Environmental Engineering Reference
In-Depth Information
11.3.2.3 Calculation of Human Exposure
The exposure is calculated as follows:
T
Q
j
(
t
i
)
f
i
(
t
i
)
×
1
T
1
BW
(
t
i
)
×
=
×
×
(
t
i
−
D
f
(
T
)
C
j
(
t
i
)
t
i
−
1
)
(11.34)
t
i
=
0
j
in which
D
f
(
T
)
average human exposure to contaminant by ingestion of animal
products for the period from
t
=
=
0to
T
[mg/kg
body weight
/d]
Q
j
(
t
i
)
=
daily average quantity of product
j
consumed at time
t
i
[in kg/d]
C
j
(
t
i
)
=
concentration of contaminant in product
j
at time
t
i
[mg/kg]
f
j
(
t
i
)
=
fraction of products
j
from the site at time
t
i
[-]
BW
(
t
i
)
=
body weight of the receptor at time
t
i
[kg]
For acute exposure,
T
is between 1 to several days, for subchronic exposure
T
is
between several days to several months and for chronic exposure
T
may range from
one year to a lifetime.
If the input parameters of Eq. (
11.34
) can be assumed constant during
T
,the
average human exposure by ingestion of animal products is as follows:
j
Q
j
×
C
j
×
f
j
D
f
=
(11.35)
BW
11.3.3 Input Parameters
11.3.3.1 Intake by Animals
Data from different guidelines, reports and scientific papers are gathered in the
Tables
11.1
,
11.2
, and
11.3
.
Some references distinguish the diet of the dairy cows from that of the beef cattle,
as the former have a higher consumption of food and water, which can lead to greater
exposure to contaminants.
Soil ingestion can be due to inadvertent ingestion of soil while eating outdoors
or to deposition of soil on forage. That is why soil ingestion is sometimes expressed
as a fraction of the consumption of forage by animals. There is little information
about soil ingestion rates, therefore the uncertainties in the values are relatively
high.
As the absorption rate or biotransfer parameters of contaminants are usually
estimated from experiments where animals were exposed via food or water, the
relative oral bioavailability (B
s
) of contaminants in these experiments is not neces-
sarily the same as the relative oral bioavailability of contaminants on soil particles.
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