other air pollution exhaust sources in various large-scale industrial facilities such as petroleum refineries, natural gas processing plants, petrochemical plants and chemical production plants. However, these are often referred to as flue gases. Catalytic converters in cars intend to break down the pollution of exhaust gases using a catalyst. Scrubbers in ships intend to remove the sulfur dioxide (SO2) of marine exhaust gases. The regulations on marine sulfur dioxide emissions are tightening, however only a small number of special areas worldwide have been designated for low sulfur diesel fuel use only. One of the advantages claimed for advanced steam technology engines is that they produce smaller quantities of toxic pollutants (e.g. oxides of nitrogen) than petrol and diesel engines of the same power. They produce larger quantities of carbon dioxide but less carbon monoxide due to more efficient combustion. Health studies Researchers from the University of California, Los Angeles School of Public Health say preliminary results of their statistical study of children listed in the California Cancer Registry born between 1998 and 2007 found that traffic pollution may be associated with a 5% to 15% increase in the likelihood of some cancers. A World Health Organization study found that diesel fumes cause an increase in lung cancer. Localised effects The California Air Resources Board found in studies that 50% or more of the air pollution (smog) in Southern California is due to car emissions. Concentrations of pollutants emitted from combustion engines may be particularly high around signalized intersections because of idling and accelerations. Computer models often miss this kind of detail. See also Air pollution#Most polluted cities Alternative propulsion Atmospheric dispersion modeling Automobile#Environmental impact Clean Air Act Congestion pricing Emission standard European emission standards Flue gas Kyoto protocol Landfill gas Low-emission zone Mobile source air pollution Motor vehicle emissions and pregnancy Rolling coal Space jellyfish United States emission standards Vehicle emissions control References External links Health and Air Pollution Publication of the California Air Resources Board About diesel exhaust: U.S. Department of Labor Occupational Safety & Health Administration: Safety and Health Topics: Diesel Exhaust Partial List of Chemicals Associated with Diesel Exhaust Diesel Exhaust Particulates: Reasonably Anticipated to Be A Human Carcinogen Scientific Study of Harmful Effects of Diesel Exhaust: Acute Inflammatory Responses in the Airways and Peripheral Blood After Short-Term Exposure to Diesel Exhaust in Healthy Human Volunteers Diesel exhaust: what you need to know Air pollution Engines Gases