Smudges behind iMac screen glass

I'm not sure exactly when these smudges appeared because I didn't notice them until I changed my desktop to a background that was white. At first I thought it was on my screen and just needed to be wiped off but when I went to wipe it off, it was still on the screen. I took a screenshot, the image was fine so the issue is physical.

I went to google and found countless threads and posts and even some youtube videos with people having the same issues. My iMac is out of warrently now, its over a year old and I actually bought a new M1 so its not my primary desktop anymore. However I have concerns, the issue is almost 12 years old and there are posts dating back to 2008 and in 2021 this is still happening with no answer as to why and no way to prevent it.

My concern is the smudges on my screen will continue to grow or that my new M1 will start to have the same problem. Nobody can say if its design flaw or environmental issues (or both). I also have a mid 2014 iMac and it sits on the same desk as the other 2 and has not developed any smudges. So it leads me to believe this is more of an issue with the problem iMac not being sealed correctly?

Can any one offer advice? will it get worse over time, is there a way to stop it from getting worse or should I pay to have it fixed? what are the odds of this reoccurring if it does get fixed?