A few weeks ago, an unusually disturbing specimen shared part of my morning commute on the MAX Green Line. It made me wonder how often the cars are wiped down and what chemicals are used, because this guy left a residue.

—Workin' for a Livin'

As I consider how best to answer your question, I'm struck by how fine the line is between "using humor to reinforce community grooming standards" and "making fun of the homeless."

I don't mean to be too hard on you, Workin', and I don't expect you to immediately adopt a Christ-like, love-thy-filthy-neighbor attitude where you run out and start licking every weeping sore you can find. But I gotta tell you, the MAX is merely one item on a long, long list of things you're better off not knowing where they've been.

Think about it: Do you really want to know what happened on that hotel mattress? What do you suppose all the mouths that Denny's fork was in before yours looked like? I wonder how many people think it's fun to put money in their butts for a while before they spend it?

Sure, many of these things are appropriately sanitized—that fork, for example, is perfectly safe to use. It's also true that a human turd that's been run through a blender with a mild bleach solution is perfectly safe to drink. I still say not thinking about it is the way to go.

Since you must know: Each night, the MAX car is swept, mopped and spot-cleaned, but only once every 60 days does it get the treatment you're probably hoping for, where the floors are steamed and the entire car is sprayed down with industrial cleaner.

On any given day, you've got a 1-in-60 chance of not sitting in dried vomit. Meh; have another drink and forget about it.

QUESTIONS? Send them to dr.know@wweek.com