Okay please prove going outside your apartment is "safe". Nope. Okay then prove staying inside it is "safe". Nope. There's no such thing either way. Life is far more complicated than that kind of black and white thinking. Going out in the sun can make you sick (skin cancer) at the same time not going out in the sun can make you sick (different kind of cancer). But the most important point here is when people get cancer it's almost never because they did something WRONG.
That belief is a really fucked up left over from the "god is judging you for your mistakes" mentality of the old days. People's cells divide every day, and every single time they do there's some random percentage chance they will screw that process up. It's actually inevitable that they will given enough time, but it can chance to happen at anytime to anyone. If you don't get run over by a car, or kill yourself, or have a heart attack, or any other common killer then you will live long enough for your body to fuck up and accidentally make cancer. AND IT IS NOT YOUR FAULT. It's not that gardening you did that one time, or that painting... you can easily find people who did the exact same thing for an entire lifetime as a profession and they're sailing into their 90s smoking cigarettes and eating fried eggs. Cancer is a random chance process that can the strike the most "pure" vegan, health nut, karma cosmonaut you ever heard of at age 5.
When you see these studies that say blah blah blah is linked to an increase in cancer risk, they're talking about an insanely small effect. One we can detect because we're super fucking good at math (like insanely good), but not one that has any real impact on your own life. Take any one million people, 4400 will get cancer this year. Add exposure to whatever fear factor of the week you want and maybe 4404 will get cancer. That's a difference of 4 in a million. Mathematically you should believe you're about to be struck by lightening walking to your car that you should be afraid of these the "tiny but measurable" cancer fears