I work in hazardous materials handling and safety, and I studied chemistry. I've done a lot of soil remediation and I'm pretty up to date on how we (Europeans) handle the safety of our air, food and water.
So, good news: your air hasn't been cleaner since basically we started burning coal. Your drinking water hasn't been this safe since, oh, pre-agrarian times. Your food is probably less nutritious per gram thanks to faster growing food, but your diet is (potentially) better than any human has ever had (depending on your personal choices).
That said, there are some things I avoid like the plague:
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Swimming in open water. It's (potentially) full of parasites, toxic algae, human and cattle feces and chemical runoff. Probably not all at once, but still. YMMV if you don't live near the sea, mountain streams are much cleaner then those at the river delta.
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Home grown food from urban gardens. Your soil is probably completely untested, and the idea of "maybe I shouldn't just pour chemical waste out of the window" is barely 4 decades old. And that's counting the dubious quality of planter soil that is basically unregulated, and what people use as decoration. (Do NOT use wooden railroad ties or tires as planters for food). And of course what people use as pesticides isn't exactly closely monitored either.
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Drinking water from wells, springs etc. see all the above.
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Ordering anything with wish/aliexpress that comes in contact with food. You know that stuff is completely unregulated, why the hell would you lick it? Nobody knows what it's made of.
And there's one thing I don't avoid, but it's super unhealthy: wood fires. Yeah, a hearth or a campfire is awesome, but the smoke is super fucking bad for you. The carcinogens are stronger and last longer than in cigarettes, and its a hell of a lot more of them. I lie to myself and say it's worth it though, and that I don't do it every day, and other bad excuses.