Airborne dust contains estrogenic chemicals, one of the most abundant ones being phthalates.
Since we Westerners spend over 90% of our time indoors, then those estrogenic chemicals we are breathing in almost all day every day could play a role in forming man boobs, or making man boobs tougher to get rid of if you already have them.
That's why it's important to invest in an air purifier if you want to get rid of man boobs, and also for improving your general health (they also work wonders for hay fever, asthma, and sinus issues).
Two important factors to look for in an air purifier are coverage area and that it has a HEPA filter.
For the coverage area, use a tape measure to measure the size of the room you intend to use the air purifier in, in square feet (width multiplied by length of the room), and then select an air purifier that has a coverage area equal to or bigger than that. If you get a cheap small air purifier for a huge room, then it will simply keep re-purifying the same small pocket of air surrounding it. Since an air purifier is basically a fan that pushes air through a filter, having a tiny air purifier in a huge room would be like trying to cool a huge room with a tiny pocket fan. This might be OK if you are using an air purifier next to your desk at your workplace, where you only want to purify the space around your desk, but if you want to purify an entire room, then it's important to get a purifier with a wide enough coverage area for that room.
HEPA filters are certified to remove 99.97% of dust, including small particles like phthalates. Do not get anything that claims to be “HEPA-like” or “HEPA-type”, as these are not the same as just “HEPA”.
It's also a good idea to get an air purifier that has an additional prefilter. Their role is to capture larger particles, thereby leaving the HEPA filter to catch the smaller harder to catch particles rather than load up with large ones.
I did a bunch of research, and here are some air purifiers that seem to be decent:
Coverage area: 1000+ square feet
Coverage area: 500-1000 sq foot
Coverage area: 250-500 square feet
Coverage area: <250 square feet