Dimethyl sulfoxide

Endpoint summary

Key value for chemical safety assessment

Toxic effect type:

concentration-driven

Effects on fertility

Description of key information

No effect was observed on the oestrus cycle, the sperm investigations (count, motility and morphology) and the reproductive organs of male and female rats after a 90-day inhalation exposure to DMSO concentrations up to 2800 mg/m3.

Effect on fertility: via oral route

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Study duration:

subacute

Species:

rat

Additional information

No 2-generation reprotoxicity study is available for dimethylsulfoxide. Considering that the potential effects of dimethylsulfoxyde on the reproduction and the developmental parameters have already been extensively evaluated in different studies, it is proposed a waiving.

The effects of DMSO on male and female fertility has been evaluated in an oral Reproduction/Developmental Toxicity Screening test in rats and by performing some specific investigations during the 13-week inhalation toxicity study.

Reproduction/Developmental Toxicity Screening Test

In a study performed according to the OECD Guideline # 421 and GLP, four groups of 12 male and 12 female Sprague-Dawley rats received DMSO (purity 99.977%), daily, by oral (gavage) administration, 4 weeks before mating and through mating and, for the females, through gestation until day 21 post-partum, at dose-levels of 0, 100, 300 or 1000 mg/kg bw/d (dosing volume: 5 mL/kg in purified water).

Clinical signs and mortality were checked daily. Body weight and food consumption were recorded weekly until mating and then at designated intervals throughout gestation and lactation. The animals were paired for mating and the dams were allowed to litter and rear their progeny until day 22 post-partum. The total litter sizes and numbers of pups of each sex were recorded after birth, pup clinical signs were recorded daily and pup body weights were recorded on days 1 and 4 post-partum and then weekly until day 21 post-partum. The males were sacrificed after completion of the mating period. The body weight and selected organs weights were recorded and a macroscopic post-mortem examination of the principal thoracic and abdominal organs was performed, with particular attention paid to the reproductive organs. A microscopic examination was performed on selected organs for all males in the control and high-dose group. The dams were sacrificed on day 22 post-partum (or on day 25 post-coitum for females which did not deliver or 24 days after the end of the pairing period for unmated females) and a macroscopic examination of the principal thoracic and abdominal organs was performed, with particular attention paid to the reproductive organs. In females that were apparently non-pregnant, the presence of implantation scars on the uterus was checked using ammonium sulfide staining technique. A microscopic examination was performed on selected organs of females in the control and high-dose group. The litters were culled on day 4 post-partumto four males and four females whenever possible and non-selected pups were sacrificed and retained. Selected pups sacrificed on day 22 post-partum and pups prematurely sacrificed or found dead were carefully examined for gross external abnormalities and a macroscopic post-mortemexamination was performed.

There were no unscheduled deaths and no treatment-related clinical signs during the study in males or females. There were no effects of treatment with DMSO on male body weight gains or food consumption. All DMSO treated female groups had slightly, but not statistically significant, lower body weight gains than the controls during the pre-pairing period (-11, -26 and –22% at 100, 300 and 1000 mg/kg, respectively). However, on day 15, the body weight differences between the treated females and the controls were less than 3% (control 268g, treated 264, 262 and 261 g at 100, 300 and 1000 mg/kg/d, respectively). No effect was observed on the body weight gains during gestation or lactation periods, as well as on food consumption.  No DMSO related effects were noted on mating and fertility parameters. There were no effects on estrus stages, on the mean number of days taken to mate and no effect on the mean duration of gestation. There were no effects of treatment with the test item on pup mortality and survival, mean pup body weight, body weight gain or sex ratio. Pup necropsy finding was limited to a slightly increased incidence of dilated renal pelvis in the group treated at 1000 mg/kg bw/d. However, this effect was not statistically significant, in the range of the historical values and there was no dose-relationship between the groups treated at 100 or 300 mg/kg bw/d. Marginally higher absolute (+10%) and relative (+8%) liver weights were noted in the F0 males given 1000 mg/kg bw/d. There were no treatment-related macroscopic findings. The treatment with DMSO at the highest dose-level did not affect the incidences of microscopic findings in testes, epididymides and ovaries.

The NOAEL for parental toxicity was considered to be 1000 mg/kg bw/d, based on marginally increased liver weights at 1000 mg/kg bw/d. The NOAEL for reproductive performance (mating and fertility) was considered to be 1000 mg/kg bw/d and the NOAEL for toxic effects on the progeny was 1000 mg/kg bw/d (Davis, 2007).

Short description of key information:
In a Reproduction/Developmental Toxicity Screening Test performed following the OECD guideline # 421, the NOAEL for parental toxicity, reproductive performance (mating and fertility) and toxic effects on the progeny was considered to be 1000 mg/kg/day.

Effects on developmental toxicity

Description of key information

The developmental toxicity of DMSO has been investigated in OECD guideline studies using rats and rabbits. In developmental toxicity studies, oral administration of DMSO to pregnant female rats or rabbits during the period of organogenesis was not teratogenic. The NOAELs for maternal toxicity and embryo/foetotoxicity were 1000 mg/kg/day in both species.

Effect on developmental toxicity: via oral route

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Study duration:

subacute

Species:

rat

Additional information

The developmental toxicity of DMSO has been investigated in OECD guideline studies using rats and rabbits.

Rat study

In a study to evaluate the potential toxic effects of DMSO on embryonic and foetal development, DMSO was administered daily by oral gavage at 200, 1000 or 5000 mg/kg/d to pregnant Sprague-Dawley female rats during the period of organogenesis (day 6 to day 15 of pregnancy inclusive). This study was conducted according OECD guideline # 414 and GLP (Richard, 1997).

DMSO was clinically well-tolerated by the pregnant female rats at all dose-levels, producing only a slight reduction in food consumption (-11%) and body weight gain (-32%) at 5000 mg/kg bw/d during the treatment period. There was no effect, at any dose-level, on the number of corpora lutea, implantation sites, post-implantation loss, number of live fetuses and sex-ratio. The fetal body weight was not affected at 200 and 1000 mg/kg bw/d, whereas it was slightly lower than that of the control group, at 5000 mg/kg bw/d (-7% and -9% in male and female fetuses, respectively), probably as a consequence of the lower maternal body weight gain There were no malformations or variations at external examination of any fetus. There was no major soft tissue malformation in any fetus, of any group. The soft tissue variations were confined to a slightly, not statistically significant, increased incidence of dilated renal pelvis, only statistically significant at 200 mg/kg bw/d, associated at 5000 mg/kg bw/d with a slightly increased incidence of dilated ureter(s). In both cases, the incidences were in the range of the historical control values. At microscopic examination, the fetal kidneys displaying dilatation of the renal pelvis had the same morphological structure in the control and in the treated groups and the contralateral kidney (in the case of unilateral change) had the same structure as the affected kidney. There were no skeletal malformations in any fetus, of any group. The skeletal variations were confined to a higher incidence of reduced ossification of rib(s) at the dose level of 5000 mg/kg bw/d (11.5 + 16.3 % fetuses affected per litter versus 1.4 + 4.0 % in controls). This finding might be considered a consequence of the lower fetal body weight.

The No Observed Effect Levels (NOEL) in terms of maternal toxicity was considered to be 1000 mg/kg bw/d and the NOAEL in terms of embryo- and foeto-toxicity to be 1000 mg/kg bw/d. No teratogenic effect was observed at any dose level.

Rabbit study

The potential of Dimethylsulfoxide (DMSO) to induce developmental toxicity after maternal exposure during the critical period of organogenesis was evaluated in rabbit according to OECD Guideline N° 414 (22nd January 2001) and US EPA, Health effects Test Guidelines OPPTS 870.3700, (August 1998) and in compliance with Good Laboratory Practices (Richard, 2002). DMSO was administered orally by gavage to four groups of 24 bred female KBL New Zealand White rabbits once daily from gestation days 7 through 28 inclusive at dosage levels of 0, 100, 300 and 1000 mg/kg/d. Clinical signs and mortality were checked daily. Body weight, food consumption and water consumption were recorded at designated intervals. On day 29post-coitum, the does were sacrificed and subjected to macroscopic examination. The gravid uterus was weighed to allow calculation of the net body weight change. The fetuses were removed by hysterectomy. The litter parameters were recorded, namely: number of corpora lutea, implantation sites, early and late resorptions, dead and live fetuses. The fetuses were weighed, sexed and submitted to external examination. A detailed examination of the soft tissue was performed by fresh dissection. Then the fetuses were submitted to a detailed examination of the skeleton (bone and cartilage) following alizarin/alcian blue staining.

There was no mortality attributed to treatment with the test item. There were no clinical signs of toxicity in any group. The body weight, food consumption and water consumption were not affected by the treatment at 100 mg/kg/day. In the 300 mg/kg/day group, there was only a slight reduction of food consumption during the first 2 days of treatment. At 1000 mg/kg/day, there was a moderate reduction of food consumption during the first part of the treatment period (days 7-15 of pregnancy) and body weight gain during the first 2 days of the treatment period (days 7 -9 of pregnancy). No macroscopic findings were observed at any dose-level that were ascribed to treatment with DMSO. No treatment-related effects were observed on the pre- or post-implantation loss, the foetal weight or the sex ratio. No malformations or variations were noted at external, soft tissue or skeletal examination that were ascribed to treatment with the test item or considered to be of toxicological significance.

Under these experimental conditions, DMSO administered daily to pregnant rabbit by gavage from day 7 to day 28post-coitumat 100, 300 or 1000 mg/kg/day produced no signs of maternal toxicity at 100 mg/kg/day and was minimally to slightly maternotoxic at 300 and 1000 mg/kg/day. The embryofetal development was not affected and there were no teratogenic effects at any dose-level. The No Adverse Effect Level (NOAEL) for embryofetal development and maternal toxicity was established at 1000 mg/kg/day. The No Effect Level (NOEL) for maternal toxicity was established at 300 mg/kg/day.

Toxicity to reproduction: other studies

Additional information

In the 90-day inhalation toxicity study in rats (Kenny, 2000) the oestrus cycle of female rats was monitored, male rats were subjected to sperm investigations (count, motility and morphology) and the reproductive organs of both sexes were examined histologically. No treatment-related effects were observed up to the concentration of 2.8 mg/l.

In repeated dose toxicity studies (see section repeated dose toxicity) involving monkeys treated orally or dermally for 18 months (Vogin et al., 1970) and rats, dogs and monkeys treated dermally for 26 weeks (Smith et al, 1968), the histological examinations of the reproductive organs were unremarkable in male and female animals.

Justification for classification or non-classification

Based on the available data, noclassification for reproductive toxicity has to be applied for DMSO according to EU Directive 67/584/EEC and EU regulation (EC) No 1272/2008 (CLP).