Funded by the OSU Superfund Research Program and led by environmental chemist Staci Simonich, a recent study discovered that emission control systems added to a Portland General Electric plant in 2011—which targeted mercury—inadvertently lowered dangerous airborne PAHs.

http://blogs.oregonstate.edu/superfund/2015/07/08/mercury-scrubbers-at-oregon-power-plant-lower-other-pollution-too/