration of large number of structurally re-lated compounds became feasible (see Munro et al.,

1998). A procedure for use by the JECFA was pro-

posed by Munro (1996), and presented to the 44th

meeting (JECFA, 1995). The essential details can be

found in JECFA Reports after this date, and in the pub-

lications ofMunro et al. (1998, 1999). The procedure

involves four principal components:

(i) allocation of the compound to one of three struc-

tural classes,


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A.G. Renwick / Toxicology Letters 149 (2004) 223234 225

(ii) consideration of the consequences of metabolism,

(iii) estimation of intake,

(iv) comparison of the intake with a series of thresh-

olds of toxicological concern.Since 1997 the procedure has been applied to a total

of 1259 different compounds (Table 1) organised by

the Flavour and Extract Manufacturers Association of

the USA into groups of structurally related substances.

2.1. Allocation of the compound to one of three

structural classes

The procedure is applicable only to the assessment

of compounds with known chemical structures, be-

cause the concept of structureactivity relationships

is the basis for allocation to one of three classes with

different levels of toxicological concern. Cramer et al.

(1978) developed a series of 33 questions into a deci-

sion tree that allocates the chemical structure to one

of three classes which were defined as follows:

Class I substances are those with structures and re-

lated data suggesting a low order of oral toxicity.

If combined with low human exposure, they should

enjoy an extremely low priority for investigation.

The criteria for adequate evidence of safety would

also be minimal. Greater exposures would require

proportionately higher priority for more exhaustive

study.

Fig. 1. The initial steps in the decision tree ofCramer et al. (1978) used to assign flavouring agents to different structural classes.

Class II substances are simply intermediate. They

are less clearly innocuous than those of class I, but

do not offer the basis either of the positive indication

of toxicity or of the lack of knowledge characteristicof those in class III.

Class III substances are those that permit no strong

initial presumptions of safety, or that may even sug-

gest significant toxicity. They thus deserve the high-

est priority for investigation. Particularly when per

capita intake is high or a significant subsection of

the population has a high intake, the implied hazard

would then require the most extensive evidence for

safety-in-use.

The initial steps in the decision tree (Cramer et al.,

1978) are shown in Fig. 1 to illustrate the approach.Although the decision tree (Fig. 2) is unsophisticated

compared with modern computer-based, predictive

structureactivity databases, the differences in po-

tency were validated by the analyses performed by

Munro et al. (1996) to develop the threshold of

toxicological concern for each structural class (see

later).

2.2. Consideration of metabolism

Predicted metabolism is an important part of the

JECFA procedure and represents the second step in the

process (Fig. 3). The way that the different thresholds


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Fig. 2. An overview ofCramer et al. (1978) structural classification scheme-adapted to show where different structural groups are evaluated

for toxic potential.

of toxicological concern are applied in the procedure is

dependent on the predicted metabolism. Compounds

that are predicted to be metabolised to innocuous prod-

ucts are evaluated using the A-side of the decision tree,

Fig. 3. The initial steps in the procedure used by the JECFA for the safety evaluation of flavouring agents.

whereas if metabolites are not predicted to be innocu-

ous they follow the B-side (JECFA, 2000a). JECFA

(1997) defined Innocuous products are products

that are known or readily predicted to be harmless


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to humans at the estimated intakes of the flavouring

agents. The prediction of metabolism is difficult and

relies on expert judgement of the members and tem-

porary advisors invited to the JECFA meeting. Thedefinition used by the JECFA relates to the metabolic

fate at the low levels of intake relevant to the intake

as a flavouring agent. In consequence detoxication

processes such as glutathione conjugation would

not be saturated, and would rapidly inactivate po-

tentially reactive molecules such as aldehydes and

,-unsaturated carbonyl compounds.

The reports of the early meetings at which the

procedure was used contained general text on the

metabolism of the different functional groups present

in the compounds evaluated at the meeting (JECFA,

1997, 1999, 2000a), but at later meetings metabolism

was considered separately for each group of sub-

stances. A large number of flavouring agents are

aldehydes or ,-unsaturated carbonyl compounds,

which are reactive chemicals, and the procedure was

considered applicable to these functional groups be-

cause of their extensive detoxication by oxidation and

conjugation reactions (JECFA, 2002b).

2.3. Estimation of intake

There are a variety of methods available for esti-mating the intakes of chemical in food (Kroes et al.,

2002). The method used in the JECFA procedure for

flavouring agents is one of the simplest methods, in

which the amount of the compound produced annu-

ally is divided across the population that may have

consumed foods containing the compound, a so-called

per capita estimate. Information on the annual pro-

duction volume for each flavouring agent in Europe

and the USA is supplied by the flavour manufacturers.

The annual production volumes are divided by 0.6,

on the assumption that only 60% of actual productionmay be reported, and allocated to 10% of the relevant

population (equivalent to 32 million in Europe and

24 million in the USA; JECFA, 1997). The intake

estimates of flavouring agents for the USA evaluated

by the JECFA in the 55th Report (JECFA, 2001), and

subsequently, were corrected by dividing the reported

poundage by 0.8 rather than 0.6 because about 87% of

the poundage data had been reported in recent surveys

in the USA. Although the intake estimates relate to ma-

jor populations that would consume flavoured foods,

one weakness of the JECFA evaluations is the lack of

intake estimates for other geographical and cultural

areas.

The per capita

10 method is simple and readilyapplicable to the evaluation of flavouring agents; most

importantly it has been shown to be appropriately

conservative. Intakes estimated by the method were

generally higher than the mean and 95th percentile

14-day average intakes found using a detailed dietary

analysis based on food consumption and composition

(Hall and Ford, 1999). An alternative intake esti-

mate for flavouring agents is the theoretical added

maximum daily intake (TAMDI) which is calculated

assuming that 160 g of food and 324 ml of drink con-

tain the flavouring substance at the upper use level

specified by the Council of Europe (Lambe et al.,

2002). While such an intake might occur rarely on

single days, it is not appropriate for comparison with

thresholds of toxicological concern that are derived

using data from chronic animal studies (see Renwick

et al., 2003). The TAMDI estimates for a range of

flavouring agents were gross overestimates compared

with the per capita 10 values, and the latter were

supported by the results of a stochastic model that

used data from the Dietary and Nutritional Survey

of British Adults combined with information from

the Irish National Food Ingredients Database (Lambeet al., 2002).

2.4. Comparison of the intake with a series of

threshold of toxicological concern values

The thresholds of toxicological concern for Cramer

et al. (1978) structural classes were derived by Munro

et al. (1996) based on an analysis of data from chronic

toxicity studies on 137, 28 and 448 compounds in

classes I, II and III respectively. The database com-

prised:

(i) NOEL (no observed effect level) values for ro-

dents and rabbits; NOEL values for dogs and

other species were not included because the stud-

ies contained too few animals to be statistically

valid,

(ii) NOEL values from sub-chronic studies were di-

vided by a three-fold uncertainty factor (WHO,

1994) to convert them into equivalent chronic

NOELs and


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(iii) NOEL values derived by the authors were used

except where these were based on physiological

rather than toxicological effects.

The NOEL from a chronic toxicity study in rodents

is the usual starting point for the determination of an

acceptable daily intake (ADI) for an approved food

additive, and assumes that there is a threshold dose

within the doseresponse relationship (see Section 1

to avoid confusion). The cumulative distributions

of NOELs for each Cramer et al. (1978) structural

class were plotted and a log-normal distribution was

fitted. The three distributions were significantly dif-

ferent from each other (Munro et al., 1996). The 5th

percentile values for the classes I, II and III NOEL

distributions were calculated to be 3.0, 0.91 and

0.15 mg/kg body weight per day. Therefore, there is a

95% probability that the NOEL from a chronic animal

bioassay on an unstudied compound would be above

the relevant 5th percentile value. The 5th percentile

NOEL values were converted to corresponding human

intakes by dividing by the usual 100-fold uncertainty

factor (WHO, 1987) that is used in the calculation of

ADI values for food additives. The intakes were then

multiplied by 60 to scale to the adult human body

weight. These analyses gave thresholds of toxicolog-

ical concern of 1800, 540 and 90g per person perday for structural classes I, II and III.

Fig. 4. The A-side of the procedure used for compounds predicted to be metabolised to innocuous products.

The way that these threshold values are used in the

JECFA procedure depends on whether the flavouring

agent is evaluated using the A-side or the B-side.

Using the A-side for substances that are predictedto be metabolised to innocuous products (Fig. 4;

based on JECFA (2000a)) there would not be a safety

concern if the intake of a flavouring agent were below

the relevant threshold. If the estimated intake ex-

ceeds the threshold then the next question determines

whether the compound is endogenous. There would

be no safety concern if the compound is an endoge-

nous body constituent. The JECFA recognised that

many endogenous compounds have important physio-

logical and other functions and that ingestion of such

a compound could give rise to adverse effects. There-

fore, within the context of the procedure, endogenous

substances were defined by the JECFA as Interme-

diary metabolites normally present in human tissues

and fluids, whether free or conjugated; hormones and

other substances with biochemical or physiological

regulatory functions are not included. The estimated

intake of a flavouring agent that is, or is metabolised

to, an endogenous substance should be judged not

to give rise to perturbations outside the physiological

range (JECFA, 1997). If the compound is not an en-

dogenous substrate, according to this definition, then

data on the compound, or a related substance, can beused for the safety evaluation.


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Fig. 5. The B-side of the procedure used for compounds not predicted to be metabolised to innocuous products.

Using the B-side for substances that are not pre-

dicted to be metabolised to innocuous products

(Fig. 5; based on JECFA (2000a)) toxicity data on

the compound, or a related substance, would be used

for the safety evaluation if the intake of a flavour-

ing agent were below the relevant threshold. A morecomprehensive risk assessment, using toxicity data on

the substance or a close structural analogue, would

be necessary if the intake were above the threshold.

There would not be a safety concern if the intake were

below the relevant classes I, II or III threshold, and

there was a NOEL that gave an adequate margin of

safety. Additional data would be required if there was

not a suitable NOEL and the intake exceeded a general

threshold of toxicological concern of 1.5g per day.

There would not be a safety concern if the intake were

less than the threshold of toxicological concern of1.5g per day.

The threshold of toxicological concern of 1.5g

per day was developed from the work of Rulis and

colleagues at the FDA (see Cheeseman et al., 1999) on

the Threshold of Regulation for food contact materials

(see Section 1). The FDA threshold of toxicological

concern was derived from an analysis of the distribu-

tion of intakes giving a one in a million cancer risk

using linear low-dose extrapolation of experimental

data in animals for the chemicals in the Carcinogenic

Potency Database of Gold and colleagues. There

were 477 animal carcinogens in the database when

the Threshold of Regulation was proposed (Federal

Register, 1993) and 709 in the recent reconsideration

by Cheeseman et al. (1999). The threshold of toxico-

logical concern of 1.5g per day was derived Munro(1990) from the distribution of estimated one in a

million cancer risks for a subset of the Gold et al.

(1989) database, which comprised the most relevant

studies in rodents, i.e. those that contained two or

more oral dose levels and a statistically significant

doseresponse relationship. This analysis showed that

there was a 63% probability that the estimated cancer

risk would be one in a million or less for a dietary

concentration of 0.5 ppb (0.5g/kg) if all chemicals

were carcinogens, but a 96% probability if only one

in ten chemicals were carcinogenic. Thus for anyunstudied compound there is a 96% probability that

the cancer risk would be one in a million or less at

a daily intake of 1.5 g per person per day. This is

probably a gross over-estimate of the real probability

because of the selective nature of compounds that

are subjected to rodent carcinogenicity testing, and

the highly conservative linear extrapolation method

used to convert the TD50 (the estimated dose giving

a 50% incidence of tumours in the animal study) to

a one in a million risk. In addition, the assumption


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A.G.Renwick/ToxicologyLetters149(2004)223234

Table 1

Summary of the results of the application of the procedure by the JECFA to the safety evaluation of flavouring agents

Group Total (n) Class I Class II Class III A-side B- side Below

threshold

No safety

concern

Reference

Ethyl esters 15 15 0 0 15 0 11 15 JECFA (1997)

Isoamyl alcohol and related esters 11 11 0 0 11 0 9 11 JECFA (1997)

Allyl esters 21 0 18 3 0 21 20 20a JECFA (1997)

Saturated aliphatic acyclic linear primary alcohols,

aldehydes and acids

38 38 0 0 38 0 27 38 JECFA (1999)

Saturated aliphatic acyclic branched-chain primary

alcohols, aldehydes and acids

25 22 3 0 25 0 25 25 JECFA (1999)

Aliphatic lactones 35 29 0 6 29 6 26A, 2B 31b JECFA (1999)

Esters of aliphatic acyclic primary alcohols withbranched-chain aliphatic acyclic acids 32 32 0 0 32 0 31 32 JECFA (1999)

Esters of aliphatic acyclic primary alcohols with

aliphatic linear saturated carboxylic acids

67 66 1 0 67 0 66 66c JECFA (1999)

Esters of branched-chain terpenoid alcohols and

aliphatic acyclic carboxylic acids

26 26 0 0 26 0 26 26 JECFA (1999)

Saturated aliphatic acyclic secondary alcohols, ketones

and related saturated and unsaturated esters

39 28 11 0 37 2 35A, 2B 39 JECFA (2000a)

Linear and branched-chain aliphatic unsaturated

unconjugated alcohols aldehydes, acids and related

esters

42 42 0 0 41 1 40A, 1B 41d JECFA (2000a)

Aliphatic acyclic and alicyclic terpenoid tertiary

alcohols and structurally related substances

23 22 1 0 22 1 19A, 1B 22e JECFA (2000a)

Carvone and structurally related substances 9 6 3 0 9 0 8 9 JECFA (2000a)

Ionones and structurally related substances 21 21 0 0 13 7 13A, 7B 20f JECFA (2000a)

Aliphatic acyclic and alicyclic -diketones and related

-hydroxyketones

22 0 22 0 22 0 19 22 JECFA (2000a)

Substances structurally related to menthol 14 9 5 0 14 0 12 14 JECFA (2000a)

Simple aliphatic and aromatic sulphides and thiols 137 97 34 6 0 137 137 137 JECFA (2000b)

Aliphatic linear primary alcohols, aldehydes andcarboxylic acids, acetals and esters containing

additional oxygenated functional groups

47 47 0 0 47 0 41 47 JECFA (2000b)

Cinnamyl alcohol and related flavouring agents 55 50 5 0 55 0 51 55 JECFA (2001)

Furfuryl alcohol and related flavouring agents 15 0 9 6 0 15 15 15 JECFA (2001)

Phenol and phenol derivatives 48 47 0 1 48 0 47 48 JECFA (2001)

Pulegone and related flavouring agents 6 2 4 0 0 6 6 6 JECFA (2001)

Pyrazine derivatives 41 0 32 9 41 0 41 41 JECFA (2002a)

Aromatic substituted secondary alcohols, ketones and

related esters

38 28 6 4 36 2 36A, 2B 37e JECFA (2002a)

Benzyl derivatives 37 37 0 0 36 1 33A, 1B 37 JECFA (2002a)

Hydroxy- and alkoxy-substituted benzyl derivatives 46 36 10 0 46 0 42 46 JECFA (2002a)

Aliphatic acyclic diols, triols and related substances 31 22 9 0 31 0 22 31 JECFA (2002a)


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A.G.Renwick/ToxicologyLetters149(2004)223234

231

Aliphatic acyclic acetals 10 10 0 0 10 0 10 10 JECFA (2002a)

Alicyclic primary alcohols, aldehydes, acids and related

esters

26 26 0 0 25 1 25A, 1B 26 JECFA (2002b)

Phenethyl alcohol, aldehyde, acid and related acetals

and esters

43 39 0 4 43 0 42 43 JECFA (2002b)

Sulphur-containing heterocyclic compounds 30 0 21 9 3 27 2A, 27B 30 JECFA (2002b)

Sulphur-substituted furan derivatives 33 0 18 15 0 33 33 33 JECFA (2002b)

Alicyclic ketones, secondary alcohols and related esters 25 6 19 0 25 0 25 25 JECFA (2002b)

Aliphatic secondary alcohols, ketones and related esters 39 11 28 0 39 0 39 39 JECFA (2002b)

Alicyclic, alicyclic-fused and aromatic-fused ring

lactones

16 4 0 12 10 6 10A, 4B 16 JECFA (in press)

Aliphatic di- and trienals and related alcohols, acids

and esters

26 26 0 0 13 13 13A, 13B 26 JECFA (in press)

Aliphatic branched-chain unsaturated alcohols,

aldehydes, acids and related esters

32 32 0 0 32 0 31 32 JECFA (in press)

Aliphatic and aromatic ethers 29 9 12 8 29 0 26 29 JECFA (in press)

Hydroxypropenylbenzenes 9 6 0 3 9 0 8 9 JECFA (in press)

Total 1259 902 271 86 979 279 1174 1249

a Allyl furoate was deferred because of inadequate data at step B4; a conclusion of no safety concern was reached when step B5 was added to the procedure ( JECFA, 1999).b Four ,-unsaturated lactones were deferred until a later meeting, at which the application of the procedure to such compounds was considered ( JECFA, 2001).c One ,-unsaturated ester was deferred until a later meeting, at which the application of the procedure to such compounds was considered ( JECFA, 2001).d The evaluation of one compound on the B-side was deferred pending evaluation of the results of a 90-day study.e One substance evaluated using the B-side had an intake below its structural class threshold but lacked appropriate toxicity data and the intake was more than 1.5 g per

day so that additional data were required for an evaluation.fOne of the substances submitted for evaluation was considered not to be a member of the group and was not evaluated.


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that only one in ten untested compounds would be

a carcinogen is probably conservative (Fung et al.,

1995).

3. The conclusions reached by the JECFA using

the procedure for the safety evaluations of

flavouring agents

The JECFA first used the procedure at a meeting

in 1996 (JECFA, 1997) to evaluate groups of ethyl,

isoamyl and allyl esters using the A-side for ethyl and

isoamyl esters and the B-side for allyl esters (Table 1).

Adequate data were not available on allyl furoate and

this compound was deferred to a later meeting because

at that time the procedure did not include the thresh-

old of toxicological concern of 1.5g per day on the

B-side. Subsequent meetings considered the general

threshold of 1.5g per day and the issue of com-

pounds such as ,-unsaturated carbonyl compounds

and their precursors in relation to the activity of detox-

ication pathways such as oxidation and conjugation

with glutathione.

To date 1259 different flavouring agents have been

evaluated using the procedure, with the majority in

structural class I (Table 1), and with most (979) be-

ing evaluated using the A-side of the procedure (onecompound was not evaluated in detail because it was

not related to other members of the group). Only 68

compounds that were evaluated using the A-side of the

procedure had intakes that exceeded the relevant struc-

tural class threshold; of these 39 were of no safety con-

cern because they were endogenous or metabolised to

endogenous compounds, and 29 were evaluated using

toxicity data on the flavouring agent or a structurally

related compound. A total of 279 compounds were

evaluated using the B-side and half of these were a

large and complex group of sulphides and thiol com-pounds. Two compounds that were evaluated using

the B-side were subjected to a more comprehensive

safety assessment because their exposures exceeded

the relevant threshold (JECFA, in press). In nearly all

other cases the other flavouring agents evaluated us-

ing the B-side were considered not to be a safety con-

cern based on toxicity data on the flavouring agent or

a structurally related compound. Only six compounds

were considered not to be a safety concern because

their estimated intakes were less than 1.5g per day,

although a total of 471 flavouring agents had reported

intakes below this level.

4. Conclusions

The JECFA procedure based on the work of Munro

and his colleagues (Munro, 1996; Munro et al., 1996)

provides a practical method for the safety evaluation

of flavouring agents. The conservative nature of the

thresholds of toxicological concern compared with the

NOELs for flavouring agents was shown by the re-

view by Munro and Kennepohl (2001), in which esti-

mated intakes were compared with the NOEL values

available from good quality, multi-dose toxicological

studies. Most of the toxicity studies were short-term

or 90-day studies, and so may have overestimated the

NOEL that would be obtained from a chronic bioassay

on the compound or a structural analogue by a factor of

about three-fold (WHO, 1994). The data showed that,

with the exception of ethanol, the margins of safety

exceeded the usual 100-fold uncertainty factor; in the

majority of case the margins of safety were over 1000,

and in many cases more than 1,000,000. This analysis

supported the conclusions reached by the JECFA us-

ing the procedure for the safety evaluation of flavour-

ing agents.The JECFA experience with the application of the

threshold of toxicological concern principle has given

rise to increased interest in its use in other risk as-

sessment scenarios. Further analyses of the threshold

of toxicological concern concept were presented by

Kroes et al. (2000) and discussed at an international

workshop organised by ILSI-Europe (Barlow et al.,

2001), which indicated that the approach could be

more widely applicable if a pre-screening procedure

removed from consideration compounds that could

show bioaccumulation, genotoxicity, allergenicity ororganophosphate-like neurotoxicity. These different

aspects have been considered by an ILSI-Europe Ex-

pert Group and a paper (Kroes et al., 2004) prepared

following discussions at an international workshop. A

new decision tree is proposed in that paper in which

compounds with structural alerts for genotoxicity are

considered first, and then any compound with very

low estimated intakes, i.e. less than 1.5 g per day,

is removed from further detailed consideration. Such

an approach would allow assessments to concentrate


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on those compounds with potentially significant

intakes.

References

Barlow, S.M., Kozianowski, G., Wurtzen, G., Schlatter, J.,

2001. Threshold of toxicological concern for chemical

substances present in the diet. Food Chem. Toxicol. 39, 893

905.

Cheeseman, M.A., Machuga, E.J., Bailey, A.B., 1999. A tiered

approach to threshold of regulation. Food Chem. Toxicol. 37,

387412.

Cramer, G.M., Ford, R.A., Hall, R.L., 1978. Estimation of toxic

hazarda decision tree approach. Food Cosmet. Toxicol. 16,

255276.

FDA, 1993. Toxicological principles for the safety assessmentof direct food additives and color additives used in food.

Redbook II. Draft U.S. Food and Drug Administration.

Center for Food Safety and Applied Nutrition, Washington.

Federal Register, 1993. Food additives; Threshold of regulation

for substances used in food-contact articles. Federal Register

58 (195), 5271952727.

Federal Register, 1995. Food additives; Threshold of regulation

for substances used in food-contact articles. Final rule. Federal

Register 60 (136), 3658236594.

Fung, V.A., Barrett, J.C., Huff, J., 1995. The carcinogen bioassay

in perspective: application in identifying human cancer hazards.

Environ. Health Persp. 103, 680683.

Gold, L.S., Slone, T.H., Bernstein, L., 1989. Summary ofcarcinogenic potency and positivity for 492 rodent carcinogens

in the carcinogenic potency database. Environ. Health Persp.

79, 259272.

Hall, R.L., Ford, R.A., 1999. Comparison of two methods to assess

the intake of flavouring substances. Food Addit. Contam. 16,

481495.

JECFA, 1995. Evaluation of certain food additives and

contaminants. Forty-fourth Report of the Joint FAO/WHO

Expert Committee on Food Additives. WHO Technical Report

Series, No. 859. http://www.who.int/pcs/jecfa/JECFA publi-

cations.htm.


contaminants. Forty-sixth Report of the Joint FAO/WHO



cations.htm.


contaminants. Forty-ninth Report of the Joint FAO/WHO



cations.htm.

JECFA, 2000a. Evaluation of certain food additives. Fifty-

first Report of the Joint FAO/WHO Expert Committee on

Food Additives. WHO Technical Report Series, No. 891.

http://www.who.int/pcs/jecfa/JECFA publications.htm.

JECFA, 2000b. Evaluation of certain food additives and

contaminants. Fifty-third Report of the Joint FAO/WHO



cations.htm.JECFA, 2001. Evaluation of certain food additives and

contaminants. Fifty-fifth Report of the Joint FAO/WHO



cations.htm.

JECFA, 2002a. Evaluation of certain food additives and

contaminants. Fifty-seventh Report of the Joint FAO/WHO



cations.htm.

JECFA, 2002b. Evaluation of certain food additives. Fifty-

ninth Report of the Joint FAO/WHO Expert Committee on

Food Additives. WHO Technical Report Series, No. 913.http://www.who.int/pcs/jecfa/JECFA publications.htm.

JECFA, in press. Evaluation of certain food additives. Sixty-first

Report of the Joint FAO/WHO Expert Committee on Food

Additives. WHO Technical Report Series.

Kroes, R., Galli, C.L., Munro, I., Schilter, B., Tran, L.-A., Walker,

R., Wrtzen, G., 2000. Threshold of toxicological concern for

chemical substances present in the diet: a practical tool for

assessing the need for toxicity testing. Food Chem. Toxicol.

38, 255312.

Kroes, R., Muller, D., Lambe, J., Lowik, M.R.H., van Klaveren,

J., Kleiner, J., Massey, R., Mayer, S., Urieta, I., Verger, P.,

Visconti, A., 2002. Assessment of intake from the diet. Food

Chem. Toxicol. 40, 327385.

Kroes, R., Renwick, A.G., Cheeseman, M., Kleiner, J.,

Mangelsdorf, I., Piersma, A., Schilter, B., Schlatter, J., van

Schothorst, F., Vos, J.G., Wrtzen, G., 2004. Structure-

based thresholds of toxicological concern (TTC): guidance for

application to substances present at low levels in the diet. Food

Chem. Toxicol. 42, 6583.

Lambe, J., Cadby, P., Gibney, M., 2002. Comparison of stochastic

modelling of the intakes of intentionally added flavouring

substances with theoretical added maximum daily intakes

(TAMDI) and maximized survey-derived daily intakes (MSDI).

Food Addit. Contam. 19, 214.

Munro, I.C., 1990. Safety assessment procedures for indirect food

additives: an overview. Report of a workshop. Regulat. Toxicol.

Pharmacol. 12, 212.

Munro, I.C., 1996. A procedure for the safety evaluation of

flavoring substances. Toxicological evaluation of certain food

additives and contaminants. Prepared for the Joint FAO/WHO


Series, Number 35, Annex 5.

Munro, I.C., Kennepohl, E., 2001. Comparison of estimated daily

per capita intakes of flavouring substances with no-observed-

effect levels from animal studies. Food Chem. Toxicol. 39,

331354.

Munro, I.C., Ford, R.A., Kennepohl, E., Sprenger, J.G., 1996.

Correlation of structural class with no-observed effect levels: a
http://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htmhttp://www.who.int/pcs/jecfa/JECFA_publications.htm


12/12


proposal for establishing a threshold of concern. Food Chem.

Toxicol. 34, 829867.

Munro, I.C., Shubik, P., Hall, R., 1998. Principles for the safety

evaluation of flavouring substances. Food Chem. Toxicol. 36,

529540.Munro, I.C., Kennepohl, E., Kroes, R., 1999. A procedure for

the safety evaluation of flavouring substances. Food Chem.

Toxicol. 37, 207232.

Munro, I.C., Hlywka, J.J., Kennepohl, E.M., 2003. Risk asses-

sment of packaging materials. Food Addit. Contam. 19, 3

12.

Renwick, A.G., 1999. Exposure estimation, toxicological require-

ments and risk assessment. In: van der Heijden, K., Younes,

M., Fishbein, L., Miller, S. (Eds.), International Food Safety

Handbook, Marcel Dekker, New York, pp. 5994.

Renwick, A.G., Barlow, S.M., Hertz-Picciotto, I., Boobis, A.R.,

Dybing, E., Edler, L., Eisenbrand, G., Greig, J.B., Kleiner,

J., Lambe, J., Mller, D.J.G., Smith, M.R., Tritscher, A.,

Tuijtelaars, S., van den Brandt, P.A., Walker, R., Kroes, R.,

2003. Risk characterisation of chemicals in food and diet. FoodChem. Toxicol. 41, 211271.

WHO, 1987. Principles for the assessment of risk to human

health from exposure to chemicals. Environmenal Health

Criteria, 70. World Health Organization, Geneva. http://www.

inchem.org/documents/ehc/ehc/ehc70.htm.

WHO, 1994. Assessing human health risks of chemicals:

derivation of guidance values for health-based exposure

limits, Environmental Health Criteria, 170. World Health

Organization, Geneva. http://www.inchem.org/documents/ehc/

ehc/ehc170.htm.
http://www.inchem.org/documents/ehc/ehc/ehc70.htmhttp://www.inchem.org/documents/ehc/ehc/ehc170.htmhttp://www.inchem.org/documents/ehc/ehc/ehc170.htmhttp://www.inchem.org/documents/ehc/ehc/ehc70.htmhttp://www.inchem.org/documents/ehc/ehc/ehc70.htm

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