Help! Brother's contamination fear getting worse.

[7Brigade]

Recently it has gotten worse. He does not let anyone get near him and is afraid of the air around other people, saying it has microscopic pieces of plastic... This is insanity. I'm just writing this for support as his older sister, I already know what are some possible solutions . But please if anyone has experienced this with someone in the family, I would just like to hear any thing that may help me deal with it.