Sulfur

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vivo

Description of key information

Sulfur did not induce gene mutations in the Ames test. An in vitro test chromosomal aberration test with CHO cells was negative.

In vivo, sulfur was negative in the micronucleus test in which mice were exposed by oral gavage at the limit dose of 2000 mg/kg bw.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vivo:

The genotoxic effect of sulfur dust was studied using the Ames test (Rallis Research Centre 2005). The study, according to OECD guideline 471 and under GLP, was conducted using TA98, TA100, TA1535 and TA1537 strains of Salmonella typhimurium and WP₂uvrA (pKM 101) strain of Escherichia coli. Two trials were carried out (with two experiments in each trial, in the presence and in the absence of metabolic activation). The test item was tested in triplicate at the concentrations of 50, 158, 500, 1581 and 5000 µg/plate in the first trial and 100, 266, 707, 1880 and 5000 µg/plate in the second trial using DMSO as vehicle. The vehicle control and the appropriate positive controls were tested simultaneously.

The mean numbers of revertant colonies for the different concentrations of the test item in the different tester strains was statistically comparable with or lower than those of the respective vehicle control plates, for both the first and the confirmatory trials, either in the presence or in the absence of the metabolic activation, while there was a statistically significant increase in the mean number of revertant colonies in the positive controls under identical conditions. The study indicated that the test item sulfur dust is not mutagenic in this Ames test up to the highest tested concentration of 5000 µg/plate.

The potential of the test item sulfur dust to induce chromosome aberrations in mammalian cells was evaluated using cultured Chinese Hamster Ovary (CHO) cells (OECD guideline 473, GLP compliant) (Advinus Therapeutics Private Limited (2005). In both trial 1 and 2, for experiments in the presence of metabolic activation, CHO cells were exposed to the test item in quintuplicate for 3 hours at concentrations of 4, 8 and 16 µg/ml of the medium in the presence of metabolic activation. These concentrations were based on results from preliminary range finding tests and the top dose of 16 µg/ml reflects the maximum non-cytotoxic concentration. In trial 1 for the experiment in the absence of metabolic activation, CHO cells were exposed to the test item at concentrations of 4, 8 and 16 µg/ml of the medium for 3 hours. In trial 2 for the experiment in the absence of metabolic activation, CHO cells were exposed to the test Item at concentrations of 2, 4, and 8 µg/ml continuously for 19 hours and 35 minutes. In a similar way, concurrent vehicle control (DMSO) and appropriate positive controls viz., cyclophosphamide in the presence of metabolic activation and ethylmethanesulfonate in the absence of metabolic activation were also tested in quintuplicate.There was no evidence of induction of chromosome aberrations by sulfur dust with experiments either in the presence or absence of metabolic activation. In each of these experiments, the respective positive control items produced a large and statistically significant increase in aberrant metaphases, under identical conditions. In both the trials, at the highest concentration tested, the reduction in the cell growth was in the range of 55.78 to 58.15% over the DMSO control, both in the presence and absence of metabolic activation. The study indicated that the test item does not have the potential to cause chromosome aberrations at the concentrations tested.

No in vitro data on gene mutations in mammalian cells is available. Sulfur is an essential element in the metabolism of all living organisms, thus chronic exposure to sulfur is the natural state. Furthermore, sulfur is insoluble and unreactive. In mammals sulfur is metabolized by intestinal micro-organisms, which are not present in in vitro tests. There are indications of absorption of metabolites but which are most likely endogenous to the body (e.g. well known to be intermediary or end products of mammalian metabolic reactions). Therefore, the performance of an in vitro gene mutation study is scientifically not justified.

Sulfur was tested for its potential to induce cytogenetic damage in bone marrow cells of Swiss albino mice by the micronucleus test (OECD guideline 474 and GLP compliant) (Rallis Research Centre 2005). The test item was administered twice with at 24 hour interval by oral gavage at the limit dose of 2000 mg/kg bw at the dosage volume of 10 ml/kg. A concurrent vehicle control group (0.5% aqueous carboxymethyl cellulose (CMC) with Tween 80 (1 ml/L)) and a concurrent positive control group (cyclophosphamide) were also included. The mice were sacrificed 23 to 24 hour after the second treatment. From each animal, a minimum of 2000 polychromatic erythrocytes (PCE) were scored for the incidence of micronucleated PCE. Sulfur, at the tested limit dose of 2000 mg/kg bw, did not affect the body weights of mice and there were no clinical signs, mortality and necropsy findings except for an incidence of liver and kidney congestion in a male mouse in the positive control group. The percentage of micronucleated PCE in the treatment group was comparable to the concurrent vehicle control group. Cyclophosphamide significantly increased the percentage of micronucleated PCE and significantly altered (reduced) the PCE:total RBC ratio in males, females and combined sex indicating the effectiveness of the methodology adopted and the sensitivity of the test system. The test item sulfur was not clastogenic in this micronucleus test in Swiss albino mice at the tested limit dose of 2000 mg/kg bw.

Justification for selection of genetic toxicity endpoint

One of three available studies.

Justification for classification or non-classification

In accordance with the EU CLP Regulation (EC No. 1272/2008), classification is not necessary for genetic toxicity based on the available data.