Assessing the environmental impact
Very low levels of chlorinated paraffins have been found in the
environment. Analysis of rivers in industrialised parts of the UK
has shown levels in the range 0 to 2 µg/l (i.e. parts per billion),
with the more toxic short-chain chlorinated paraffins typically
accounting for one-quarter to one-third of the total amount
present. Higher levels of typically 0 to 10 mg/kg have been found
in sediments collected close to industry.
In areas remote from industry chlorinated paraffins were either
found at much lower levels or could not be detected.
Chlorinated paraffins are considered to be relatively
persistent. They have been shown to break down under the action of
bacteria, but this biodegradation takes place relatively slowly and
none of the grades tested was judged to be 'readily biodegradable'.
The rate of biodegradation was found to be higher for grades with
lower chlorine content and where bacteria had become acclimatised
to chlorinated paraffins (e.g. in the immediate vicinity of a
Do chlorinated paraffins bioaccumulate?
Laboratory tests have been carried out to measure the levels
present in fish exposed to chlorinated paraffins compared to those
present in the water; this ratio is called the bioconcentration
In tests carried out with trout, the BCF was found to be
approximately 8,000 for short-chain grades and approximately 1,000
for medium-chain grades, whilst for long-chain grades it was only
about 50. These values are very much lower than for substances such
as polychlorinated biphenyls (PCBs) and chlorine-based pesticides
(dieldrin, DDT etc).
Studies have also shown that there is no biomagnification of
chlorinated paraffins by fish; the levels in fish eating food dosed
with the product were no higher than those in their normal
Toxicity to fish and other aquatic species
In laboratory tests short-chain grades have shown 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 the environment.
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 (see previous
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
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, 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.
Do chlorinated paraffins act as oestrogen mimics?
There is nothing in the biological profile of chlorinated
paraffins to suggest that they would have this effect.
Last update: 09/2011