(N) :
alt=A computer graphic showing how many PM particles can be wrapped around a human hair and how several PM particles can be wrapped around PM|thumb|PM and PM compared with a human hair in a graphic from the Environmental Protection Agency
(N) :
alt=A computer graphic showing how many PM particles can be wrapped around a human hair and how several PM particles can be wrapped around PM|thumb|PM and PM compared with a human hair in a graphic from the Environmental Protection Agency