Chlorinated paraffins are of very low acute toxicity following a single exposure. Various different grades have been tested and doses of 4-10 g/kg show no signs of toxicity to laboratory animals. An equivalent dose in humans would be drinking about 250-600 ml of liquid chlorinated paraffin for an average person.
In longer-term studies on laboratory animals, chlorinated paraffins produce toxic effects on the kidney and liver. The highest dose that can be given without showing an adverse effect (the No Observed Effect Concentration - NOEC) is 10 mg/kg/day for rats. This amount is many orders of magnitude higher than the highest exposure likely to be encountered in industrial conditions and conditions under which people are likely to be exposed in everyday life.
Coming into contact with chlorinated paraffins
The three routes by which any chemical can enter the body are ingestion (via the mouth), inhalation and skin contact. During industrial use, inhalation and skin contact are of particular concern. Since the vapour pressure of chlorinated paraffins is very low, exposure to CP vapour by inhalation is minimal. However, there is potentially more exposure to aerosols of mixtures containing CPs. For most workers, skin contact is the most likely source of exposure to chlorinated paraffins. Studies have shown that skin and eye irritation is low and that they are not absorbed significantly through the skin.
There have been reports that workers exposed to metalworking lubricants may suffer from allergic reactions or skin sensitisation. There is no evidence that this effect is caused by chlorinated paraffins in the lubricants. Animal studies, together with evidence from humans, have confirmed that chlorinated paraffins do not have the potential to be skin sensitisers. The effect is attributable either to other components in the lubricant or to certain stabilisers that have been used. Today, most CP suppliers use stabilisers which have been shown not to cause skin sensitisation
Volatility
All chlorinated paraffins have very low vapour pressure. Under normal conditions of use, the quantity of chlorinated praffin likely to be inhaled is extremely small. However, if chlorinated paraffins are heated during handling, some fumes may occur. These may contain a small proportion of HCl (an irritant) and in these circumstances adequate ventilation is recommended.
Aerosol mists can be produced during use of metal working fluids in the engineering industry and these mists may contain a proportion of chlorinated paraffins. It has been calculated that exposure in this way does not present a risk provided that the Occupational Exposure Limit (OEL) for oil mists (5 mg/ml in the UK) is met.
Carcinogenicity
Lifetime animal studies have been carried out with two grades of chlorinated paraffins. A short-chain grade with 58% chlorine caused tumours in rats and mice. Male mice exposed to a long-chain grade with 40% chlorine showed an excess of tumours at one site which was most probably not due to exposure to CPs. It has been shown that the mechanisms by which short chain chlorinated paraffins cause tumours to be formed are specific to rodents and, therefore, of no relevance for human health. Furthermore, chlorinated paraffins have been clearly shown to be non-genotoxic. Based on this evidence it is concluded that the carcinogenic findings in animals do not give rise to concern for human health.
Chlorinated paraffins have been classified as carcinogens in some countries
Short-chain chlorinated paraffins are carcinogens in laboratory rodents. The basis for the regulatory classification of carcinogens differs from country to country. Some systems give less weight to the more recent mechanistic studies which indicate that the animal results are of little relevance for man than others.
In the USA, the short-chain (C12), 58% chlorine product is the only CP to be classified and labelled as a carcinogen. However, some suppliers in the US have decided to label other short-chain CPs in the same way.
In Germany, the MAK Commission has classified virtually all chlorinated paraffins as Category IIIB (i.e. suspect carcinogens). However, they have not been included in the list of substances (TRGS 905) required to be labelled.
All EU Member States have been required to implement the EU decision in 1998 to classify short chain chlorinated paraffins as Category 3 carcinogens.
