Pollutants dubbed "forever chemicals" have been found in vegetables in University of Newcastle research, raising concerns about contamination of the food chain.
The research found that chemicals were potentially getting into vegetables through use of alternate sources of fertiliser such as biosolids and composts, Laureate Professor Ravi Naidu said.
The study investigated the forever chemicals - also known as PFAS - in 53 fruit and vegetable samples collected from a wholesale and retail market in Sydney and a supermarket in Newcastle.
The highest concentrations were found in garlic, parsley and dill.
PFAS were also found in broccoli, kidney beans, carrot, spinach, bitter gourd, cucumber, bok choy, pumpkin, okra, bean sprouts and lettuce.
Six PFAS chemicals were tested and results showed that the concentrations of these contaminants depended on the type of PFAS chemical and the type of vegetable.
Professor Naidu said there had previously been "limited information about PFAS levels in vegetables".
"Our study aimed to fill this gap and assess potential risks for humans through consumption of these vegetables," he said.
"This is limited sampling and we do need to invest more time conducting much more detailed study."
This class of chemicals don't break down in the environment and pose a risk to human health.
PFAS chemicals are also involved in the pollution problem at Williamtown.
Once in our bodies, these chemicals can bind to proteins and accumulate in organs.
This may increase the risk of cancer and other illnesses, Professor Naidu said.
Professor Naidu heads crcCARE [Cooperative Research Centre for Contamination Assessment and Remediation of the Environment].
It is also examining PFAS in soil and water and developing techniques to remove them, or at least make them safe.
The researchers examined how PFAS were getting into vegetables.
"We figured out that many of our vegetable farmers have been using alternate sources of nutrients such as biosolids, manure, composts and they are the source of PFAS."
Biosolids make good, cheap fertiliser that is rich in phosphorus, nitrate and micronutrients.
They're a by-product of wastewater treatment and can be used for agriculture and landscaping.
The US Environmental Protection Agency announced in March that it had set legal limits for drinking water for six of the most toxic PFAS chemicals.
More than 14,000 types of PFAS exist, according to the US EPA.
The European Union is planning to regulate the entire class of chemicals.
Research has linked PFAS exposure to birth defects, cancer, kidney disease, liver problems and decreased immunity.
While recent reports suggest a decline in PFAS concentrations in human blood, Professor Naidu said it's "still a concern that constant long-term exposure to PFAS could lead to adverse health effects in humans". As well as drinking water, PFAS have previously been found in dairy, meat, fish, livestock and air.
Professor Naidu said it's a concern that PFAS could accumulate over time to high levels in people.
Professor Naidu's research, through crcCARE, has also found "ultra low trace levels of PFAS in treated effluent".
The research found that PFAS travel from the effluent, which is used for irrigation, into soil and water.
"These chemicals seem to be everywhere. Every one of us will have a trace level of the chemicals in us," he said.
"There was a time when we all used non-stick frypans, [which contain PFAS]. There's a huge shift now towards stainless steel and stone pots and pans."
The non-stick PFAS pans, though, are still sold and used.
Governments have previously denied that exposure to PFAS could lead to adverse human health threats.
Then came class actions and rulings against companies in the US.
Professor Naidu said the recent research shows "there is a potential link between PFAS and adverse human health impacts".
"It could be the vital organs, cancer as well," he said.
"No matter which way we look at it, the chemicals will be there because of the carpets and furniture we have in the house, for example."
The chemicals are also in dental floss, non-stick cookware, stain-resistant fabrics, stainguards, waterproof clothing, shampoo, suncream, cosmetics and food packaging.
"So we will be exposed to that. The key question is about the exposure pathways, such as the food and water we drink."
Some levels of exposure can lead to "exceedance of what is defined as the total daily exposure limit".
"When you go beyond that, it causes serious threats."
However, Professor Naidu said PFAS chemicals "can be made harmless".
Scientists are developing ways to "lock up" the chemicals, so they don't travel into food products and build up there. But questions remain about whether governments will regulate and industry accept the higher costs that come with this.
Professor Naidu said changes to the law are needed to address the problem.
The federal environment department said the government is "working with the state and territory and New Zealand governments" on the issue.
They are developing "nationally agreed standards and guidelines to manage, reduce and prevent" PFAS pollution.
The National Chemicals Working Group recently concluded a five-month consultation process on new standards and guidance in a draft PFAS National Environmental Management Plan.
The draft proposes "national risk-based criteria for biosolids application to land for beneficial reuse".
However, biosolids are regulated by state and territory governments.
Food Standards Australia New Zealand considered PFAS levels in "the general food supply" in its "27th Australian Total Diet Study".
"The results show that Australian consumers' exposure to PFAS through the general food supply is very low and poses no food safety concerns," a statement said.
The federal Department of Health and Aged Care said "health-based guidance values" for PFAS have been developed.
"These guidance values indicate the amount of a chemical in food or drinking water that a person can consume on a regular basis over a lifetime, without any significant risk to health," a statement said.
"For communities where PFAS contamination has been identified, local authorities may issue specific advice on food or water consumption."
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