Scientists have found clear evidence that whales are absorbing high levels of toxic heavy metals, with cadmium found in the brains of pilot whales which washed up in Scotland.



Chemists at the University of Aberdeen said they had found cadmium in all the organs of adult long-finned pilot whales which stranded in 2012, including their brain.

The research shows for the first time that cadmium – known to pass into the brains of infant and unborn whales - had also passed across the so-called blood-brain barrier in adult whales.

They said their findings also suggested that mercury concentrations could be increasing high enough in the seas “to lead to additional toxic stress in the long-lived marine mammals”, with higher concentrations increasing with age. The team, lead by Dr Eva Krupp, an environmental analytical chemist, tested the remains of 21 long-finned pilot whales which died in a mass grounding between Anstruther and Pittenweem in Fife in September 2012. There have been a series of recent whale strandings, with the most dramatic in the UK taking place in Norfolk in January and early February. Six sperm whales washed up over a series of days along beaches in East Anglia, in a stranding linked to other recent groundings by sperm whales in Germany and France. Cetacean experts are currently testing samples to investigate possible reasons why.

“We were able to gather an unprecedented number of tissue samples from all the major organs including the brain and as a result we can see for the first time the long term effects of mammalian exposure to the environmental pollutants,” Krupp said of the whales that stranded in 2012.

“This pod of whales provides unique new insights because we were able to look at the effects on a large number of whales from the same pod and how this varied according to age.”

The university said that in three of the whales aged nine years or older, the mercury concentrations were higher than the toxic levels which would cause severe neurological damage in humans. The industrial revolution and the use of mercury in gold-mining have greatly increased mercury concentrations in the seas, leading to their absorption by marine species. “As well as an increased concentration of mercury in the brain as the whales become older, we see a similar effect with cadmium, which has not been previously reported,” Krupp added. “It is known that cadmium can penetrate the blood brain barrier in the new-born or developmental stages but it was not thought to do so in adults. Our findings are significant because we can demonstrate for the first time that cadmium is in the brain tissue and that its levels increase with age. “Although the body has a natural defence mechanism in the form of the element selenium, which detoxifies these harmful chemicals, we found that the majority of selenium is not available for the synthesis of essential proteins in older animals. This indicates that the longer mammals live, the less able they may be to cope with the toxic effects.” “So far, we have no indication that the mercury and cadmium levels in the brain cause disorientation, which in some cases can lead to strandings, but there is a potential for higher stress in these iconic animals due to rising toxic metal concentration in the oceans,” Dr Krupp added. “More research is needed to investigate whether this is a factor in strandings, particularly where other explanations such as illness or weather events cannot be found.”

The findings are reported in the journal, Science of The Total Environment.