Smog from Los Angeles contributes to the haze in the Grand Canyon, as well as spreading into other states, according to a recent air-pollution study.

A six-year study conducted by Washington University in St. Louis found that Los Angeles air pollution travels at least 240 miles and reaches the Grand Canyon, contributing to a haze that limits visibility there, said university researcher Warren White.Scientists from Desert Research Institute in Reno and the Scripps Institution of Oceanography in La Jolla, Calif., participated in the study.

Smog was tracked from Los Angeles to Meadview, Ariz., 15 miles south of the northwestern mouth of the Grand Canyon. The study does not show whether the city's pollution reaches Phoenix, White said.

"The significant result of the study is that Los Angeles air reaches an area where the air should be so clear," White said. "If it weren't for Los Angeles, the air in Meadview would still be clear."

Although the study implicates the California air as a source of Grand Canyon haze, it does little to clarify the debate over other sources of the haze, White said.

The Salt River Project is embroiled in a controversy with the National Park Service and U.S. Environmental Protection Agency over sulfur-dioxide emissions from its Navajo Generating Station and the role they play in canyon haze. The SRP has blamed much of the haze on California smog.

The project next will check to see whether Los Angeles pollution is reaching Colorado, White said.