Introduction to Contaminated Site Management - Dealing with Contaminated Sites: From Theory Towards Practical Application - page 24

(benzene, toluene, ethylbenzene and xylenes). They were, or are, used on a large
scale in cleaning applications such as degreasing.
Sort-term effects due to exposure of monocyclic aromatic hydrocarbons usually
relate to skin and sensory irritation, as well as effects on the respiratory system and
the central nervous system. Prolonged exposure to these contaminants also affects
these organs as well as the kidney, liver and blood systems (Oregon Department
of Human Services 1994 ). According to the US Environmental Protection Agency,
there is sufficient evidence from both human epidemiological and animal studies to
denote benzene as a human carcinogen. Workers exposed to high levels of benzene
in occupational settings have been found to have an increased number of cases of
leukaemia.
1.3.3.5 Persistent Organic Pollutants
Persistent Organic Pollutants (POPs) are organic contaminants that are resistant
to chemical and biological degradation processes and to photolytic processes. For
this reason they are capable of persisting in the environment and bioaccumulate
in human and animal tissue. POPs are often halogenated, usually with chlorine.
The United Nations Environment Programme Governing Council (GC) includes
the following contaminants as POPs: aldrin, chlordane, DDT, dieldrin, endrin,
heptachlor, hexachlorobenzene, mirex, polychlorinated biphenyls (PCBs), poly-
chlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, toxaphene, certain
brominated flame-retardants, some organ metallic contaminants such as tributyl tin
(TBT), as well as some Polycyclic Aromatic Hydrocarbons (PAHs). Many POPs are
pesticides which are banned in many countries, but still are found in soils and will
reside in the soil for many more decades. In addition, POPs can originate from the
production of solvents, polyvinyl chloride, and pharmaceuticals. Generally speak-
ing, POPs have a high molecular mass and show a low water solubility, high lipid
solubility and limited volatility.
According to the Stockholm Convention, POPs can lead to serious health effects,
including certain cancers, birth defects, dysfunctional immune and reproductive
systems, greater susceptibility to disease and diminished intelligence (Stockholm
Convention 2009 ).
1.3.3.6 Volatile Organic Contaminants
Volatile organic contaminants (VOCs) are generally characterised by high enough
vapour pressures under normal conditions to significantly vaporize. There is not one
univocal exact definition for these contaminants. Under European law, the defini-
tion of VOCs is based on evaporation into the atmosphere, rather than reactivity.
In the European Union Directive 2004/42/CE, for example, VOCs are defined as
an 'organic compound having an initial boiling point less than or equal to 250 ◦ C,
measured at a standard atmospheric pressure of 101.3 kPa' (European Union 2008 ).
The US Environmental Protection Agency defines VOCs as 'any compound of car-
bon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides