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1,1-dichloroethene (Vinylidene chloride)

Report

To read the report, please click here.

Summary

Applications of 1,1-dichloroethene

The intermediate 1,1-dichloroethene is only manufactured in France and is not imported into Europe. Less than 60,000 tonnes were produced in 2004. A small amount is believed to be produced and used in Russia.

Between 40 and 50% of the 1,1-dichloroethene produced in France is used for the production of polyvinylidene chloride (PVDC), on-site and in Germany. PVDC is mainly used for food and pharmaceutical packaging. Another 40-50% is used for the manufacturing of dichlorofluoroethane (HCFC-141b) and 1-chloro-1,1-difluoroethane (HCFC-142b). Under 10% is sold to industrial customers for the production of other chemicals or plastics.

Evaluation of environmental risk

To evaluate environmental risk implies comparison of likely exposure – in this case derived from monitoring data – with effects on organisms, which is derived from laboratory toxicity data.

Monitoring data

The environmental concentrations measured for 1,1-dichloroethene indicate concentrations in water in the ng/l range. Data from The Scheldt estuary and the North Sea were used to calculate actual exposure (PECs).

The results of the statistical evaluation are shown in the table below. The mean value and 90th percentile of the concentration distribution of this combined data set represents the typical and worst case concentrations used for the risk assessment.

Toxicity

Data available for algal, invertebrate and fish species for both the marine and freshwater environments are for single species laboratory studies. Most of the information available is concerned with acute exposure, although there are a few studies available on chronic (long-term) exposure. Based on acute data, there is no indication of a difference between fresh and saltwater species sensitivities. The effects concentration for saltwater species lies in the middle of the range of acute effects concentrations for the fresh water dataset. This justifies a combination of the two datasets.

Because of the high volatility of 1,1-dichloroethene, studies carried out in closed systems where volatilisation is restricted and using analysed exposure concentrations are considered more reliable than those carried out under static conditions using nominal concentrations.

Sufficient good quality data are only available to apply a safety factor of 10000. This requires the lowest short-term L(E)C50 from fresh or saltwater representatives of three taxonomic groups (algae, crustaceans and fish) of three trophic levels.

The lowest, most reliable data is for:

• a 72-hour EC50 (chlorophyll a content) 9.12 mg/l for Chlamydomonas reinhardtii
• a 48-hour EC50 11.6 mg/l for D. magna
• a 7-day LC50 of 29 mg/l for fathead minnow.

From these studies the lowest relevant and reliable concentration is the EC50 of 9.12 mg/l for Chlamydomonas reinhardtii. Applying an assessment factor of 10000 to this value, as required by the Technical Guidance Document, results in a PNEC of 0.9 µg/l, which is proposed as the PNEC for the protection of marine life.

Risk assessment conclusion

The calculated PEC/PNEC ratios give a safety margin of 257-500 between actual exposure (PEC) and the level at which no effect on the environment would be expected (PNEC). This indicates that the current use of 1,1-dichloroethene does not pose a risk to the marine environment.