And have I been leaching dangerous levels of plastic into my body for the past several decades?
For my purposes, I use the microwave for making up my morning breakfast cereal, and reheating stuff like rice and take-out stuff. The last two things are definitely ‘reheat,’ but not the first thing. My containers all say ‘reheat only.’
If there’s any danger, at this point the damage is already done, so I’m not too worried about continuing using my ‘reheat only’ containers, but still curious.
I can’t speak to your plastic problem or if it is even a problem.
I can say your microwave is safe to use. Even if it is leaking microwaves you are probably fine. Ionizing radiation is the dangerous stuff and your microwave is not that.
If you are exposed…you heat up. Akin to sticking your hand in an oven. You start to cook. While that is not a good thing for you chances are you will remove yourself from that situation before it becomes really serious. The thing about microwaves is they heat things (water, which you mostly are) faster than putting your hand in an oven so you will get burned quickly if you manage to put your had in a running microwave oven (they have safety features to prevent this but there always seems to be that one guy who circumvents those safeties and gets in the news).
Know what else hits you with microwaves? Your cell phone. You are not hurt by it because it is very low power. It warms you up a teeny bit.
The sun, and the entire galaxy. It warms you up a teeny bit as well.
They’ve judged it safe to reheat food but not the prolonged, high heat needed to cook food.
The “microwave safe for reheat only” label on a plastic container means the plastic is only rated to go to a temperature high enough to reheat already-cooked food. It is not rated for the higher temperature required for the cooking of raw food, because the plastic will either melt or leach chemicals into the food.
Not to be pedantic or anything, but ekshooally you mispelled universe. 
I kid, but the Cosmic Microwave Background is pretty universal as far as we can tell.
There was a famous case many years ago where someone suffered brain damage because they were sitting in an office chair separated by a thin partition from a leaky old microwave cooker.
Really? This sounds awfully like an urban myth…
Thanks for the replies. It told me nothing that my own Googling indicated, but I appreciate the effort nonetheless. I’ll revisit this question sometime later with a more tersely worded question in the topic and not implicitly buried in the post.
IMHO, that’s not the right way to look at the issue. Any harmful effects are likely cumulative, so it would be good to eliminate or at least reduce future exposure if possible, regardless of past exposure.
We don’t tell smokers not to bother quitting smoking because “the damage is already done,” for example.
For what it’s worth, I no longer heat or reheat any food in a plastic container. I use Pyrex glass containers instead.