Sulfur

Specific investigations: other studies

Description of key information

Exposure to 451 mg/m3 sulfur has been demonstrated to produce mild sensory irritation in the upper airway of male Swiss-Webster mice.

A comedogenicity study has demonstrated that two weeks of treatment with the addition of 3% colloidal sulfur to white petrolatum had no discernable effect on the development of acanthosis, i.e. on cell proliferation in humans.

Additional information

The potential of sulfur dust to produce sensory irritation was evaluated in mice. Male Swiss-Webster mice (n=4/concentration) were exposed by head-only inhalation to 106, 263 or 451 mg/m³ sulfur dust (Bevan and Whitman, 1991). Mice were first exposed for 10 minutes to fresh air, followed by an exposure period to sulfur dust for 30 minutes. After the exposure period the animals were monitored for an additional 5-10 minutes to measure recovery (Alarie test protocol). Breathing frequency and patterns were monitored before, during and after exposure to evaluate the animal’s sensory irritation response to the test atmosphere. Group average breathing rates were 7 and 17% below pre-test values at 106 and 263 mg/m³, respectively; however, breathing patterns appeared normal, indicating that there was no sensory irritation. Mice exposed to 451 mg/m3 showed an increase in breathing frequency of 7%, with one of the four mice displaying very slight signs of pulmonary (deep lung) irritation. Some of the mice in the low- and high-dose groups exhibited signs of slight eye irritation immediately after exposure, but all mice had recovered 1 day later. The average particle size (MMAD 5.5 to 5.8 µm), although larger than that considered respirable for mice, was considered small enough to be inhalable and to be deposited primarily in the nasal turbinates. Only a small portion of the sulfur dust was considered to have reached the lower airways, as shown by one mouse exposed to 451 mg/m³ which exhibited a change in breathing pattern that indicated some deep lung or pulmonary irritation and resulted in a 24% increase in breathing frequency. On the basis of the findings, exposure to sulfur dust up to 263mg/m³ did not produce any sensory or upper airway irritation in mice. Exposure to 451 mg/m³ sulfur produced mild sensory irritation in the upper airway.

In a comedogenicity study (Pullman et al., 1977), 10 humans were dermally exposed to 3% colloidal sulfur (in petrolatum).The sulfur was applied to the uncovered skin (left side of the upper arm) twice daily for two weeks with the right upper arm serving as the vehicle control.After exposure, biopsies were taken for investigated histology and autoradiographical examination with 14C and 3H-Thymidine.

 

The skin remained clinically normal; a typical acanthosis caused by  petrolatum with increased proliferation of cells (3H-Thymidine-labelling-Index 

(H3-I) on the left side 5.1 ± 1.8%, on the  right side 5.3 ± 2.3%; normal values: 2.8 ± 1%) was observed. The DNA synthesis time (ts) and average cell 

cycle-time (tc) of the epidermal cells were not significantly different in the two sides, but tc was  shortened in comparison with normal epidermis.

 

It was evident that after two weeks of treatment the addition of 3% colloidal sulfur to white petrolatum had no discernable effect on the development 

of acanthosis, i.e. on cell proliferation.