Polycyclic Aromatic Hydrocarbons - Organic Pollutants: An Ecotoxicological Perspective - page 191

were observed (Livingstone 1985). The lowest level of dosing with diesel oil (29 ppb
for 4 months) caused a doubling of P450 levels, a reduction in lysosomal stability,
and an increase in cytochrome P450 reductase. Thus, strong evidence was produced
for the harmful effects of PAH on M. edulis near an oil terminal, but it was not estab-
lished whether these were sufficient to cause a population decline.
As discussed earlier (see Chapter 6, Section 6.2.5), several studies have linked the
presence of high PAH levels in the marine environment with a high incidence of tumors
in fish. The ecological significance of these observations, however, is not known.
9.7 Summary
On the global scale, most PAH release is the consequence of incomplete combustion
of organic compounds. In the marine environment, however, there can be significant
levels of PAH pollution locally, due to the large-scale release of crude oil—especially
due to the wreckage of oil tankers, but also to leakage of crude oil during offshore
oil operations. PAHs can be biomagnified by some aquatic invertebrates, but not in
organisms higher in the food chain in which they are relatively rapidly metabolized.
PAHs do not have high acute toxicity to terrestrial animals. To fish, however,
they can show considerable toxicity in the presence of UV light, as a consequence
of their photooxidation. In human toxicology, the main concern has been about the
mutagenic and carcinogenic properties of some PAHs. The metabolic activation of
such compounds leads to the formation of DNA adducts, which can be stabilized as
mutations of oncogenes or tumor suppressor genes, genes that have a role in growth
regulation. There is growing evidence that PAHs can also form DNA adducts in
wild vertebrates; however, there is controversy about the significance of this from an
ecological point of view. PAHs cause the induction of P450 1A1/2, a response that
has been utilized in the development of biomarker assays for these and other planar
lipophilic organic pollutants.
furtHer readIng
Clark, R.B. (1992). Marine Pollution , 3rd edition, Clarendon Press, Oxford—Offers a read-
able account of marine pollution caused by crude oil, but does not deal with biochemical
aspects.
Environmental Health Criteria 202 (1998). WHO, Geneva—Gives a very detailed account of
the environmental toxicology of PAHs seen from the global point of view. However, it
largely ignores marine pollution caused by oil spills.