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EC number: 903-919-3 | CAS number: -
Table 7: Mean achieved actual and nominal test atmosphere concentrations
Target Concentration (mg/L)
Mean of all samples
Mean of daily exposures
Mean of all investigated samples
Table 8: Incidence of skin lesions through experimental groups
Thin fur/alopecia (focal)
*Isolated scar was observed in one of 2 males with thin fur (4008 and 4006)
Table 9: Mean body weight values on Day 90 and overallbody weight gainsbetween Days 0 and 90 of males and females.
Terminal Body weight (g)
Overall body weight gain (%)
Cumulative body weight gain (%)
* =p<0.05; DN = Duncan's Multiple Range Test; NS = not significant
Table 10: Mean weights of selected organs
Body weight relative (%)
Brain relative (%)
* = p<0.05, ** = p<0.01 , DN = Duncan's Multiple Range Test; U = Mann-Whitney U-Test, NS = Non Significant
difference % =percentage differences versus control mean
Table 11: Main microscopic findings
Accumulation of alveolar macrophages
Infiltration peribronchial mild, multifocal
Repeated inhalation toxicity of test item reaction mass of 2,2'-oxybisbutane (DSBE), DIPE, SBA and 2-methylpropan-2-ol (TBA) was tested according to OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day). Wistar Crl:WI (Han) rats were exposed 6 hours/day on a 5 day per week basis to the test atmosphere at concentrations of 10, 3 and 0.8 mg/L, as the High, Mid and Low Concentration, respectively. Analytical concentrations of 1.02, 3.01 and 11.35 mg/L were achieved in the respective groups. The control animals were exposed in similar way to filtered air. Forty Hannover Wistar rats of both sexes (twenty males and twenty females) were involved in the study, 10 males and 10 females in each experimental groups. Parameters monitored during the study included mortality, clinical observations, neurological investigations, ophthalmoscopy, terminal examination of oestrus cycle, body weight, food consumption and clinical pathology evaluation (haematology, coagulation, clinical chemistry and urinalysis). Gross macroscopic examination was performed at necropsy and selected organs were weighed.
Full histopathology was performed in control and high dose groups. In addition, lungs were investigated in Mid and Low dose groups.
The test atmosphere concentration was monitored based on the gravimetric analysis and by a validated GC method. The results of the test atmosphere characterization were considered suitable for the study purposes.
Under the experimental conditions of this study, there was no mortality. There were no clinical signs related to treatment at the low and mid concentration levels. At the high dose (12 mg/L), slight and transient ataxia was observed in all animals at following the end of the exposure. There were no treatment related effects noted during neurological assessment. No test item related changes compared to pre-treatment were noted at ophthalmoscopy examination. Evaluation of the vaginal smears prior to necropsy showed the expected distribution of the oestrus cycle phases within the normal population of female Wistar rats. Body weights and body weight gains were slightly suppressed in males at 12 mg/L. The mean body weight 6% lower compared to controls and the overall body weight gain (D0-90) was decreased by 12% (not statistically significant).The lower body weight values were in agreement with decreased food consumption (overall value lower than control by 4%). Body weight and body weight gain values of high dose females did not differ significantly from the control mean, however the food consumption was slightly lower than in controls . No significant differences were noted in body weight, body weight gain and food consumption at 3 or 1 mg/L. There were no test item related adverse effects in haematology, blood coagulation or urinalysis parameters at any dose level. At 12 mg/L, cholesterol was slightly higher in both males and females. Albumin concentration, total protein and albumin to globulin ratio were also slightly higher than in control for both sexes and total bilirubin concentration was slightly higher in males. There were no test item-related macroscopic findings noted at necropsy. Liver weights were increased in both sexes at 12 mg/L (by approximately 28-30% for values relative to body weight). The increased liver weight was in agreement with hypertrophy of centrilobular hepatocytes revealed during microscopic examination and increased serum cholesterol concentration. This hypertrophy was of minimal grade and was observed in 4/10 males and 5 of 10 females. It was not associated with cellular necrosis/degeneration and was considered to be an adaptive response. Slightly higher liver weights compared to controls were noted in both males and females at 3 mg/L and in females at 1 mg/L. Slightly increased kidneys weights were noted in both males and females at 12 mg/L and at 3 mg/L. This finding was accompanied by minimal tubular basophilia , in 4/10 males and 2/10 females at 12 mg/L. This finding is a common observation in rats and therefore considered to be not adverse. Nevertheless, a relation to treatment cannot be excluded (only high dose was examined). Thymus weights were slightly lower than control in both sexes at 12 mg/L but they were not correlated with any microscopic change. Weight of adrenals was higher in both males and females at 12 mg/L and in males at 3 mg/L without any microscopic changes (only high dose was examined). In lungs, focal/multifocal accumulation of the foamy alveolar macrophages was observed with low incidence in all treated groups and was regarded as no adverse effect.
In conclusion, the exposure to the test item reaction mass of 2,2’-oxybisbutane (DSBE), DIPE, SBA and 2-methylpropan-2-ol (TBA) in the form of a vapour to Hannover Wistar rats for 91 days for 6 hour/day on a 5 day per week basis at analytical concentrations of 1.02, 3.01 and 11.35 mg/L was associated with the following effects:
At the high dose, transient and slight ataxia was noted following the end of the exposure in both sexes and slight body weight gain suppression was found in males associated with decreased food consumption. A slight increase in liver weights in both sexes consistent with slightly increased serum cholesterol concentration and minimal centrilobular hypertrophy of the hepatocytes were also noted. The weight of adrenals was slightly increased, while thymus weight decreased without any microscopic finding. In the lungs, focal/multifocal accumulation of foamy alveolar macrophages was observed with low incidence in all treated groups.
None of these findings was considered to be adverse.
In conclusion, under the conditions of this study, a no observed adverse effect-level (NOAEL) of 11.35 mg/L was established for reaction mass of 2,2’-oxybisbutane (DSBE), DIPE, SBA and 2-methylpropan-2-ol (TBA) administered to Hannover Wistar rats as a vapour by the inhalation route, for for 91 days 6 hour/day on a 5 day per week basis.
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