It's called PCE, a solvent used by some dry cleaners, and officials say it may have leaked into the ground, here in the Truckee Meadows.
The Division of Environmental Protection is currently investigating five locations -- three in Reno and two in Sparks.
According to documentation from a state official, all but one of the sites is where a dry cleaning business is located or where one had been in the past.
One official tells KOLO PCE was found in groundwater, near at least two of the sites.
But he says even if the contaminant reaches water used for drinking, special equipment will remove it from the water long before it reaches your facet. He says there's no danger from drinking water from your tap. A Washoe County official says casual exposure out in the environment to PCE is also unlikely.
The government says: PCE, in its liquid form, can irritate your throat, and breathing its vapors, in extreme cases, can kill you.