About Hexachlorocyclopentadiene (HCCPD)
From The Agency of Toxic Substances and Disease Registry
HCCPD is a light, lemon-yellow liquid that has a sharp, musty odor. It easily turns from a liquid to a vapor when exposed to air. The vapor looks like a blue haze. This chemical is also called percyclopentadiene, hexachloropentadiene, and hex. Some of its former trade names, still listed in chemical reference documents, are C-56, Graphlox, and HRS 1655.
HCCPD is a manufactured chemical and does not occur naturally in the environment. It is made by adding chlorine to cyclopentadiene, or by removing chlorine from octachlorocyclopentane. HCCPD is used to make a group of related pesticides (aldrin, chlordane, dieldrin, endosulfan, endrin, heptachlor, isodrin, mirex, and pentac). Only two of these pesticides, endosulfan and pentac, are currently registered for use in the United States. Thus, your exposure to these compounds is expected to be limited. Endosulfan and pentac are the only two of these pesticides that you can buy in a store. HCCPD is also used to make flame retardants, resins that won’t burn, shock-proof plastics, esters, ketones, fluorocarbons, and dyes.
Most of the HCCPD in the environment results from releases during its production and disposal. Releases can also occur as a result of the manufacture, use, and disposal of pesticides made from HCCPD. Most people can smell HCCPD in the air at 30 parts HCCPD per billion (ppb) parts of air. Most people can smell it in water when it is present at 1.4 ppb. The amount of HCCPD that you can taste in water has not been measured and the taste has not been described.