A RECENT study, conducted in collaboration with Loro Parque Foundation, has concluded that contaminants accumulated in the sea, such as DDT, PCBs and persistent organic pollutants, together generate a toxic cocktail.
And it affects the immune system of orcas to a greater extent than if the animals were exposed to the same volume of each substance separately.
The project, supported by Loro Parque Foundation in 2017, investigated how these toxic pollutants affected the immune system of orcas specifically.
Dr Javier Almunia, Loro Parque Foundation’s Director of Environmental Affairs, said the value of this study was down to the toxic components being measured together, and not individually, which is how they are found in nature.
The components were selected because of the frequency of their detection in the corpses of the stranded animals in Antarctica.
Scientists from Denmark’s University of Aarhus then implemented the analysis.
The study was conducted in a laboratory with blood extractions, about half-a-litre each, taken from the orcas in Loro Parque’s OrcaOcean installations.
The samples were processed to separate the blood cells responsible for the immune system, which were subjected to an in-vitro test (test tube), and then exposed to the toxic cocktail.
Dr Almunia said the scientific community had knowledge about how each of these components, DDT for example, affected the immune system of orcas.
But he added that there was not a lot of research carried out to analyse the effect produced by a combination of different toxic components.
The study concludes that the combined impact is greater: several of these substances together can cause a major, pathogenic effect (capable of causing disease), than each individual component in a similar concentration.
The toxic agents, when combined, start to produce an effect on the immune-response capacity in orcas faster than expected. It is also possible that these pollutants influence the reproductive system of the animals, because some of them are similar to hormones in structure.
In fact, a group of resident orcas in Scotland has not bred for years, and it is suspected that this down to pollution. A toxicology analysis on a recently-stranded female orca showed a really high concentration of persistent, organic pollutants.
At its greatest impact, this toxic cocktail can shorten the life of the animals because their immune systems are forced to fight constantly against the pathogens, which has actually been seen previously in dolphins.
Dr Almunia emphasises: “It is obviously difficult to demonstrate that pollution was a direct cause of the death of an animal because, logically, an animal dies eventually as a result of a pathology, an infection, a tumour or a parasite infestation.”
The question raised by the Loro Parque Foundation expert is: “How much easier it is for a pathogen to affect the health of an animal, whose immune system is depressed?”
Further, extensive studies are needed to answer that, which is why Loro Parque Foundation is working together with the University of Las Palmas de Gran Canaria, to identify and analyse the concentration of toxic substances in animals stranded in the Canary Islands.
Until now, the toxicology has focused on studying each single compound. And this study, supported by Loro Parque Foundation, helps to bring forth a different perspective, which can determine whether toxic compounds, once accumulated in an organism, interact in any particular way among themselves, causing, as a result, a greater impact on the immune system in animals.
As far as the regulation and control of these toxic substances is concerned, Dr Almunia said that the results of this study have been published in the Environmental Science & Technology magazine, and they are available to the scientific community.
The next step would be to deliver this information to political level, for appropriate decisions to be made to address the matter.
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