New research says whales which washed up on UK beaches contained high levels of toxic chemicals which were banned decades ago.
Scientists studied hundreds of stranded cetaceans, including creatures found at Hunstanton and other Norfolk beaches.
In a report, they say more than half had levels of highly-toxic PCBs which were 30 times higher than the threshold at which the animal would have suffered harm.
PCBs, once used in the manufacture of paints, glues and sealants, were banned by an international convention in 2001 after they were found to cause cancer.
But Dr Rosie Williams, lead author and researcher from the Zoological Society of London’s (ZSL) Institute of Zoology, said scientists were still finding "concerningly high concentrations in wildlife".
"This is a huge wake-up call," Dr Williams told the Guardian. "We rely on the same ecosystem for some of our own food – so these findings ring alarm bells not only for the future of marine life but indicate a risk to human health also."
READ MORE: Norfolk's history of washed-up whales
READ MORE: Whale stranded on Hunstanton Beach
The report says marine mammals are exposed to "a barrage of legacy pollutants", which can combine to create toxic mixtures even when levels of individual chemicals are within safe thresholds.
Toxins ingested by plankton become more concentrated as they travel up the marine food chain.
"We identified exposure to PCBs as the greatest risk to health, in terms of their contribution to toxicity and slow decline in comparison to other pollutants," the report says.
"Other pollutants are present at toxic concentrations and account for a substantial proportion of the risk to the immune and endocrine systems."
It concludes as well as pollution, marine mammals face increasing threats from acoustic disturbance, prey depletion and the marine impacts of climate change.
Other explanations for whale strandings include starvation, injuries caused by boat strikes or fishing gear and disorientation caused by sonar.
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