Entry into the marine environment
Hexachlorobutadiene (HCBD) is a by-product of chemical
industries that produce chlorinated hydrocarbons,
such as tetrachloroethylene and carbon tetrachloride.
It is mainly used as an industrial solvent.
HCBD is considered a List 1 compound and there
have been a number of reviews outlining the fate
and behaviour and aquatic toxicity of this compound
(e.g. WHO 1984 and CCME 1992).
The presence of HCBD in the environment results
from anthropogenic sources and occurs as a tarry
by-product. Volatilisation and solublisation from
this waste are the primary mechanisms for dispersal
into and throughout the environment. Waste holding
areas and wastewater from industry are likely to
be significant source of contamination.
The main pathways of entry into the environment
are emissions from waste.
Recorded levels in the marine
Monitoring data from the National Rivers Authority
and the National Monitoring Programme Survey of
the Quality of UK Coastal Waters are presented in
Appendix D. However, hexachlorobutadiene was not
monitored in either survey.
Insufficient data are available to assess expected
hexachlorobutadiene concentrations with toxicity
data or relevant standards for the protection of
Fate and behaviour in the marine
Intercompartmental transport will chiefly occur
by volatilisation, adsorption to particulate matter,
and subsequent deposition or sedimentation. Hexachlorobutadiene
accumulates in sediment. Photolysis, oxidation and
hydrolysis are not expected to be significant removal
processes from the aquatic environment. However,
sorption to sediments is considered to be an important
mechanism for its removal from the water column.
Effects on the marine environment
Toxicity to marine organisms
An exhaustive literature review on the toxicity
of hexachlorobutadiene to marine organisms has not
been carried out for the purposes of this profile.
The information provided in this section is taken
from existing review documents (WHO 1984, CCME 1992).
The most sensitive groups of organisms have been
Hexachlorobutadiene is moderately to highly toxic
to aquatic organisms.
Fish species and crustaceans have been found to
be the most sensitive, 96-h LC50 values ranging
from 0.032 to 1.2 and 0.09 to approximately 1.7
mg l -1 for crustaceans and
fish respectively. In one 28-day early-lifestage
test with fathead minnows, reproduction was unaffected
at concentrations of up to 0.017 mg l-1,
whereas increased mortality and a decreased body
weight were observed at 0.013 and 0.017 mg l-1.
Sediment dwelling organisms
No data appear to be available on the toxicity
of HCBD to sediment-dwelling organisms, but given
that HCBD may accumulate in sediments, adverse effects
on benthic organisms cannot be excluded.
The substance has a high bioaccumulating potential
which has been confirmed by laboratory and field
observations. Average steady-state bioconcentration
factors of 5,800 and 17,000, based on wet weight,
have been determined experimentally in rainbow trout.
Concentrations of hexachlorobutadiene in aquatic
organisms, birds and mammals indicate bioaccumulation
but not biomagnification. In polluted waters, levels
of over 1,000 µg kg-1
wet weight have been measured in several species
and 120 mg kg-1 (lipid base) in
one species. Present levels generally remain below
100 µg kg-1 wet weight
away from industrial outflows.
Potential effects on interest
features of European marine sites
Potential effects include:
- toxicity of hexabutadiene to invertebrates (particularly
crustacea) and fish at concentrations above the
EQS of 0.1 µg l-1 (annual
average) in the water column;
- bioaccumulation of hexabutadiene in aquatic
organisms, birds and mammals. However, there is
little evidence of biomagnification through food