What we know about the Williamtown contamination chemicals
15 October 2015
In early September, the New South Wales Environment Protection Authority warned people living and working near the Williamtown RAAF base that elevated levels of toxic chemicals had been found in the surrounding area.
The chemicals – perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) – were historically used in fire fighting foam at the RAAF base and had been found in surface water, groundwater and some fish species in nearby waterways.
But what exactly are the chemicals, and what effects do they have on humans and the environment?
Toxins are man-made ‘super chemicals’
Professor Ravi Naidu is the head of the Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), an independent organisation studying chemical contaminants and is based in Newcastle.
He has been researching PFOS and PFOA since 2004, and his organisation is considered leaders in the study of the chemicals. They have also helped inform government policy on contamination issues.
PFOS and PFOA are both chemicals which belong to the broader perfluorinated chemical group, and were prevalent in fire fighting foam for decades until the early 2000s.
Professor Naidu said the chemicals were man-made and their origins dated back as far as the 1940s.
“You can say that these are ‘super chemicals’ because they tolerate such high temperatures; but at the same time, they were so effective in helping people manage and control fire,” he said.
“These chemicals can persist in the environment, they don’t easily degrade, they are recalcitrant, they bio-accumulate in plants.
“So we have come up with a chemical that poses a very significant risk to the environment.”
Prior to the late 1990s, Professor Naidu said the potential toxicological effects of PFOS and PFOA were not overly considered.
When the chemicals are mixed, they appear as a detergent-like substance.
They tolerated very high temperatures – up to 1,200 degrees Celsius – which made them ideal for fighting fires.
“When you apply that to a fire, it coats the particles, and in doing so it prevents oxygen from getting through, and that is how fire is doused,” Professor Naidu said.
Research has shown that the two chemicals move quickly, because they are surfactants – a substance that lowers surface tensions when dissolved.
“For example, if you spill it in soil … and the concentration is high enough and there is rain, it can help the [chemicals] to move in the sub-surface environments,” Professor Naidu said.
“The difference between these chemicals and toxic metals, is that soil has the ability to bind with toxic metal.
“With this chemical, while soil could bind it, it is a surfactant [and] surfactants change the surface tension properties of these chemicals and soil particles. In doing so, they make them mobile, which is why they’re moving.”
Prof Naidu said the large storm which swept across the Hunter region in April, bringing torrential rain and flooding, most likely exacerbated the spread of the toxins.
“The geology of this region that we have, irrespective of the intensity of rain, will allow chemicals to move,” he said.
“Heavy rain means the groundwater table can rise as well; so if you have any pollutant in the soil that will allow it to get into ground water as well.”
Known impacts of the chemicals
Not a lot of concrete information is available about the impacts PFOS and PFOA have on people and the environment.
The chemicals are considered as being ‘stable’, which makes them difficult to breakdown in the environment.
That is because the atoms in the chemicals are bonded to other atoms.
“Carbon-fluorine bond is the hardest bond that you could think of, so it is not easy to break,” Professor Naidu said.
“In this case, if you try to break the carbon-fluorine bond, you end up forming another toxic substance which will kill microbes, and that’s why bio-remediation hasn’t been found to be effective.”
It is understood the chemicals can adversely impact sensitive soil microbes, and can bio-accumulate in plant matter – meaning birds and animals that consume the plants could be at risk.
“The presence of these chemicals can impact the metabolic cycle that we have in the soil, and therefore, soil health,” Professor Naidu said.
“The entire critical zone can be impacted by the presence of these chemicals; and if they’re present in elevated doses, the risk can be much more elevated.”
Since news of the contamination broke, there has been much conjecture about the health risks the chemicals pose to humans.
It is not definitively known if PFOS and PFOA can cause health problems for people, however residents living near the affected area have been urged to abide by the health warnings.
NSW Health said that while a blood test could determine a person’s exposure to the chemicals, the test did not provide useful information about health effects on people.
Professor Naidu said for adverse impacts to be possible, the chemicals would need to have been consumed for a sustained period.
However, research has not determined how long a ‘sustained period’ is in the case of PFOS and PFOA.
Laboratory studies on animals have shown PFOS and PFOA can impact the liver, kidney and endocrine system of subjects.
Professor Naidu said the remediation of contaminated soil was possible.
He believed a risk-based management approach to remediate the area was needed.
“It is not a difficult approach: it is not at all impossible,” he said.
“The way forward in soils is to convert this toxic substance into a form where it’s no longer toxic.
“We need to [make] barriers between the source of contaminants and receptors.
“The next step should be active remediation. Yes, you can remediate it up to a certain point, but you cannot take it to a background level.”
Having studied the chemicals for over a decade, Professor Naidu said he doubted the contamination would ever be completely cleaned up from the Williamtown area because the chemicals spread rapidly in water.
“Unless you spend a lot of money, in which case you could remediate and bring it back down to a level where it is close enough to background, you’ll always be left with trace levels of this in the soil,” he said.
“Once in groundwater, it can be quite a challenge to remediate.
“It can be quite expensive as well, and I see Defence is investing a lot of money trying to remediate, which is really good. The key thing is how soon it can be remediated.”