Long-term exposure is harmful. Rubber products contain sulfur. Be very careful when coming into contact with carbon disulfide, hydrogen sulfide and sulfur dioxide. Sulfur dioxide can combine with water in the lungs to form sulfurous acid, which can cause lung bleeding and suffocation. Hydrogen sulfide is very toxic, even more toxic than cyanide. Although the smell of hydrogen sulfide is initially very strong, the human sense of smell is quickly overpowered by it. So the victim may not be aware of its presence.