Around 10g of botulinum toxin released into central milk storage tanks would be enough to poison almost half a million people, according a new report by Yifan Liu and Lawrence Wein of Stanford University.
The report, which was quashed by US authorities last month and then released unchanged last week, criticised the Food and Drug Administration for not imposing stricter regulations on the food and drink industry generally.
"It is not clear how quickly and thoroughly the dairy supply chain is being secured," say the researchers, adding that voluntary measures in the FDA's proposed guidelines should be enforced more strictly.
These include: locking all tanks, trucks and silos when they are not being drained or filled; security checks for people who have access to prebottled milk; and requiring one person from each of stage of the supply chain to be present when the milk is transferred from one stage to the next.
The report also calls for the widespread introduction of a rapid and effective detection system that could be used to test each truck. Even if this cost $50 per 5,500-gallon truck it would only increase the cost of milk by one cent per gallon.
A test used to detect antibiotic residues has been adapted for harmful toxins such as Botulinum by US firm BioVeris. The test takes around 15 minutes to carry out.
And apart from the obvious human tragedy an attack could bring - the report estimates 60 per cent of those poisoned would die due to a lack of ventilators in the health service - the economic costs would also be colossal.
Wein and Liu estimated that if 50,000 people were poisoned it would cost the US economy around $8.6bn.
Questions of liability in the supply chain could also open up the possibility of lawsuits to recover lost funds.
The Terrorism Risk Insurance Act, which insures businesses against terrorist attack, also runs out at the end of this year, though a proposal in the US Senate would keep this alive while new cover could be thrashed out.
One answer for the industry would be a switch to ultra-high temperature pasteurisation (UHT) milk, which the report says "appears capable of completely inactivating botulinum toxin in milk".
And, while it acknowledges that US consumers have not embraced UHT products, the report calls for more pasteurisation studies "to determine whether a more potent inactivation process can be used without compromising nutrition or taste, particularly because the inactivation rate appears to be quite sensitive to the pasteurisation temperature and time".
The researchers say the US government is "working diligently" on this, but warn that there are not enough controls in place to safeguard consumers. They say that more studies are also needed to assess the impact of a botulinum release on other areas of the food and drink industry.