Hexyl chloroformate

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.015 mg/L

Assessment factor:

1 000

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.15 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.002 mg/L

Assessment factor:

10 000

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

14 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

0.119 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.012 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.015 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Additional information

Derivation of PNECs

Dissolved hexyl chloroformate is expected to rapidly hydrolyse under formation of hexanol (CAS 111 -27 -3), hydrogen chloride (CAS 7647-01-0) and carbon dioxide (CAS 124-38-9). PNECs are based on the worst case environmental fate data and ecotoxicity data available for both the parent substance hexyl chloroformate and its main expected hydrolysis product hexanol*.

In the short-term fish toxicity study performed with the parent substance hexyl chloroformate rapid hydrolysis to hexanol and hydrogen chloride may be expected to have occurred. However, remarkably the toxicity in the study with hexyl chloroformate is considerably higher (96 -h LC50 of 15 mg/L) than the toxicity observed in the study with the hydrolysis product hexanol (96 -h LC50 of 97.2 mg/L). Considering that the pH in the study with hexyl chloroformate remained within acceptable limits, no effects are considered to be attributable to the formation of hydrogen chloride. The clearly higher toxicity of hexyl chloroformate may be expected to be due to reactivity of un-hydrolysed parent substance at the beginning of the test. On a larger geographical and temporal scale hexyl chloroformate may be expected to exist in aqueous environments mainly, if not only, as its hydrolysis products and therefore the short-term reactivity effect is considered likely to be of little relevance for environmental assessment. However, inter-species differences as well as inter-laboratory differences between the two studies cannot be excluded. Therefore, as a worst case approach, the LC50 value of 15 mg/L from the study with the parent compound is used for derivation of PNECs.

* Hydrogen chloride and carbon dioxide are not considered in the environmental assessment of hexyl chloroformate for the following reasons.

The hazard of hydrochloric acid for the environment is caused by the proton (pH effect). For this reason the effect of hydrochloric acid on the organisms depends on the buffer capacity of the aquatic ecosystem. There is a possibility that the emission of hydrochloric acid could locally decrease the pH in the aquatic environment. However, normally the pH of effluents is measured frequently to maintain water quality and the range of pH can be managed properly to prevent adverse effects on the aquatic environment. Therefore, a significant decrease of the pH of the receiving water is not expected. Generally the changes in pH of the receiving water should stay within the natural range of the pH, and for this reason, adverse effects on the aquatic environment are not expected due to anthropogenic or naturally occurring hydrochloric acid (OECD SIDS, 2002).

For carbon dioxide no information on environmental fate and pathways or ecotoxicological information is available. However, the formation of carbon dioxide is considered to be of limited environmental relevance as carbon dioxide in aqeous environments is an important component of the carbonate buffering system.

Conclusion on classification

The substance needs to be classified as Aquatic Chronic Category 3, H412 (Harmful to aquatic life with long lasting effects) according to regulation EC/1272/2008 (CLP).

This classification is based on the worst case classifcation of both the parent substance hexyl chloroformate and its main expected hydrolysis product hexanol. Hydrogen chloride and carbon dioxide are not considered for environmental classifcation for the same reasons as presented above.

Hexyl chloroformate:

For hexyl chloroformate short-term aquatic toxicity data are available for one trophic level (fish). The 96 -h LC50 value of 15 mg/L is derived from a study with zebrafish (D. rerio). Long-term aquatic toxicity data are not available and the substance is qualified as not readily biodegradable. Based on this information, the substance needs to be classified as Aquatic Chronic Category 3, H412 (Harmful to aquatic life with long lasting effects) according to regulation EC/1272/2008 (CLP).

Hexanol:

For hexanol short-term aquatic toxicity data are available for three trophic levels (fish, aquatic invertebrates and algae). The lowest observed acute effect concentration is a 72-h ErC50 value of 79.7 mg/L as derived from a study with algae (P. subcapitata). Long-term aquatic toxicity data are available from the same algae study in which a 72 -h ErC10 value of 19.8 mg/L was determined. The substance is qualified as readily biodegradable. The log Kow value is <4 (no experimentally determined BCF value is available). Based on all this information, the substance needs not be classified for the environment according to regulation EC/1272/2008 (CLP).