Big Bend National Park in Texas frequently has the dirtiest air of any of the national parks in the Western U.S., says the National Park Service. On clear days, visibility at the remote park can reach 180 miles or more, but such days are becoming less and less common. Last year there were only 43 days when visibility stretched beyond 100 miles, while there were 61 days with visibility of less than 30 miles. The Texas government claims that Gov. George W. Bush’s voluntary emissions reduction plan has cut the smog and haze at the park by 3 percent, but critics dispute that figure and say that Texas needs tougher air standards. While much of the pollution contributing to problems at Big Bend comes from power plants and other facilities in Texas, a good deal also comes from Mexico, and some activists say Texas and U.S. officials are using Mexico’s contributions to the smog as an excuse not to act.

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