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Environmental impact

There is no evidence that the low levels of chlorinated paraffins, which have been shown to occur in the environment, have any lasting adverse effect. However, results from laboratory experiments indicate that certain grades are toxic to some sensitive aquatic species and may be of potential concern in areas where higher levels of such chlorinated paraffins are present.

The overall assessment of environmental impact is often based on measures of persistence, bioaccumulation and toxicity and each of these topics is addressed below:

In the environment

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.

Persistence

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 production site).

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 factor (BCF). 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 diet.

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 paragraph). 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 sensititivity, 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, 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.

Reducing the environmental impact

From the information presented in this section, it can be concluded that only short chain chlorinated paraffins present a significant environmental risk. The UK government prepared in 1999 and revised in 2005 a risk assessment report on short-chain chlorinated paraffins within the framework of the EU Existing Substances Review and is now (2005) working on medium chain chlorinated paraffins. A draft of the environmental part has been completed and can be read on the European Chemicals Bureau (ECB)web site.

The SCCP Risk Assessment was completed at the end of 1999. A summary is available in Adobe PDF format on the web site of the ECB. It requires risk reduction measures to be implemented on emissive uses in metalworking fluids and in leather treatment. The European Commission has issued a Directive (2002/45/EC) for that purpose.

In the meantime, the Oslo and Paris Commissions (OSPAR) recommended the phase-out of the use of short-chain chlorinated paraffins in most applications in 1999 (although the UK government was not bound by this decision and many other governments have failed to implement it because it was in contradiction to the EU risk assessment).

European producers of chlorinated paraffins are also voluntarily taking steps to reduce sales of these grades to the metalworking and leather treatment industries, which are believed to present the greatest potential environmental risk.

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.