According to Dr Williams, the study directs attention towards the lessons that still need to be learned today, and the haste with which they need to be addressed.
“Even now, we have lots of chemicals that show similar profiles in terms of toxicity, persistence, and the ability to transport – such as PFAS at the moment, but we haven’t yet banned them or regulated them properly. It’s crucial that we learn from the mistakes of the past to be more reactive of regulation in the chemical space.”
But chemicals are just one part of the problem. Increasing sea surface temperatures are now altering species distributions, disrupting food webs, and changing how pathogens move through marine systems. These warmer waters have, too, been associated with higher disease rates across multiple marine species.
The results of the study showed a statistically significant association between both sea surface temperature and PCB concentration with infectious disease mortality. In fact, for each 1mg per kilogramme of lipid increase in PCB blubber concentration, risk of infectious disease mortality in the beak-nosed common dolphin population increased by 1.6%.
Meanwhile, and just as shockingly, for each 1°C rise in sea surface temperature corresponded to a 14% increase in mortality risk.
“We have traditionally looked at these threats in isolation. We have a bunch of people looking at the impacts of bycatch, people looking at pollution, and people looking at climate change, but it’s really important to account for the interconnected nature of these threats,” said Dr Williams.
“This study is the first time that we have tried to do this, and there is a lot more that can be done to bring data of other threats into the same conversation, so this study is really highlighting that we just can’t regulate and think about these things in isolation because they often have this synergy that we can see here.”
Armed with such findings, researchers at the Zoological Society of London are clear on the next steps they would like to see implemented – and that’s in the swift strengthening of regulations on the kind of chemicals – those with similar traits to the PCBs banned in the 1980s – currently used across all manner of consumer products.
“Countries like France have already agreed to ban the use of PFAs chemicals in non-essential products by 2026, but the UK is severely falling behind on making a move on this issue,” said Dr Williams. “We’ve been promised a new chemical strategy since 2020 and we’re yet to see it. We are falling behind, and we need to make sure this isn’t the case because these chemicals are so costly and damaging to clean up.
“When it comes to the climate piece, this study also illustrates just how little we know about what some of the impacts might be on some of these animals. It’s not intuitive that a sea temperature rise would have an adverse effect on a warm water species, so this highlights that we just need to know a lot more about the impact of climate change and until we do, minimize the impacts of it.”