No that isn't it. Else all animals would have at least similar life spans. A dog doesn't die at 8 from cancer because of eating and breathing pollutants. And neither does a human at 80. The only thing most pollutants do is make it worse.

The underlying cause is our body not being able to maintain itself over even short timescales, with or without pollutants.

Historically, the population of the world was exposed to much higher doses of common pollutants than today in much of the world. One example, see link below. If what your second line describes were so directly the case, then, for example, the people of late medieval Europe or the time of the early industrial revolution would have been saturated with diseases like cancer, alzheimers, diabetes etc. Maybe they were, since medical records from those times are barely above non-existent, never mind being clinically accurate, but the evidence either way definitely shows how much higher accumulations of common toxins were in people's bones, hair, blood etc prior to modern times.

https://link.springer.com/article/10.1007/s00204-012-0866-7

I'm not an expert in any of this, but from reading this stuff a long time it almost always goes back to inflammation.

I doubt it. In the book Outlive, they show the overall rates of mortality after subtracting for the 8 leading infectious diseases, and the death rate is mostly flat over the last 70 or so years. His conclusion was that neither environmental factors nor medical research has made much progress on things like cancer, etc.

That doesn't make sense, if pollution was literally slowly killing us, and the planet, surely we would take some action to decrease pollution, and yet for my entire lifetime we've exuberantly increased it, recently going so far as to build bitcoin, a popular competition to pollute as much as possible in exchange for prizes.

Weirdly, if I do any amount of research, it does seem like there's strong correlations between pollution and most kinds of cancer, what a wild coincidence.