Food Chemistry

496 9 Food Contamination

life (aqueous ozone solution) of 20 minutes at
room temperature. To disinfect process water,
0 .5–5 mg/kg of ozone are used for<5 minutes.
Apart from disinfection, ozone also delays the
ripening of fruit (cf. 18.1.4.1).

9.10 Polychlorinated

Dibenzodioxins (PCDD)

and Dibenzofurans (PCDF)

Polychlorinated dibenzo-p-dioxins (PCDD) and
polychlorinated dibenzofurans (PCDF), infor-
mally called “dioxins”, occur as companion
compounds or impurities in a large number of
bromine- and chlorine-containing chemicals.

(9.13)

Furthermore, they are formed in many thermal
processes (600◦C>T≥ 200 ◦C) in the pres-
ence of chlorine or other halogens in inor-
ganic or organic form. Consequently, they
are widely distributed in the environment.
The number of isomers (congeners) is large,
For rodents, 2,3,7,8-tetrachlorodibenzodioxin
(2,3,7,8-TCDD, “Seveso dioxin”) has proved
to be expecially toxic (LD 50 = 0 .6μg/kg,
guinea-pig) and carcinogenic. With the exception
of PnCDD, the toxicity of other congeners is
lower and is generally expressed as toxicity
equivalent factors (TEFs), based on 2,3,7,8-
TCDD (TEF=1) (Table 9.17). With the help of
these values, 2,3,7,8-TCDD equivalents (TCDD
equivalents, TEQ) can be calculated, which are
a measure of the total exposure to corresponding
compounds (cf. Table 9.17 and 9.18).
The daily intake of dioxin in industrial countries
is estimated at 1–3 pg TEQ/kg body weight. The
half life and the absorption rate are assumed to
be 7.5 years and 50% respectively. In 1997, the
WHO set a value of 1–4 pg TEQ per kg body
weight and day as a tolerable, lifelong intake (tol-
erable daily intake, TDI). Table 9.18 shows the
estimated dioxin intake with food. Due to the con-
centration of dioxins in the fat phase, mother’s
milk in the industrial countries has on average

Table 9.17.Risk assessment of dibenzo-p-dioxins and

dibenzofurans

Congener TEFa

Dibenzo-p-dioxins

2,3,7,8-TCDD 1

1,2,3,7,8-PnCDD 1

1,2,3,4,7,8-HxCDD 0.1

1,2,3,6,7,8-HxCDD 0.1

1,2,3,7,8,9-HxCDD 0.1

1,2,3,4,6,7,8-HpCDD 0.01

OCDD 0.0001

Dibenzofurans

2,3,7,8-TCDF 0.1

1,2,3,7,8-PnCDF 0.05

2,3,4,7,8-PnCDF 0.5

1,2,3,4,7,8-HxCDF 0.1

1,2,3,6,7,8-HxCDF 0.1

1,2,3,7,8,9-HxCDF 0.1

2,3,4,6,7,8-HxCDF 0.1

1,2,3,4,6,7,8-HpCDF 0.01

1,2,3,4,7,8,9-HpCDF 0.01

OCDF 0.0001

aToxicity equivalent factors (2,3,7,8-TCDD = 1).

Table 9.18. Average daily intake of 2,3,7,8-tetra-

chlorodibenzo-p-dioxin (2,3,7,8-TCDD) and related

compounds with the food (pg/day)a

2,3,7,8-TCDD ΣTEQb

Meat products

(including poultry) 7 23.5

Milk 6.2 28.5

Eggs 0.8 4.2

Fish 8.6 33.3

Vegetable oil < 0. 2 c < 0. 6

Vegetables < 2. 4 c < 2. 4 c

Fruits < 1. 4 c < 2. 6 c

Sum: 24.6 93.5d

aBased on an “average food basket”.

bSum of the compounds taken in, expressed as toxicity

equivalents TEQ (cf. text).

cThese numbers are included in the sum with 50%.

dAt present, the TDI value (cf. text) is 1–4 pg/kg body

weight and day. In outdoor air that is not directly con-

taminated, it can be assumed that the intake through

breathing is 0.03 pg TEQ/kg body weight and day.

10–35 pg TEQ per g of fat and in the developing

countries, 10 pg TEQ per g of fat.