Toxic chemicals found in beached whales in Fife
A pod of whales stranded in Fife had high concentrations of toxic chemicals, some of which had reached the mammals' brains, scientists have found.
The pod of long-ﬁnned pilot whales were stranded on a beach between Anstruther and Pittenweem on 2 September 2012.
Out of the 31 mammals which beached, only 10 could be refloated and 21 - 16 females and five males - died.
The tests were led by the University of Aberdeen and the Scottish Marine Animal Stranding Scheme.
Scientists found mercury at levels high enough to cause severe neurological damage in humans and demonstrated for the first time that the toxic element cadmium can cross the blood-brain barrier.
The scientists said there was no indication that the mercury and cadmium levels in the brain caused disorientation, which in some cases can lead to strandings, but there was a potential for higher stress in the whales.
Navigating off course
Their report, published in the journal Science of the Total Environment, showed a "clear" correlation between the increased levels and the age of the mammals, suggesting toxic stress increases the longer the mammals live.
They said this could demonstrate that this species of marine mammal was less susceptible to mercury poisoning than humans, but they could not entirely discount the possibility that it was a factor leading to whales navigating off course.
Dr Eva Krupp, an environmental analytical chemist from the University of Aberdeen, collected and analysed samples from the whales with PhD students Cornelius Brombach and Zuzana Gajdosechova.
She said: "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.
"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."
Analysis of samples revealed that the level of mercury in the whales increased in correlation to the age of the mammals, which ranged from under a year to 36 years.
The scientists found very high concentrations of mercury in the brain of all the whales older than nine years and in three the concentration was higher than levels at which severe neurological damage would occur in humans.
Dr Krupp added: "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."