Perc, which we've established is the standard dry cleaning solvent, is a nasty piece of work. It does real damage when it leaches into the soil, where it can enter groundwater supplies. And that sweet smell that comes off clothes when they're fresh from the dry cleaner's? That's perc you're inhaling.
The good news, according to the Agency for Toxic Substances and Disease Registry, is that most people are at little risk for contamination. And the extremely low level of exposure that dry cleaners' customers get is relatively harmless. However, in situations where workers are exposed to high levels of perc on a regular basis, danger rises dramatically. While perc hasn't been shown conclusively to cause cancer in humans, the International Agency of Research on Cancer has designated it a probable human carcinogen. Let's put it this way -- if you have a bottle lying around, don't drink it.