Environmental Engineering Reference
In-Depth Information
example, prevention of crop diseases), while the load for soil and groundwater must
be acceptable. The consequence is that the soil inputs from agriculture have been
regulated in specific legislation in practically all countries in the world.
1.3 Contaminants
1.3.1 Terminology
No chemical substance leads to toxic effects by definition. Whether substances will
cause toxic effects depends on the combination of exposure, the nature of the sub-
stance and the characteristics of the receptor (a human being or an organism). The
overall exposure depends on the dose which humans or organisms are exposed to,
the period over which this exposure takes place, the frequency of the exposure and
the form (
speciation
) in which the chemical substance is available.
Several terms are used for the very generic term 'chemical substance' in con-
taminated site management. Often the term 'compound' is used. However, this term
is considered too generic in the context of this topic. Moreover, it literally does
not cover all chemical substances in soil, since 'compound' refers to chemical sub-
stances that are composed of two or more elements, which means that pure metals
are excluded. Alternatively, the term 'compound of concern' (or 'chemical of con-
cern') (COC) is sometimes used. Of all the terms used, the word 'pollutant' evokes
the most negative association, since definitions include adjectives such as 'harm-
ful', 'unsuitable' or even 'toxic'. The term 'contaminant' is used throughout this
topic, although it also has a negative ring, but this term does the best justice to the
'potential' aspect of causing adverse effects.
1.3.2 Daily Life
Potentially toxic chemical substances in the soil (
contaminants
) are part of our daily
life. In modern times, humans and organisms are continuously exposed to a wide
spectrum of contaminants. Humans are surrounded by all kinds of materials that
contain a variety of potentially harmful chemicals, on a daily basis. Cloth, fur-
niture, decorative objects or children's toys, all contain chemical substances that
are potentially toxic. Humans even eat and drink materials and inhale air that con-
tains contaminants that are designated on several lists of Soil Quality Standards.
Analogously, soil organisms are surrounded by all kinds of contaminants. They also
feed on contaminant-holding materials.
Actually, humans have been in contact with contaminants since early human exis-
tence, due to the presence of metals in the soil, for example, or through PAHs from
the burning of wood and roasting of meat. However, as long as humans lived in
equilibrium with nature, exposure was limited and the threat to human health from
contaminant exposure was generally negligible.
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