From Google's OpenRTB spec (https://developers.google.com/authorized-buyers/rtb/openrtb-...):

> Site

> This object is present in the bid request when the impression will be rendered on a website rather than a non-browser application.

Contains a "page" field:

> URL of the page where the impression will be shown with URL parameters removed.

EDIT: If you don't think that counts as personal info then that's that, just trying to prove GP's claim that Google will happily tell a bunch of advertisers that you're visiting a porn website.