Something is going on at the Science Center at Harvard-- Oxford Street is shut down from the junction of Kirkland and Oxford up past 60 Oxford Street, and even foot traffic is being routed away from the part of Oxford closer to the junction:
Here's a shot of the end of Oxford Street, taken from the junction. The Science Center is on the left of the shot:
Traffic was (maybe still is) backed up into Porter Square, Union Square-- stop and go, bumper to bumper. I've heard rumors of a gas leak or a chemical leak. WHDH is on the scene:
Unfortunately, the WHDH website reports that the problem is "abilene glycol". I'm no scientist, but I've never heard of abilene glycol. So being the dutiful internet geek I went to Google, and searched for abilene glycol, and got exactly one hit... which was WHDH's page reporting the possible leak of abilene glycol at Harvard's Science Center today.
My guess is that somebody reporting misheard "ethylene glycol", about which you can read here on Wikipedia, which is never, ever wrong. In fact, by lunchtime I'm sure you'll be able to find "abilene glycol" on Wikipedia, too.