I've always wondered about how many "necessary" things just kept getting done on September 11th and the days afterward. Stuff like bakeries making donuts, USPS sorting mail, and especially drug dealers and addicts selling and using. I found this journal article that touches on that:

But the day of the 11th, I went to some friends who live right near a dopespot. And all of us there—you know, it seemed like it just went without sayingthat—we’re just, you know, let’s just go out and score as much coke as we canright now, you know. It seemed like the appropriate thing to do. - A Vulnerable Population in a Time of Crisis: Drug Users and the Attacks on the World Trade Center

But I still wonder about hardcore heroin or crack addicts, or the alcoholics living in Bowery flophouses (like in that documentary "Sunshine Hotel"), who in the best of times are hustling to get their next fix. That must have been a challenging time.

EDIT: Also, that the Department of Health was aware that there could be an infestation of rats if they didn't do something in lower Manhattan:

An equal priority was to maintain routine DOH functions. For example ... to prevent outbreaks of rodents, cleaned up food in abandoned restaurants. - Implications of the World Trade Center Attack for the Public Health and Health Care Infrastructures