As public concern around the prevalence of per- and poly-fluoroalkyl substances (PFAS) in drinking water continues to make headlines, water community experts are rallying to discuss next steps in terms of drinking water guideline limits and remediation efforts.
University of Sydney Head of School of Civil Engineering Professor Stuart Khan said the current issues with PFAS derive from historic negligence, which offers learnings around appropriate regulation and remediation efforts, but should not trigger a change in how limits are set.
"We are in an outrageous situation where a chemical company has been able to produce a product without doing, in retrospect, very necessary environmental assessments to understand persistence and toxicity. That’s negligent,” he said.
“We should not be in this situation and it’s a situation that is very difficult to reverse.
“At the very least, we need to learn from this and try to prevent it from happening again. We need to establish more stringent rules around what we allow to be included in consumer products and be more careful about testing those products.”
Regulation aside, Khan said a key discussion that should be occurring around PFAS is how to facilitate and fund remediation efforts.
"There will be a cost involved in fixing this problem. If we end up with more stringent drinking water guidelines, water treatment plants will have to apply additional treatment processes, and that cost will get passed directly onto customer bills,” he said.
“That would be a secondary disaster, to let the companies that should be responsible for this off the hook by making consumers pay to improve the drinking water quality.
"We need to make sure the cost involved in figuring out how to remediate systems, as well as remediation implementation, actually goes back onto the companies that have profited from these chemicals, rather than onto consumers."
In 2018, the Australian Drinking Water Guidelines (ADWG) were revised to reflect health-based targets around PFAS.
“At that time, we rightfully saw lots of different end points being recorded regarding the toxicology of PFAS. But there was not a general consensus that these chemicals were carcinogenic to humans. That question is quite a recent development,” Khan said.
“The International Agency for Research on Cancer made a balance of evidence assessment at the end of 2023. This triggered a review of the ADWGs, which is totally appropriate. We should absolutely be looking to see if a cancer end point should lead to a lower level of exposure than we currently have in our ADWGs.”
The National Health and Medical Research Council (NHMRC) is currently conducting an independent review of the health-based guideline values for PFAS. The review is underway, with public consultation scheduled for late 2024 to early 2025.
“Firstly, the very low levels that are currently being reported in raw water sources are extremely unlikely to cause anyone any health concern. Those levels are way below the level of risk that we would tolerate for other chemicals,” Khan said.
“We should be waiting to see what the outcome of the NHMRC process is before making any further comments about adjusting the ADWGs. We definitely should not adopt the US approach, as we don’t do that for any other chemicals.”
Khan said the way the US EPA approaches PFAS levels utilises a different method to Australia, with the US limits configured around detectability, rather than health-based targets.
"Zero detection of PFAS is a nice thing to aim for in theory, but not something you can achieve or verify in practice. In the US, they aim for zero detectability and set the maximum contaminant level at what is practical to detect and achieve,” he said.
“This is not our approach in Australia. Our guidelines are health-based guidelines. We have gone through a lot of work over the past decade to ensure our guidelines reflect health-based targets.
“We identify a tolerable level of risk, which is relatively consistent across most chemicals. And this is the approach we should be taking for PFAS, as well. We have a different approach here, a different philosophy in terms of working through how guidelines should be set."
Khan said water sources that exceed the acceptable limit for PFAS within the ADWGs certainly need intervention, but the answer is not to revert to creating limits configured around practice, rather than health-based targets.
“It is right for us to review the ADWG, but people should not expect that process to lead to an adoption of the US limits. The US limits are not configured around health-based values, they are configured around detectability values,” he said.
There is a difference between the way various countries and international organisations set their PFAS limits, which Khan said is largely due to different philosophies and approaches.
"Compared to the World Health Organisation (WHO), sometimes we take a more stringent approach here in Australia. Often, the WHO will calculate guidelines to a 1 in 100,000 risk, whereas in Australia we will calculate to a 1 in 1,000,000 risk,” he said.
“There is a fair bit of subjective decision making that goes in to setting guidelines. There are a lot of uncertainties. Very often we need to assess our level of confidence in a particular figure involved in calculation. Different use of uncertainty factors can lead to different outcomes.
“The key thing driving difference in limits internationally is the difference in the toxicological end point. Different concentrations or lifetime exposures will have an impact on where we end up with the guidelines.”
While the NHMRC conducts its review into the ADWGs around PFAS, Khan said it’s important to maintain confidence in Australia’s approach to health-based targets.
“What we should not do is resort to guideline shopping,” he said.
“It’s not about taking a look around the world and picking another guideline. We need to stick to the practices we have in Australia. And if those practices are found to be criticised under the review conducted by our experts, that’s fine and we can move to change them.
“Once we identify the appropriate way to set our guidelines, it doesn’t make sense to follow the lead of other countries that have a lower limit if it is not reflective of our own processes.”