An example of metaphor in science journalism:
" 'The problem with nitrosamines is that the levels that they have to be controlled to [in pharmaceuticals] are so super low that proving a negative is, in many cases, beyond the capability of the testing technology at present,' explains Michael Burns, principal scientist at Lhasa.
The function of the software is to highlight to manufacturers when the various factors combine that could give rise to an important impurity, Burns says. 'Then it's up to them to assess that risk.'
But this is a huge job, Burns explains, because if you've got any secondary amine of any description in your product, it could form a nitrosamine, and secondary amines are everywhere: in drugs but also in food and in our bodies.
'This is part of the context that can get lost with the focus on the pharmaceutical world - that your stomach is an incredible reaction vessel, which is full of nitrites from our natural environment,' Burns says. 'It's very acidic, which is prime conditions for any amines in your stomach, you will generate absolutely tonnes of these chemicals anyway that you can't control'."
Julia Robinson (2023) Chemistry World, October 2023, pp.16-19, https://www.chemistryworld.com/news/addressing-the-saga-of-nitrosamine-contamination-in-drugs/4018123.article
A tonne is a megagramme, a thousand kilogrammes. However, here 'tones' seems to be used not in its scientific sense, but in the figurative sense of 'lots of'* (and moreover, in a contextual sense of 'lots of' – that is 'lots of, when we are concerned with very small quantities'!).
* Otherwise (if to be taken literally): A person may typically live for something in the region of 20 000-30 000 days (c.60-90years), so if we assume 'tonnes' (plural) means 2-3 tonnes over a whole lifetime then a person would have to produce a tonne of nitrosamines in 10 000 days – or about (0.1kg = ) 100g per day.
An article in the Encyclopedia of Toxicology confirms that:
"Nitrosamines can also be formed in the mouth or stomach if the food contains nitrosamine precursors. Under acidic pH in the mouth or stomach, nitrite or nitrates added to food or naturally occurring may combine with amines to form nitrosamines."
H. Robles (2014) Nitrosamines, Encyclopedia of Toxicology (Third Edition), Academic Press. https://www.sciencedirect.com/science/article/abs/pii/B9780123864543005236
But this same entry reports how the toxicity of these compounds is such that they are considered to be risk factors for cancer at a level of fractions of mg per day (note above: "the levels that they have to be controlled to are so super low …beyond the capability of the testing technology") – many orders of magnitude lower than would be generated in people's stomachs if the reference to 'tonnes' was taken literally – even as lifelong total.
