Isopropyl acetate

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Species:

rat

Additional information

A two generation reproduction toxicity study in rats examined oral gavage exposure of isopropanol at doses of 100, 500 and 1000mg/kgbw/day. There were signs of parental toxicity at the highest dose, including effects on body weight gain, liver and kidney weights and liver and kidney histology. There was some evidence of increased mortality in the pups in the early post natal period in the high dose animals and this dose group also showed a trend towards reduced pup weights. No treatment related post-mortem findings were seen in any offspring. The only reproductive parameter that appeared to be affected by treatment was a statistically significant reduction in the P1 male mating index in the high dose animals. The reduction to 73% from a control value of 97% was slightly below historical control values (80 -97%). The absence of a similar effect in the P0 males, the lack of an effect on females, litter size, or histopathological findings in the testes means that, whilst a treatment related effect cannot be excluded, this finding could be a statistical outlier. Support for this conclusion comes from the fact that most of the animals in the high dose group became pregnant. The authors hypothesised with supporting references that the high number of offspring deaths in the F2 post-weaning period in the high dose group was treatment related and possibly due to underdeveloped metabolism capacity in the young animals causing isopropanol poisoning. This theory is based on the fact that the LD50 is lower in animals <14 days old. The NOEL for reproductive effects is 500 mg/kg bw/day based on reduced male mating index in high-dose P2 males.

A one generation fertility study using isopropanol administered in the drinking water to rats showed clear signs of general toxicity in the parental generation at the top dose. Dosing in the drinking water was 0.5, 1.0 and 2.0%. Palatability affected the consumption of the drinking water. For males, dosing was reasonably constant, averaging out at ~365, 660 and 1070mg/kg in the three dose groups respectively during the study. However, for females, the doses varied markedly during the three phases of the study, being lowest during premating (456, 835, 1206mg/kg) and highest during lactation/postpartum (1053, 1948, 2768mg/kg). General toxicity was manifest through reductions in food and water intake, a reduction in body weight and weight gain and increases in organ weights. There was no impact on reproductive capacity of either the males or females or any of the reproductive parameters. In the F1 animals, there was a reduction in pup survival in the high dose group and all dose groups showed an increase in liver weights in both sexes and at all dose groups. There were no other effects seen on the offspring. For the parental generation, the NOAEL was 625mg/kg in males and 825mg/kg in females, based on the lowest observed intake figures and general toxicity seen at the high dose. For the F1 generation, the critical effect was increased liver weight, seen at all dose levels, although due to the high consumption of drinking water during this critical period, this equates to a dose of in excess of 1000mg/kg. The effect may be an adaptive response to the high metabolic load at such doses. From this study, isopropanol does not appear to show any reproductive toxicity up to a dose of at least 1000mg/kg.

In view of the discrepancy between the single and two generation studies in terms of the male reproductive parameters, Faber et al (2008) examined the two generation study in detail to check for any methodological flaws that could have produced unreliable results. In this case, there did appear to be a flaw in that the general toxicity at the higher doses resulted in higher mortality in the females than the males. During the mating period, males and females were co-habited for one week. If mating did not occur, another male (that had not bred) was cohabited for a week. The process was repeated for a third week if required. Using this procedure resulted in some males having up to three opportunities to breed whereas others only got a single opportunity. Since positive fertility was determined by a single successful mating, it is clear that the animals did not have equal opportunity to demonstrate this. Therefore the mating index in the two generation study should be regarded as unreliable. It is feasible that the fact that since the F2 males in the two generation study received isopropanol during the juvenile stage (which the single generation study rats did not), that there could be a developmental effect, but this is not supported by any other findings that might be expected if this were the case, either in terms of pathology or reproductive performance.

Based on the difference in molecular weight of isopropanol and isopropyl acetate, it can be predicted with confidence that the NOAEL for reproductive toxicity of the latter will be in excess of 1000mg/kg.

Effects on developmental toxicity

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

400 mg/kg bw/day

Species:

rabbit

Additional information

No data is available for isopropyl acetate. However, data is available for isopropanol, the in vivo metabolite of isopropyl acetate.

In a well conducted developmental toxicity test using isopropanol, New Zealand rabbits were dosed during GD 6-18 at doses of 120, 240 and 480mg/kgbw/day by oral gavage. The NOAEL for maternal toxicity was determined to be 240 mg/kgbw/day with no evidence of teratogenicity up to the maximum tested dose of 480mg/kgbw/day (Tyl, 1994). At 480mg/kgbw/day, maternal mortality was clearly evident. Adverse effects of maternal toxicity included reduced dam weight gain following commencement of treatment along with reduced food consumption and adverse clinical signs typical of intoxication. There was also significant mortality in the top dose group. In contrast, there was no impact on the number of does becoming pregnant, the number of abortions, implantation loss, losses by resorption, pregnancy duration, reduction in number of live offspring, sex ratio, external, skeletal or visceral malformations. The only change was a reduction in average litter weight, which was statistically significant for trend only in the females but not statistically significant overall and almost certainly mirrored the doe weight loss as a consequence of maternal toxicity. The study clearly showed that isopropanol is not developmentally toxic in rabbits up to the maximum tolerated dose.

Tyl (1994) also conducted a parallel study in rats. In this similarly well conducted developmental toxicity test using isopropanol, rats were dosed at 400, 800 and 1200mg/kgbw/day by oral gavage over GD 6-15. As in the rabbit study, pregnancy rates were high. The NOAEL for maternal toxicity was 400 mg/kgbw/day based on a small increase in mortality but one which was associated with treatment. There was no evidence of teratogenicity up to the maximum tested dose of 1200mg/kgbw/day. At the highest dose, there was also reduced gestational weight gain. Fototoxicity was seen in the form of reduce gravid uterine weight and reduce male and female average fetal weights, which were reduced by ~5% at the mid dose and more in the high dose group. There was no impact on the number of does becoming pregnant, the number of abortions, implantation loss, losses by resorption, pregnancy duration, reduction in number of live offspring, sex ratio, external, skeletal or visceral malformations. The NOAEL for maternal and foetal toxicity was therefore 400mg/kgbw/day.

In a GLP developmental toxicity study, rats were subject to doses of isopropanol in drinking water at concentrations of 0.5, 1.25 and 2.5% of the period GD6 -16 (Faber, 2008). The doses were equated to oral exposures of 596, 1242 and 1605mg/kgbw/day respectively. Maternal toxicity was evident in both the mid and high dose groups, which manifested in the form of a reduced food and water intake along with a suppression in body weight growth. In the high dose group in particular, water intake fell by 50% after dosing started and remained suppressed until dosing ceased, when both water and food intake bounced back to exceed control levels. The reduced water intake was believed to be due to palatability of isopropanol at the relatively high concentrations used. There was no evidence of adverse effects on maternal developmental toxicity. All reproductive parameters were normal across all dose groups. The only sign of foetotoxicity was a slight reduction in average litter weights in the medium and high dose groups, but these changes mirrored the weight loss seen in the dams and were likely a secondary consequence of the latter. No external or visceral malformations were seen. Two minor skeletal variations were seen at all doses; there were dose dependent decreases in the number of fetuses with the 4th sacral arch present and in the number of fetuses with more than 2 caudal arches.  It should be noted that the latter of these did not show any variation across the dose groups and could have been made significant purely due to an unusually high rate in the control animals. In the mid and high dose groups there was an increase in the number of fetuses with less than 2 caudal arches of the vertebrae and in the high dose group there were some additional significant increases in variations of the sternebrae. In the mid and high dose groups these changes are likely to be linked to the reduced foetal weight, which was in turn linked to maternal toxicity. The remaining isolated vertebrae findings are unlikely to be biologically relevant in the absence of any other adverse skeletal findings. Based on these considerations, the NOAEL for maternal and developmental effects is 596mg/kgbw/day.

In a study to examine the developmental potential of isopropanol, pregnant SD rats were exposed by inhalation to measured concentrations of 3500, 7000 and 10000ppm isopropanol vapour over the period GD 0 -19. Animals were exposed whole body for 7 hours per day. A satellite group of non-pregnant rats was co-exposed to provide blood samples for the measurement of isopropanol blood concentrations at the end of the exposure periods 1, 10 and 19 days into the study. These showed that there was no build up of isopropanol at the low dose but that intake was faster than metabolism for the mid and high dose groups, with blood concentrations of ~600 -800mg/dL resulting. The mid and high dose groups showed maternal toxicity, manifest as narcotic effects, reduced body weight gain and food intake. Effects in the high dose group were severe. There was a reduction in number of offspring in the high dose group which was attributed to failure of implantation as well as losses from resorption. There was a dose dependent drop in fetal body weight across all groups. This was small (4%) in the low dose group and, whilst statistically significant, the change is slight and the NOAEC will be close to this level. The NOAEC for the study for both developmental and maternal effects was determined to be 3510ppm (estimated to be equivalent to ~875mg/kgbw/day by the oral route) with effects seen at higher doses attributable as secondary to general maternal toxicity and also above what would equivalent to an oral dose well in excess of the limit dose of 1000mg/kgbw/day. This study does not demonstrate that isopropanol presents a selective hazard to the the developing conceptus.

The three studies in rats show that isopropanol causes maternal toxicity in the range 800-1000mg/kgbw/day and above, manifesting in reduced food and water consumption, body weight loss and in the extreme, increased incidence of mortality. The similarity between the results from the gavage, drinking water and inhalation studies suggests that this is due to toxicity of isopropanol rather than reduced food and water intake. At a similar dose, foetotoxicity starts to occur, manifesting in reduced fetal and litter weights that mirror the loss of dam weight, suggesting it is a linked effect. There was no evidence of other adverse effects on any reproductive parameter in either study. There were no external or soft tissue malformations seen in either study. The drinking water study did show a statistically significant increase in a small number of variations of the vertebrae, but as these were not seen in other bones nor in the gavage study, they are not likely to be biologically relevant. Dose levels of up to maternally toxic doses are without developmental effects; the NOAEL is in the range 400-600mg/kgbw/day. In the rabbit, the NOAEL for maternal toxicity was 240mg/kgbw/day. At the maximum tolerated dose, clear maternal toxicity was seen (reduced body weight, mortality). In parallel, a small but linked reduction in litter weight was seen in the same group of animals. There was no other evidence of foetoxicity and no external, visceral or skeletal malformations were seen at any dose.

The studies in isopropanol can be used as a source to predict the developmental toxicity potential of isopropyl acetate and to predict with confidence that the latter will not show any evidence of reproductive toxicity at doses at or below 1000mg/kgbw/day.

Justification for classification or non-classification

Two toxicity to reproduction studies are available for the source substance isopropanol. Using a weight of evidence approach, it can be concluded that the NOAEL for isopropanol as ~700mg/kgbw/day and the LOAEL around 1000mg/kgbw/day. These are equivalent on a molecular weight basis to 1190 and 1700mg/kgbw/day respectively for isopropyl acetate). These figures are well above the limit dose normally considered for classification purposes and therefore it can be concluded with confidence that isopropyl acetate does not need to be classified for reproductive toxicity.

There was no evidence of any developmental effects in rabbits beyond mild foetotoxicity that could be linked to maternal toxicity (body weight loss in both cases.) The data from rats indicates no evidence of developmental effects that are not secondary to maternal toxicity. Based on the data from rabbits, the NOAEL corrected for the molecular weight of isopropyl acetate would be 408mg/kgbw/day for both maternal and developmental effects and for rats it would be 680-1020mg/kgbw/day.

In conclusion, based on the source substances, there is no evidence that isopropyl acetate would exhibits any specific reproductive or developmental toxicity that would warrant classification and that any effects that are seen occur at maternally toxic doses and, for the rat, above the normal limit dose threshold of 1000mg/kgbw/day.