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Description of key information

Isobutyl acrylate is of low toxicity after a single ingestion and of moderate toxicity after short-term inhalation. Isobutyl acrylate is of pronounced toxicity after short-term skin contact.
Oral: LD50 = 4895 mg/kg bw (rat, BASF Test)
Dermal: LD50: 793 - 4000 mg/kg bw (rabbit, occlusive)
Inhalation: LC50 = 10.5 mg/L (rat, 4h)

Key value for chemical safety assessment

Additional information

Oral exposure route:

 

In an acute toxicity study conducted by BASF AG (1962) groups of 5 rats were administered doses of 178, 1424, 2848, 3560, 4450, 5696 mg/kg bw by gavage and observed for 7 days for lethality and clinical signs of intoxication. No mortality was observed during the 7 day observation period in the 178 to 3560 mg/kg bw dose groups. One rat died within the first 24 hours in the 4450 mg/kg bw dose group. In the 5696 mg/kg bw dose group, all 5 rats died within the first 24 hours. The LD50 was found to be approx. 4895 mg/kg bw. Clinical symptoms in the highest dose group were narcosis, staggering gait, apathy and abdominal position. Some animals of the other dose groups showed slight apathy after dose administration. At necropsy, hyperemia of the kidneys was found in 4 of the sacrificed animals.

Other studies reported an LD50 of 6639 mg/kg bw in rats without clinical symptoms, (Union Carbide 1968) and 6292 mg/kg bw (clinical signs: heavy breathing at the highest dose level of 17800 mg/kg bw) (Union Carbide 1971, Carpenter et al. 1974). The LD50 in mice was 2910 mg/kg bw, the observed symptoms were piloerection, narcosis and laboured breathing (BASF, 1962). Tanii (1982) reported an LD50 of 6105 mg/kg bw (no information about clinical symptoms).

Dermal exposure route:

 

The dermal LD50 in rabbits after occlusive application (under Vinylite) was approx. 793 mg/kg bw (Union Carbide 1968). Mortalities were 0/4, 3/4 and 3/4 animals at 445, 890, 1780 mg/kg bw, respectively. No clinical symptoms were observed; necropsy findings were skin irritation (ecchymosis, edema and marked erythema), congestion of the lungs and the abdominal viscera and mottled liver. In order to prevent the inhalation of vapour from the chemical the rabbits were placed in a hood with their heads protruding into the room.

In another study an LD50 of approx. 4000 mg/kg bw was reported for rabbits after occlusive application (Union Carbide 1971, Carpenter 1974). Lethalities were 1/4, 1/4 and 4/4 animals at 1780, 3560 and 7120 mg/kg bw, respectively. No clinical signs were observed apart from skin irritation (erythema, edema, ecchymosis) at the site of application. At necropsy, findings included congestion throughout the lungs and the abdominal viscera in the victims and livers mottled with prominent acini.

In another study conducted by BASF AG (1963) an LD50 of > 445 - < 890 mg/kg bw was determined in rabbits after a 24-hour occlusive application of IBA.

Inhalation exposure route:

The inhalation 4-hr LC50 for rats was determined to be 2000 ppm (corresponding to approx. 10.5 mg/L) (Union Carbide 1968). Groups of six rats were exposed to isobutyl acrylate vapours at metered concentrations of 1000, 2000 and 4000 ppm (corresponding to approx. 5.2, 10.5 and 21 mg/L). No mortality was observed in the 1000 ppm dose group; 3/6 animals died at 2000 ppm on days 4, 5, 6 after exposure; all animals died in the high dose group on the day of exposure. Clinical signs were gasping and irritation of eyes, nose, respiratory tract and extremities. The animals of the high-dose group were hyperactive 30 min after the exposure and prostrate after 1-1.5 h after exposure. Necropsy findings included capillary injection and consolidation of the lungs.

Another 4-hr LC50 for rats is reported to be 2828 ppm (corresponding to approx. 14.8 mg/L), clinical symptoms were irritation to eyes, extremities and respiratory tract, gasping and hypersensitivity to stimuli in the tested concentrations of 2000 and 4000 ppm (10.5 and 21 mg/L) (Union Carbide 1971, Carpenter 1974).

In an inhalation hazard test, saturated vapours of IBA (37.3 mg/L) were extremely irritating to the eyes, nose and skin (Union Carbide 1968).

Taking all the presented data into consideration, isobutyl acrylate is of low toxicity after a single ingestion and of moderate toxicity after short-term inhalation and after short-term skin contact.

Justification for classification or non-classification

EU classification according to Annex VI of Directive 67/548/EEC: Xn, R20, 21

GHS classification (GHS UN rev.3, 2009):

- Oral route: Acute Category 5

- Dermal route: Acute Category 4

- Inhalation route (vapour): Acute Category 4