Human Exposure Pathways - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 462

in which

Exposure vegetables = exposure due to vegetable consumption

[mg/kg body weight /d]
Q vegetable i =

consumption rate of vegetable i [kg dw /d]

C vegetable i = contaminant concentration in vegetable i [mg/kg dw ]

f home-grown = fraction of vegetables that is home-grown [-]

f bioavailability = correction for relative bioavailability in the human body [-]

=

W body weight [kg body weight ]

Ideally, calculation of exposure through vegetable consumption should relate
directly to vegetables that are generally grown in home gardens and vegetable gar-
dens. However, statistics on this type of vegetable production are lacking in most
countries. For this reason, exposure through vegetable consumption is generally
related to the overall consumption pattern , i.e., the vegetables that humans con-
sume, independent of their origin (grocery, supermarket or home-grown). In the
Netherlands, for example, a consumption-weighed vegetable package has been con-
structed for Risk Assessment purposes (Swartjes et al. 2007 ). This package is based
on the average consumption rates of 32 vegetable types for all age groups and
both sexes. Subsequently, the overall vegetable consumption is considered to be
proportional to the contribution of each separate vegetable to the total vegetable
consumption rate for adults and children.

11.2.3.2 Metals

For metals, a vegetable-consumption-rate-weighed BCF (BioConcentration Factor),
BCF veg-cr-weighed , is calculated. This is the relation between the metal concen-
tration in vegetables and the metal concentration in soil. The basis for these
vegetable-consumption-rate-weighed BCF are plant-soil relations, i.e., equations
which describe the relation between contaminants in specific vegetables as a func-
tion of (total) soil concentration and soil properties (for metals; see Chapter 8 by
McLaughlin et al., this topic). In the Netherlands, a geometric mean of BCFs from
the literature is used, which is corrected with a so-called soil specific correction
factor , in case no significant plant-soil relations are available for a specific veg-
etable (Swartjes et al. 2007 ). This soil specific correction factor is a function of
the organic matter and clay contents of the soil and accounts in a practical way
for bioavailability. The equation for the vegetable-consumption-rate-weighed BCF
(BioConcentration Factor), BCF veg-cr-weighed ,isasfollows:
BCF veg-cr-weighed = w i × BCF pl - soil relation + w j × BCF geo mean / STcf BCF

(11.2)

in which

w i = vegetable-consumption-rate-weighing factor, for vegetables for which a

plant-soil relation is available [-]