Technical Factsheet on: HEXACHLOROCYCLOPENTADIENE (HEX)
List of Contaminants
As part of the Drinking Water and Health pages, this fact sheet is part of a larger publication:
National Primary Drinking Water Regulations
Drinking Water Standards
MCLG: 0.05 mg/L
MCL: 0.05 mg/L
HAL(child): none
Health Effects Summary
Acute: EPA has found hexachlorocyclopentadiene (HEX) to
potentially cause the following health effects from acute
exposures at levels above the MCL: gastrointestinal distress;
damage to liver, kidneys and heart.
At present, EPA has issued no drinking water health advisory
providing guidance on safe levels for short-term exposures to
this chemical in drinking water.
Chronic: HEX has the potential to cause the following health
effects from long-term exposures at levels above the MCL: damage
to the stomach and kidneys.
Cancer: There is no evidence that HEX has the potential to
cause cancer from a lifetime exposure in drinking water.
Usage Patterns
It has been estimated that between 8 and 15 million lbs. of HEX
are produced each year.
Its greatest use is as an intermediate in chemical manufacture,
including the synthesis of chlorinated pesticides, flame
retardants, resins, dyes, pharmaceuticals, plastics, etc. HEX has
no end uses of its own.
Release Patterns
Major sources of release of hexachlorocyclopentadiene to the
environment are emissions and contaminated wastewater from
facilities which manufacture or use this compound as a chemical
intermediate, and from the application of pesticides where it may
remain as an impurity. Other sources are air emissions from the
incineration of certain chlorinated wastes, and from water
treatment plants receiving contaminated wastestreams.
From 1987 to 1993, according to EPA's Toxic Chemical Release
Inventory, HEX releases to land and water totalled only 78 lbs.,
all of which was to water. These releases were primarily from
alkalis and chlorine industries. The largest releases occurred in
New York.
Environmental Fatev
Hexachlorocyclopentadiene is not a persistent environmental
contaminant. If released to soil, it is predicted to be
relatively immobile. In moist soil, this compound would be
subject to breakdown by light and chemical reaction (half-life
hours to weeks). Volatilization from soil surfaces is expected to
be minor.
If released to water, this compound will degrade within minutes
to hours primarily by photolysis and chemical hydrolysis. Though
HEX can adsorb to sediments, this does not slow its rate of
degradation. Volatilization from water is expected to be a
significant removal mechanism, although high turbidity could
extend the half-life to several weeks. Biodegradation is expected
to be of minor importance.
Hexachlorocyclopentadiene could potentially bioaccumulate in some
aquatic organisms depending upon the species. Bioconcentration
factors of hexachlorocyclopentadiene in a laboratory model
ecosystem: alga, 341; snail, 929; mosquito, 1634; and fish, 448.
Chemical/ Physical Properties
CAS Number: 77-47-4
Color/ Form/Odor: dense, oily, yellow green liquid with a pungent
odor.
M.P.: -9 C B.P.: 239 C
Vapor Pressure: 0.08 mm Hg at 25 C
Octanol/Water Partition (Kow): Log Kow = 3.99
Density/Spec. Grav.: 1.7 at 25 C
Solubility: 2 m/L of water at 25 C; Insoluble in water
Soil sorption coefficient: Koc measured at 4,265; low mobility in
soil
Odor/Taste Thresholds: N/A
Bioconcentration Factor: BCFs range from 100 to 1230 in fish;
some potential to bioconcentrate in aquatic organisms.
Henry's Law Coefficient: 2.7x10-2 atm-cu m/mole;
Trade Names/Synonyms: HEX, Hexachloropentadiene
Other Regulatory Information
Monitoring For Ground/Surface Water Sources:
- Initial Frequency- 4 quarterly samples every 3 years
- Repeat Frequency- If no detections during initial round:
- 2 quarterly per year if serving >3300 persons;
- 1 sample per 3 years for smaller systems
- Triggers - Return to Initial Freq. if detect at > 0.0002 mg/L
Analysis:
| Reference Source |
Method Numbers |
| EPA 600/4-88-039 |
505; 508; 508.1; 525.2 |
Treatment- Best Available Technologies:
Granular Activated Charcoal
For Additional Information:
EPA can provide further regulatory and other general information:
EPA Safe Drinking Water Hotline - 800/426-4791
Other sources of toxicological and environmental fate data include:
Toxic Substance Control Act Information Line - 202/554-1404
Toxics Release Inventory, National Library of Medicine - 301/496-6531
Agency for Toxic Substances and Disease Registry - 404/639-6000
National Pesticide Hotline - 800/858-7378
List of Contaminants
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