"not permitted" vs. "not allowed" vs. [something else] in a table of permitted bacterial counts

Question

Let's say I have a document, a specification for a vitamin mix for addition into animal fodder. This document has a table listing the maximum permitted contents of bacteria in the mix.

The first line reads: "Maximum overall bacterial count, in cells/g: 500 000".

The second, third, and fourth to tenth lines read "E.Coli and coliform bacteria", "Proteus", etc. The column value is "not allowed" for each of these, meaning that it's a no-no to have any such bacteria in the mix.

Is "not allowed" a proper combination of words? I came up with "not permitted" as an alternative, but there could be more idiomatic word combinations.

The Russian original is "не допускаются" ('are not admitted', in a blunt translation; meaning the very existence of such bacteria in a sample of the product is a no-no)

Answer 1

There are many similar examples out there:

The United States EPA sets standards for drinking water contaminants:

Di(2-ethylhexyl) phthalate zero

I have seen this switched to the numeral 0 in city water quality fact sheets.

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In strict terms, though, we can't say that a concentration is zero - only that it cannot be detected. So some standards will say non-detectable. That invites the question of how hard one has to look before declaring something non-detectable.

The U.S. FDA sets limits for bacteria in animal-sourced fertilizer with that issue specifically adressed:

L. monocytogenes Not detected using a method that can detect one CFU per five gram analytical portion

Not permitted would be well understood by the public, but doesn't really specify how to determine the absence.

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The examples above reflect the usage when issuing regulations. If you are looking for a way to provide testing results, it is common to report non-detects as being less than the detect threshold. For instance, if your test can detect 0.1 ppm listeria, you could report a non-detect as:

Listeria <0.1 ppm

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Answer 2

Not allowed is a more informal way of saying not permitted. Not permitted is more formal, as shown by the definition - officially allow (someone) to do something.