Exhaust gas 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. 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
Diesel exhaust to low levels. The $11.5 million Diesel Exhaust in Miners Study (DEMS) followed 12,315 miners, controlling for key carcinogens such as cigarette smoke, radon, and asbestos. This allowed scientists to isolate the effects of diesel fumes. For over 10 years, concerns have been raised in the USA regarding children's exposure to DPM as they ride diesel-powered school buses to and from school. In 2013, the Environmental Protection Agency (EPA) established the Clean School Bus USA initiative in an effort to unite private and public organizations in curbing student exposures. Diesel particulate matter (DPM), sometimes also called diesel exhaust particles (DEP),