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Short-term toxicity to fish

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Description of key information

Parent compound: Acutely toxic to fish.
Hydrolysis product methanol: With high probability acutely not harmful to fish.
Hydrolysis product HCl: Acutely toxic to fish (pH dependent).

Key value for chemical safety assessment

Additional information

The parent compound methyl chloroformate hydrolyses rapidly to methanol (CAS 67-56-1), HCL (CAS 7647 -01 -0) and CO2 (CAS 124 -38 -9).

Parent compound: 96-h LC50 = 4.5 mg/L (Hoechst AG, 1981);

Hydrolysis product methanol: 96 -h LC50 ≥ 15400 mg/L (OECD, 2004);

Hydrolysis product HCl: 96 -h LC50 = 4.92 mg/L (OECD, 2002). These data have not been taken into consideration to evaluate aquatic toxicity as observed effects are caused by a pH-shift in the test medium.

Since methyl chloroformate hydrolyses rapidly to methanol (DT50 < 10 min at 25 °C and pH 7) and the pH in the key study test remained within acceptable limits, the clearly higher toxicity compared to methanol must be due to the reactivity of unhydrolysed methyl chloroformate at the beginning of the test. The higher toxicity may be explained by reactions with nucleophiles (such as -NH2, -SH and –OH) on biological macromolecules.





Leuciscus idus

LC50 (96 h) = 4.5 mg/L (nominal), static fish acute toxicity test (similar to German Industrial Standard DIN 38412, part 15)

reliability: 2, key study

Hoechst AG, 1981

several species with Lepomis macrochirus being the most sensitive

LC50 (96 h) ≥ 15400 mg/L (nominal), fish acute toxicity test, flow-through, with analytical monitoring

Hydrolysis product methanol; reliability: 2, key study

OECD, 2004

 Cyprinus carpio

LC50 (96 h) = 4.92 mg/L (acid equivalent to pH 4.3), semi-static, with analytical monitoring, OECD TG 203

Hydrolysis product HCl; reliability: 2, key study

 OECD, 2002
Oncorhynchus mykiss 

LC50 (96 h) = 7.45 mg/L (acid equivalent to pH 4.12), fish acute toxicity test

Hydrolysis product HCl; reliability: 2, supp. study

 OECD, 2002