Which one of the following pollutants causes surface deterioration of leather goods?

Sulphur dioxide : It is one of the several forms in which sulphur exists in air. The others include H2 S, H2 S04 and sulphate salts. Sulphur dioxide (S02) is a colourless gas with a sharp odour, results from the combustion of sulphur containing fossil fuel, the smelting of sulphur-containing ores, and other industrial processes. Domestic fires, power generation and motor vehicles can also produce emissions containing sulphur dioxide. S02 can affect the respiratory system and the function of lungs, and causes irritation of eyes. Inflammation of the respiratory tract causes coughing, mucus secretion, aggravation of asthma and chronic bronchitis, and makes people more prone to infections of the respiratory tract. Hospital admissions for cardiac disease and moality increase on days with higher S02 levels. When S02 combines with water, it forms sulphuric acid; this is the main component of acid rain which is a cause of deforestation. It causes deterioration of leather items. A S02 concentration of 500 ug/m3 should not be exceeded over average periods of 10 minutes duration. Studies indicate that a propoion of people with asthma experience changes in pulmonary function and respiratory symptoms after periods of exposure to S02 as sho as 10 minutes. The revision of 24-hour guideline for so2 from 125 to 20 ug/m3 is based on the health effects known to be associated with much lower levels of so2 than previously believed Ref: Park 25th edition Pgno : 771-773