When the orca known as Lulu washed up on the shores of Scotland after being tangled in fishing gear, it came as a major blow. Not only was it a sad loss to those studying the cetaceans, but the number of orca in the UK’s last known resident pod, which she belonged to, has now fallen to just eight individuals.

A new report looking into her death shows that things for this pod may be even worse than imagined. Detailed analysis of Lulu’s blubber found that she had some of the highest levels of toxic pollutants ever recorded in an orca found in this region. The levels of PCB found in the orca are thought to be 100 times greater than what is considered the minimum toxic level for marine mammals.

Known officially as polychlorinated biphenyls, PCBs are now known to accumulate up the food chain, and can cause poor health, damage to the immune system, increased susceptibility to cancer, and even infertility. After testing Lulu, they found that she had an astonishing 957 milligrams of PCB per kilogram of blubber, far higher than anything anyone has seen before in marine mammals, and way over the limit that is thought to cause harm.

The carcass of Lulu found in Tiree. Scotland’s Rural College

The pod of killer whales Lulu belonged to is balancing on the edge of extinction. As the last known group of orca surviving in UK waters, they have never been observed interacting with any other pod from other waters, which some believe is a contributing factor to why their numbers are dwindling. But after studying her carcass, the researchers came to an even more alarming conclusion.

It seems that despite being at the prime breeding age of 20 Lulu had never born a calf in her entire life, suggesting that the high levels of pollution found in her blubber may have made her infertile. This has worrying implications for the rest of the pod, as in the last 23 years not a single calf has been observed in the Scottish group, which might suggest pollution levels have caused the whole pod to be barren.

“Lulu’s apparent infertility is an ominous finding for the long-term survivability of this group; with no new animals being born, it is now looking increasingly likely that this small group will eventually go extinct,” Dr Andrew Brownlow, veterinary pathologist at Scotland's Rural College, who helped analyze Lulu, said in a statement. “One of the factors in this groups’ apparent failure to reproduce could be their high burden of organic pollutants.”

Despite having been banned in the 1970s, PCBs still persist in the oceans, and researchers are only really now understanding how much damage they may be causing. They are now calling for more to be done to eliminate the chemicals from the environment.