Saturday, 18 June 2016

Sixties’ pesticide still harms orcas

Scientists thought that a dangerous chemical, that was used in the 60s in among others pesticides and plastics, was no longer harming the sea life. But recent studies have made clear that they still do.

Dangerous wonder chemicals
The dangerous chemicals are so-called polychlorinated biphenyls. These chemicals don’t easily break down or degrade, making them very useful in the chemical industry. This is also the reason they were widely used in the 60s, until they turned out to be really dangerous. Polychlorinated biphenyls can cause rashes, liver damage and cancer. When this was discovered, the chemicals were quickly forbidden, and it seemed that the biphenyls disappeared quickly from the oceans. But the amount of biphenyls in the oceans can still cause harm to sea life. Because the chemicals don’t easily break down, the amount of these chemicals has stopped decreasing. Scientists are trying to find a way to get rid of the excess polychlorinated biphenyls anyway.

Poison accumulates in orcas
The polychlorinated biphenyls especially affects the sea animals that are high in the food chain. The explanation for this is that animals can’t digest the biphenyls. So, when a small fish eats plankton that has the chemicals in it, the biphenyls end up in the flesh of the fish. When that small fish then gets eaten by a larger fish, like a mackerel, that fish also eats all the chemicals from all the plankton that the smaller fish ate. And the mackerel can’t digest it either. Then, an even larger fish, like a tuna, eats the mackerel. And the tuna also eats all the biphenyls eaten by all the mackerels it ate. So the amount of polychlorinated biphenyls in the food increases if you go higher up the food chain. For the animal at the top of the food chain, for example a shark or an orca, that amount can be so high that the shark or orca dies.

Remove before 2028
With new studies, scientists hope to find out how the polychlorinated biphenyls move through the oceans. If they know this, they can predict where sea life will be most affected by the chemicals, and where they can try to remove the biphenyls from the oceans best. With this new knowledge, scientists hope to significantly reduce the amount of polychlorinated biphenyls in the oceans by 2028, which will benefit both sea life and people alike.

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