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CHAPTER
4 CONTAMINANTS OF CONCERN
| 4.4 |
Total
Polycyclic Aromatic Hydrocarbons (PAHs) |
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| 4.4.1 |
Environmental
Implications of PAH Pollution |
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Polycyclic
aromatic hydrocarbons (PAHs) are a large class of
fat-soluble organic compounds which depending on
the compound concerned, can be markedly carcinogenic.
They are widespread and form through the incomplete
combustion of organic compounds which represents
an important source of human exposure(71). Major
sources of PAHs to the marine environment are likely
to be from hydrocarbon combustion sources such as
vehicle emissions and coal combustion (eg from coal-fired
power stations). Aquatic organisms are very sensitive
to certain PAHs and toxicity increases as molecular
weight and lipophicity increase(72). Toxicity to
aquatic organisms is also affected by ambient light
conditions. In the presence of UV light, certain
PAHs accumulated in tissues can undergo photo-oxidation
thus elevating toxicity to aquatic organisms(73).
Not all PAHs absorb light to the same degree and
hence toxicity differs between the congeners. For
example, phenanthrene and fluorene do not absorb
light efficiently, and hence, did not cause photoinduced
toxicity in Daphnia , whereas anthracene, fluoranthene
and benzo[a]pyrene absorbed significantly more light
energy and were highly toxic(74) . Clearly, PAH
toxicity to organisms will be largely influenced
in the marine environment by factors such as ambient
irradiation and water column turbidity.
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| 4.4.2 |
SUSDEV
21 Baseline Monitoring Results |
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Total
PAHs were not recorded above detection limits
(402 mg kg-1, wet weight) in any tissue sample
during this baseline Study. Individual PAH congeners
were also only rarely recorded in tissues analysed
(see Table 3.4a and 3.4b). Of all PAHs, Naphthalene
was detected consistently at concentrations above
detection limits in tissue samples from most stations
(ie 12% in December 1998, 27% in January, 27%
in August and 33% in September 1999).
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