"The problem with traditional dry cleaning is a liquid solvent called "perc," short for perchloroethylene. (Despite the moniker, dry cleaning isn't really dry; it just doesn't involve water.) Perc is what dissolves the gunk off of your clothes. It's highly effective without being labor-intensive and—unlike the cleaning chemicals of old—it's not likely to burst into flames. That's why cleaners have been using it for the past 50 years."

"People have been concerned about the chemical's health risks since the 1970s. Perchloroethylene (also known as tetrachloroethylene) is considered a toxic air pollutant by the EPA, meaning that it's "known or suspected to cause cancer or other serious health effects." Short, intense blasts of perc can cause dizziness, headaches, or loss of consciousness. But how dangerous is long-term exposure? Indoor and outdoor air usually contains a few micrograms of perc per cubic meter. At those background levels, the New York State Department of Health estimates that there's a theoretical risk of up to five additional people in 1 million developing cancer after a lifetime of exposure. (Some agencies have calculated slightly higher risks; California's Air Resources Board, for example, estimates an additional six to 30 cases of cancer at those background levels.)"