There's reason to doubt freeway traffic is the primary source of pollution at Tubman Middle School. Just across the freeway from the school is a non-trivial amount of industrial activity including:

* A Calportland cement facility (2500 ft mi)

* A Union Pacific rail yard (4000 ft)

* Tyree Oil, a small petroleum distributor (1200 ft)

* What looks like a power transfer station (2000 ft)

* At least two glass-makers and a ceramics studio (<1000 ft)

* A sheet metal fabricator and neon sign manufacturer (1100-1400 ft)

This article appears to have originated with a Bike Portland (and No More Freeways) campaign against freeway expansion and for decongestion pricing.