Human Exposure Pathways - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 481

oxidizable or hydrolyzable. If known, a metabolism factor can be applied to improve
concentration predictions. However, it should be noted that the metabolised forms
of a contaminant are sometimes as toxic as, or even more toxic than the parent
compound.
11.3.3.3 Human Consumption of Products
Product Consumption
For site-specific Risk Assessment, region specific or country specific data must
be used for the diet, since cultural and climatic differences have a large influ-
ence on this parameter. The European Exposure Factors Sourcebook (ExpoFacts
2006 ) gathers exposure data from 30 European countries. Data regarding diet are
defined according to country, region, age, gender and social economic criteria. For
some countries, statistical distributions of food consumption rates and patterns are
provided.
Depending on the site and the level of detail required in modelling, several cat-
egories of data on the human consumption of animal products has to be gathered.
Dairy products, eggs and meat are usually taken into account. Because of the differ-
ences in exposure conditions between animals, meat from beef, pork and lamb are
sometimes distinguished.
For lipophilic contaminants, such as dioxins, which tend to accumulate in fat, it
can be more relevant to sum the quantities of products from one category on the
basis of their fat content. For these contaminants, dairy products have very differ-
ent contaminant concentrations when expressed on a fresh weight basis as their fat
contents range from 2 or 3% (milk) to more than 80% (butter).Therefore it is prefer-
able to calculate the weight of fat consumed via the different animal products and
to multiply it by the contaminant concentration in fat.
Fractions Related to on the Site
To assess human health risk due to a contaminated site, only the fraction of food pro-
duced on the site must be taken in account. The fraction of the diet which has a local
origin varies substantially between farmer and non-farmer families (see Table 11.4
for data for France, as an example).
11.3.4 Reliability and Limitations
It is generally recognised that the calculated concentrations in animal products are
relatively uncertain. The approaches proposed in this Section are simple. They are
based on models where animals are represented by only one box. This high sim-
plification assumes a single, uniform concentration in tissues, while in reality the
contaminants are heterogeneously distributed throughout the tissues. More sophisti-
cated models exist, like the model of McLachlan ( 1994 ), but they require more data
that may not be readily available.