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Specific investigations: other studies

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Expert Judgement 
Due to the absence of chemical groups or other structural alerts this substance is not considered to exhibit an high hazard potential.
Triethylene glycol butyl ether or 2-(2-(2-butoxyethoxy)ethoxy)ethanol as member of “The High Boiling Ethylene Glycol Ethers category“ is of low priority for further work based on a low hazard potential.
Therefore testing for Specific investigations: other studies does not need to be performed.
There are some Specific investigations: other studies for from supporting substance (structural analogue or surrogate).
See below:

Additional information

Expert Judgement

Due to the absence of chemical groups or other structural alerts this substance is not considered to exhibit an high hazard potential. Triethylene glycol butyl ether or 2-(2-(2-butoxyethoxy)ethoxy)ethanol as member of “The High Boiling Ethylene Glycol Ethers category“ is of low priority for further work based on a low hazard potential.

Therefore testing for Specific investigations: other studies does not need to be performed.

There are some Specific investigations: other studies for from supporting substance (structural analogue or surrogate).

See below:

- In a study (Green, T., Toghill, A., Lee, R., Moore, R. & Foster, J,2002) designed to establish the mode of action of forestomach tumours in mice following chronic exposure, mice given single oral doses of either 2-butoxyethanol or 2-butoxyacetic acid, daily for 10 days, developed a marked hyperkeratosis in the forestomach. 2-Butoxyacetic acid was more potent than 2-butoxyethanol, the NOEL for the former being 50 mg/kg and for the latter, 150 mg/kg. Although a dose dependent increase in cell replication was also seen with both chemicals, the results were confounded by a high labelling rate in the controls. There was no evidence of significant binding of radiolabelled 2-butoxyethanol to proteins in stomach tissues.

- Sensory irritation was evaluated using an in vivo method with mice.( Kane LE, Dombroske R and Alarie Y, 1980.) Male Swiss-Webster mice (4/group) were exposed whole body to a series of chemicals (including 2 -butoxyethanol). The measured response was the maximum percent decrease in respiratory rate, averaged over 4 mice, simultaneously exposed for 10 minutes. The responses obtained for various concentrations of solvents were utilized to develop a concentration-response relationship, for this, the concentration associated with a 50 % decrease in respiratory rate (RD50) was calculated. The response obtained within the 150 -1500ppm concentration range tested was less than a 50 % decrease in respiratory rate, ie a relatively shallow dose response curve. The RD50 calculated by extrapolation was 2825 ppm, a value well in excess of the saturated vapour pressure. This was in excellent correlation with a QSAR model for RD50 generated at a later date, which predicts a value of 2818ppm. When compared with the author's criteria of evaluation, 0.01 RD50 (about 28 ppm) would cause minimal or no sensory irritation whereas 0.1 RD50 (about 280 ppm) would cause definite but tolerable sensory irritation.

- In a study (Park, J., Kamendulis, L. M. & Klaunig, J.E.) to assess the hypothesis that the rat is relatively resistant to liver neoplasia because if its ability to resist oxidative damage secondary to hemolytic deposition of iron in the liver and that the mouse is susceptible to such effects, a set of in vitro studies were carried out using rat hepatocytes and exposure to 2-butoxyethanol, 2-butoxy acetic acid (a major metabolite of 2-butoxyethanol) or iron (FeSO(4)) to assess the level of oxidative stress caused by each substance. Oxidative stress was examined by measuring oxidative DNA damage (OH8dG), lipid peroxidation (MDA formation) and cellular vitamin E concentrations. Neither 2-butoxyethanol or 2-butoxyacetic acid induced changes in the oxidative stress parameters examined in either rat hepatocytes. In contrast, FeSO(4) produced an increase in OH8dG and MDA but only at the highest dose tested and there was no associated decrease in vitamin E levels following 24 h treatment. Mouse hepatocytes were more sensitive than rat hepatocytes to the oxidative damage induced by the FeSO(4). FeSO(4)-induced oxidative stress was not increased by co-treatment of FeSO(4) with either 2-butoxyethanol or 2-butoxy acetic acid. These results support the proposal that the induction of hepatic oxidative stress by 2-butoxyethanol in vivo occurs secondary to induction of hemolysis and iron deposition in the liver rather than as a direct action of 2-butoxyethanol or its main metabolite, 2-butoxy acetic acid.

- In a study (Park, J., Kamendulis, L. M. & Klaunig, J.E., 2002) which used the Syrian Hamster Embryo (SHE) cell transformation assay as a surrogate in vitro model for carcinogenesis in vivo, 2-butoxyethanol, 2-butoxyacetic acid, or iron (ferrous sulfate) were examined for their ability to produce cell transformation. SHE cells were treated with either 2-butoxyethanol (0.5-20 mM), 2-butoxyacetic acid (0.5-20 mM), or ferrous sulfate (0.5-75 microg/ml) for 7 days. 2-Butoxyethanol and 2-butoxyacetic acid did not induce cellular transformation. In contrast, treatment with ferrous sulfate increased morphological transformation. Cotreatment of ferrous sulfate with the antioxidants alpha-tocopherol (vitamin E) or (-)-epigallocatechin-3-gallate (EGCG) prevented ferrous sulfate-induced transformation, suggesting the involvement of oxidative stress in SHE cell transformation. The level of oxidative DNA damage (OH8dG) increased following ferrous sulfate treatment in SHE cells; additionally, using single cell gel electrophoresis (comet assay), ferrous sulfate treatment produced an increase in DNA damage. Both DNA lesions were decreased by cotreatment of ferrous sulfate with antioxidants. These data support the hypothesis that iron, produced indirectly through hemolysis, and not 2-butoxyethanol or its metabolite 2-butoxyacetic acid, is responsible for the observed carcinogenicity of 2-butoxyethanol.

- In a study (Ghanayem BI, Long PH, Ward SM, Chanas B, Nyska M and Nyska A,2001) to compare the differences in haemolytic potential of 2 -butoxyethanol (2BE) between sexes, male and female rats were dosed daily with 250mg/kg 2BE for periods of up 3 days. A progressive time-dependent hemolytic anemia (macrocytic, hypochromic, and regenerative) was observed in both sexes of rats exposed to 2BE. Additionally, 2BE caused significant morphological changes in erythrocytes, first observed 24 hr after a single dose, including stomatocytosis, macrocytosis with moderate rouleaux formation, and spherocytosis. These morphological changes became progressively more severe as BE dosing continued and included the occasional occurrence of schistocytes and ghost cells, rouleaux formation in rats of both sexes, and an increased number of red blood cells with micronuclei in female rats. Overall, the progression of hemolytic anemia and morphological changes as a function of the number of days of exposure varied with gender and suggested a faster onset of hemolysis in female rats. The range of 2BE-related histopathological changes noted in both sexes was comparable; however, while these lesions were observed in female rats following a single dose, similar effects were first observed in males after 3 consecutive days of exposure to BE. Pathological changes involved disseminated thrombosis in the lungs, nasal submucosa, eyes, liver, heart, bones and teeth, with evidence of infarction in the heart, eyes, teeth and bones. Hemoglobinuric nephrosis and splenic extramedullary hematopoiesis were also noted.

- A study ( Corthals SM., Kamendulis, L. M. & Klaunig, J.E., 2006) examined whether 2-butoxyethanol and its metabolites, 2-butoxyacetaldehyde and 2-butoxyacetic acid, damaged mouse endothelial cell DNA using the comet assay. No increase in DNA damage was observed following exposure to any of these substances in endothelial cells after 2, 4, or 24 h of exposure. Further additional studies examined the involvement of hemolysis and macrophage activation in 2-butoxyethanol carcinogenesis. DNA damage was produced by hemolyzed red blood cells, ferrous sulfate, and hydrogen peroxide in endothelial cells. Hemolyzed RBCs also activated macrophages, as evidenced by increased tumor necrosis factor (TNF) alpha, while neither 2-butoxyethanol nor butoxyacetic acid increased TNF-alpha from macrophages. The effect of activated macrophages on endothelial cell DNA damage and DNA synthesis was also studied. Coculture of endothelial cells with activated macrophages increased endothelial cell DNA damage after 4 or 24 h and increased endothelial cell DNA synthesis after 24 h. These data demonstrate that 2-butoxyethanol and related metabolites do not directly cause DNA damage. Supportive evidence also demonstrated that damaged RBCs, iron, and/or products from macrophage activation (possibly reactive oxygen species) produce DNA damage in endothelial cells and that activated macrophages stimulate endothelial cell proliferation. These events coupled together provide the events necessary for the induction of hemangiosarcomas by 2-butoxyethanol.

- A study (Ghanayem BI, Sanchez IM and Matthews HB,1992) was undertaken to undertaken to investigate the effect of repetitive daily dosing of 2 -butoxyethanol (2)BE on the hematologic parameters of rats. Treatment of rats with 2BE daily (125 mg/kg/day) for 1 to 3 consecutive days resulted in a time-dependent increase in the hemolysis of erythrocytes. However, when daily treatment with BE continued beyond 3 days, the number of erythrocytes began to recover and approached pretreatment levels within 12 days despite continued daily exposure, suggesting development of tolerance to the hemolytic effect of 2BE. Further statellite in vivo and in vitro studies to investigate the underlying mechanism of tolerance were undertaken . These studies consistently suggested that tolerance is due, at least in part, to greater resistance of young erythrocytes formed in response to the initial haemolysis.

-In an in vivo study (Bartnik FG, Reddy AK, Klecak G, Zimmermann V, Hostynek JJ and Kunstler K,1987), a dermal dose of 200 mg/kg did not cause any haemolytic effect. Other tested doses from 260 -500mg/kg caused haemolytic effects indicated by increase in mean cell volume, lower erythrocyte count and haemoglobin level and hemoglobinuria. No dose response relationship was found but this could be attrributed to the inherent biologic variation in percutaneous absorption and haemolytic susceptibility and also to the limited number of animals used per dose group in this study. Following a IV injection of 62.5 mg/kg, no hemolysis was detectable whereas a dose of 75 mg/kg produced slight effects.

- In a study ( Nyska A, Moomaw CR, Ezov N, Shabat S, Levin-Harrus T, Nyska M, Redlich M, Mittelman M, Yedgar S and Foley JF, 2003) to further explore the mechanism of thrombosis formation, 2-butoxyethanol (2BE) induced haemolysis and thrombosis was used as a model to study the histology and immunohistochemical expression of vascular cell adhesion molecule-1 (VCAM-1), endothelial intercellular adhesion molecule-1 (ICAM-1), and P-selectin in the eyes of the female rat exposed to 2, 3, or 4 daily doses of 250 mg/kg of 2BE. In this BE hemolysis and thrombosis model, positive VCAM-1 expression occurred only in eyes of rats exposed to 3 and 4 doses and was localized in the iris (epithelium lining the posterior surface, anterior mesenchymal epithelium), ciliary processes (lining epithelium, stromal cells), and retina (hypertrophic retinal pigment epithelium). Only weak immunolabeling was seen in eyes exposed to 2 doses. The appearance of VCAM-1 immunostaining correlated with the development of thrombosis located in the same structures. No change in ICAM-1 or P-selectin expression was seen. This immunolabeling distribution suggests that VCAM-1 functions in the pathogenesis of BE-related thrombosis by promoting adhesion of erythrocytes to the endothelium.

- A study (Nyska A, Maronpot RR and Ghanayem BI,1999) designed specifically to examine the occular toxicity of 2 -butoxyethanol in female rats subjected them to 3 daily doses of 250mg/kg prior to sacrifice and examination of the eyes histopathologically. Following treatment, petechial hemorrhages were noted on the sclera as well as hemorrhages localised in the posterior layers of the retina. Thrombi were identified in ciliary processes and limbal blood vessels as well as disseminated thrombosis, necrosis and infarction of other organs. It is likely however that these changes are secondary to haemolysis.