Technically they're not forever but are long-lived and don't easy break down in the environment.

The chemicals are contained in countless everyday products and known as per- and poly-fluoroalkyl substances, or PFAS for short.

Experts say their use in everything from food packaging and non-stick cookware to cosmetics and carpet, mean they're now part of us - literally.

"We all have some PFAS in us," Jen Martin, who's involved in researching exposure in livestock, told a recent conference in Sydney.

"They are ubiquitous in the environment, and in humans. Many of these can bioaccumulate (become concentrated inside the bodies of living things), are persistent and can have toxic properties."

Authorities can't agree on how many PFAS there are with estimates ranging from 4000 to 8000.

What's certain is they are now present in rainwater and snow in even the world's most remote locations, where there are no obvious sources of contamination, a Stockholm University study recently found.

Worse, they've been found at levels that exceed US drinking water guidelines and scientists say there's an urgent need to rapidly restrict their use.

The jury is still out on human health effects but many nations now warn of increased cancer risks and advocate limiting exposure to chemicals in use since the 1940s.

The EU's environment agency says PFAS can lead to health problems such as liver damage, thyroid disease, obesity, fertility issues and cancer.

Of the relatively few well-studied PFAS most are considered moderately to highly toxic.

The US Environmental Protection Agency says certain PFAS are known to cause human health risks.

The group points to studies showing certain exposure levels may heighten cancer dangers, hurt fertility and birth weights and accelerate puberty.

Australia - which is about to get a new draft of its national management plan - appears to be more cautious.

The federal government's expert health panel points to "fairly consistent reports of an association with several health effects" while noting they are "generally small and within normal ranges for the whole population".

"There is also limited to no evidence of human disease or other clinically significant harm resulting from PFAS exposure at this time," the panel found.

It's also concluded there's no evidence suggesting an increase in "overall cancer risk".

Regardless, there's a vast amount of work being done to assess Australia's PFAS problem, what levels are already locked in, and what should happen to stop an "emerging" contaminant becoming more entrenched.

One critical concern is how to limit further exposure given Australians already have at least three types of PFAS in their bodies.

Experts hope the latest draft of the PFAS plan, due for release this month, will contain improved risk management systems.

One of the many things it's expected to address in greater detail is the issue of PFAS in biosolids, a by-product of the wastewater treatment industry that's routinely repurposed as fertiliser for Australian farms.

Biosolids are essentially treated and dried sewage sludge - a mud-like residue the reflects everything Australian families put down the drain or sewer, including poo and dirty water used to wash dishes, clothes and bodies.

It can also include the leftovers from water-borne trade waste.

Once the sludge is treated and dried it's spread over the nation's farmlands to improve soil condition. Last year, more than 70 per cent of the 349,000 tonnes of dried solids was disposed of in this way.

Water companies say reusing the waste has many benefits, including reducing reliance on man-made fertilisers, but they also know it's distributing low levels of PFAS.

They say the process is carefully managed to guard against risky levels of contamination.

But experts say the existing system of state-based guidelines is not good enough and must be consistent nationally.

"We don't have consistent guidelines in Australia for biosolids quality and risk management. They are sort of all over the place," University of NSW professor Stuart Khan says.

"In NSW our guidelines date back to the 1990s and haven't really been updated since. There are big gaps.

"If we don't sort out our risk management, and make sure we practise safe handling of biosolids particularly where it's being reused to grow food crops, we might run into difficulties in the future."

If people want a sobering case study about what's at risk from PFAS contamination, they need look no further than the Heart Morass Wetlands in Victoria.

The area is connected to East Sale RAAF base, which historically used PFAS-loaded firefighting foams.

Wildlife in the wetlands now have concerning levels of PFAS and for some years authorities have been telling duck hunters and fishers not to eat what they kill.

At a biosolids symposium in Sydney last week, PFAS researcher and University of Newcastle Professor Ravi Naidu explained how typically low and safe levels of PFAS found in Australian bodies could rise over time.

"The question is really the exposure pathways. The utensils, the food you eat, the water you drink. If all of these introduce PFAS into your system, you'd become an outlier," he told delegates.

"Exposure pathways, and duration of exposure, they all play a significant role in risk."

Prof Naidu is due to present a new study on PFAS levels in vegetables sold at Sydney markets at a conference in Adelaide this week.

Last year's Australian Total Diet Study, conducted by Food Standards Australia New Zealand, tested for 30 different types PFAS in 112 common foods sourced from all over Australia.

It found consumers' exposure to PFAS through food and beverages is very low and poses no food safety concerns.

Australian Associated Press