WHALES beached on a Scottish shore had high levels of toxic metal in their brains, a study has found.
More than 30 pilot whales became stranded on a Fife beach in September 2012, only ten of which were saved.
Now tests on the 16 females and five males that died have shown high levels of mercury and cadmium in all organs, including the brain.
The work by Aberdeen University proves for the first time that cadmium – a carcinogen also found to cause bone softening, kidney damage and respiratory problems in humans – can cross the blood-brain barrier for the first time.
Some of the whales tested showed mercury levels high enough to cause severe neurological damage in humans.
Environmental analytical chemist Dr Eva Krupp, who led the work, told The National more work is needed to establish a link between metal poisoning and whale strandings.
However, she said the food chain is compromised and that the problem is global and getting worse as a result of mining and other industrial activities.
Krupp said: “We know that for the last 400 years or so, the overall mercury [level] in the seas has tripled.
“Concentrations are much higher and we can assume that this means overall the burden of mercury or other toxic elements will continue to rise over time.”
Krupp’s team gathered an unprecedented number of tissue samples from all the major organs of whales aged from a year to 36 beached between Anstruther and Pittenweem in the incident.
Levels of toxins rose in correlation with age, with very high concentrations of mercury, which affects co-ordination and heart rate in humans, detected in all whales aged nine or over. Three had rates linked by doctors to severe neurological damage.
It is not known where the pod had come from, but the species is known to circulate around Scotland and travel towards Iceland and the Faroes.
Krupp, who carried out the work in conjunction with the Scottish Marine Animal Stranding Scheme, which performs autopsies on whale remains, said: “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 newborn 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.”
She explained: “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.”
She added: “There are already limits in place about mercury in fish for humans to eat.
“We know for pregnant women, mercury transfers to the foetus.
“Fish eat fish and the whales are at the top of the food chain.
“Whales can’t choose which fish to eat – everything they are eating is already contaminated.
“One of the babies we tested only had one tooth – it got its mercury through its mother.”
Calling for caution over the implications of the findings, Krupp went on: “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.
“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 from the study have been published in the journal Science of the Total Environment.
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