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Description of key information

A repeat-dose oral toxicity study has been conducted on MV31.  The results of the study are: 
A 28 day oral gavage study resulted in a NOAEL of 450 mg/kg/day when tested according to OECD 407.

Key value for chemical safety assessment

Additional information

The toxicity potential of the test article was evaluated in male and female Wistar rats administered the test material daily for 28 days via oral gavage following OECD guideline 407 (1995). The test material was administered as received. Based on the results of a 5-day rangefinding study, the animals (5/sex/group) were administered 0 (Milli-U water), 150, 450 and 1000 mg/kg/day via oral gavage. The following parameters were evaluated: clinical signs (daily), functional observation tests (week 4), body weight (weekly), food consumption (weekly), clinical pathology (termination), macroscopy (termination), organ weights and histology on selected tissues. During the first week of the study, deaths occurred in each of the 150 (two males), 450 (one male and one female), and 1000 (one male and three females) mg/kg/day groups. Necropsy revealed fluid in the thoracic cavity and dark red discoloration of the lungs in most cases. Histology revealed no major target organ toxicity in these animals; only a minor acute inflammation in the lining of the thoracic viscera. It was determined that these deaths were consistent with the dosing procedures along with the properties of the test material as the most probable cause of death and were considered unrelated to toxicity via the ingestion route. No clinical signs were noted during the study period and functional observation tests revealed no abnormalities. Females at 1000 mg/kg/day showed reduced food consumption in weeks 1 and 4, but body weights remained similar to controls. At 150 mg/kg/day and higher and number of clinical biochemistry changes were noted (reduced total protein, albumin, cholesterol and bilirubin) that were within or only slightly outside the normal range for rats and were considered to not represent toxicity. At 1000 mg/kg/day, liver weights were increased (1.2-fold greater than control mean) which was supported by an increased incidence/severity of hepatocellular hypertrophy and thyroid follicular hypertrophy. The morphological changes were considered adaptive, however the magnitude of the increase was considered adverse. No toxicologically significant changes in liver weights were noted at 150 and 450 mg/kg/day and the incidence and/or severity of hepatocellular hypertrophy at these dose levels was lower than observed at 1000 mg/kg/day. Based upon the results of this study (in particular the increased liver weight at 1000 mg/kg/day), a No Observed Adverse Effect Level (NOAEL) for the test article of 450 mg/kg/day was established.

Justification for classification or non-classification

The results of the test do not meet the requirement to classify MV31 as dangerous.

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