2-isopropoxyethanol

Endpoint summary

Description of key information

ORAL rat (28 day studies)

- LOAEL=30mg/kg, 195mg/kg (effects seen at lowest dose)

INHALATION

- Rat, 6 month NOAEL=25ppm (all effects), 100ppm (excluding haemolytic effects)

- Rabbit 6 month NOAEL=50ppm (200ppm excluding male kidney weight effects)

- Dog 6 month NOAEL=50ppm (LOAEL heart effects at 200ppm)

- Guinea pigs (6 months)=50ppm (LOAEL heart weight, clin chemistry females, body weight males

- Rat (5 weeks) LOAEL=390ppm

- Rat (4 weeks) NOAEL=30ppm

- Rat (2 weeks) NOAEL=300ppm

- Rat (2 week) NOAEL=100ppm

Note: 100ppm = 433mg/m3

The highest NOAEL observed that is lower than a LOAEL is 100ppm.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Study period:

1982

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well reported study. not to GLP. Rationale for using a read across substance is included in overall remarks section.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

Deviations:

yes

Remarks:

6 week test period. Not all end points examined.

GLP compliance:

no

Limit test:

no

Species:

rat

Strain:

other: CR, COBS, CD, BR albino

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories
- Weight at study initiation: 235.7+/-15.1g
- Housing: individual in suspended wire bottomed cages.
- Diet (e.g. ad libitum): ad libitum, Purina rodent chow 5001
- Water (e.g. ad libitum): ad libitum via automatic watering system
- Acclimation period: 2 weeks


ENVIRONMENTAL CONDITIONS
- no data

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: Doses recalculated weekly to allow for animal growth.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

6 weeks

Frequency of treatment:

daily, 5 days per week

Remarks:

Doses / Concentrations:
195, 390, 780, 1560 mg/kg bw/day
Basis:
nominal in water

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

Post-exposure period: none
- Dose selection rationale: based on 50%, 25% , 12.5%, 6.25% of the fasted LD50.

Positive control:

A number of other glycol ethers were assessed in the same study effectively acting as reference controls.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily, except weekends.
- Cage side observations: signs of systemic toxicity, appearance and behaviour. Urine and faeces appearance. Mortality.

BODY WEIGHT: Yes
- Time schedule for examinations: days 0, 3, 6, 13, 20, 27, 34, 41.

FOOD CONSUMPTION AND COMPOUND INTAKE - measured at same times as body weight.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes / No / No data
- Time schedule for examinations:

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: from vena cava immediately prior to autopsy.
- Anaesthetic used for blood collection: Yes (identity) / No / No data
- Animals fasted: No data
- Parameters checked : Hgb, Hct, RBC count and indices, total and relative WBC count,

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: from vena cava immediately prior to autopsy.
- Animals fasted: No data
- Parameters checked: glutamic oxaloacetic transaminase, glutamic pyruvic transaminase (GPT), ALP, LDH, BUN, creatinine and glucose.

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

OTHER: Animals that died spontaneously were autopsied as soon as possible. Moribund animals were sacrificed and similarly autopsied.

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Survivors killed by CO2 inhalation. Tissues examined: lung, heart, thymus, kidney, liver, spleen, brain, salivary glands, stomach, cecum, colon, duodenum, jejenum , ileum, pancreas, esophagus, adrenals, pituitary, thyroid, parathyroid, trachea, mesenteric lymph nodes, testes, epididymides, prostate, seminal vesicles, coagulating gland, bone marrow, tongue, nasal cavities, eyes.

Statistics:

No information

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY: No significant mortality seen that could be attributed to the substance. All animals showed bloody urine after first dose. This resolved for the low dose groups but persisted for the mid and high dose animals. Clinical signs (third and high dose groups only) were weakness, prostration, laboured breath and rales.

BODY WEIGHT AND WEIGHT GAIN: Slight but statistically non-significant body weight gain reductions seen in all dose groups. A slight reduction in terminal body weight was seen in the top dose group only.

FOOD CONSUMPTION:The high dose group showed a statistically significant reduction in food consumption during the first 2 weeks.

HAEMATOLOGY: Decreased Hgb, total RBC and in all dose with a clear dose response relationship. No effect on packed cell volume or WBC count. The mid and high dose groups produced increased MCV and MCH and decreased MCHC. The two lower dose groups had no impact on the red cell indices.

ORGAN WEIGHTS: All dose groups showed increased spleen weights. The absolute and relative values were statistically significant in the top two dose groups. Slight but statistically significant increases in liver weight (both relative and absolute) were seen but not regarded as toxicologically significant. All other organ weights, including testes, were normal.

GROSS PATHOLOGY: Enlarged dark spleens at the two higher dose in around half the animals. A single animal showed this in the second dose group but none were seen in the lowest dose goup.

HISTOPATHOLOGY: NON-NEOPLASTIC: Splenic congestion and extramedullary hematopoesis were seen in all but the lowest dose group. Renal proteinaceous casts were seen along with haemosiderin in the proximal convoluted tubules. Liver effects were focal haemosiderin in the high dose group only.

Dose descriptor:

NOAEL

Effect level:

< 195 mg/kg bw/day (nominal)

Sex:

male

Basis for effect level:

other: Clinical signs (discoloured urine), Haematology (RBC effects), Gross and histological effects on spleen.

Critical effects observed:

not specified

Conclusions:

The most significant toxic effects seen were adverse changes to the red blood cells followed by splenic congestion, enlargement and extramedullary haematopoesis. A true no effect level was not observed.

Executive summary:

In a 6 week sub-acute gavage study using 2 -n-propoxyethanol that broadly followed the standards for such tests pertaining at the time, standard toxicological end points were studied for rats in doses up to 1560mg/kg. . The most significant adverse effects were changes to the red blood cells, manifest as reduced RBC count, decreased haemoglobin and increased MCH and MCV from the low dose group upwards. . Splenic congestion and enlargement along with extramedullary hematopoesis were also seen, possible as a secondary consequence of the apparent haemolytic effects. No no effect level was observed because of the haemolytic effects. Because of the structural similarities, 2 -isopropoxyethanol is likely to show similar toxicity.

Synopsis:

NOAEL(6 week, rat, oral gavage) = 195mg/kg/day

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LOAEL

30 mg/kg bw/day

Study duration:

subacute

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

433 mg/m³

Study duration:

subchronic

Species:

rat

Quality of whole database:

Good, multiple species available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

ORAL

 

In a 6 week sub-acute gavage study using n-propoxyethanol, standard toxicological end points were studied for rats in doses up to 1560mg/kg. . The most significant adverse effects were changes to the red blood cells, manifest as reduced RBC count, decreased haemoglobin and increased MCH and MCV from the low dose group upwards. . Splenic congestion and enlargement along with extramedullary hematopoesis were also seen, possible as a secondary consequence of the apparent haemolytic effects. A no effect level was not observed because of the haemolytic effects. A full and detailed justification for using a category approach to fulfil the data requirements for glycol ethers is attached to chapter 13 of the IUCLID dossier submitted by the lead registrant. The situation is complex for the repeat dose end point as more than one toxic effect is seen and there are different trends within the glycol ether family for each end point. However, significant repeat dose toxic effects are generally limited only to the monoethylene glycol alkyl derivatives. The monoalkyl glycol ethers around the C3-C4 range exert detrimental effects on mature red blood cells in the peripheral blood, as seen in this study; the erythrocyte membranes show increased osmotic fragility and are subject to intravascular lysis. The haemolytic effect is species-specific. Mice, rats and rabbits show haemolysis; guinea pigs are more resistant;itdoes notoccur in humans, even in sub-populations that might be considered more vulnerable. Work by Yamada (J Toxicol Sci, 37(3), 503-15, 2012) on a category approach to predicting repeat dose effects for glycol ethers reached a similar conclusion that this effect is limited to the propoxy and butoxyethanols. It would appear that a sub-category can be defined of the C3 and C4 monoethylene glycol alkyl ethers which produce similar effects following repeat dosing. On this basis, it would seem to be scientifically justified to use n-propoxyethanol to predict the toxic effects of isopropoxyethanol.

2 -isopropoxyethanol was administered orally by gavage to male and female rats for 28 days. Recovery groups were included. In this study, the following were found: occult blood and bilirubin in urinalysis, anemia like changes in hematology, increase of erythroid cells and decrease of myeloid cells in bone marrow myelogram, increased weight of spleen, histopathological findings in spleen and bone marrow. These findings were recognized in male and female groups at 500 mg/kg bw/day, and some of findings were also found at 125 mg/kg bw/day. The findings in bone marrow myelogram were observed even in both sex groups at 30 mg/kg bw/day.The NOAEL for repeated dose oral toxicity was therefore considered to be below 30 mg/kg bw/day.

The results for n and isoproxyethanol are consistent which further backs up the justification for using data from the former to support the latter. It should be noted however that data is not required for this route of exposure since a sub-chronic study is available for the more important inhalation route.

INHALATION

 

Numerous studies are available by the inhalation route.

 

Ethylene glycol isopropyl ether was studied in a 6 month inhalation toxicity in rats. Marginal Hemolytic effects occurred marginally at 25 ppm and clearly at 50 ppm and 200 ppm. The osmotic fragility of the of the erythrocytes of rats was significantly changed at 25, 50 and 200 ppm. Changes not associated as primary or secondary effects of haemolysis were only observed at 200ppm (changes in heart and liver weight).  Ethylene glycol isopropyl ether was also studied in a 6 month inhalation toxicity in rabbits at concentrations of 0, 25, 50, or 200 ppm for 26 week, 6 h/day, 5 day/week. The only significant effect observed was a decrease in adjusted kidney weight in male rabbits in the 200 ppm group. A NOAEL of >=200 ppm for females and 50ppm for males based on kidney weight changes can be deduced from this study. In another sub-chronic study, guinea pigs were exposed to Ethylene glycol isopropyl ether at concentrations of 0, 25, 50, or 200 ppm for 26 week. In clinical chemistry increased in SGOT and decreased adjusted heart weight was observed in female guinea pigs in the 200 ppm group. In male guinea pigs, body weights were significantly decreased at 200ppm. A NOAEL of 50ppm for male and female guinea pigs can be deduced under the conditions of this study.

Ethylene glycol isopropyl ether was studied for subacute inhalation toxicity in rats according to the guideline OECD 412 at concentrations of 0, 142, 441, or 891 ppm for 4 weeks, 6 h/day, 5 day/wk. Since a no-observed-adverse-effect level (NOAEL) was not established, a second similar study was performed, using exposure concentrations of 0, 10, 30, or 100 ppm; in addition, 5 rats/sex/group were kept for a 14-day recovery period. At the end of the exposure period, hemolytic anemia was observed in male and female rats exposed to 142, 441, or 891 ppm. Mild hemolytic anemia was found in female rats exposed to 100 ppm, but had disappeared after the 14-day recovery period. Lower plasma bilirubin values were observed in rats exposed to 891 ppm, and decreased urinary pH values occurred in rats exposed to 441 or 891 ppm. Increase in spleen weight recognized in rats in the 441 and 891 ppm groups. Extramedullary hematopoiesis was observed in the spleen of rats in the 142, 441 and 891 ppm groups. Brown pigment accumulation was observed in rats in the 441 and 891, and in females in the 142 ppm group. Extramedullary hematopoiesis was also observed in the spleen of rats in the 10, 30 and 100 ppm groups and in controls. The NOAEL was concluded to be 30 ppm in male and female rats and 100ppm if the reversible haemolytic anaemia is not regarded as an adverse effect. In an old sub-acute inhalation study, rats were exposed to 2 -isopropoxyethanol at a single concentration for 5 weeks. At the end of the study hematological and microscopic examinations were conducted. A significant decrease in erythrocyte counts and hemoglobin was observed, as well as increases in reticulocytes and inmature granulocytes. Microscopically there was deposition of hemosiderin in the spleen. 

Male rats were exposed to 2 -isopropoxyethanol by inhalation at 300ppm or 1000ppm for 2 weeks. Animals at 1000ppm experienced marked hematuria on the first day of exposure which was reversible. In addition, significant reductions in hemoglobin concentration, red blood cell count, mean corpuscular hemoglobin concentrations, and increases in mean cell volumes and mean cell hemoglobin were observed in the 1000ppm group. No significant changes were observed at 300ppm. In another similar study, male and female rats were exposed to 2 -isopropoxyethanol at 100, 300 or 1000ppm for 2 weeks. The animals at 300 and 1000 ppm showed initial hematological and urinary effects and congested lungs in histology. The NOAEL was established as 100ppm.

DERMAL

 

No data available.

 

OTHER INFORMATION

 

It should be noted that the most sensitive effect noted in a number of the animal test species is haemolysis. Glycol ethers such as isopropoxyethanol are known to cause this effect. Other glycol ethers in the same family such as butoxyethanol are also known to have similar properties. The haemolytic effects of butoxyethanol have been welll studies and it is now well understood that humans are remarkably resistant to such haemolytic effects. ECETOC (2005) This needs to be taken into account in deriving appropriate assessment factors.

 

Reference

 

ECETOC (2005) The Toxicology of Glycol Ethers and its Relevance to Man (4^thed), Technical report 95, ECETOC,.

Repeated dose toxicity: via oral route - systemic effects (target organ) cardiovascular / hematological: other

Repeated dose toxicity: inhalation - systemic effects (target organ) cardiovascular / hematological: other

Justification for classification or non-classification

There are no significant effects that are relevant to humans from repeated dose exposure by the inhalation route that occur below the threshold for classification as a category 1 STOT. There is no clear evidence of any effects occuring by the oral route that are both relevant to humans and occur at doses that would trigger classification as category 1 STOT. A classification as STOT category 2 might be considered. However, excluding the haemolytic effects, the only effects seen within doses that could trigger classification that might be considered are changes to male kidney weights in one rat study (unclear if this is an effect relevant to humans) and changes to heart weights in guinea pigs (decrease and dogs (increase) at 200ppm (866mg/m3). Because these effects are inconsistent and, in the case of the kidney effects, possibly rat specific and taking into account the fact that they occur upper limit of the classification threshold (and discounting the haemolytic effects as not relevant to humans), on balance these effects are not regarded as significant enough to warrant classification.