MERCURY levels high enough to cause severe neurological damage in humans have been found in the brains of whales stranded on a Scottish beach three years ago.

Scientists found the chemical, along with the toxic element cadmium in the cadavers of the whales, which died after they came ashore between Anstruther and Pittenweem in Fife.

The experts from Aberdeen University believe the discovery shows that increasing pollution of oceans may help explain why some of the mammals end up stranded on seashores.

Out of the 31 beached whales, only 10 could be refloated and 21, 16 females and five males, died in the incident in September 2012.

Dr Eva Krupp, an environmental analytical chemist from Aberdeen University, collected and analysed samples from the whales together with two PhD students

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.”

In addition to the mercury, which could have caused brain damage in people, the study demonstrated for the first time that the toxic element cadmium can cross the blood-brain barrier.

The university, in collaboration with the Scottish Marine Animal Stranding Scheme, led the investigations into the pod of long-?nned pilot whales.

Their report, published in the journal Science of the Total Environment, shows a clear correlation between the increased levels and the age of the mammals, suggesting toxic stress increases the longer the mammals live.

They say this could demonstrate that this species are less susceptible to mercury poisoning than humans, but that they cannot entirely discount the possibility that it is a factor leading to whales navigating off course.

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.

They 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, who collected samples with PhD students Cornelius Brombach and Zuzana Gajdosechova, added: “We can see clear evidence that mercury is being transported through the blood stream to all organs where it accumulates over the lifespan."

“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. 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."

In the Northern hemisphere long-?nned pilot whales' range is the North Atlantic Ocean from the Azores to Greenland, the North Sea and the western Mediterranean

Dr Krupp said previous scientific studies had shown that mercury concentrations in the oceans have notably risen since the industrial revolution and through gold-mining activities, which may in turn lead to an increase of mercury levels in marine mammals.

“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,” she said.

Thirty sperm whales have also lost their lives in the North Sea this year, including four which washed up on beaches in Lincolnshire and Norfolk.

There have also been dead whales washed up in France, the Netherlands and Germany.