Dimethyl sulfoxide

Endpoint summary

Additional information

DMSO is used world wide as a solvent for poorly water-soluble substances in the genotoxicity tests and it has beeen tested in a large number of assays using a wide range of methods.

In Vitro Studies – Gene Mutations Assays

In a study performed with a method comparable to the OECD Guide-line no. 471, DMSO was tested in two separate laboratories in the gene mutations assay in bacteria. Concentrations of DMSO (100, 333, 1000, 3333, and 10,000 µg), overnight culture of Salmonella typhimurium strains TA97, TA98, TA100, TA1535, TA1537, and S-9 mix or buffer were incubated without shaking for 20 minutes. The top agar was added and the contents of the tubes were mixed and poured onto the surfaces of petri dishes. His+ (histidine dependent) colonies arising on plates were machine-counted after two days incubation. Initial testing was without metabolic activation, with 10% rat liver S-9, or with 10% hamster liver S-9. After a negative result was obtained, DMSO was retested without S-9 and with 30% S-9 from rat and hamster. Positive controls were sodium azide (TA 1535 and TA100), 9-aminoacridine or ICR-191 (TA 97 and TA1537) and 4-nitro-o-phenylenediamine (TA98) without S9 and 2-aminoanthracene (all strains) with S9: The positive control chemicals induced a significant increase of the revertant frequency in all tester strains, either with or without metabolic activation. DMSO was negative, in the presence and absence of metabolic activation, in all tester strains (Zeiger et al., 1992; NTP, 1987 & 1988).

In addition DMSO was not mutagenic in the Salmonella typhimurium strains TA97, TA98 and TA100 using the standard plate incorporation protocol, both in the presence and absence of metabolic activation (De Flora, 1981 and Brams et al., 1987).

In a study to test the compatibility of organic solvents with the Microscreen prophage-induction assay, DMSO was tested up to a concentration of 10% in the culture medium on Escherichia coli WP2s(l). (Dee Marini et al., 1991). DMSO was genotoxic in the presence and absence of S9.

No guideline compliant assay for gene mutations in mammalian cells is available for DMSO. Three tests performed only without metabolic activation are available, two L5178y/TK-/+ assays (Amacher et al., 1980 and Wangenheim et al., 1988) and one CHO/HGPRT assay (Amacher et al., 1984). At very high concentrations of DMSO (> 1 mmol/ml = 78 mg/ml), well in excess of the limit concentration recommended by the OECD guidelines (5 mg/ml), an increase of the mutation frequency was observed in one mouse lymphoma assay (Wangenheim et al., 1988), both 2 others assays were negative.

In Vitro Studies – Chromosomal aberrations Assays

In a study performed with a method comparable to the OECD Guide-line no. 473, DMSO was tested with Chinese hamster ovary (CHO) cells in culture at concentrations of 0, 499, 1500 and 4990 µg/ml, in the presence and absence of liver microsomal fraction (S9) from Aroclor 1254-induced male Sprague-Dawley rats, to determine its in vitro cytogenetic potential (Loveday et al., 1990). Medium control was used with each assay with or without S9. Mitomycin C was used in the experiments without metabolic activation, and cyclophosphamide was used in the experiments with activation as positive controls. The positive control chemicals induced a significant increase of the frequency of the chromosomal aberrations. DMSO did not induce cell toxicity or cell cycle delay, and did not induce an increase in the incidence of chromosomal aberrations.

In Saccharomyces cerevisiae, strain BR1669, DMSO failed to induce mitotic chromosome gain or arg4-8 reversion and had no effect on meiotic hyperploidy or reversion (Whittaker et al., 1990).

In Vitro Studies – other genotoxicity endpoints

DMSO was tested in CHO cells to a maximum concentration of 5000 µg/ml. DMSO did not induce cell toxicity or cell cycle delay, and did not induce an increase in the incidence of SCEs potential (Loveday et al., 1990).

DMSO did not increase the SOS-inducing activity when tested on Escherichia coli PQ37 (Brams et al., 1987).

In vivo studies

In an in vivo micronucleus assay performed according to the OECD guideline no. 474 and GLP, groups of 6 male and 6 female Han Wistar rats received 5 daily i.p. injections at the dose levels of 0, 200, 1000 and 5000 mg DMSO/kg bw/d. The animals were sacrificed 24 hours after the last dosing and bone marrow collected and evaluated for the presence of micronucleated polychromatic erythrocytes. The negative and positive controls in the study were purified water and cyclophosphamide, respectively. There was no increase in the incidence of micronuclei in the polychromatic erythrocytes of the bone marrow of male and female Han Wistar treated with DMSO as compared to concurrent controls (Marshall, 2002).

Additional in vivo studies - dominant lethal assay in mice (Chauhan et al., 1975), interchromosomal mitotic recombination, sex-linked recessive lethal mutations and sex chromosome loss assays in Drosophila melanogaster (Vogel and Nivard, 1993; Mollet et al., 1974), micronucleus assay in Pleurodeles waltl (Fernandez et al., 1993) and sister chromatid exchanges assay in mice (Sharma et al., 1985) - have resulted in uniformly negative results.

Short description of key information:
In studies performed with methods compliant to OECD guidelines, no genotoxic activity was observed for DMSO in gene mutations assays in Salmonella typhimurium, an in vitro cytogenetics assay in CHO cells and an in vivo micronucleus assay in rats. With few exceptions, a large battery of additional in vitro and in vivo non-guideline studies confirmed the lack of genotoxic potential.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

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