I've been plateaued for months. I can't increase my reps even by one more (I do, among other things, pushups with weights in a backpack, ≈30kg). Currently, I train any particular group of muscles, e.g. arms, once in three days. I tried everything I could think of (follow the link for additional information), and I recently started to wonder, what if my struggles with the sport are due to poor air quality? I live in a city with "very dirty" air, officially – near a wastewater treatment facility and coal CHP plant, at that. I've been doing daily exercises at home for years – pretty intensively if you ask me – I've breathed a lot of this bad stuff in. Can air pollution negatively affect your physical performance? What do studies say on that?
So the answer to the question based on the studies is yes, it will affect your performance.
Although to attribute your plateauing to just that, unless we are talking about incredible levels of pollution, seems unlikely.
Sometimes you need to change the exercises themselves and shake things up a little.
Also, it might be you are overtrained and need to stop for a while and deload - there are several deloading schools and you can ask about the best one for you on a different question - but how long it's been since you've lowered your intensity?
You might need to take it easy one or two weeks to come back to increases.
Oh, and are you eating enough and sleeping well enough? Those are another important variables...
And finally, as @alephzero pointed out in the comments, there is also a genetic physical limit that we can't overcome without drugs (This is not recommending you should do drugs, at all. Just stating a documented fact)
Absolutely pollution can affect physical performance, particularly if one has an existing respiratory condition. It might be a bit anecdotal but I can vouch that this is the case from my own experience where I have seen a coorelation between higher level of air pollutants, which I monitored, and stanima as I would struggle to breathe sufficiently much sooner where pollution levels are higher. Over a longer time higher levels of air polution are thought to cause such respiratory problems, the effect gases like nitrogen oxides have on children linking to conditions like asthma has been the main reason to extend low emission zones to more residential areas of London.
More scientific studies are found at (for example) https://ehp.niehs.nih.gov/doi/full/10.1289/EHP2239 https://pubmed.ncbi.nlm.nih.gov/22267572/ https://journals.sagepub.com/doi/10.1177/1757913917726567 which quite consistantly suggest a negative correlation between polution levels and performance.