Big bend national park’s superintendent, John King, calls the 801,163-acre reserve on the West Texas border with Mexico a “destination park,” meaning for most folks there’s little other reason to venture into the area at all. Reaching it takes four hours on a two-lane road from Midland, the nearest major airport. In between is the flat, scraggly PermianBasin, the state’s historic oil patch, dotted with dying and dead “horsehead” walking-beam pumps and filled with the pungent odor of black gold wafting from those still in production. But even in scorching summer heat, when temperatures average more than 90 degrees, the trip is worth it. Mesas and buttes pop up as one nears the oversize oxbow in the Rio Grande that gives the region its name, and the terrain turns to the classic ChihuahuanDesert of purple-tinged prickly pear, spiny ocotillo, sharp-barbed lechuguilla, and yuccas spikier on top than any punk rocker.

Since the late 1980s, the remote park has been plagued by an unexpected problem: haze. “I’ve had people come out, take a look around, and tell me they had to get going back to Houston for some clean air,” says Big Bend’s air quality technician, John Forsythe. Hall Hammond, a San Antonio jewelry sales consultant who has visited the park 60 times since 1969, is an activist with the private Friends of Big Bend National Park, a group that supports the Texas park. He remembers when he used to ask friends to float down the river with him and stare up from the canyon at what he called Big Bend blue. “The sky would just be cobalt,” he recalls. But lately that hue is rarer and rarer. In 1998, Hammond hiked up EmoryPeak in the ChisosMountains, looked down from its 7,825-foot height and saw “this yellow layer sitting down on the desert to the north and east. It just completely threw me.”

The air has been going bad in many parks for decades, affecting views and endangering the health of visitors, plants and wildlife. Last year, the National Parks Conservation Association (NPCA), a nonpartisan watchdog group based in Washington, D.C., listed the five most polluted national parks. Relying almost entirely on data from the National Park Service and the EPA, the group says the parks with the worst visibility and most severe ozone and acid rain levels are the Great Smoky Mountains Park on the Tennessee-North Carolina border, followed by Mammoth Cave in Kentucky, Shenandoah in Virginia, Acadia on the Maine coast, and the jointly operated Sequoia and Kings Canyon National Parks in California’s Sierra Nevada. Many parks have been hard hit by sulfur dioxide and nitrogen oxide from coal-fired power plants, which are responsible for nearly 70 percent of sulfur dioxide and 22 percent of nitrogen oxide emissions nationwide. The park service, while it disagrees with the way the NPCA assessed some of the pollution data, has little quarrel with the report’s general tenor.

Eastern parks, many downwind from huge coal-fired power plants in the Ohio RiverValley and elsewhere, are the worst hit, in keeping with national pollution patterns. Over the past century or so, man-made haze has cut average visibility in the eastern half of the country from 90 miles to between 15 and 25 miles. In the arid and naturally clearer western states, visibility has dropped from 140 miles to 35 to 90 miles. Parks famed for their views—Grand Canyon in Arizona, Yellowstone in Wyoming, Montana and Idaho, Yosemite in California, Colorado’s RockyMountain, and Big Bend—have long bouts of murky, polluted air each year.

Because federal rules have long mandated that national parks and other wilderness areas should have the cleanest air in America, regulators have been authorized to take action against known polluters, typically by suing them for noncompliance. But as pollution-control laws have become increasingly complex, companies accused of violating park airquality standards have gone to court to delay enforcement, stalling cleanup efforts. The Bush administration has proposed overhauling air pollution regulations, replacing the current, plant-specific air quality standards with a barter system; power plants would buy or trade pollution credits, allowing them to exceed pollutant limits in some places. Proponents say the administration’s Clear Skies Initiative will ultimately improve air quality by lowering emissions. But critics say that the changes will reverse progress against dirty air—and allow egregious polluters to stay in operation.

The political debate over air pollution laws underscores the plight of the parks. “There is still that vision that you can go out to the parks and breathe fresh mountain air, and get away from the urban problems that we all see, and stand in that pristine natural world,” says NPCA president Tom Kiernan, who worked from 1989 to 1992 as an EPA official in the first Bush administration. “Yet we see, by god, that we have some of the worst air in the country in the national parks.”

Why? An extraordinary scientific study conducted in an isolated stretch of Texas is yielding some answers. The implications—for the regulatory debate, for the health of the parks, even for the health of parkgoers—give new meaning to the idea of far-reaching.

Big bend is a historic place. Comanche, Apache and other tribes defied 300 years of Spanish and Mexican rule in the rugged badlands. It was the last redoubt of Indian warrior Victorio and his Mescalero Apache, finally scattered in 1880 by U.S. Army troops. The park’s center is crowned by the rugged escarpments of the ChisosMountains massif, giving it the look of a fortress.

In the 1990s, Big Bend’s growing haze spurred wide suspicion that the pollution originated across the river, 140 miles to the southeast. By 1995, two big coal-fired Mexican power plants, Carbón I and II, were generating 2,600 megawatts of electricity without significant emission controls.

In a joint effort, the EPA, the park service, the Texas Commission on Environmental Quality, the U.S. utility industry’s Electric Power Research Institute and the National Oceanic and Atmospheric Administration launched the Big Bend Regional Aerosol and Visibility Observational (BRAVO) Study. From July through October 1999, a small tent and trailer city sprang up in a scrubby corner of the park. Instruments sprouted at dozens of locations in or near Texas. Scientists around the state injected different perfluorocarbon chemicals into the sky, and monitors in the park recorded the tracers as they arrived. Mexican officials, apparently afraid they were being set up to take the blame for Big Bend’s bad air, had backed out of the study; so U.S. scientists, unable to put tracers directly into the Carbón plants’ plumes as hoped, released them from a tower in the Texas border town of Eagle Pass, 20 miles from the plants.

The BRAVO researchers made their results public this past September. The short version? Don’t blame Mexico. In fact, the park’s worst haze comes from the eastern United States and East Texas. Mexico’s Carbón I and II plants remain the biggest single contributors to Big Bend’s sulfate haze. But on the haziest days, they contribute just 9 percent of the total, and the rest of Mexico another 7 percent. Texas adds 11 percent, the eastern United States 22 percent and the western United States 4 percent. The rest of the haze arises from windblown soil, smoke from agricultural and forest fires, manufacturing activities and vehicle exhaust. Mark Scruggs, assistant chief in the National Park Service’s air resources division, which monitors pollution in the parks, says the big surprise was how much sulfate originates in the eastern United States, borne on prevailing winds that blow across East Texas or loop down to the Gulf of Mexico and north through the Mexican mainland. Mexican officials had been arguing since 1996 that Big Bend’s problems came from north of the border—including a string of power plants along the Ohio RiverValley—but the Americans were skeptical until the BRAVO data came in.

Ever since Congress created the first national park, at Yellowstone in 1872, the parks have enjoyed special legal protections. In 1916, the National Park Service was set up to maintain areas “unimpaired for the enjoyment of future generations.” Additional legal backing came in 1977 when amendments to the Clean Air Act gave parks the highest priority, designating them as Class I areas. The law is emphatic: “Congress hereby declares as a national goal the prevention of any future, and the remedying of any existing, impairment of visibility in mandatory class I Federal areas which impairment results from manmade air pollution.”

“It was visionary to try to protect these areas without even knowing how difficult it would be,” says air resources division director Chris Shaver. The division has outfitted most major parks with filters to gather aerosols, or ultrafine solid and liquid particles in the air; nephelometers to measure how haze scatters sunlight; and transmissometers that gauge scattering and absorption of light by pollution, dust, mist or other material in the air. Chemical samplers scrutinize the concentration of such problematic molecules as ozone, which can be harmful to humans at ground level.

Shaver remembers standing on the rim of the Grand Canyon with her then 6-year-old daughter, Courtney, in 1990. The girl looked at the barely visible cliffs on the other side and said, “Mom, I don’t know how to tell you this, because I know how hard you are working, but you’re not doing a very good job.” Courtney graduated from college this year, and Shaver still sees haze in the park system. When researchers started measuring the Grand Canyon’s air quality in the 1970s, “Congress and most people thought we had a problem with [only] a few power plants in the four corners,” she says of the region where Arizona, New Mexico, Colorado and Utah meet. Since then, while these power plants have slashed their overall sulfur emissions by 72 percent, the canyon’s haze remains—evidence that the problem isn’t merely local.

Whether the Bush administration’s proposed air quality regulations will more effectively reduce pollution in the worst-hit parks is hotly debated. The present system “is tied up in the courts,” says Jim Connaughton of the White House Council on Environmental Quality. The Clear Skies Initiative aims to replace the strict limits governing an individual power plant’s emissions of sulfur dioxide and nitrogen oxides with a “cap-and-trade” system. Aplant that exceeds a limit for a pollutant would buy or trade credits from an operator that was under the limit for the same compound, keeping the nation’s overall pollution in check. Proponents, including many Republicans and most industry lobbies, say the plan is simpler, allows companies to be flexible, and lets some stay in business without buying expensive clean-up equipment. If a plant goes over its limit and has no credits to buy its way clear, EPA officials can levy fines with fewer hearings and lawsuits.

Connaughton also says that the proposal preserves longterm national goals on clean air and will improve visibility in the national parks. The proposal aims to reduce emissions of sulfur dioxide, a prime cause of haze and acid rain, by 73 percent by 2018—down 8 tons from the 11 million tons emitted in 2000. At the same time it would cut nitrogen oxides, a cause of ozone, by 67 percent.

But opponents see Clear Skies as a sellout to industry. They say the proposal is less aggressive than current regulations, and they complain that it would let dirty power plants operate as long as their owners buy credits elsewhere. Many environmental organizations have attacked the proposals. “Why is the Administration bragging about a plan that will actually result in more pollution than if we simply enforced the existing Clean Air Act?” the Sierra Club asks. In 2002, Eric Schaeffer quit his job as the EPA’s regulatory enforcement head, protesting what he says is the Bush administration’s soft approach to power company pollution. “If you allow them to buy their way out of reducing emissions, then the parks may not get better for a long time,” he says. Clear Skies opponents also say the plan would put park air at risk because the cap-and-trade credit system takes the teeth out of the parks’ Class I designation. Park superintendents would no longer have clear authority to demand that the EPA or other agencies go after individual polluters. The Clear Skies legislation is currently stalled in a Senate committee.

Bartering has worked in the past. Since 1990, power plants have been allowed to use a cap-and-trade system to help reduce acid rain, produced largely by coal-fired plants spewing nitrogen and sulfur. Consequently, sulfur emissions went from 17.3 million tons in 1980 to 10.6 million tons in 2003.

Park service expert Mark Scruggs is guardedly optimistic about the Clear Skies Initiative. “If the caps are stiff enough, sure, it will help a lot,” he says. “A 70 percent cut in sulfur dioxide is going to make a difference, especially for the East Coast parks.” But Scruggs says that when the current system is at its best—when agencies work together to prosecute individual polluters—results are impressive. EPA pressure on industry led to improvements in scrubber technologies, which reduce smokestack emissions, with 95 to 98 percent elimination of some pollutants now commonplace. Scruggs says similar improvements are possible for other pollutants.

But park lovers shouldn’t expect big improvements soon. The EPA’s deadline for returning park air to normal is 2064, a date instructive both in its temporal distance and legalistic precision. To be sure, there have been isolated gains. Sulfate haze tends to be dropping in the East, even as nitrate pollution and ozone are rising a bit in the West. In January, the park service said it met its 2004 performance goal of achieving stable or improving air quality in at least 62 percent of monitored parks, with 15 getting cleaner and 16 staying the same. Still, 18 got worse—including high-profile destinations such as Acadia, Death Valley, Grand Canyon and Yellowstone.

“We’re at the end of the tailpipe,” says Ken Olson, president of the Friends of Acadia. Pollutants emitted as far away as the Ohio RiverValley cook in the sun as they are blown east, their ozone and acid levels rising as they move. “We get days when the visibility is just terrible [and] palpably polluted,” he says.

And don’t let the SmokyMountains’ name fool you. The nation’s most popular park, at 9.2 million visitors a year, once offered terrific views year-round. The “smoke,” known to the Cherokee long before the Industrial Revolution, is a bluish haze of moisture and natural organic particles that hangs on the hills.

Today, one of the worst pollutant concentrations in any national park has created a more unwelcome haze. Jim Embry, an architect in the tourist-happy town of Gatlinburg, Tennessee, north of the park, built a house in 1966 on MountHarrison, facing the park. Two walls are almost all glass, with a scenic vista of majestic 6,593-foot MountLeConte. Good views of the mountains are less and less common, he says. “I am watching them disappear before my eyes.”

The air in California’s Sequoia and KingsCanyonNational Parks is essentially hostage to geography and climate. In the southern Sierra overlooking California’s broad San JoaquinValley, the 865,952-acre pair of parks range from rolling foothills and oak woodlands to granite peaks. Founded in 1890, Sequoia is the nation’s second-oldest national park, after Yellowstone. Its eastern border crosses the summit of Mount Whitney, at 14,494 feet the loftiest point in the 48 conterminous states. The parks hold 30 groves of giant sequoia, the world’s largest tree. Many are thousands of years old, 30 feet or more across at chest level, and taller than a 26-story building.

In winter, when the air is clearest, the vista from a snowy scenic outlook toward the San JoaquinValley seems etched in crystal. From late spring through fall, though, dawn typically brings an ugly sight: a gray-brown murk that rises like a tide as the day warms. The miasma, says air resources specialist Annie Esperanza, even looks like a river as it flows into the park. Natural visibility at Sequoia should be 122 to 158 miles, the EPA says. But summer views average less than 40 miles, and on the worst days can drop below 6.

Though the parks are just 230 miles from Los Angeles, the problem is not Southern California sprawl. Instead, scientists have found that the pollution originates as fresh air off the Pacific picks up pollutants from the urban industrial complex around San FranciscoBay. As the air spreads south into California’s sun-blasted Central Valley, it picks up more fine aerosols, sulfur dioxide, soot, dust and ozone-making nitrogen compounds from fast-growing cities, intense agriculture, busy Interstate 5 and other highways crowded with cars and diesel tractor-trailer rigs. The air is walled in by the Coast Ranges to the west, the Sierra Nevada to the east and the Tehachapi Mountains to the south, creating an eddy of recirculating and concentrated pollution before it wafts into Sequoia and Kings Canyon.

Bill Tweed, Sequoia and KingsCanyon’s chief park naturalist, figures that the southern San JoaquinValley is the nation’s most efficient smog pot. The air, Tweed says, “just cooks and cooks and cooks in a warm, summer, cloudless climate.” To make things worse, the valley’s population is on track to double over the next four decades, to more than seven million. “We’ve already gone from a broth to a stew, and if we’re not careful our stew will turn into a chowder,” Tweed says. “The best way to enjoy a park is to just go out and walk. You must get out of your car to enjoy a park. But on a fair number of days, it is not even healthy to get outside and walk. That is a most direct assault on our mission.”

Ozone, park officials say, has hurt 90 percent of the parks’ Jeffrey pines. So far, the mature giant sequoia appear to be OK, but their seedlings may be suffering. In the Foothill Visitors Center at Ash Mountain, park workers post air advisories for the public and staff. On bad days, a sign tells visitors to avoid extended hikes. On 52 days last year, the parks’ ozone levels exceeded the EPA “unhealthy air” standard of 85 parts per billion for eight hours. And 2004 was a good year; 2002 saw 80 unhealthy days, contributing to a 305-day unhealthy air total for the span 1999-2003—just 68 fewer than Los Angeles.

“I can’t even bring my kids up here unless I know we’re going to have clean air,” says Laura Whitehouse, NPCA’s local representative. Her three children all have severe asthma. In May 2004, thinking the air would be tolerable, she took them into the park. Her 9-year-old son, Aaron, complained of chest pains in the parking lot and plunked down on a bench, wheezing badly. Paramedics had to bring a nebulizer to clear up the boy’s lungs. “It’s sometimes worse up here than in the valley,” Whitehouse says.

In 1967, Bill Tweed was 18 and working as a bellboy at the lodge at Sequoia and KingsCanyon. With July 4 coming up, veteran employees let him in on a local tradition: load up backpacks with beer and other refreshments and scale Moro Rock, a bald monolithic knob near park headquarters. For generations, its lordly 6,725-foot-high view across the San JoaquinValley to the west had provided a granite throne for simultaneously looking down on fireworks spouting from Fresno, Visalia, Dinuba and other communities. But that year not a flicker was to be seen. “Everybody said it had been happening more and more often,” Tweed recalls. Within a few years, the Fourth of July climb was kaput, killed by haze.

As Tweed lists the man-made threats to the parks—climate change, invasive species, forests choked by overzealous fire suppression, nitrogen air pollutants that overfertilize plants, ozone—he’s not optimistic that Moro Rock Independence Day viewing will return any time soon. “We are making it harder and harder to carry out the legal mandate to maintain these parks in their natural state,” Tweed says. “What we don’t know now is, can we ever get back?”