Physico-chemical properties & ecotoxicology
The term chlorinated paraffins is usually taken to encompass a
wide range of liquids and solids from C10 to
>C24 and containing 30-72% chlorine content.
Properties (including ecotoxicology) differ significantly across
this range and for this reason, they are best considered in three
- The C10-13 liquid products from 40-72%
- The C14-17, C18-20 and chlorinated
paraffin wax liquids from 40-60% C12 content.
- The powder chlorinated paraffin waxes of >69% C12
CPs have very low vapour pressure with the most volatile
(C10-13 types) < 10-3 mbar. They are
chemically very stable but dehydrochlorinate on heating at high
temperatures (or for prolonged periods). Dehydrochlorination also
occurs on prolonged exposure to light.
All CPs have low solubility in water but C10-13 types
at up to 150 μg/l are significantly more soluble than the other
classes which show decreased solubility with increasing chain
length (down to below 5 μg/l).
Studies have confirmed that CPs adsorb strongly onto suspended
materials or sediments in an aqueous environment. True solutions
(at the low solubility limit) do degrade without added
Laboratory studies often fail to indicate biodegradation
occurring, but longer-term studies in biological effluent treatment
plants do reveal substantial degradation and the undegraded residue
is removed by adsorption onto the biological sludge.
The short-chain grades
The short-chain grades have been shown, in laboratory tests, to
have toxic effects on fish and other forms of aquatic life after
long-term exposure to concentrations close to their water
solubility, and significantly higher than those found typically in
Mid-chain chlorinated paraffins show a significantly-reduced
spectrum of toxicity compared with the short-chain grades, as would
be expected from their lower bioaccumulation. No measureable short
or long term toxicity has been found in studies with numerous
species of fish.
Only one of several aquatic invertebrate species that have been
tested showed any sensitivity, but again at levels considerably
higher than those found in the environment. Similarly, certain soil
and sediment organisms are affected, but only at levels of hundreds
of mg/kg (parts per million), whilst others are unaffected at
thousands of mg/kg.
Long chain grades
Long chain grades, because of their large molecular size and
very low solubility, have shown no toxicity to fish and other forms
of aquatic life at and above their solubility limit.
Last update: 09/2011