PFAS and the Australian Drinking Water Guidelines (ADWG)

I have received a few questions and comments suggesting that there is something deficient with the Australian Drinking Water Guidelines (ADWG) and that we should simply adopt the PFAS maximum contaminant levels (MCLs) published by the US EPA.

I did previously explain -as best I could- some of the fundamental differences in the approach to setting water quality guidelines in the two countries, and why I believe the approach used in Australia is preferable.

But the questions I am receiving are more practical than fundamental. Essentially: “doesn’t the US approach protect people better?”.

First, for the sake of perspective, it’s worth comparing the public health records of the USA and Australia. Despite the US having a much more expensive health care system, Australia has statistically better health outcomes practically anywhere you look: life expectancy, infant mortality rates, chronic disease prevalence, etc. This reflects different decisions and prioritisations the two countries have made in protecting public health. My point is simply, the fact that we are different doesn’t automatically mean we have worse outcomes.

In my view, the most important document in Australia, after the Constitution, is the Australian Drinking Water Guidelines. Throughout the last 25 years, the ADWG have led the world in providing a more robust risk management approach to protecting drinking water quality. There are many aspects of that approach that go beyond what I will describe here. For some insight, you could read this editorial perspective I wrote with Prof. David Cwiertny (University of Iowa) in 2020 titled “What is ‘safe’ drinking water, anyway?”.

One important aspect of the ADWG is a very serious focus on assessing the best available science to establish drinking water guidelines. Despite being seriously underfunded by the Commonwealth Government to do this, the National Health and Medical Research Council has relied on contributions from health regulators from the Australian states and water quality experts from around the country, who all understand the preeminent importance of the document.

Having first finalised drinking water guideline values for PFAS in 2018, the ADWG were six years ahead of the US EPA, who took until 2024 to finalise their MCLs. Those six years have been a particularly intensive period for PFAS toxicology research and many newer developments have been made.

One of those has been the global acceptance that, on the balance of evidence, exposure to some important PFAS can cause cancer in humans. That particular change underpins the basis of the US EPA MCLs. There are important fundamental differences in the way the US regulates (known or suspected) cancer-causing chemicals, compared to practically the rest of the world. That’s what I tried to explain in The Guardian. I don’t believe Australia should (or will) adopt that approach.

Another important aspect of the ADWG is the fact that it is constantly under revision, described as being ‘under rolling revision’. This means that when new evidence becomes available, Australia is quick to respond with an updated evidence review, and sometimes that leads to a change in guideline values.

An updated evidence review for PFAS was triggered, and that review has been underway for well over a year now. It’s not a simple or quick process and the outcomes have wide-ranging implications. Therefore, it’s not something that should be rushed in response to media, community, or even government pressure.

Once completed, the evidence review may be used as the basis for proposed new guideline values for PFAS in the ADWG. If new guideline values and/or new fact sheets are proposed, these will go on public exhibition for a public consultation period.

Comprehensive consultation is essential for the ADWG for several reasons. One reason is that the ADWG are not a legally binding document from any Commonwealth Government legislation. If they are to be implemented, this only happens through decisions and actions of the individual Australian State and Territory governments. So having state government acceptance that requirements in the ADWG are well-founded is absolutely essential.

Following the consultation period and then further review to consider the feedback received, new PFAS guideline levels and/or factsheets may be finalised. If it gets to that point, the current timeline looks like early 2025. In that case, Australia would have completed its first update to drinking water PFAS regulation within a year of the US EPA producing its first MCLs. In order to keep up the pace with Australia, the US would need to be producing a first update around 2031. I know its not a competition, but I sometimes wonder whether others do.

So what about the intervening year between the first US PFAS MCLs and the first ADWG PFAS update? I am seeing comments along the lines “If we were in the US, we wouldn’t be drinking water with these levels of PFAS since it would not be allowed”. This is a misguided view. The US did not suddenly introduce PFAS MCLs this year and expect their drinking water supplies to instantly -magically- meet them.

In fact, if you were in the US, you probably wouldn’t even know what PFAS concentrations are in your drinking water, since in most states, there is not yet a broad requirement to report them. US public water systems have been instructed to start monitoring (not reporting) for PFAS and must do so for three years (until 2027). Monitoring is to be quarterly (4 times per year) and must maintain a running average below the MCLs. Those that don’t achieve that will need to implement solutions to reduce PFAS by 2029.

The part about the ‘running average’ recognises that individual PFAS exceedances are not really the issue here. Calculated safe levels of PFAS exposure are based on an assumption of exposure over a 70-year lifetime. Real toxicology is always more complex than the model, but the model is based on assumptions of exceeding (or not exceeding) a particular level of exposure ‘on average’ over many decades.

Finally, ADWG values have been (and continue to be) established on the basis that there is uncertainty about the actual toxicity of specific chemicals. They deal with this by applying several ‘safety’ or ‘uncertainty’ factors. These are applied in favour of the chemicals actually being more -not less- toxic than we confidently know.

The ADWG PFAS guidelines are also divided by a further factor of 10, on the basis that drinking water is not assumed to be the primary source of exposure to PFAS by people. This means most of our exposure is coming from elsewhere, so we allocate even less of the allowable exposure to drinking water. If it was assumed drinking water was the primary source of exposure to these chemicals, the calculated ADWG values would be 10x higher than they are.

But if we accept that drinking water is not the primary source of exposure (and the evidence supports this), then we really need to understand that significantly enhanced levels of water treatment probably wont significantly reduce our overall exposure, and thus won’t have a significant public health benefit. Nonetheless, that’s the level of public health protection that we hold the ADWG to and I wouldn’t argue for anything less.