11.   Palladium is used in catalytic converters, which remove pollutants from vehicle emissions.

12.   Palladium is used by the electronic industry and is a component in automotive catalytic converters, which remove air pollutants from exhaust emissions.

13.   Pollutants are removed before natural gas is allowed into pipelines.

14.   Reducing sulfur in gasoline enables a catalytic converter to remove pollutants from engine exhaust more efficiently.

15.   Sulfur, which occurs naturally in crude oil, coats the catalysts in a catalytic converter and makes them less effective in removing other pollutants from the exhaust.

16.   The changes come at a sizable expense to refiners, as the costs to remove pollutants such as sulfur increases exponentially as standards get stricter.

17.   The other main method used by the city to remove pollutants is the addition of pathogen-consuming bacteria.

18.   The remaining liquid wastes are then piped to the treatment plant, where the wastes trickle through layers of sand and gravel to remove pollutants.

19.   Pollutants are formed in a more concentrated stream when a gassifier is used instead of a furnace, and the pollutants can be removed before they are emitted.

20.   Incineration was expensive and researchers began looking for cheaper ways to remove pollutants.