13-Week Inhalation Toxicity Study in the Wistar Rat /Mn metal/OECD 413/GLP/

In this 13 - week inhalation toxicity study Mn Metal Powder was administered 6 hours daily for 5 days/week to rats by nose-only, flow-past inhalation exposure. The reversibility or progression of any test item related effects or any delayed toxicity was assessed during a 4 - week treatment free recovery period following the treatment period. The study comprised four groups containing 25 male and 25 female rats in group 1 and 31 male and 31 female rats in groups 2 to 4. The rats of the control group (group 1) were exposed to air only. Groups 2 to 4 were exposed to target concentrations of 0.5, 5 and 20 µg/L Mn Metal Powder, respectively.

Throughout the study all animals were observed for viability and clinical signs. In addition body weights and food consumption were recorded. Detailed clinical signs and functional observation battery were performed. Ophthalmoscopic examinations were performed and blood and urine samples were taken for clinical laboratory investigations. Blood, brain and lungs were taken for measurements of Mn levels in different blood compartments as well as brain areas. Following completion of the treatment and recovery period, a detailed necropsy was performed on all animals and

Conclusion

In accordance to the findings above the lung was considered to be the target organ for the exposure to Mn Metal Powder mainly because it was the port of entry. There was indication of reversibility of the findings, however, the 4 week duration of the recovery period was considered insufficient to demonstrate full reversal of all findings.

Based on the histopathological findings in this study a No-Observed-Adverse-Effect-Level (NOAEL) was established at 0.5 µg/L Mn Metal Powder.

selected organs were weighed. Various tissues and organs were placed in fixative, processed and examined microscopically. Neuropathology was performed in selected animals.

 

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