Like you, I've spent a lot of time in airports. Some are impressive; others depressing. 

Now, a new study by says the nastiest, dirtiest place in major commercial airports is not the one you think it is.

During the 2017 holiday season, fanned out at three major U.S. airports for a cleanliness study--or perhaps a lack of cleanliness study-- within the terminals themselves and aboard planes. 

Admittedly it was not the most comprehensive examination possible, but they identified several types of surfaces in all airports and tested them for "the average number of viable bacteria and fungal cells per square inch, or colony-forming units (CFU)."

The results are back from the lab. Here are the germiest, most disgusting places they found. They're listed below starting with the dirtiest.

1. Self check-in kiosks

These were by far the worst offenders, which is a bit surprising at first--but makes sense when you think about it. On the one hand, it's really only our hands that are touching these, but then again: Good Lord, our hands! On average, self check-in screens had more than 253,000 CFU's per square inch.

To put it in perspective, that's nearly three times as many CFUs as the second-nastiest surface they found.

2. Lavatory flush buttons

You thought this would have been the worst one, right? But they came in at just over 95,000 CFUs--still very nasty, but not as bad as the kiosks. Please remember to flush and wash your hands.

3. Airport gate bench armrests

Another surprising one, explainable perhaps by the sheer number of passengers using them each day. These clocked in at an average 21,630 CFUs.

4. Water fountain button

These averaged 19,181 CFUs, which would seem horrible if it weren't for the comparison to the self check-in screens. One possible explanation is simply that almost every passenger uses the check-in screens now, but many fewer use the water fountain. We're a plastic bottle nation, now.

5. Tray tables

I admit, I was pretty sure these would be on here. They came in at 11,595 CFUs. How often do airlines wash them, anyway? (Answer below.)

6. Seat belt buckle

Given where the rest of these are coming in, the seat belt buckle's rating of 1,116 CFUs seems rather tame, like you could almost perform surgery. 

Compare these six surfaces to the average home toilet seat (172 CFUs), bathroom doorknob (203 CFUs), or kitchen sink (21,000 CFUs).

"Cleanliness standards are up to the individual airline, as the FAA doesn't regulate how often or how thoroughly airlines are required to sanitize aircraft," reported The Points Guy. "Cleaning crews typically just remove trash and wipe down lavatories ... while deep cleaning only takes place every month or so at best."

Bottom line: We can't stop traveling. So start carrying hand sanitizer.