The diesel engine exhaust doubled the background particulate matter levels found outdoors at its peak.

BBC: Image of a smoke filled room

Corning thinks those filters, which strip particulate emissions out of the exhaust of diesel engines, will soon be its next big hit.

FORBES: Magazine Article

One of the pollutants was a fine particulate substance known as PM2.5, a major component of diesel exhaust which EPA had determined to be unsafe for inhalation at any level, particularly for health-impaired and elderly populations.

FORBES: EPA Charged With Lethal Experiments On Hundreds Of Unsuspecting Subjects