From Huntington Breast Cancer Action Coalition:

The most commonly used dry cleaning chemical is perchloroethylene (Perc). The federal government considers Perc to be a probable human carcinogen. It is a drinking water contaminant, and has been the culprit in numerous hazardous waste sites, including on Long Island. To avoid these concerns, the market has responded by developing alternatives to this chemical to professionally clean clothes.   Read more…

http://www.preventionisthecure.org/images/stories/greendrycleaning_0315/dry_cleaning_final_3_31_15.pdf

dry cleaning