The grossest news of the day comes out of San Francisco, where officials say that a prime reason escalators in their BART public transit stations break down is the voluminous amounts of human excrement that "gum up" their gears. San Francisco commuters are, no doubt, already horrified, but we're most interested in the sort of sad resignation with which the San Francisco officials describe the problem.

The human excrement comes from homeless people who camp out at the bottom of BART station stairs. The San Francisco Chronicle's Will Kane's lead is stunning:

When work crews pulled open a broken BART escalator at San Francisco's Civic Center Station last month, they found so much human excrement in its works they had to call a hazardous-materials team. While the sheer volume of human waste was surprising, its presence was not.

Ugh. BART police tell the Chronicle it's nearly impossible to combat this problem, because it's hard to catch people in the act, and the transit security doesn't have much control over how their stations have become such a popular camping spot. So, while they hammer out a solution, we suppose there's always cabs. (No wait, those are gross too.)

Meanwhile, we can't help noting that escalator breakdowns aren't isolated to San Francisco's public transit. It's a big complaint among D.C.'s metro users, too. So far though, there's no evidence that the causes are quite as putrid -- just inconvenient. Let's all just cross our fingers that it stays that way.