I've read the same articles on health concerns... and it is a valid concern. First, the 133 doesn't get as much traffic as a regular freeway (which is the closest hwy to the development). I would actually argue that a street like Jamboree or Culver (and soon to be Jeffrey and Sand Canyon) would create just as much traffic as that portion of the 133 (which doesnt really bottle neck until the lanes merge). They do have a set-back and a buffer from the hwy, and I'm guessing (I haven't measured) that is is at least 500 yds from the 133. On the other side, unless you are in the Sienna homes closest to the 405, it's not that close (you can drive up to the cul-de-sac that ends ath the trail on that side of the development). Also, you may not realize it, but LA is elevated over the road (you may not realize it because of the wok effect of the zombie barriers).
Really, what are the options with regards to air quality? Maybe Newport, CDM, Laguna, Dana Point? I think I could live with it and would like to stay in Irvine. There are worse places. Rossmoor, which is considered a very desireable area, is flanked on two sides by the 605 and the 405. And there isn't much of a buffer. (That part of Rossmoor would cause me greater concern that LA does). I also grew up in Arcadia (now popular with the Chinese/Taiwanese) which is not a cheap place to live and has excellent schools. Do you think Arcadia is nice? I used to ride my bike around Arcadia/ Pasadena growing up.. and its rough. Air quality (check AQI in the summer) in the SGV can be VERY bad. Nonetheless, Arcadia and South Pasadena are very desireable... and you have San Marino (the ultimate unicorn). If you are in general saying LA is bad because of general proximity to 405, then MANY parts of Irvine are bad.
We all love to hate Irvine... overrated schools, bad air quality, small lots, uninspiring elevations, and overall poor value prop... so what's the deal? I figure we just have to pick our poison and make a decision for ourselves. Either that or we all move to John's Creek...