IPC

M I U 1 :4 .19 FAI MUMM 2MICIUJAM I

4C44eI4

WORLD HEALTH ORGANIZATION
p

.

This repc

ternation,

IA SERIES represent

United Na

1998)0 .

tional La

ate (N 131,1992) Organizat

1 989) No i 14 091) P

o 48

ad chemical etiology and

rinciples of studies on

pesticides, ethylenethiourea, an

d

general introduction t- Envirc s (No . 137, 1992 )

94)

miology, guidelines on

983)

33,

5, 1985)

ncy (ELF) fields (No . 35,

3 .1992)

IM)

No . 36, 1984) MET

minants in food,

assessment of

1989)

n populations ,

of (, 10, 1985)

4)

lorocyclohexanes First draf

United St

ne (No. 120, 1991

981) , principles for

m chemicals

cc)

a (No . 2-~ 1 982) '~IibhShi

ts (No . 85, 1989) e-Unii

7) *0.

Inte

o .77,1988) and"the

ts (No. 86, 1989)

.1991)

ethanol, and their

V(A
1 . SUMMARY

1 .1 properties and anatytical method s

Methyl ethyl ketone (MEK) is a clear, colourless, volatile,

highly flammable liquid with an acetone-like odour. It is stable

under ordinary conditions but can form peroxides on prolonged

storage; these may be explosive . MEK can also form explosive

mixtures with air. It is very soluble in water, miscible with many

organic solvents, and forms azeotropes with water and many

organic liquids . In the atmosphere MEK produces free radicals,

which may lead to the formation of photochemical smog .

Several analytical methods exist for the measurement of MEK

at environmental levels in air, water, biological samples, waste and

other materials . In the more sensitive methods, MEK is trapped

and concentrated either on a solid sorbant or as a derivative of

2,4 -din itropheny1hydrazine (DNPH) . Absorbed MEK and othet

volatile organic compounds are desorbed, separated by gas

chromatography and measured with a mass spectrometer or flame

ionization detector . Derivatized MEK is separated from related

compounds by high performance liquid chromatography and

measured by ultraviolet absorption. In media such as solid waste

and biological materials, MEK must first be separated from thE

substrate by methods such as solvent extraction or stearr

distillation . High concentrations of MEK in air can be monitorec

continuously by infrared absorption . Detection limits are 3 'Ug/m~

in air, 0 .05 Mg/litre in drinking-water, 1 .0 jag/litre in other type!

of water, 20 Mg/litre in whole blood and 100 pg/litre in urine .

1 .2 Sources of exposure and uses

1 .2.1 Producdon and odw sources

Recent values for annual industrial manufacture (in thousand!

of tonnes) are : USA, 212 to 305 ; western Europe, 215; Japan, 139

In addition to its manufacture, sources of MEK in the environment are exhaust from jet and internal combustion engines, an(

industrial activities such as gasification of coal . It is found ii

substantial amounts in tobacco smoke . In the USA, production o

MEK by engines is no more than 1% of its deliberate manufacture

In smog episodes, photochemical production of MEK and othe

carbonyls from free radicals can be far greater than direc

anthropogenic emission. MEK is produced biologically and ha
EHC 143: Med7y4 Eby Ketone

been identified as a product of miclabial-metabolism . It has

been detected in a wide diversity of natural products includ

higher plants, insect pheromones, animal tissues, and h.un

blood,--u-rine and exhal-ed-air. It is probably-a--minor product

norfii-af-mammalian metabolism .

1.2.2 Uses and loss to dw errWronmen t

The major use of MEK, application of protective coatings a

adhesives, reflects its excellent characteristics as a solvent . It a,

is used as a chemical intermediate, as a solvent in magnetic ta

production and the dewaxing of lubricating oil, and in fo,

processing . In addition to industrial applications, it is a comml

ingredient in consumer products such as varnishes and glues .

most applications MEK is a component of a mixture of organ

solvents . Losses to the environment are mainly to the air ar

result principally from solvent evaporation from coated surface

MEK is released into water as a component of the waste from i

manufacture and from a variety of industrial operations . It h-,

been detected in natural waters and could have originated froi

microbial activities and from atmospheric input, as well as froi

anthropogenic pollution .

1 .3 Environmental transport and distributio n

MEK is highly mobile in the natural environment and subjec

to rapid turnover . It is very soluble in water and evaporata

readily into the atmosphere. In air MEK is subject to rapi(

photochemical decomposition and is also synthesized b5

photochemical processes . In water containing free halogens oi

hypohalites, it reacts to form a haloform that is more toxic than

the original compound. MEK is distributed by both air and water,

but does not accumulate in any individual compartment, and does

not persist long where there is microbial activity . It is rapidly

metabolized by microbes and mammals . There is no evidence of

bioaccumulation. MEK occurs naturally in some clover species

and is produced by fungi to concentrations that affect the

germination of some plants .

1 .4 Environmental levels and human exposure

General population exposure to low levels of MEK is

widespread. In minimally polluted air, the concentration is less

than 3 pg/M3 (< I ppb), but a level of 131 ug/m' (44 .5 ppb) has

been measured under conditions of heavy air pollution . Away

14
P. 5

f Eby Ketone

of the toxicity of other solvents 2

.

IDENTIM PHYSICAL AND C

AND ANALYTICAL

.iates the neurotoxicity of hexacarbon compounds

hyl-n-butylketone and 2,5-hexanedione) and the

y toxicity of haloalkane (carbon tetrachloride and

te) solvents . 2.1 Identity

H ltion of the neurotoxic effects of hexacarbons has Chemical structure :

I I

ited for all three hexacarbons in animals . The H- C -

opathies observed in humans followed changes in I

is of solvents to which they had been exposed, H

~y or occupationally . The mechanism by which thi s

!urs is unclear.

potentiation of the liver and kidney toxicity of Chemical formula: C,,H,O

tes from animal studies . MEK probably activate s

netabolism to tissue-damaging species as a result Synonyms: Butanone,

the relevant oxidation enzymes . ethyl meth

methyl ace

CAS registry number: 78-93-3

RTECS registry number: EL 64750(

UN registry number: 119 3

ber: 606-002-( EC registry nurn

Relative molecular mass : 72 .1 0

2

.2 Chemical and physical propertii

Methyl ethyl ketone (MEK) is a

chemical. The physical properties

Table 1 . it is a highly flammable, v

that is stable under ordinary col

explosive mixtures with air over a

12% (vol./vol.). The odour is acetor

as sharp, fresh or sweet. The o,

around 5

.9 Mg/M3 (2 ppm) althou

147 .5 Mg/M3 has been reported (Ru

soluble in water; the solubilit,

temperature . it is miscible with or

e R-a- t er h-d benzene, and forms azc

organic liquids .
p. 6

EHC 143. Methyl Eb*

Ketone Identrilly, Physical and Chemical Properties and Ar

Table 1 . Physical properties of MEK (catalysed with acid or base), oxidation via concer

acids or acidic peroxides, and reduction with hyd

Reference catalysts. None of these reactions is likely to

Appearance cOlourless liquid nature. On the other hand, MEK and other me~

react with halogens and hypohalides in aqueous

Relative molecular mass 72 .10 Papa & Sherman (1978) a carboxylic acid and a haloform . The reaction p i

test for methyl ketones, and may produce Specific gravity (liquid density)

(at 20 -/4 oC)a chlorinated water supplies contaminated with

0 .805 Krasavage et al . (1982) V'MEK and other ketones are photochernically reac

Vapour density (air = i .oo) 2.41 VerSchuren (198a) ~by wavelengths occurring in the atmosphere a

radicals which lead to the formation of pho

Vapour pressure at 2o C (torr) 77 .5 Weast (1986) Grosjean et al ., 1983).

Boiling point (oC) 79.6 Weast (iqw) ion factors

Melting point (IC) .86 Weast (1986) 1

ppm = 2.95 mg/ml; I mg/m'= 0.34 ppm

water solubility at 20 oC (g/litre) 275 Windholz (1983) (at 25 'C and 101 .3 kPa)

Refractive index 1 .3788 Krasavage et al, (1982) Pling and anaVical methods

Flash point (closed cup) CC) -6 Papa & Sherman (1978) considerations

Log P./, 0-26V Verschuren (1983)

0 .29 Banergee & Howard (1988) Analytical methods for MEK depend on the

Saturation concentration in Marized in Table 2.

air (g/m3 at 20 IC) 301 Krasavage et al, (1982) here MEK is present in a substantial co

own to be the only or the dominant org

lified methodology is feasible . The occup,

Specific gravity at 20 'C relative to the density of water at 4 *C sure limits, currently in the range 295-5~

), permit monitoring in the workplace

edures .

The value in Table I for log p./, (logarithm of water partition ratio) of the octanol/ he precise determination of MEK wh 0 .26 is taken from Verschuren

Banergee & Howard (1983) . ronment at low concentrations is a comp (1988) quoted a slightly higher value of 0 .29.

ide variety of other organic compounds Other partition values for MEK (at

blood/air =

37 *Q are: water/air = 254; the many possibilities for error,

oil/blood = 1

202

.3

; olive oil/air = 263; olive oil/water = 1 .0, and olive mination. MEK, other ketones and (Sato & Nakajima, 1979) . Perbellini et al. (1984), tances are so prevalent in laboratory an(

however, determined partition values for saline solution/air and be taken in all determination!

olive oil/air of 193 and 191 respectively. of contamination of samples, equi ~

e taken to avoid contamination ir

The physical and chemical properties of MEK are determined I

largely by asily, unnoticed sources like PVC its carbonyl group. MEK engages in reactions typical flection equipment may leach a si : of saturated aliphatic ketones . These include condensations with 0 water samples (Kent et al ., 1985).

amines, aldehydes and many other organic compounds, hydrolysi s

20
p. 7

7

'npounds 4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION tion, but AND TRANSFORMATIO N

Iving its 4.1 Transport in the environment iale an d

,1985). MEK appears to be highly mobile in the natural environment

(Lande et al., 1976). It is water soluble (Windhoiz, 1983) and

1984) evaporates rapidly in air. The generally low values for MEK in

MEK outdoor air probably stem mainly from its rapid removal b y

)n 3 .j).

photodecompo-sition . Scavenging by aqueous droplets and dry

tribute deposition, which also represent potential routes of loss from the

atmosphere, are balanced to an unknown extent by evaporation of

MEK from water and soil . There is no specific information on

partitioning of MEK in the environment . Although Basu et al .

(1981) estimated from its physical properties that MEK will

"exhibit low sediment-water and soil-water partitioning and be

susceptible to substantial leaching from soils to which it is not

extensively chemically bound", there is no information on

chemical binding of MEK to sediment particles. As mentioned

above, MEK has, however, been detected in ground water and the

leachate from hazardous waste sites (section 3 .3) .

4.2 Bioaccumulation and biodegradation

On the basis of its octanol/water partition and water solubility,

bioconcentration factors (13CF) of approximately I and 0 .5,

respectively, have been calculated for MEK (US EPA, 1985b). In

view of its high water solubility, ecosystem modelling (Metcalf et

al ., 1973 ; Chiou et al., 1977) indicates that it

-

is unlikely that MEK

will accumulate in food webs . It is absorbed and metabolized by

organisms present in the environment, e .g ., in waste water (Dore

et al ., 1975, Bridie et al., 1979a) and in soil (Perry, 1968). It is

rapidly metabolized by mammals (Di Vincenzo et al ., 1976, 1978 ;

Dietz et al ., 1981 ; Miyasaka et al ., 1982) and by many microbes

(Gerhold & Malaney, 1966; Dojlido, 1977; Urano & Kato, 1986). MEK is nearly completely degradable at concentrations up to 800

Mg/litre on the basis of biochemical oxygen demand (BOD), and

the rate of degradation decreases with increasing concentration of

MEK . Using activated sludge there was complete degradation of

MEK in 8 days at a concentration of 200 mg/litre (200 ppm) and

in 9 days at a concentration of 400 mg/litre (400 ppm) (Dojlido, 1979) . At a concentration of 20 mg/litre in river water containing

Preadapted microbes, MEK was completely degraded in 2 .5 days

(Doilido, 1977) . Delfino & Miles (1985) reported a slower rate o f

35
EHC 143. MeMyf Edryt Ketone

decomposition in aerobic ground water ; I mg/litre was fully

degraded in 14 days . However, a bacterial species (Alcaligenes

faecalis) found in sewage sludge metabolized MEK slowly if at all

(Marion & Malaney, 1963). The data on mammals and microbes

suggest that MEK is rapidly absorbed and metabolized by most

living organisms (Basu et at ., 198 1).

MEK in air is rapidly decomposed by photochemical processes,

mainly through o)Ckdation -by hydroxyl free radicals as well as some

decomposition by direct photolysis (Levy, 1973; Laity et al., _F9_73 ;

Dillirik et al ., 1976; Grosjean, 1982; Seinfeld, 1989). Basu et al .

(1981) estimated a half-life of 5 .4 h for photochemical

decomposition in urban atmospheres . They further concluded that

the lower concentration of photochemically produced oxidants in

rural air will lead to a substantially lower rate of photochemical

decomposition in these areas . The concentration of MEK and

other carbonyls is higher in urban air (Grosjean & Wright, 1983;

Snider & Dawson, 1985). Greater anthropogenic emissions and

photochemical synthesis of carbonyls from free radicals (Grosjean

et al., 1983) may overwhelm the more rapid photochemical

decomposition in urban atmospheres . Scavenging by aqueous

droplets and dry deposition may also be important processes in the

removal of atmospheric MEK (Grosjean & Wright, 1983) .

MEK (and other saturated aliphatic carbonyls) is not chemically

reactive under conditions found in most natural waters and in

general will not degrade rapidly from physical causes once

deposited in water (US EPA, 1985b) . The exception is water

containing free halogens (such as chlorine) or hypohalides . MEK

reacts with these to form a haloform and propionic acid (Basu et

al., 1981). This can be a cause for concern in chlorinated waste

water and water supplies, since the chloroform thus produced is

more toxic than the original MEK (US EPA, 1985a).

36
MW Ketone

aerobic ground water;

I mg/litre was fully

5. ENVIRONMENTAL LEVELS AND HUMAN iys . However, a bacterial species (Alcaligenes sewage sludge metabolized MEK slowly if at all EXPOSURE

,y, 1963). The data on mammals and microbes

is rapidly absorbed and metabolized by mos t 3asu et al ., 198 1). Environmental levels

pidly decomposed by photochemical processes, Air dation by

hydroxyl free radicals as well as some Although MEK is widely present in the natural environment, 'irect photolysis (Levy, 1973; Laity et al ., 1973; Grosjean, 1982; Seinfeld, 1989). Basu et al . concentrations are always low even under conditions of pollution

a half-life of 5.4 h for photoche (Table 4) mical . In minimally polluted outdoor air, the level is less than

(I ppb), but '"g/M3 131 Lg/M3 (44.5 ppb) has been measured -ban atmospheres . They further concluded that 3

tion of photochernically produced oxidants in under conditions of heavy air pollution in the Los Angeles basin .

o a substantially lower rate of photochemical Volatilization of MEK from building materials and consumer iese areas . The concentration of MEK and products can pollute indoor air to levels above adjacent outside air .

igher in urban air (Grosjean & Wright, 1983;

In a study of 15 Italian urban homes, De Bortoli et al . (1985, 1986) 1985). Greater anthroPogenic emissions and reported 8 Ug/M3 as a mean indoor air value and 38 t1g/M3 as a

tesis of carbonyls from free radicals (Grosiean maximum value. Maximum and average values for MEK in

Overwhelm the more rapid photochemical outdoor air adjacent to these homes were 12 and 3 .8 Ag/m' -ban atmospheres . Scavenging by aqueous respectively. Shah & Singh (1988) reported four observations of

osition may also be important processes in the MEK in indoor air in the USA; the median and mean values were ,ric MEK (Grosjean & Wright, 1983). 21 and 27 jug/m' (7.1 and 9.2 ppb), respectively . In a confined and

tightly sealed space, however, MEK concentrations can be much

iturated aliphatic carbonyls) is not chemically higher. Liebich et al . (1975) measured 1 .9 to 4 .4 Mg/M3 (665 to

itions found in most natural waters and in 1505 ppb) in Space Lab IV.

grade rapidly from physical causes once Human activities, other than the deliberate manufacture and US EPA, 1985b).

ens (such as chlorine) or hypohalides The exception is water use of MEK, may in some circumstances contribute significantly

orm a haloform and proPionic acid (Basu et . MEK to environmental levels. MEK is a minor component, :5 2 .95

mglm' (1 .0 ppm), of gasoline engine exhaust and also has been

oe a cause for concern in chlorinated waste detected in the exhaust from diesel engines ,lies, since the chloroform thus produced i ano jet aircraft. The s riginal MEK (US EPA, 1985a) . US Environmental Protec-tio--n X-g-e-j~c-y estimated thi-t1_09 tonnes

of MEK was emitted in motor vehicle exhaust in the USA in 1987

("Mobile source estimates for methyl ethyl ketone" ; personal

communication by J.H. Somers, 1989). In addition, Grosjean et al .

(1983) concluded that synthesis of MEK and other carbonyls from

hydrocarbons in vehicle exhaust by photochemical reactions in the

atmosphere may greatly exceed their direct production by motor

vehicles . Thus, away from industrial areas where MEK is

manufactured or used, it is likely that motor vehicles are an

important and possibly major source of atmospheric pollution by

MEK . Sm king cigarettes and other tobacco products contributes io

slightly to individual exposure . Although the concentration of

MEK in cigarette smoke (Table 4) may exceed recommended

levels of permissible occupational exposure (Table 5) by several

37
EHC 143 : Methyf Edryf Ketone

times, the total amount of MEK generated by smoking a single

cigarette is about 1/74th of the acceptable human daily chronic

intake in the USA (1 5 .43 mg/day) (US EPA, 1986). MEK also has

been detected in the gases from structural (building) fires (Lowry

et al., 1981).

5.1.2 Water

MEK concentrations in exposed natural waters are less than 0 . 1

mg/litre (0. 1 ppm) and are usually below the level of detection,

Ewing et al . (1977) analysed 204 samples from rivers with

industrialized basins ; only one sample contained MEK (0 .023

mg/litre). Jungclaus et al . (1978) measured significant levels of

MEK in waste water from a chemical plant but could not detect

it in either water or sediment of the brackish Delaware River

receiving this waste . Despite its rapid disappearance from water,

trace amounts of MEK have been detected widely in drinkingwater (US EPA, 1985b). A potential source is solvent leached

from the cemented joints of plastic pipe (Wang & Bricker, 1979;

Boettner et al ., 1981). A single unexpectedly high value of 0 .47

mg/litre (0.47 ppm) in mist from the landward edge of the Los

Angeles basin probably resulted from scavenging of heavily

polluted air (Grosjean & Wright, 1983) . Data on MEK in sediment

(US EPA, 1985b) were based on four samples and are difficult to

interpret. Sawhney & Kozloski (1984) studied organic pollution

of leachates from municipal landfill sites in Connecticut, USA .

MEK concentrations ranging between 4 .8 and 8 .2 mg/litre were

measured over a two-year period at one site. This high value may

have resulted not only from a substantial input but also from

reduced microbial activity and no evaporative loss to the air .

Environmental concentrations in a number of media are shown

in Table 4 .

5.1 .3 Foodstuffs

MEK is produced in small amounts by animals, higherpiants,

algae a

-

nd microbes, and is a widespread, although generally minor,

comP6ne nt of iis_tF and odo u-r- Tn Tood-s_TZakhari__e t al .,-l 97 7). It

has been identified in some foodstuffs and beverages. Using the

DN.PH method with coluffin or p a-peif-c~hf-o-mato-graphy, it has been

identified (but not quantified) in white bread (Ng et al., 1960),

tomatoes (Schormfiller & Grosch, 19C4)-, cooked turkey meat (but

not in raw me t-and with more MEK in roaiV~d-ib-an in boiled

meat, the level increasing with roasting time) (Hrdlicka & Kuca,

40
14 Kelctne Environmental Levels and Human E)q3osure

)unt of MEK generated by smoking a single 1965), and in egg white (Sato et al., 1968) . Using gas

/74th of the acceptable human daily chronic chromatography, or

4

traces of MEK were found in fresh chicken meat 5 .43 mg/day) (US EPA, 1986). MEK also has (pectoral muscle) with a marked increase in samples kept f

gases from structural (building) fires (Lowry V days at room temperature . It was not found in caecal gas from

living chickens but was detected in the gas 18 and 24 h after death

(Grey &

Shrimpton, 1967) . MEK has also been detected in

cottonseed o

9i164()

D,ornseifer et al ., 1965), honey (Cremer &

Riedmann, c9flf-ee (Gianturco et. al., 1966), roast barley

ons in exposed natural waters are less than 0. 1

ind are usually below the le' (Shimizu et al., 1969), and in the mushroom Agaricus bisporus

vel of detection . Y ,

analysed 204 samples from rivers with (Starible & Rast, 197 1). By means of GC/MS, Wong et al . (1967)

only one sample contained MEK (0.023

detected MEK in codfish and Kahn et al . (1968) reported its

et al. (1978) measured significant levels of presence in a low-boiling distillation fraction of Canadian whisky .

from a chemical plant but could not detect In a study of compounds relate d to milk flavour, Wong &

sediment of the brackish Delaware River Patton (1962) determined MEK concentrations using the DNPH

Despite its rapid disappearance from water, method with column separation and paper chromatography . The

~'K have been detected widely in drinking

-

concentrations in two samples of untreated milk were 0 .77 and 5b). A Potential source is solvent leached 0 .79 mg/litre and in two samples of cream'were 0 .154 and 0.177 )ints of plastic pipe (Wang & Bricker, 1979; mg/litre. Gordon & Morgan (1972) examined the influence of . A single unexpectedly high value of 0 .47 volatile compounds in milk on "feed" flavour and reported MEK

in mist from the landward edge Of the Los

bly resulted from scavenging of heavily concentrations of 0 .25-0.35 mg/litre in moderately "feed"

flavoured milk and 0 .50-1 .0 mg/litre in strongly flavoured milk, & Wright, 1983). Data on MEK in sediment with a highest concentration detection of 1 .4 mg/litre. They

e based on four samples and are difficult to concluded that MEK is one of the compounds responsible for

, Kozloski (1984) studied organic pollution producing the unpleasant "feed" flavour in milk. Using the

nicipal landfill sites in Connecticut, USA. DNPH method and paper chromatography, Harvey & Walker ranging between 4.8 and 8 .2 mg/litre were

~ear Period at one site . This high value ma

(1960) detected MEK in New Zealand cheddar cheese one day

y after manufacture . The concentration increased during ripening,

; y from a substantial input but also from reaching 0 .9 mg/kg at 40 weeks, and was related to the

Ivity and no evaporative loss to the air. development of typical Cheddar cheese flavour . In another study

,entrations in a number of

media are shown of the chemical nature of USA Cheddar cheese flavour, Day et al.

(1960) analysed the volatile flavour fraction of cheeses over I year

1~. old using DNPH and column partition chromatography, and

reported approximate MEK concentrations of 12 .5 mg/kg. Keen

et al . (1974) postulated that the formation of MEK in New

Zealand Cheddar cheese, for which levels as high as 19 mg/kg had

I small amounts by animals, higher plants been reported, occurred in steps carried out by different microbial

~.

is a widespread, although generally minor' species including Streptiococcus cremaris, Pediococcus cerevisiae, I odour in foods (Zakhari et al

., 1977). 1; Lactobacillus plantarium and Lactobacillus brevis . They considered

ome foodstuffs and beverages . Using the that MEK was an important flavour constituent in the cheese .

umn or paper chromatography, it has bee n

ntified) in white bread (Ng et al ., 1960), In another investigation of monocarbonyl compounds as flavour k

Grosch, 1964), cooked turkey meat (but components, Mookherjee et al . (1965) measured MEK in fresh and

ith more MEK in roasted than in boiled stale (8 weeks old) potato chips with the DNPH method and

ig with roasting time) (Hrdlicka & Kuca, liquid-liquid chromatography. In fresh potato chips the

41
EHC 143-- Meby EffV Ketone

concentration of MEK was 1 .8 Mmoles/kg, and this increased to

2 .2 pmoles/kg in state chips .

Amylomaize starches are heat treated in the production of films

and fibres to concentrate the amylose . Bryce & Greenwood (1963)

used gas chromatography to measure pyrolysis products (including

MEK) of potato starch, potato amylose and amylopectin, maltose,

isomaltose and glucose . MEK was not detected in untreated starch

nor in starch pyrolysed in vacuo for 20 min at 200 and 220 *C. With increasing temperatures the concentration of MEK increased ;

at 230, 250, 300, 350 and 400'C the MEK concentrations were 10,

15, 50, 65 and 70 moles x 10'/g starch, respectively.

Small quantities (up to 2 ng/1 .5 g bean) were found in soybeans

(Clycine max) and winged beans (Psophocarpus tetragonolobus) by

means of dynamic headspace GC/MS (Del Rosario et at ., 1984).

However, the repofted concentrations of MEK in foods are low

and food consumption is not considered a significant source of

population exposure .

5.2 General population exposure

Stofberg & Grundschober (1984) calculated the consumption

ratio between the quantity of a flavouring material consumed as

an ingredient of basic and traditional foods and the quantity of

that same flavouring material consumed as a component of added

flavourings by a certain population . If the consumption ratio is

more than 1, this substance is consumed predominantly as an

ingredient of traditional foods . For MEK, this ratio may be up to

41 1 . The annual consumption in the USA of MEK via apple juice

is 85 kg, white bread 70 132 kg, butter 34 kg, carrot 154 kg,

Cheddar cheese 30 139 kg, Swiss cheese 198 kg, fish 81 kg, potato

chips 31 kg, tomato 31 878 kg, and yoghurt 1104 kg. Assuming a

population of 230 millions, the estimated average daily intake in

the USA amounts to 1 .59 mg/kg foodstuff. Some information on

the MEK contents of various foodstuffs is given in Table 6 . The

European Economic Community regulates the level of MEK in

certain foodstuffs; these are given in Table 7 .

In addition to the MEK that is naturally present, foods may

also contain MEK absorbed from plastic packaging materials . This

can be derived from solvent left in the plastic during manufacture

(Kontominas & Voudouris, 1982) or represent one of the many

42

/ z