A new study led by the University of Colorado at Boulder reveals that air quality regulations may not effectively target a large source of fine, organic particle pollutants that contribute to hazy skies and poor air quality over the Los Angeles region.
According to the study, a much smaller percentage of organic haze than was previously thought is directly emitted by vehicles and industrial processes. Instead, 75 percent of fine, organic particle pollutants form when reactive gases called VOCs, or volatile organic compounds, are oxidized and condense onto existing particles in the air.
"Air quality regulations today effectively target most sources of 'primary,' or directly emitted particles," said lead author Ken Docherty, a researcher with the university's Cooperative Institute for Research in Environmental Sciences. "Yet our study indicates that the 'secondary,' or chemically formed particles contribute more significantly to poor air quality, even in very polluted urban regions.
"Our study suggests that regulations need to focus much more attention on the gases -- such as gasoline vapors -- that form secondary organic particles and create visible haze," he said. Other examples of VOCs include vapors from paints, varnishes, cleaning supplies, automotive products and dry-cleaned clothing.
The study will be published in the journal Environmental Science and Technology and was posted online Sept. 23.
According to California state regulatory agencies, motor vehicles and household products are both significant sources of VOCs in the Los Angeles region.
"Although current regulations do target many sources of VOCs, these regulations will need to further reduce VOC emissions and perhaps target still unknown sources to effectively reduce fine particle concentrations," said Docherty. He and his colleagues cautioned that it is not clear which VOCs are most responsible for haze formation.
|Contact: Ken Dochery|
University of Colorado at Boulder