Oil in organisms
Many scientific studies on the fate of oil in organisms have been carried
out. They have shown that certain hydrocarbons
can provoke abnormal cellular proliferation (tumours) when they are injected
or implanted in the flesh. Repeated contact with these substances can provoke
lesions or necrosis, in particular in the eyes and nose, as well as chromosomal
alternations in reproductive cells. After some
oil spills, various mutagenic, carcinogenic, pathological or metabolic
effects have been observed in the long term on diverse aquatic species.
However, the direct link between the pollution and these effects has never been clearly demonstrated, as many other factors of natural or human origin interfere in the lives of species. As a consequence, claims for long term damage to ecosystems are often rejected due to insufficient evidence to support the causal link between the pollution and the perceived impacts.
The tainting of taste and odour in the flesh of certain species is however perfectly observable and measurable. This “oil-like” taste can form in a few hours to a few days in contaminated water. It then disappears in a few weeks when the contamination ceases. This alteration assumes particular importance for the species which are depended upon for fishing or other aquacultural activities, which can cause them to become temporarily unfit for sale. This necessitates quick decisions to ban fishing or selling sea produce.
Mussel contamination follow-up during the Erika and Prestige disasters (Source: Ifremer)
These bans, based on analysis of flesh or organoleptic tests, are an indisputable precautionary measure. Decisions to resume activities are not easy matters as consumers may have difficulty in accepting seafood which was tainted by oil even once its taste has returned to normal.
It is out of the question to have consumers take the slightest risk. They must be reassured as to the quality of the produce, which may have been declared irremediably contaminated during the days immediately following the disaster. On the other hand, the additional negative economic impact on certain industries of an excessive ruling on these matters is also a cause for concern and should be avoided.
In practice, as it is materially impossible to know which wild fish and crustaceans have been contaminated, fishing is reauthorised as soon as repeated chemical or organoleptic tests ensure that there is no more contamination in the whole area. As for fish and shellfish farms, stocks are sometimes destroyed before recommencing sales, in order to guarantee irreproachable produce for consumers.
Each country manages bans on marketing sea produce according to their own regulations, thus assuring consumers of the level of protection they are entitled to, without banning beyond reasonable limits or excessively destroying stocks. This is neither easy to establish nor to put into effect. The results of tests carried out on samples can be interpreted in very different ways according to the nature and severity of the selected criteria.
During the Aegean Sea pollution in Galicia, the Spanish authorities chose organoleptic testing as a point of reference, with the destruction of contaminated sea produce.
In the case of the Erika in France, the French food safety agency chose to analyse the content of “packages” of 16 known carcinogenic polycyclic aromatic hydrocarbons, without destroying stocks (except for oiled mussels).
Shellfish marketing in China (Source: Ifremer)