It has been half a century since governments around the world, faced with overwhelming evidence, started banning early generations of what we now call forever chemicals. Industrial chemicals known as polychlorinated biphenyls, or PCBs, and the notorious pesticide DDT had been widely used – DDT is credited with saving millions of lives from insect-borne disease, while PCBs were vital in electrical safety – before it was understood that they were serious environmental toxins.
“The problem with these legacy contaminants,” environmental scientist Chantel Foord says, “is that they’re amazing in our products because they don’t break down, but they’re equally devastating in our environment because they don’t break down.”
PCBs and DDT were banned in Australia in 1975 and 1987 respectively, and are now prohibited under the Stockholm convention on persistent organic pollutants. But, as Foord’s latest research shows, both are still prevalent in our environment.
Her study, published in the Environmental Research journal, has found that Victorian dolphins, including the critically endangered Burrunan species that only live in Victoria’s coastal waters, have some of the world’s highest levels of DDT and PCBs.
The study was conducted on dolphins stranded on the Victorian coast between 2002 and 2022. Foord says that nearly two-thirds of all specimens, and 90% of the endangered Burrunan, recorded PCB and DDT levels greater than health thresholds, potentially contributing to the deaths of some individuals.
DDT and PCBs build up in the body over time, with higher concentrations found in organisms higher up the food chain. The study found that PCB levels weren’t declining over time in dolphins around the Gippsland Lakes in Victoria’s east, suggesting pollutants were still entering the environment.
Foord says understanding the pathway of the contamination is crucial to controlling it.
“We know we’re finding alarming concentrations of PCBs and DDT within dolphins,” Foord says. “I don’t believe it is fully understood how we are getting persistence of these concentrations – is it because it’s running off the land, is it being leached from waste or is it stored in sediments and it’s just slowly making its way into today’s animals?
“There’s not a lot of regular water or sediment monitoring information, at least that’s available to the public or the scientific community, so there’s a lot we need to do if we want to understand our waterways. Without understanding the source, we can’t mitigate any of this risk.”
A spokesperson for Victoria’s Department of Energy, Environment and Climate Action says it is monitoring the situation.
“Many of the past practices that have led to legacy pollutants in our marine environments have now stopped, and we’re actively monitoring pollutant levels and their impact to make sure our marine wildlife can thrive,” the spokesperson says.
“We work with multiple agencies to monitor the level of pollutants in Port Phillip Bay. The Port Phillip Bay Seafloor Integrity Report developed over three years found very low to negligible levels of DDT and PCB in Port Phillip Bay’s seafloor ecosystems.”
While DDT has not been used in Australia for nearly 40 years, some older electrical equipment still contains PCBs. In 2006 the national implementation plan for the Stockholm convention estimated that 21,000 tonnes were still in use in Australia. Some of this has since been destroyed, but the amount remaining in the environment is uncertain.
Dr Kathryn Hassell, the Australasian president of the Society of Environmental Toxicology and Chemistry, says legacy toxicants such as DDT and PCBs are considered relatively harmless when bound in soils and marine sediments. Problems arise when polluted areas are disturbed, either through human or natural processes.
“What we’re seeing happening now, and this relates to changing climatic conditions, is the re-suspension of contaminants that would otherwise be locked up,” Hassell says. “The big one is flooding events … You might not see these contaminants for ages then suddenly they’re present because there’s been these huge flooding events and you not only have a lot of storm water wash off terrestrial surfaces, but re-suspension of sediments in waterways.”
Another potential source of contamination is landfills, particularly older or unlicensed sites not designed to modern containment standards.
Despite the challenges, Hassell believes contaminants, once identified, can be managed successfully through bioremediation, removal or containment.
For the Burrunan, however, time is running out. Previous studies have found alarming levels of mercury and Pfas in these dolphins, which have also suffered a mass mortality event from a condition known as fresh-water skin disease, which has been linked to climate breakdown.
Dr Kate Robb, Foord’s co-author and head of the Marine Mammal Foundation, says the Burrunan dolphin was first listed as endangered in 2013, and in 2021 its status was downgraded to critically endangered. Despite this, she says, the foundation was hamstrung in its conservation efforts while it waited for the state government to formulate an action plan for the species.
“We continue to do our work and keep pushing for things to be taken seriously,” Robb says. “We’ve found the species has globally high levels of Pfas, globally high levels of mercury and now globally high levels of legacy PCB and DDTs. We have all of these compounding issues, and yet we still don’t have an action plan to actually mitigate any of them.”
