Butyl chloroformate

Short-term toxicity to fish

Description of key information

Parent compound butyl chloroformate (CAS 592-34-7, rapidly hydrolyzing): Acutely harmful to fish.

Hydrolysis product hydrogen chloride (HCL, CAS 7647 -01 -0): Acutely toxic to fish (pH dependent).

Hydrolysis product butanol (CAS 71 -36 -3): With high probability acutely not harmful to fish.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

4.64 mg/L

Additional information

Data for parent compound butyl chloroformate (CAS 592-34-7):

Data on the acute toxicity of butyl chloroformate (CAS 592-34-7) to fish are available from a study performed according to DIN 38412 (L1 and L15). L. idus was used as test organism. The 96 -h LC50 value was determined to be ca. 4.64 mg/L (nominal; BASF AG, 1988).

However, the substance rapidly hydrolyses in contact with water to butanol (CAS 71 -36 -3), hydrogen chloride (HCL, CAS 7647 -01 -0) and carbon dioxide (CAS 124-38-9). The assessment is, therefore, additionally based on the available data of the hydrolysis products.

 

Data for Hydrolysis product - hydrogen chloride (HCL, CAS 7647-01-0):

For the hydrolysis product hydrogen chloride (HCL, CAS 7647-01-0) a short-term study with fish (C. carpio) according to OECD guideline 203 is available (OECD SIDS, 2002). The 96-h LC50 value was determined to be 4.92 mg/L (acid equivalent converted from pH 4.3).

 

Hydrolysis product – butanol (CAS 71-36-3):

For the hydrolysis product butanol (CAS 71-36-3) a number of results from fish studies are available. The key effect value is a 96 -h LC50 > 100 mg/L as observed in a study with O. latipes. The study was conducted according to OECD guideline 203 and in compliance with GLP criteria and the test concentrations were analytically verified (NITE, 1992). Another key study followed with OECD 204 guideline showed the 14-d LC50 to be 85 mg/L (analytically verified, NITE, 1984). In addition, several acute ecotoxicity studies with fish (Fathead minnow, Bleak) are also available for CAS 71-36-3. According to these supporting data the lowest effect LC50 value was 1376 mg/L (96 h, analytically verified, OECD 201, SIDS 2001).

For the hydrolysis product carbon dioxide, no fish toxicity data are available.

 

Assessment:

In the study with the parent substance butyl chloroformate (CAS 592-34-7; BASF AG, 1988), all observed mortality occurred between 1 to 24 hours after the start of the exposure period. However, the substance rapidly hydrolyses in contact with water to butanol (CAS 71-36-3), hydrogen chloride (HCL, CAS 7647-01-0) and carbon dioxide (CAS 124-38-9). Furthermore, the observed effect values from studies with the hydrolysis product butanol (CAS 71-36-3) are much higher than the effect values determined for the parent compound. Therefore, the observed toxicity in the study with butyl chloroformate (CAS 592-34-7) itself is considered to be related to the high reactivity of unhydrolyzed butyl chloroformate at the beginning of the test rather than to exposure to the hydrolysis product butanol. Additionally, the the obsereved toxic effects are considered to be not due to pH caused by the hydrolysis product HCl (CAS 7647 -01 -0) as the pH of the test solutions remained close to the pH of the control solutions.

 

Summary of acute fish toxicity data:

Compound	Species	Results	Guideline	Reference
Parent Compound (CAS 592-34-7)	Leuciscus idus	96-h LC50 = ca. 4.64 mg/L	DIN 38412 L15	BASF AG (1988)
Hydrolysis product (CAS 7647-01-0)	Cyprinus carpio	96-h LC50 = 4.92 mg/L (pH-dependent; acid equivalent)	OECD 203	OECD SIDS (2002)
Hydrolysis product (CAS 71-36-3)	Oryzias latipes	96-h LC50 ≥ 100 mg/L	OECD 203	MOE, Japan (1996)
Hydrolysis product (CAS 71-36-3)	Oryzias latipes	14-d LC50 = 85 mg/L 7-d LC50 ≥ 100 mg/L	OECD 204	MOE, Japan (1996)
Hydrolysis product (CAS 71-36-3)	div.	96-h LC50 >1000 mg/L	div.	OECD SIDS (2001); (summary of div. test results)