There is a lot of commentary going on right now about miasma, often erroneously connecting into concept of sin wherein more accurately it is a state of uncleanliness attached to oneself, object or place which may repel or make communion with the gods difficult. Not a great definition on my part but basic and workable. I tend to shy away from general definitions and commentary anyway because the subject is so nuanced that it us better to be addressed case by case. As each deity has things which may be music in association with such deity that is not for others.
For A pollon there is very little observable things which are miasmic. This is likely in credit to A pollon as purifying, renewing and cleansing god extraordinaire. It is his job to deal with natural pollutants: death, decay. At times in the household where every shrine and altar is covered during times of death or birth his shrine can be open and utilized. In fact prayers and offerings to A pollon and Artemis for the first seven days of a baby’s life in which it is most fragile and the successful passage through is credited to these deities would certainly be wise. And although Artemis cannot witness death, A pollon is there and is great to petition following the death of loved ones and when visiting cemeteries. He is lord of ash and decay, and as such would not be the most nefariously picky about a bit of dust or dry remains of offered flowers. Women need nor be obey concerned about it being that time of the month as he is often served by women and loves them in the natural growth and release of the natural body. Just be sure of proper respect. Do not dedicate or allow another creature to do so in his sacred space (so dont put him in the bathroom or near the litter box). And please was your hands before praying since people tend to pick their nose and wipe their ass.
On the otherhand there are things I would consider particularly miasmatic given what is read in text. Acts of injustice (the case of his encounter with the erinyes only makes sense when viewed this way). Do not approach him with acts of injustice on your hands ir expisure via other people without purification. Dishonesty/lying I would put there given he is of the right word/truth. At any rate these are my observations. In short for Apollon it seems more a matter of abstract indirect miasma rather than common pollutants and human activity. It makes you by needs more aware of your character and those whom you associate with that may have influence on your person. Rather than natural processes it is the most foul human activity to which one needs to be aware.