Very disconcerting and discouraging.
Top pix is the view west from Crown Pass, overlooking the San Joaquin Valley choked in smog which ends up filling the interior canyons of the Sierra. Several contrails as a bonus.
Then, the view south from the same vicinity. Even objects only a few miles away are obscured.
Below, the view leaving Woodchuck Lake: trees clear in the foreground but the far side of the lake starting to fade.
Photos: View West—Sierra Nevada, 2009; View South—Sierra Nevada, 2009; Trees, Woodchuck Lake—Sierra Nevada, 2009