We put a lot of trust in food producers. We like to believe they all have stringent quality assurance systems to safeguard consumers and should anything ever go wrong our government watchdogs will do their job to protect and inform us.
Now for the first time Today Tonight can reveal the shocking story of one of the worst cases of toxic food contamination you're ever likely to hear and how big business and government agencies did nothing to warn those most at risk.
It unfolded in Flagstaff, a sprawling property on the edge of Burra in South Australia's mid north and home to six generations of the Tiver family. Back in 1993 it was one of the state's biggest feedlot dairy farms.
The Tivers grew all the grain they fed to their Fresian herd. To keep it settled they would mix the feed with tallow, an animal fat bought in 200 litre drums- a common practice among dairy farmers at the time.
It's no longer allowed today but back in June of 1993 it was a critical turning point for the Tivers after they placed their usual order of eight drums with Master Butchers, a co-operative of South Australian meat processors and livestock producers.
By the time they got to the last drum a month later many cows were hit by a mystery illness, much to the distress of John, his wife Margie and their son Ben.
"We never believed anything was wrong with the drums, that was the least of our worries, we presumed they were cleaned before ever filled, never thought anything wrong with that side of it," says John.
As milk production dropped, abortions in the herd surged. Then came a troubling episode when they found several calves had died after being fed milk by one of the affected cows, later found dead in a paddock.
So the worried Tivers notified National Foods, the dairy giant which bought all their milk providing for half the daily needs of Port Pirie and other regional towns and which continued the supply for two years after the Tivers alert.
Margie Tivers told us: "I asked them to test for pesticides. They said they would but we never saw any results."
If the 115 abortions and unexplained animal deaths didn't raise any danger signals then what followed over ensuing months certainly should have had alarm bells ringing loudly.
The Tivers started seeing shocking birth defects.
So what caused it? After eliminating their farm as a source of the poisoning the Tivers analysed some tallow residue in the one last empty drum they kept from master butchers. The results were simply terrifying.
"Our toxicologist told us the toxins were so bad that the drums should be glowing," says John.
There were high levels of radio active materials like barium, gallium, strontium and uranium. Lead, PCB's and DEET, together a lethal chemical cocktail of some of the worst elements imaginable� results which were never made public - until now.
The Tivers say when they approached National Foods they were told their milk would have been diluted with other milk supplies and not pose a health risk. They also raised the issue with Government authorities but they did not act with any urgency.
Leading Australian toxicologist Dr. Peter Dingle says the milk would not have been safe to drink. He is dismayed the public was never told and even if it did happen 15 years ago, he says people could still be affected by those toxins.
"They would have got through in toxic levels, certainly in levels to build up in humans and maybe cause problems but we just don't know," Dr. Dingle said.
"The likely concentrations we have seen here would contribute to birth defects, still births, cancers and a lot of other diseases. The Health Departments have a responsibility for the health of the public. That means if there's contamination, they need to let the public know to take steps."
Within three years the Tivers' livelihood was in meltdown. Pastoral company Elders which had financed their herd and knew their history still sold off many cows at the Gepps Cross livestock markets. Elders told us they couldn't locate their sales records but say some affected cows had been destroyed.
As for Master Butchers, they claimed they couldn't trace the source of those suspect drums. They settled a civil action with the Tivers without admitting any liability. They came in for some scathing criticism from Canadian toxicologist Dr. Robert Coppock in a report he had prepared for the Tivers defence.
"A seminal fact is that Master Butchers was producing tallow that was entering the human food web and apparently took no precautions to prevent contamination of the "tallow" that was being shipped to Flagstaff Dairy," wrote Dr. Coppock..
We asked Master Butchers to explain why they didn't make any public announcement at the time. A spokesman dismissed the contentious analysis of their drum as hearsay, but promised to get a senior board member to call us. We're still waiting.
National Foods told us they didn't consider there was a public health risk at the time. While they did conduct tests on the Tivers milk, they couldn't say whether it was for chemical contaminants. However we can report food safety standards in the dairy industry have since been dramatically upgraded and improved.
15 years on John Tiver has Addisons Disease, a life threatening immune illness he believes is directly related to consuming his milk. Margie Tiver has also had health problems, but sadly we may never know what impact it had on others.