Pollutant linked to bronchitis in toddlers
They found a component of pollution known as polycyclic aromatic hydrocarbons, or PAHs, was strongly linked with cases of bronchitis among children aged 2 to 4 and a half.
The study is one of the first to look at PAHs, which are produced when fuels that contain carbon such as wood, coal, diesel or tobacco are burned.
Most environmental regulations in the United States and Europe focus on controlling particulate emissions -- tiny particles in the air -- as well as sulfur dioxide and ozone.
"Our work strongly suggests that regulators consider efforts to curb PAHs as well," Irva Hertz-Picciotto of the University of California, Davis, who led the study, said in a statement.