A NASA [Images] research team, examining air pollution levels over the Indian subcontinent, has found an immense pollution pool over Bihar, about five times larger than those typically found over Los Angeles.

"Blanketing around 100 million people, primarily in the Ganges [Images] Valley, the pollution levels are about five times larger than those typically found over Los Angeles," NASA said in a release.

The discovery was made by researchers analysing four years of data collected by the Multi-angle Imaging Spectro-Radiometer (MISR) onboard the Terra satellite, the flagship of NASA's Earth Observing System Programme.

"This study is the most comprehensive and detailed examination of industrial, smoke and other air pollution particles over the Indian subcontinent to date, and reveals how topography, meteorology and human activity help determine where these particles are concentrated," said Larry Di Girolamo, a professor of atmospheric sciences at the University of Illinois at Urbana-Champaign and a co-investigator on the MISR mission.

While high pollution levels were found over much of India, a concentrated pool of particles was discovered over Bihar.

Researchers attributed the Bihar pollution pool to the inefficient burning of a variety of biofuels during cooking and other domestic use.

Particles in the smoke remain close to the ground, trapped by valley walls, and unable to mix upward because of a high-pressure system that dominates the region during winter.

"The result is a pollution episode that can affect both human health and local climate," Di Girolamo said.

The airborne particles can damage delicate lung tissue, and by altering the radiative heating profile of the atmosphere, the particles may change temperature and precipitation patterns, Di Girolamo said.

Prior to the MISR study, atmospheric models had predicted a tongue of pollution extending across the middle of India. The MISR observations, however, show the pollution lay much farther north.

"Bihar pollution pool must be having a tremendous impact on the local climate and the health of the approximately 100 million people that reside within this pool.

"Our long-term goal is to better predict the occurrence of these pollution episodes and their impact on public health and local climate," Di Girolamo said.

The work, funded by NASA, involved collaborators from Illinois, the Jet Propulsion Laboratory, the National Centre for Atmospheric Research and Scripps Institution of Oceanography. The researchers published their findings in the December issue of the journal 'Geophysical Research Letters'.