In an editorial accompanying the study, he wrote: “All the critical information in this article that could be useful to a terrorist” - such as the size of tanks at dairies - “is immediately accessible on the world wide web through a simple Google search.” Publishing the analysis, he says, will lead to more scientific studies, and to a defence.

The study considered a typical US dairy, at which numerous trucks make two deliveries a day, each from a number of farms. The deliveries are pooled in huge holding tanks, then pasteurised and bottled.

These tanks are constantly being drained and refilled, and are only emptied and cleaned every three days. So toxin concentrations in the bottled milk depend on when the toxin is added, how much is added, and how much is de-activated by pasteurisation. Limited data on that, and on what doses of botulinum are toxic in people, says Wein, meant the calculations could not be precise.

But the model showed that 1 gram of toxin or less in a milk delivery would poison 100,000 people - mainly children, who are more sensitive and drink more milk. Ten grams would poison most of the dairy’s 568,000 consumers, regardless of age. Such quantities are not considered beyond the capabilities of terrorists. [keep reading]