2009_Book_FoodChemistry

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), informally
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 presence
of chlorine or other halogens in inorganic
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 (tolerable
daily intake, TDI). Table 9.18 shows the
estimated dioxin intake with food. Due to the concentration
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
TEF a
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
a Toxicity equivalent factors (2,3,7,8-TCDD = 1).
Table 9.18. Average daily intake of 2,3,7,8-tetrachlorodibenzo-p-dioxin
(2,3,7,8-TCDD) and related
compounds with the food (pg/day) a
2,3,7,8-TCDD
ΣTEQ b
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 93.5 d
a Based on an “average food basket”.
b Sum of the compounds taken in, expressed as toxicity
equivalents TEQ (cf. text).
c These numbers are included in the sum with 50%.
d At present, the TDI value (cf. text) is 1–4 pg/kg body
weight and day. In outdoor air that is not directly contaminated,
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.