What we don't know is if those CT scanners are also able to do regular X-ray scans and if the CT function is only invoked when the staff are wanting a better look at what's in a bag.
I don't think so. The physical construction and working principle of a CT scanner is different from an X-Ray scanner
Here's a quote of interest, pertaining to radiation doses, from a relevant article which seems legitimate:
Data from dosimeter badges passed through a traditional carry-on baggage machine showed from none to very small amounts of measurable radiation. On page 24, the study notes that the highest dose measured on a dosimeter that was passed 36 times through the machine was 4 mrem or 0.04 millisievert (mSv).
Dosimeters that were passed through the "checked baggage" system that randomly activates the x ray had highly variable doses. If the dosimeters were near the area randomly selected by the software to activate the x-ray source, a higher dose would be measured. The average dose, after 10 passes through this type of system was about 28 mrem per scan (0.28 mSv per scan).
Dosimeters that were passed through the type of "checked baggage" system that stayed active for the entire screening process had an average dose of 156 mrem per scan (1.56 mSv) per scan. The newer carry-on screening systems are expected to deliver similar doses.
Source:
https://hps.org/publicinformation/ate/q12361.html
This suggests that taking your film through a CT scanner will give results in the same ballpark as running it through checked baggage scanners. The latter is known and demonstrated to be devastating even for one or two passes and for slower films.
I've read somewhere—cannot for the life of me find the reference—that lower ISO films (20 to 100) are less sensitive to the x-ray scan and therefore not as susceptible to getting fogged.
That's correct; the slower the film, the less prone to x-ray damage it will be. This is easy to understand if you keep in mind that this is all about electromagnetic exposure of the silver particles in the film - whether this happens through visible light or 'light' (electromagnetic radiation) of a shorter wavelength does not matter all that much in principle. This also means that faster will be more sensitive to light, as well as to x-rays, and vice versa.
For the older x-ray machines the distinction between fast (notably 1600-3200 speed film) and slower film (anything up to 800 or so) was still relevant; 'slow' film up to at least 400 would typically not suffer visible damage from airport xrays, while 1600/3200 film could suffer visible damage especially after a few passes. I myself never hesitated to run my film (typically 100 and 400 speed) through the older xray machines and never had any problems with it.
The new CT scanners are different in the sense that the radiation doses are typically high enough to give visible damage to the film even in a single pass, and for slower films as well as faster ones. Verifiable reports of this including images have popped up, also on Photrio, and film manufacturing companies have issues warnings about this.
Since the advent of CT scanners, I consistently ask for manual inspection and I carry my film in a dedicated zip-lock bag along with a printed Kodak 'do not xray' leaflet.
As to the scanner situation in Europe: it's a mixed bag. In my experience so far especially the less affluent Mediterranean countries have not yet converted to CT and continue to use xray machines, while especially in NW-Europe CT scanners can be found. For instance Eindhoven Airport in The Netherlands only has CT these days, and Amsterdam Schiphol Airport (a place you should avoid at all cost BTW) has at least partly (but possibly by now completely) converted to CT.
There is usually no information on the websites of airports that clearly indicates what kind of scanner your carry-on luggage will go through. This means that if you are traveling by air, you will have to be prepared to encounter CT scanners along the way, but there's no guarantee you will.
www.standard.co.uk
