The federal Department of Health has been accused of giving people in the red zone a "false sense of security" with advice widely distributed to GPs and residents about how to interpret the results of blood tests for the per- and poly-fluoroalkyl chemicals [PFAS]. 

The advice set out a level for each of six age groups that was "consistent with background exposure in the general population" and at which "patients should be reassured". 

However instead of using Australian averages, it relied on an estimation of the levels present in the 95th percentile of the population, taken from a research paper from 2014. 

The paper's lead author admitted to the Herald there were areas of "uncertainty" in their calculations, including a lack of blood samples for children under four. 

But Rhianna Gorfine from the Williamtown and Surrounds Residents Action Group said the most worrying aspect was that many locals did not realise the fact sheet provided a list of levels that were higher than 95 per cent of the population.  

"The everyday person hasn't gone through a statistical analysis course," Ms Gorfine said. "The way they have presented it is normalising high levels." 

In the fact sheet, a level of 13 ng/ml was given as the ‘background’ level for one of the chemicals - perfluorooctane sulfonate, or PFOS - in an infant under the age of four. 

That represents more than six times the Australian average for children that age – which was put at 2 ng/ml in a recent study - and nearly three times the German safe level of 5 ng/ml. 

The German Human Biomonitoring Commission last year judged that at or below a level of 5 ng/ml there was "no risk for adverse health effects and, consequently, no need for action." 

Robert Bilott, an American attorney who has spearheaded a successful class action over the health effects of the chemicals in the United States, was incredulous at the advice. 

"To suggest that an individual should feel ‘reassured’ because five per cent of the population has higher levels in their blood makes no sense," he said.

"After all, there is no ‘normal’ or natural ‘background’ level for either PFOA or PFOS in human blood. Neither chemical occurs naturally in humans. Both are completely man-made substances ... so their presence in anyone's blood is the result of man-made activities." 

Mr Bilott said clarification was needed around whether the ‘background' levels included individuals who had a high exposure to the chemicals through their occupations or drinking contaminated water. 

That would "artificially raise the upper end of the group's blood levels beyond those that are otherwise now found", he said. 

Mr Bilott rejected the Australian government's position that there is no consistent evidence the chemicals cause health impacts, saying the evidence in relation to PFOA was “strong and consistent”. 

The Newcastle Herald sent a detailed list of questions to the Department of Health on Tuesday, but it did not provide a response. 

However the lead author of the research paper, Lesa Aylward, defended the approach taken in the government advice. 

Ms Aylward is a principal of Summit Toxicology, a consultancy based in Virginia in the United States. She said that in medicine, 95th percentiles were often favoured over averages when trying to determine if a group of people had an elevated exposure to a chemical. 

"If we use a measure of central tendency, such as a median...then half the general population will be defined as having 'elevated' levels," she said. 

Ms Aylward described the science of assessing health risks in individuals exposed to pollutants in the environment as "very uncertain". 

"For some people, knowing that many or most people have or have had levels that are similar to their own measured level provides some level of reassurance," she said. 

But a senior advisor to the National Toxics Network, Dr Mariann Lloyd-Smith, said levels of PFAS in the general Australian population were “unacceptably” high, and were well above those generally seen in Europe. 

“[This] reflects the fact that the EU has taken action on these contaminants and Australia has not,” she said. 

Restrictions on the sale of products containing PFOS were introduced by the Council of the European Union in 2008. 

Dr Lloyd-Smith argued a responsible approach would be to compare Williamtown residents’ blood levels with the German guidelines. 

“The current Australian approach is just another way of downplaying the government’s responsibility for the contamination and for Australia’s ongoing failure to address PFAS. 

“And while the authorities continue their nonsensical claims of ‘no consistent evidence of PFAS health effects’, we can unfortunately expect nothing better,” she said. 

Further doubt has been cast over the government guidelines amid revelations the original report was mostly based on estimates – rather than actual blood samples – for children under four. 

The report said that “no data were [sic] available from the various population representative surveys for the youngest age group … and the coverage of the next oldest age group (5 to 15) was only partial.” 

It did not break the numbers down by gender, even though adult males “often” show higher levels than females. 

And there were concerns the data, from 2011, did not take into account falling PFOS levels in Australians over the last five years. 

There was a “rapid decrease” between 2002 and 2011, a trend expected to continue due to a world-wide phase out of the chemicals. 

“It’s not until you delve into the statistics that you realise that they’re using outdated data, and for children they’re using computer models instead of actual blood samples,” Ms Gorfine said. “They would have been better off putting in a range if they didn’t think an average was a good way to go. What we want is transparency.”

Ms Aylward acknowledged the downward trend had probably continued since 2011, but said it was also likely to have slowed due to the “ongoing recycling of low-level contamination in the environment.” 

She said the problems highlighted with the study were relevant if testing whether people in Williamtown had levels “exactly” like the rest of the population. 

But while they were not necessarily the “precise” numbers, they were the best estimates that could be made based on the available data, she said. 

“[The estimates] give a guide that can be used to make a general assessment of whether levels are markedly elevated or not,” Ms Aylward said. 

The study was published in peer-reviewed journal Environment International. A member of the journal’s editorial board is Dr John Butenhoff from 3M, the company which has been the major manufacturer of PFAS in the United States. 

In the past, Ms Aylward has also done consulting work for the American Chemistry Council, a peak trade organisation for chemical manufacturers including 3M. 

 But she said she had no financial ties to the company. 

“I do not think I have ever met Dr Butenhoff, nor have I ever worked for 3M,” Ms Aylward said. “The majority of my funding over the past five years, including this year, has come from Health Canada.”