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Description of key information

Acute oral toxicity: LD50 > 2000 mg/kg bw
Acute inhalation toxicity: LD50 > 3.8 mg/L air
Acute dermal toxicity: LD50 > 2000 mg/kg bw

Key value for chemical safety assessment

Additional information

Acute oral toxicity:

The key acute oral toxicity test was conducted according to the OECD 401 guideline and in compliance with GLP. Both male and female Sprague Dawley rats were exposed to a suspension of MCS-1980 in corn oil via oral gavage, in one of the following concentrations: 1984, 2500, 3150 or 5000 mg/kg bw. Following administration of the test substance the animals were observed for 14 days. The following LD50 values were reported: 2604, 2925 and 2304 mg/kg bw, combined for both sexes, for males and for females, respectively. Toxicity to the nervous system was suggested by several of the clinical abnormalities that were observed. Furthermore, necropsy findings indicated that MCS-1980 affected the gastrointestinal tract.

Several supporting acute oral toxicity studies were available as well. Three studies with a K2 score were available. These studies performed with MCS-1980, Santowax MP and MCS-2073 reported LD50s of 3690 mg/kg bw (males only), > 5000 mg/kg bw (male/female) and > 10 000 mg/kg bw (male/female). Furthermore there are two additional supporting studies (K4) with MCS-1980 and Santowax R which report LD50 values of 2600 mg/kg bw (male/female) and > 50 000 mg/kg bw (male/female).

Acute inhalation toxicity:

To assess acute inhalation toxicity a test was set up according to the OECD 403 guideline (GLP-compliant) (= key study), in which Therminol 75 was administered to Sprague Dawley rats via aerosol during 4 hours, after which the animals were observed for a period of 14 days. Exposure concentrations were 3.6, 3.7 and 3.8 mg/mL (two concentrations with heated chamber air and test material and one with ambient chamber air and heated test material). An LD50 (male/female) > 3.8 mg/L air was reported. Immediate post exposure observations included red encrustation around eyes and nose, labored breathing and salivation. On post-exposure days 7 and 14 these observations were no longer evident. No gross pathology abnormalities were observed in any of the animals during necropsy examinations.

Acute dermal toxicity:

The key study for acute dermal toxicity was conducted according to a GLP and OECD 402 guidelines. New Zealand White rabbits were exposed to 5000 mg/kg bw MCS-1980 during 24 hours. The post exposure observation period was 24 hours. For both females and males the LD50 reported was > 5000 mg/kg bw. At necropsy most of the findings reflected the effects of direct contact of the skin with the test material.

Three additional supporting studies (K2) are available. These were performed with Santowax MP, MCS-2073 and the p-terphenyl isomer resulting in respective LC50 values > 5000 mg/kg bw (male/female), > 2000 mg/kg bw (male/female) and > 2000 mg/kg bw (male/female). The studies supporting studies with a K4 score were also indicative of a lack of acute dermal toxicity since these reported LD50 values (male/female) of > 5010 mg/kg bw (MCS-1980) and > 12500 mg/kg bw (Santowax R).

Justification for classification or non-classification

Based on the lack of acute toxicity via the different routes, no acute classification is warranted.